'Bausch & Lomb ©pticaf Co. • . * ^ Projection Apparatus * * i Balopticons and Accessories Apparatus for Every Known Form of Optical Projection, Including Most Complete and Diversified Methods for Scientific Demonstrations Copyrighted 1917, by Bausch & Lomb Optical Co Bausch & Lomb Optical Co. Rochester, N. Y. New York Washington Chicago San Francisco London Frankfurt B-5, XII-16 Branches and Foreign Agencies We maintain branch offices in New York, Chicago, Washington and San Francisco, where sample lines of our products are carried for the inspection of our customers. Our representatives will be found well versed in all the phases of our business, glad to extend every courtesy and to give any desired information. Our products are supplied also by dealers in the United States and Canada and by agents in foreign countries. Branches NEW YORK: Bausch & Lomb Optical Co., 200 Fifth Ave. WASHINGTON, D. C.: Bausch & Lomb Optical Co., 613 Fifteenth St., N. W . CHICAGO, III.: Bausch & Lomb Optical Co., 122 South Michigan Boulevard. SAN FRANCISCO, Cal.: Bausch & Lomb Optical Co. of California, 154 Sutter St. Germany, Frankfurt, a. M.: Bausch & Lomb Optical Co., G. m. b. H., 30 Schillerstrasse. ENGLAND, London.: Bausch & Lomb Optical Co. Ltd., 37 & 38, Hatton Garden, E. C. Foreign Agencies France, PARIS: E. Krauss, 16-18-20 Rue de Naples. RUSSIA, PETROGRAD: E. Krauss, Rue Gogol 5. JAPAN, Tokyo: E. Krauss, No. 1, Yurakucho, 1— Chome. AUSTRALIA, Sydney, N. S. W.: Donald Ross & Co., Ltd., Angel Place, off 127 Pitt St. CHINA, SHANGHAI: Edward Evans & Sons, Ltd., 30 North Szechuen Road. BAUSCH & LOMB OPTICAL CO. EXECUTIVE OFFICE AND MANUFACTORY ROCHESTER, N. Y. Preface H E position of optical projection in education, as well as for general entertainment purposes, has become thoroughly established. Its value in both advanced and elementary work is now so widely recognized that the institution is not considered fully equipped, which does not possess enough high grade projection outfits to meet the varying needs of its different departments. At the same time the projection lantern is more popular than ever before in the church, Y. M. C. A., lodge and home. Its usefulness in all of these fields has increased with the practical development of its different forms and applications. That we have played a leading role in this development is evidenced by the Grand Prix awarded our line of projection apparatus, for excellence of construction and originality of design, at the Panama-Pacific Exposition. The trade name “ Balopticon”, by which we designate our lanterns, is a word in common use among those interested in the highest grade projection apparatus. The prefix, “Bal”, is derived from the Greek verb, “ballein”, meaning to throw or project. Incidentally it contains the initials of our company and is rightfully used only by us. This new edition of our projection catalog we believe to be the most complete ever published, for in it we present what we consider the most comprehensive pro- jection line ever placed on the market. The user of projection apparatus will also find in the following pages much information of interest and value regarding the various possibilities and applications of optical projection. Special attention is called to the following noteworthy features: New, Simplified, Double Dissolving Balopticon, Improvements in Projection of Opaque Objects, Especially with Alternating Current, Application of Gas-Filled Mazda Lamps, Improvements in Microscopical Projection, New Balo Projection Lenses, Projection of the Spectrum, Convertible Balopticon for All Known Forms of Projection, New Combined Balopticon with 1000-Watt Mazda Lamp, Home Balopticon for Opaque Objects and Lantern Slides, Balopticon for Large Opaque Objects. Back of our projection apparatus, as all of our products, are more than sixty years of scientific and productive experience as optical manufacturers. The differ- ent instruments offered are results of the combined efforts of our Scientific and Technical Bureaus, working frequently in co-operation with the users of such apparatus, whose suggestions are always given serious attention. In the actual manufacture of our projection apparatus we enjoy the advantage of producing practically all parts — mechanical as well as optical — in our own works. This enables us not only to assure the effective co-ordination of the different parts, but to give all of our Balopticons and accessories the unqualified guarantee which our name conveys. BAUSCH & LOMB OPTICAL CO. Terms W HEN ordering from this catalog please give catalog number, the name of article and size (when necessary). For telegraph orders use code words. Our prices are f. o. b. Rochester, N. Y. Transportation on goods sent on memorandum, or for examination, is at the expense of the customer. Satisfactory references are required to open accounts, otherwise remittances in cash, postal orders, or New York or Chicago current funds should accompany the order. If local check is more convenient, /-6 of 1% (on amounts less than $100.00, 10c) should be added to cover bank exchange. Goods sent on approval and returned in damaged condition will be repaired at the customer’s expense. Goods made on special order will not be sent C. O. D. nor on memorandum. Goods returned for any reason should be plainly tagged with the sender’s name and address. Goods ordered to be sent by mail are at purchaser’s risk and expense. Postage should be forwarded with cash orders, otherwise we shall ship express collect. No charge is made for packing. Unless otherwise specified we shall use our best judgment in the mode of shipping, prepaying transportation if desired. Our responsibility ceases when we have delivered the package to the common carriers and have received their receipt. All claims for breakage should be reported to the transportation companies at once. Please examine all packing minutely for small items. We exercise the utmost care in manufacturing and packing; in case faulty goods inadvertently reach our customers, we shall feel under obligation if our attention is called thereto. The prices in this catalog are subject to change without notice. BAUSCH & LOMB OPTICAL CO. Introductory Optical Projection and Its Various Applications Bausch & Lomb Optical Company Optical Projection Although unappreciated and undeveloped for generations, optical projection has come into its own at last. It is to-day an agency of widely recognized value in the scientific and educational world and in many other fields of usefulness. Starting in the institutions of higher learning the projection In Education ^ ^ bto very general use in high schools and grammar schools in many branches of instruction. Its serious recognition by educators is apfaren. in the fact .ha, the New Yotk State Education, Depart- ment has organized a Department oi Visual Instruction, possessing a collection » more than 300,000 slides which may be obtained free of cost by schools under e Department. Movements are on foot in other states looking to similar ends. A large number of churches and Sunday schools now possess projection outfits for the double purpose of instruction and enter- tainment. The interest and value of Sunday evening addresses and Bible lessons are greatly enhanced by projected views. Lodges and fraternal organizations, too, are coming to use the lantern extensively in their ritualistic work. Always popular in the home as an entertainer .t now has a stronger hold there than ever before by virtue of the really high grade apparatus which can be produced at a moderate cost. Many camera clubs and individual enthusiasts are numbered Supplement amQng Qur patrons . The projection lantern renders a two-fold to Camera ^ enables the individual to reproduce specimens of his art most effectively, while clubs find it an invaluable aid in the study and discussion of photographic processes. In Church, Lodge and Home Historical Resume While optical projection in this scientific and universal application is of comparatively recent development, the basic principles have been known and exemplified in various primitive forms of apparatus for several centuries. In many Latin writings between the years 1500 and 1700 we find the projection lantern described as the camera obsc or “laterna magica”. Who the inventor was seems to be unknown. The achiev - men^has been^variously aactibed to Bacon, Potta, Dacha,*, Kitche, and o.he, authors who have handed it down in literature to succeeding generations. This impression is erroneous, however. None of these writers has claimed the distinction, and all have written as though treating facts and principles which even at that early period, had been established for some time. It is quite probable that several different experimenters in light and optics devised crude lanterns independently of each other. Those pioneers in the field were regarded for the most part Work ° f as wizards, and the primitive outfits which they fathered excited “ WUardS ” curiosity, mingled with awe, and little more. Optical projection occupied scarcely any stronger position during the intervening centuries down to comparatively modern times. 6 Bausch & Lo m b Optical Company Ealer, the great Swiss mathematician, recognized its possibilities more than a century ago but was prevented from developing them by an utter lack of efficient illuminants. Sunlight was about the only form which was sufficiently bright, and that was impracticable for projection purposes. Thus the modern achievements already alluded to may be attributed to the development of illuminants as well as There are six applications of optical projection available to- Six Different day _ pro j e ction of lantern slides, of opaque objects, of micro- Applications objectSj of horizontally placed objects by transmitted light. projection with polarized light and projection of the spectrum. In our various equipments we provide for all six of these applications in a thoroughly practical and efficient manner. Lantern Slide Projection This is the primary form of projection. It is effected by sending light from a suitable source through a set of condensing lenses, which serve to direct the rays in even distribution through every part of the transparent glass slide bearing the object to be projected and then through the projection lens, or objective, which casts the enlarged image on the screen. S Path of Light in Lantern Slide Projection. The arrangement of parts is indicated in the accompanying diagram, in which E is the ilium inant, C the condensing system, D the slide, O the diaphragm plane of the objective, or projection lens, and S the screen. Projection of Opaque Objects The projection of opaque objects, such as post cards, photographs, book illustrations, type matter, maps, drawings and even solid objects, is one of the latest forms of projection to be developed to a truly high standard of efficiency. It has become very popular, however, among educators and all users of projection, since an almost unlimited amount of illustrative material is thus rendered immedi- ately available for the purpose at a very low cost. 7 Bausch & L o m b O ntical Company Path of Light in Projection of Opaque Objects. Difficulties Involved This form of projection is based on the principle of reflection, as indicated by the accompanying diagram, m which A is the illuminant, B condensing lenses, D the opaque object to be pro- jected E the projection lens and F a mirror to direct the image to the screen in correct position. The fewest reflections possible are thus shown to e two, 1 one wishes to produce a picture “ ^reflect, ons mulTLlrm” which at best is a poor reflecting medium. When it is further considered that in the projection of opaque objects the direction o beam of light is altered and considerably dispersed, so that a smaller percen age light rays reaches the projection lens than in the case of lantern slide projectio , is obvious that the screen image so obtained cannot equal in brilliancy that pro- duced from a lantern slide, providing lens equipment and illuminant are the sam . To overcome these handicaps we employ a projection lens of large diameter (4 inches or more) and a more intense hg t. The diameter of the lens in this form of projection is a very important consideration, since, all other things being eqnal, the .Horn, natron *, vary inversely as the square of the diameter of the lens being used. Next in importance to the aperture, or illuminating value, of a lens t quality Of correction for definition and flatness of field, and the larger a given focal length, the more complex become, its correct™. '' J then that lenses used for the projection of opaque objects on our higher priced Balopticons are necessarily of an exceptionally high grade, because of the very a field they give in spite of their large diameter. Means Employed Bausch & Lomb Optical Company Because of the large area usually covered in the projection Projection opaque objects, as compared with that of lantern slides, it is necessary to use lenses of two or more times the focal length of those used for lantern slides, in order to obtain images of the same size from both slides and opaque objects (see tables, page 18). In order to obtain satisfactory illumination, we consider it necessary to main- tain the ratio between the aperture and the focal length of the lens at about 1 to 4 or 5. Hence there are limits of focal length, beyond which, for optical reasons, we cannot go. Therefore, it is not practical to attempt the projection of opaque objects at the extremely long distances at which lantern slide projection may be satisfactorily undertaken. Required Conditions To accomplish really satisfactory results it is necessary to have a totally darkened room and a good quality of screen, one with either a white opaque or an aluminum coating. Except in the case of the Home Balopticon, intended for use at short projection distances, the only illuminants we recommend for the projection of opaque objects are the arc lamp, using from 25 to 35 amperes of current, and the 1000-watt, gas-filled stereopticon Mazda lamp. Microscopical Projection This form of projection has become a very useful agency in the sciences, in class room and general demonstration work. An efficient projection microscope is of great value in supplementing table work with individual instruments. With it an instructor can demonstrate to all the members of a class simultaneously objects which are not available for individual examination. He finds it a great convenience, too, when he wishes to explain a slide to the class as a whole or to present a specimen quickly for comparison and discussion by members of the class, also in reviewing past work or assigning work in advance. Illustrated lectures on micro- scopical subjects are rendered possible, time is saved and the students interest is stimulated. Optically considered a projection microscope is a projection Its Early lantern with an objective of short focus for displaying very small ° ngin objects greatly enlarged. Historically it dates back nearly as far as the “laterna magica” itself. We find the latter used as a projection microscope as early as 1665. Fahrenheit, inventor of the thermometer bearing his name, devised a projection microscope before the year 1736 and exhibited it in Amsterdam. Among those who saw this instrument of Fahrenheit’s was Lieberkiihn, the anatomist, who was greatly interested in it as an aid in his work. He accordingly had one made and took it with him to England, where it aroused considerable interest. Thus it came about that Lieberkiihn was wrongfully regarded as the inventor, although he never claimed the honor. 9 Bausch & Lomb Optical Company The projection microscope was quite widely used throughout Europe by the middle of the 18th century, although, of course, in a very crude form. Both sun- light and lamplight were used as illuminants, and the optical and mechanical devices were of a primitive nature. The scientific endeavor which finally led to the present high Efficiency development of this instrument was concerned with the improve- ment of illuminating devices, as well as optics and mechanical appliances for operating the instrument. The compound projection microscopes, which we offer to-day, are as high grade scientific instruments in every respect as any regular table microscope and provide possibilities not to be had in regular microscopes. While some may have experienced a feeling of doubt in the past as to the real efficiency of microscopical projection, they may now rest assured of obtaining absolute satisfaction with any of our higher grade outfits, especially designed for this kind of work. One of the latest developments in microscopical projection we offer in our combined horizontal and vertical type of microscope, which provides for the projection of microscopic objects held in a horizontal plane as well as in the usual manner. The small diameter of the microscope objectives and the high Problem o magnifications which they produce require intense and uniform Illumination 6 . „ illumination of the slide or object to be projected. 1 o accomplish this we have adapted the scheme originally introduced by Kohler, which consists of projecting the evenly illuminated image of a condensing lens into the object slide by means of a substage condenser. i V * u Figure I — Kohler Illuminating System. The arrangement is shown in the accompanying diagram. It consists of a light source, L, a single condensing lens of suitable focus, C, a diaphragm, D, a substage condenser, E, with an object slide, S. The condenser, C, forms an in- verted image of the light source, L, at L', or the plane of the iris diaphragm of the substage condenser, E. The substage condenser is so placed that it focuses the image of the first condenser, C, in the plane of the object, giving C'. The size of the illuminated aperture is regulated by the diaphragm, D, of the condenser, which diaphragm is imaged by the substage condenser in the plane of the object slide at a point nearly coincident with C\ giving a sharply defined margin of the projected image. The Kohler illuminating system is made use of, without modification, in our Simplified Micro-Projection Apparatus. (See page 83 ). 10 Bausch & Lomb Optical Company c Figure 2 — Application of Kohler Illuminating System to Model D Balopticon. „ ... In adapting this illuminating scheme to our model D Balop- Our Illuminating Systems ticon we have substituted for the single condensing lens, C in Figure 1, our triple condensing system (see Figure 2). This change of condensers was made to enable a quick interchange between microscopical and lantern slide projection. We furnish a substage condenser of a suitable numerical aperture and optical construction to meet the special requirements. The regular Abbe condenser is not suited to this purpose because of its short focal length. In the case of our Universal Balopticon the large projection lens for opaque objects, supplemented by a special condensing lens, is substituted for the front lens of the triple condensing system. Figure 3 — Application of Kohler Illuminating System to Convertible Balopticon. Still another adaptation of the Kohler system is now used to give the excep- tional results possible with the Convertible Balopticon, especially in higher power work. The path of light is shown in Figure 3. To obtain this the condensing lens directly back of the lantern slide carrier, which lens is mounted in a swinging arm, is thrown out of the optical axis, and a small double convex lens, mounted in the dark chamber, is swung into position directly in front of the large rear condensers. This produces a gradually converging pencil of light, which finally forms a large image of the arc at the diaphragm plane of the substage condensers and fully fills the aperture of the high power condenser. With the improved substage condensers this arrangement is used for all the different powers of objectives that may be required. An important consideration in selecting apparatus for micro- Magnifications sco P' ca l work is the optical equipment required to obtain the desired magnifications. The following table will be found of value. It gives the approximate magnifications obtained at different projection distances with the objective alone and with the objective combined with our 3X or our 5X projection eyepieces (see “Accessories”). The projection distances given are 11 Bausch & Lomb Optical Company those at which microscopical work is most commonly carried on in the lecture room and are measured from the objective to the screen. Objectives in Terms of Focus Optical Arrangement Projection Distance 10 ft. 15 ft. 20 ft. 25 ft. 72 mm Objective alone 40 65 85 105 Objective alone 65 100 130 165 48 mm With 5x eyepiece 120 180 240 300 Objective alone 95 145 190 240 32 mm With 5X eyepiece 240 360 480 600 With 3x eyepiece 410 615 820 1025 16 mm With 5X eyepiece 595 895 1195 1495 With 3X eyepiece 850 1275 1700 2125 8 mm With 5X eyepiece 1195 1795 2395 2995 With 3X eyepiece 1790 2685 3580 4475 4 mm With 5X eyepiece 2575 3885 | 5160 6450 Mechanical Excellence Mechanically our projection microscopes have been equally well perfected. They are provided with adjustments, both coarse and fine, which are marked by careful workmanship and very accurate movements, so esential to satisfactory micro-projection. Microscopical projection will be more effective if an aluminum screen is used, because of the greater brilliancy of the image thus afforded. Projection of Horizontally Placed Objects by Transmitted Light It is often desirable for certain physical, chemical and biological demonstrations to have the objects to be projected in a horizontal position. Among these may be mentioned such objects as a glass dish of iron filings set in commotion by a magnet or by vibrations of the air, as those caused by a pulsating violin string; also different animal organisms moving in water, or drooping plant formations. To accomplish this we furnish a simple vertical attachment, the principle of which is apparent from the accompanying diagram. B is the beam of parallel light, which has come from the illuminant through the two rear lenses of our triple condensing system. It strikes the inclined mirror, M, in the dark chamber, E, and is reflected vertically through the plano-convex condensing lens, C, placed over the opening in the top of the dark chamber. The object to be projected is placed on the flat surface of the condensing lens, C, and the light rays focused by C in the projection lens, P, which is supported by the upright standard, S, image the object on the second inclined mirror, M 1 , which directs the image toward the screen. 12 Bausch & Lomb Optical Company For Large Specimens We have increased our facilities for projecting large objects placed horizontally by using the same principle for the construc- tion of an especially large apparatus which enables one to project X-ray plates, brain sections or transparencies of eight inches or less in diameter, without first reducing them. This apparatus is designed for the Convertible Balopticon page (68) and is described and illustrated under that model. Projection with Polarized Light For general demonstrations with polarized light, in lectures on physics for instance, we recommend a Projection Polariscope which, being an adaptation of the apparatus first described by Delezenne, is really a Norrenberg apparatus with an additional mirror for the purpose of keeping the axis of the polarization apparatus parallel to the axis of projection. The diagram illustrates the scheme as used with convergent light for the purpose of showing interference figures, etc. The light coming from the light source is made parallel by a triple condensing system and strikes the silvered glass mirror, M, under an angle of incidence of 57°. From there it is reflected under 13 Bausch & Lomb Optical Company the same angle to the mirror, M', which stands parallel to M and reflects the beam in a direction parallel to the axis of the projection apparatus. The mirror, M', is made of black glass and covered with two plane glass plates The light becomes polarized by reflection from this mirror and passes through a pair of quarter-wave mica plates, P, one of which may be rotated so as to rotate the plane of polarization. It is then converged by the condenser, C, on the speci- men, placed on the stage, S, so as to pass through the specimen under all angles. The interference figure, I, is formed in the focal plane of the other lens system, C' which is exactly like C and arranged symmetrically with respect to the object. The interference figure, as well as any micrometer scale, pointer, etc., which may be introduced at I, is imaged on the screen by the single achromatic lens, O e analyzer prism, A, is placed between O and the screen at the point where the pencils cross. i n' For work in parallel polarized light the two lens systems, C and b, are swung out. Petrographical For illustrating lectures on petrography, chemistry, etc., we offer for the first time a number of accessories, by means of which . oner iui me moi umv Projection with pro j ec tion microscope can be readily employed for projection Microscope ^ polarized light . Thes e accessories can be added to our Large Projection Microscope only and are described under Projection Microscopes. (See “Accessories.”) , , For all projection with polarized light we recommend strongly the use of an aluminum screen. Projection of the Spectrum For the projection of absorption spectra we place upon the optical bed an adjustable slit, upon which the condenser forms an image of the light source. he slit thus illuminated is imaged on the screen by the projection lens. 14 Bausch & Lo m b Optical Comp any The flint prism, or bottle prism with carbon bi-sulphide, (equilateral 60°) is placed on an adjustable table in front of the projection lens. If then the axis of the projection apparatus is given the proper inclination toward the screen, the sequence of colored images of the slit, which forms the spectrum, will appear on the screen. For the projection of emission spectra, or for the projection of comple- mentary colors, we offer special accessories accommodated on an accessory optical bed, which may be attached to the regular optical bed. This equipment is partic- ularly effective, projecting an exceptionally bright and pure spectrum. These accessories are fully described and illustrated under Accessories (see index). General Construction There are several features to be noted in the general construction of our projection apparatus, which play an important part mechanically in achieving the high degree of efficiency sought. To obtain portability in our B and C types of construction, the standards are made of heavy sheet metal by special forming tools. This method greatly reduces the weight of the apparatus, and the standards equal castings in rigidity. When the first Balopticon was designed with optical bed of the lathe type, there was adopted a certain size of bed, height of standard, etc., which has been adhered to in all instruments of this type, namely the Model D, Universal and Convertible, and their accessories, so that the same fittings and optical centers are insured upon all. This policy has resulted in securing that standardization of apparatus and interchangeability of parts which .characterize our entire line of projection apparatus. When a Balopticon is equipped with optical bed, any stand- ard carrying accessories, or any piece of apparatus provided with the necessary clamp, can be adjusted along the bed and the simple act of clamping secures the accessory in accurate optical alignment. Our instruments are finished with a dull, black lacquer thoroughly baked in a high-temperature oven. This treatment produces a rich, black finish which is both serviceable and appropriate. Illuminants While a number of different illuminants may be utilized to supply the light for projection purposes, we confine our attentions almost entirely to the arc lamp and the new gas-filled, Mazda stereopticon lamp, where electricity is available, or to the acetylene burner, where electricity cannot be used. The arc lamp is a most satisfactory form of illuminant and Lamp tor some kinds of projection, such as the projection of micro- scopical slides, of the spectrum and complementary colors — wherever, in fact, a very concentrated, homogeneous spot of light is required, it is the only light source we recommend. 15 Bausch & Lomb Optical Company We use only the 90° type of arc lamp, i. e. with the carbons at right angles to each other, and most of our lamps are so mounted that one carbon (the positive in case of direct current) is in alignment with the optical axis of the apparatus. This is the only form of arc lamp that can be used where accurate centering is absolutely essential to satisfactory results, since it keeps the horizontal crater always in the optical axis, while with other styles of arc lamp the position of the crater with reference to the optical axis would be constantly shifting as the carbons burned Arc lamps operate best on about 50 volts across the arc. Consequently it is necessary to use a resistance, or rheostat, in series with the arc to reduce the line voltage (either 110 or 220 volts) to that required. Rapid strides in illuminating engineering have been made in Gas_FUIed another direction during the past year, with the result that the Mazda Lamps ^ gas .fiU e d, Mazda stereopticon lamps with concentrated filament will replace the arc lamp in many Balopticons designed only for the pro- jection of lantern slides and opaque objects, both on account of simplicity of operation and high degree of efficiency per amount of current consumed. This is particularly true where only alternating current is available, since an arc lamp (especially of high amperage) is not very satisfatory to operate on alternating current and is very low in efficiency compared to one operating on direct current. These new Mazda lamps have an efficiency of from 0.8 watt per candle, in the lower wattage, to 0.55 in the higher. For either lantern slides or opaque objects they are far more effective than the alternating current arc lamp, using approximately one-third the amount of current to produce equal illumination. The Mazdas are, of course, entirely automatic and silent, burning with the stead- iness that characterizes the ordinary incandescent lamp. Furthermore, the light is very pleasing to the eye and gives a very good rendition of color values. These lamps are made in sizes from 250 up to 1,000 watts and are used wit either a portion of the globe silvered or in conjunction with an optically corrected, crlass reflector The reflector is recommended because the unsilvered lamp is Tess expensive to renew. In order to secure the full efficiency of the reflector for lantern slide projection it should be set at a fixed point with reference to the filament and should be mounted to move with the lamp when adjusting the latter with reference to the condensers. See pp. 104-105. The length of life of these lamps cannot be positively stated. They are very carefully made, however, of a much heavier filament than that used in the ordinary illuminating Mazda lamp and should give an average life, according to the manu- facturer, of approximately 200 hours. Even with this as the maximum life of each lamp, however, it will be found upon investigation that the replacement of Mazda lamps is less expensive than the operation of an arc lamp, when the con- sumption of current and carbons is taken into consideration. The acetylene burner, while not equal to some other forms Acetylene q{ non _ electric illuminants, is nevertheless the form generally Burner use( ^ w h e re electricity is not available. Its use has been rendered very convenient by the introduction of charged tanks of acetylene gas, such as 16 Bausch & Lomb Optical Comp any those used on automobiles and motorcycles for headlight illumination. These can be rented or exchanged at almost any automobile supply store. This illuminant is very popular among institute workers and others lecturing in rural districts, where electricity is not often available. The oxyhydrogen burner gives illumination exceeding in Oxyhydrogen brilliancy that of the acetylene burner, but is not so convenient Burner ' . , , and costs somewhat more to operate. An oxyhydrogen generator is recommended as a source of supply. Projection Lenses Selection of Lenses Improvements on the optical parts of our Balopticons have been in keeping with the mechanical development, as evidenced by our new series of Balo projection lenses. These superior objectives are of an entirely new type of con- struction, particularly well corrected for flatness of field and critical definiton. They are made in three series as described under “Accessories” (see index). These new lenses are now supplied on all but two of our Balopticon models. In purchasing an apparatus for the projection of either lan- tern slides or opaque objects a point which should receive careful attention is the selection of an outfit with the correct focal length of lens to meet the specific requirements satisfactorily. The focal length of the projection lens, all other conditions being equal, determines the size of picture on the screen. In selecting an apparatus, therefore, one should determine the distance at which the lantern is to be placed from the screen and the size of picture desired. With these two factors given, the focal length of lens required can readily be determined by reference to one of the tables here given. We would particularly caution Balopticon users not to make the mistake, too often made when working with a projection lantern, of deciding upon too large a picture. Any picture out of proportion in size to the distance at which it is being viewed appears unnatural and lacking in perspective and is a strain to the eyes of the observer. Another point to bear in mind is that the intensity of illumination per unit of area varies inversely as the square of the width of the picture; therefore, the smaller the picture the more brilliant it will be. On the other hand, the picture should be large enough, of course, to enable those seated at the farthest points from the screen to see all of its details without difficulty. A fairly safe rule to follow, according to Prof. S. H. Gage, of Cornell University, is to determine upon a picture equal in width to about % or Ys the distance from the screen to the farthest point at which it will be observed. Having thus established the two determining factors men- tioned, one has only to refer to that table below which covers the kind of projection and the size of projected area offered by his apparatus. The focal lengths here tabulated are those which are listed with some one of our different Balopticons for either lantern slides or opaque objects. The Projection Tables 17 Bausch & Lomb Opt ical Company tables give in feet the length of one side (the longer in the case of lantern slides) of the screen image to be obtained at the different projection distances and with the different lens foci indicated. Table 1: For Lantern Slides, 2 % x 3-inch Mat Opening Example:— A 10-inch lens used at a distance of 40 feet from the screen will project an image measuring 12 feet on its longer side. Table 2: For Opaque Objects, 5 x 5-inch Opening Focus of Lens Distance from Lantern to Screen 15 ft. 20 ft. 25 ft. 30 ft. 35 ft. 40 ft. 45 ft. 15-inch 4l4 6 8 914 ii 'A 13 18-inch 4 5 'A b'A 8 9'A 11 25-inch 4 % 5l4 b)A 7'A S'A Example:— A 15-inch lens used at a distance of 25 feet from the screen will project an image 8 feet square. Table 3: For Opaque Objects, 6 x 6-inch Opening Focus of Lens Distance from Lantern to Screen 15 ft. 20 ft. 25 ft. 30 ft. 35 ft. 40 ft. 45 ft. 15-inch 514 7'A 914 11 % 18-inch 414 6 8 9 14 11 25-inch 4>4 514 b'A 8 9 10 Table 4: For Opaque Objects, 8 x 8-inch Opening Distance from Lantern to Screen 15 ft. 20 ft. 25 ft. 30 ft. 35 ft. 40 ft. 15-inch 7'A 10 13 18-inch 6 8 10 14 2 5 -inch 514 7 9 10 14 12 18 Bausch & Lomb Optical Company Condensing Systems The condensing lenses play an important part in the optical system of any projection apparatus, inasmuch as the uniformity of illumination and the size of the illuminated field are dependent on the purity of the glass they are made from (freedom from striae, bubbles, etc.) and on the correctness of their focal length. We furnish two different condensing systems, a double system, consisting of two plano-convex lenses with the convex sides facing each other, and a triple system composed of a meniscus and a plano-convex lens mounted in close proximity and another plano-convex lens mounted separately, as shown in the illustration. Both systems provide for the insertion of a water cooling cell between the plano-convex lenses, if desired. Sectional View of Triple Condensing System, Showing Light Rays Coming from Illuminant, L, Rendered Parallel by Rear Condensers, C, and Converged Again by Front Condenser, C', at L\ The two rear lenses of the triple system render the light parallel. This system permits a more universal application of the light, since by simply removing the front lens a parallel beam is obtained for any other form of projection which may require it, without necessitating the substitution of a special system. A difficulty encountered with all condensing systems is the liability of breakage, due to unequal expansion or contraction caused by sudden extreme changes in temperature. We have devised and patented a ventilated mount, which we believe to be the best safe- Our Ventilated Mount Patent Ventilated Condenser Mount. guard on the market against the breakage of lenses. The rear lens, which comes in closest proximity to the lamp, is one-half inch smaller in diameter than the front 19 Bausch & Lo mb Optical Company lens, or lenses, being set in an inner rim within the larger rim of the mount. The intervening space of one-quarter inch around the circumference is left open, except at the connecting points, permitting a nearly even circulation of air on both sides of the lens. Either of these condensing systems will give satisfactory results with lantern slides. With most of our outfits we supply the triple system. Better optical corrections are possible with three elements than with two, enabling a sharper focusing of the light rays in the diaphragm plane of the projection lens. The second plano-convex lens is of the exact focal length to do this, 1. e. same focus as that of the projection lens. Screens White Opaque and Aluminum The brilliancy of the picture on the screen is largely dependent upon the per- centage of light rays that are reflected back from the screen to the eye of the observer. The character of the screen, then, is an important element to consider. The reflecting quality of a screen is determined by its opacity and surface finish. A well finished white wall serves the purpose admirably, but as such a wall is not often available a good, heavy cloth such as shade cloth, properly treated and coated with either a white opaque or an aluminum finish, makes a very desirable screen. This screen should be mounted on a spring roller so that it may be rolled up, when not in use, and thus protected from dust and dirt. The aluminum finished surface has about twice the reflecting value of the ordinary white surface, but a narrower field. Thus, while an aluminum screen is very advantageous, particularly in the projection of opaque objects, it should only be installed where the audience can be seated within a total angle of 60 from the center of the screen. For portable screens, which can be readily folded up into a small space, white sateen is perhaps the most efficient, because of its highly finished surface. Sateen 20 Bausch & Lomb Optical Company Model B Balopticon Figure 1 — Model B with Mazda Lamp and 2%6-Inch Diameter Lens. This compact, efficient little instrument met with instant success when placed on the market and is now one of the most popular projection lanterns in its class. It meets the growing demand for a really high grade stereopticon at a moderate price and is designed for use with lantern slides only in class rooms, Sunday schools and the home. It is a great favorite with the amateur photographer. He can easily make slides for it from his negatives, or with attachments he can use it effectively as an enlarging lantern for negatives up to 3 Y\ x 4 % inches. We equip this model with either the 250-watt, gas-filled Mazda lamp, or with the small arc lamp and 4j4-ampere rheostat, where electricity is available. On account of its high efficiency and simplicity of operation, the former type of illuminant is usually preferred. It equals the illumination given by the 5-ampere arc lamp, yet consumes only iVz amperes of current and is entirely automatic. Where electricity is not available, a double-jet acetylene burner is used with a special spherical mirror. The same style of lamp house is used with both the acetylene burner and the Mazda lamp (Figure 1). Special features of this lantern are : the method of ventilating both lamp house and condenser mount, permitting the use of lantern slide films if desired without the expense and inconvenience of a water cell; the extreme compactness and light weight, which make it a very desirable equipment for traveling lecturers or salesmen who use lantern slides in demonstrating their lines. Specifications Base — Consists of front and rear metal standards carried on sliding rods. Lamp House — Of sheet metal with special ventilation; two styles — one for arc lamp measuring 6/4 x 214 x 5 in., and that for Mazda or acetylene lamp measuring 6}4 x 7 x 5 in.; both styles fit in grooves to rear standard and can be instantly interchanged by lifting out one and sliding in the other. Illuminant — Our 250-watt, gas-filled, Mazda stereopticon lamp, Adjustable Baby Arc Lamp with small 4/4-ampere rheostat, or double-jet acetylene burner with mirror, as desired; carbons of arc lamp can be adjusted independently and then easily fed forward by turning a single convenient button. Condensing System — Our regular double system, 4/4-in. diameter, in special ventilated mount from which lenses can be easily removed for cleaning. * Slide Carrier — Our double carrier, No. 4430, with elevating device. Bellows — Mounted on metal frames which slide in m et al ways. *The quick changing slide carrier, No. 4449, giving a dissolving effect, may be substi- tuted for $1.50 extra. We can supply to order carriers for small slides, so that one may use either the standard slide or the special small size now being offered. 21 Bausch & Lomb Optical Company Figure 2— Model B with Baby Arc Lamp and 4 >4 -Ampere Rheostat. Projection Lens — Special achromatic lens of 10-in. focus in spiral focusing mount regularly supplied; either 8-in. or 12-in. focus lens can be furnished without extra charge. Dimensions — Length (ready for operation), 20 in. over all with arc, or — in. with other lamps; height 9 Y\ in. Weight — Complete in case, 13-15 lbs., depending on equipment. Case— Sheet metal, 7% x 9^ x 15 in., lacquered in black; with carrying strap. With Mazda Lamp Code Word 1 Cat. No. Specifications Price Dermopteran Destrer Dermopteri Deserite Dermoblast Dermomstric BM 8 s BMlOs BM 12 s BM 10 BM 12 BM 15 Model B Balopticon with 250-watt, 115-volt Mazda lamp with reflector, 15 feet of cord and plug; special 8-in. focus lens in spiral focusing mount Same as above, but with 10-in. focus lens Same as above, but with 12-in. focus lens • f m ■ Same as above, but with a regular quality, 2 5 Ae-in. diam., 10-in. focus lens in rack and pinion mount in place of special lens . . • • Same as above, but with 12-in. focus lens Same as above, but with 15-in. focus lens $22.00 22.00 22.00 30.00 30.00 30.00 Note— While the Model B is here listed with the 250-watt Mazda, a 400-watt Mazda lamp will be supplied for $2.00 extra. (t . For Mazda lamps on higher voltages we supply resistances (see Accessories ). With Arc Lamp Code Word Cat. No. Specifications Price Dermophyte Destroy Dertnoplasty BA 8 s BA 10 s BA 12 s Model B Balopticon with arc lamp, 4^-ampere, 110 volt rheostat, 15 feet of cord, switch and plug; special 8-in. focus lens in spiral focusing mount . Same as above, but with 10 -in. focus lens Same as above, but with 12-in. focus lens $24.00 24.00 24.00 With Acetylene Burner Code Word Cat. No. Specifications Price Demography Dorp Dermoidal Derne Demful Dernhead BG 8 s BG 10 s BG 12 s BG 10 BG 12 BG 15 Model B Balopticon with double-jet acetylene burner and special glass reflector; special 8-in. focus lens, in spiral focusing mount . Same as above, but with 10-in. focus lens Same as above, but with 12-in. focus lens ^ . Same as above, but with regular quality, 2%e-in. diam., 10-in. focus lens in rack and pinion focusing mount Same as BG 10, but with 12-in. focus lens . Same as BG 10, but with 15-in. focus lens . $20.00 20.00 20.00 28.00 28.00 28.00 22 Bausch & Lomb Optical Company Special Traveling Outfits The use of the stereopticon is constantly increasing among institute workers, county agriculturalists and others who travel about delivering lectures — in which ■class may be included salesmen of machinery and similar non-portable articles, as well as promoters of educational campaigns in the industrial field. The Model B Balopticon naturally appeals for such use be- cause of its compactness, light weight and simplicity of operation. We have designed a special carrying case of wood covered with black lealheret and provided with metal corners and locks (Figure 3). Space is provided for the Model B with Mazda lamp also compartments for an extra Mazda bulb and for an acetylene burner, the holder of which will interchange with that on the Mazda lamp. As a source of sup- Figure 3 — Special Portable Model B Balopticon pjy f or acetylene burner we re- BMP m Case. commend the acetylene gas tanks, as used on automobiles. If one does not wish to carry the tanks about, they can be rented in almost any locality where a lantern would be used. The Model B with the two forms of illuminant in the special carrying case has proved very popular. The outfit in its case weighs 20 pounds, and the latter measures 22 x 20/4 x 7^4 inches Code Word Cat. No. Specifications Price Despuile BMP 10 Model B Balopticon with 250-watt, 115-volt, Mazda lamp, 2%o-in. diameter, 10-in. focus lens in rack and pinion mount; in special carrying case of wood cover- ed with black leatheret, with metal corners and locks $37.50 Despume BGP 10 Same as above but with double-jet acetylene burner in place of Mazda lamp and with special glass reflector fitted in lamp house ..... 35.50 Desputeson BMGP10 Model B Balopticon with 250-watt, 115-volt Mazda lamp and with acetylene burner to interchange with Mazda lamp; with lens and carrying case as described above ....... 42.00 NOTE — We are listing with this outfit the 10-inch focus lens, which is the one generally required. The 12 or 15-inch focus lens can be supplied at the same price. If one of these is preferred, substitute “12 or 15’’ for the numeral “10” in the above catalog numbers. We recommend that an extra Mazda lamp be included in traveling outfits to guard against possible breakage or burning out. The 250-watt Mazda with clear globe is $3.00 net. 23 Bausch & Lomb Optical Company Model B Equipment for Enlarging and Lantern Slide Making Figure 4— Model B Outfit Set up for Enlarging (with Mazda Lamp). We have devised a set of accessories by means of which the Model B Bal- opticon can be readily converted into an efficient enlarging lantern, or a camera for making slides, as desired. Since the Balopticon is always readily available for projection work, one obtains three complete outfits in one apparatus by adding these accessories to his regular Model B. Amateur photographers can thus make enlargements of their negatives, they can make lantern slides as well and project the slides — all with one apparatus. Negatives up to 4 x 5 inches may be used, although the area that can be covered is limited to approximately 4 inches in diameter. For enlarging the outfit is set up as illustrated above. The sensitized paper is attached to the easel and the Balopticon moved on the tracks to the proper dis- tance for making an enlargement of the desired size, the negative being placed in the special holder which is substituted for the lantern slide holder on the Bal- opticon. Lantern slides can be made from negatives up to 5 x 7 inches in size. The lamp house of the Balopticon is attached to the back of the easel board, the central portion of which is removed to take the negative frame, the special frame carrying the plate holder taking the place of the regular slide holder, while the former with bellows and lens is set up the same as for enlarging. A special circular describing more fully these accessories and their use will be sent upon request. Cpde Word Cat. No. Specifications Price Delignate 5338 Set of Accessories for making enlargements and lantern slides with the Model B Balopticon complete $18.00 Dab 4006 Balo Projection Lens of highest grade; 6-in. focus, 1^-in. diam. in rack and pinion focusing mount; (for making enlargements at shorter working distances) ...••• 10.50 Dapedium 5335 Flange for adapting photographic lens to Balopticon, permitting it to be substituted for regular projection lens. (Be sure to specify what lens is to be adapted, when ordering) . 2.00 24 Bausch & Lomb Optical Company Model BB Dissolving Balopticon It is an accepted fact that the most pleasing way of projecting lantern slides is with a dissolving view lantern, by means of which the “racing” of the slide across the screen or a short interval of darkness between slides is entirely eliminated. This not only relieves eyestrain, but the dissolving of one view into the succeeding one produces a very pleasing effect. A number of devices have been produced for use on a single lantern for which claims of producing dissolving views have been made, but they either show move- ment of the slide upon the screen or produce momentary darkness. True dissolving effects can only be produced by the use of two lanterns fitted with a device by means of which the pictures are projected alternately by one lantern and then the other. Believing that this feature in a projecting lantern makes a strong appeal, we have designed the Model BB Balopticon, which is very compact and extremely simple to operate. This is truly two lanterns in one, as there are two light sources and two complete optical systems side by side in the one lantern body. This construction makes possible the maximum compactness and eliminates the setting up and adjusting of the average double dissolving lantern. No more adjustments are required than in the ordinary lantern, except the adjustment of the lenses by means of sliding plates on the front standard, so that the pictures are superimposed on the screen. By means of the construction employed the complete equipment can be put in one carrying case — a decided advantage to travelling lecturers or to those who cannot leave their apparatus permanently installed. The dissolving effect, or the change from one picture to the next, is accomplished by a switch which gradually cuts off the current to one lamp and turns it on in the other at a corresponding rate so that the screen is never dark. While the effect is not quite as gradual and completely dissolving as when using one of our patented Iris diaphragm dissolvers, the device will be found extremely satisfactory and considerably less expensive. 25 Bausch & Lomb Optical Company Two 400-watt Mazda lamps are used, but due to the particular way in which they are connected up, there are never more than 400 watts drawn at one time, so that the apparatus requires only one lead of wire and can be connected to any regular lighting socket. In addition to this advantage the cutting off of the lamp when not required increases the length of service and materially reduces the heat. Specifications Base— Consists of front standard supporting projecting lenses, and sliding rods connecting with lamp house. Lamp House — Of sheet metal, specially ventilated, with removable top for access to lamps; measures 7 x 9)4 x 10/4 in. Illuminant — Two 400-watt gas-filled Mazda lamps with glass reflectors; connected with dissolving switch. Condensing System — Two regular double systems, 4)4 in. diameter, in special ventilated mount from which lenses can be easily removed for cleaning. Slide Carrier Permanently fastened in front of condensing system, with grooves for either American or English size of slide. Bellows — Mounted on metal frames which slide in metal ways. Projection Lens — Two of our regular Balo lenses, either 1)4 in. diameter or 2%6 in. diameter, as desired. Dimensions— Length (ready for projection with 15-in. focus lenses) over all, 26/4 in. Weight Complete in case with 2 5 /ie in. diameter lenses, 30 lbs. Case Sheet metal, 15)4 x 10>4 x 10)4 in., lacquered in black; with hinged side door, two catches and carrying strap. Code Word Cat. No. Specifications Price Default BBM 8q Model BB Dissolving Balopticon with two 400- watt, 110-volt gas-filled Mazda lamps with glass reflectors, dissolving switch, pass-through, cut-out switch, and 15 feet of extension cord; two l)£-in. diam., 8-in. focus projection lenses and carrying case $55.00 Defaulter BBM 10q Same as above but with 10-in. focus projection lenses 55.00 Defeasance BBM 10 Same as above but with 2%e-in. diam. 10-tn. focus projection lenses . 65.00 Defeasible BBM 12 Same as above but with 12-in. focus projection lenses 65.00 Defeat BBM 15 Same as above but with 15-in. focus projection lenses 65.00 26 Bausch & Lomb Optical Company Model G Balopticon Figure 1 — Model C Balopticon with Arc Lamp. The Model C Balopticon, on account of its high degree of efficiency, adapt- ability to varying requirements and ease of manipulation, has proved itself to be a most satisfactory lantern for general use in the graded school, high school and university where an inexpensive but thoroughly high grade lantern for lantern slide projection is desired. It is, of course, equally desirable for general illustrative work in the church, Y. M. C. A. or lodge. Another feature of the Model C is that it accommodates attachments for the projection of opaque objects and for projecting transparent objects held in a horizontal plane, as well as the simple microscope attachment. The body of the lantern is made of heavy sheet metal, the different parts being stamped out by special forming tools. This provides for an instrument of light weight, but at the same time one of the required rigidity. Figure 2 — Model C Balopticon with Gas-Filled Mazda Lamp, Two styles of lamp houses are offered : the small lamp house, Figures 1 and 2, and the large light-tight, or Underwriter’s Model, lamp house, Figure 3. The latter meets the requirements in every way of the Boards of Underwriters and is especially recommended where more than 15 amperes of current are to be used or where an opaque attachment is to be operated, as this style of lamp house entirely shuts off all the rays of light which would otherwise affect the brilliancy of the picture on the screen. We list this instrument with four different illuminants : the arc lamp, gas-filled Mazda lamp, acetylene burner and oxyhydrogen burner, all of which are provided with the same type of base so that they are readily interchangeable in the lamp house. 27 Bausch & Lomb Optical Company Figure 3— Model C Balopticon with Large Lamp House and Water Cell. Where electricity is available and an outlet is provided with a carrying capac- ity of 15 or more amperes, we recommend the arc lamp and a rheostat of 15 amperes or more capacity. Should no other outlet than the ordinary lighting socket be available, the carbon holders of the arc lamp can be fitted with bushings and the small pencil carbons used in connection with one of our 4/4 -ampere rheostats. This feature makes it possible to use the lantern under different wiring conditions by having a combination 5, 10 and 15-ampere rheostat. The arc lamp supplied is a 90° hand -feed arc lamp with horizontal and vertical carbons and with feeding gears controlling the carbons independently or together. A very desirable form of illuminant, and one that is rapidly taking the place of the arc lamp for general class room use, is the new 400-watt, gas-filled Mazda lamp with its reflector. It is entirely automatic and noiseless in operation, can be attached to any convenient lamp socket and gives illumination considerably exceeding that of a 5-ampere arc lamp. For large lecture rooms, or auditoriums where the lantern is placed 50 feet or more from the screen and a fairly large picture is to be projected, we recommend the 1000-watt, gas-filled Mazda lamp, which draws about 9 amperes but gives illumination fully equal to the 15 or 20-ampere arc lamp. The size of this lamp necessitates the use of the large, light-tight lamp-house, as shown in Figure 3. In cases where electricity is not available, either the acetylene or oxyhydro- gen burner is a very satisfactory substitute. The acetylene burner which we supply consists of two jets with a special, spherical glass reflector. The consumption of gas per hour is 1J4 cubic feet. The illumination from this burner equals that from a four-jet burner and is entirely free from flare streaks or flicker. The most convenient and satisfactory source of gas supply is the acetylene tank, as used on motorcycles and automobiles. The oxyhydrogen burner gives illumination exceeding in brilliancy that of the acetylene burner, but is not so convenient and costs somewhat more to operate. An oxyhydrogen generator is recommended as a source of supply. 28 Bausch & Lomb Optical Company The projection lenses supplied on the Model C Balopticon are of the new Balo series, the highest grade lenses made for lantern slide projection. They are furnished in two diameters: 1^4 and 2 %g inches. The former is quite satisfactory when used with the arc lamp, since the light source is small compared to that of the Mazda lamp or acetylene burner. The 2%6-inch diameter lens should be used for all focal lengths over 10 inches and by all means with such illuminants as the Mazda lamp and acetylene burner. In the latter cases the larger size lens gives an increase of about 40 per cent, in illumination. Double Dissolving Outfits Figure 4 — Double Dissolving Model C Balopticon. To avoid the eyestrain and disagreeable effect produced by the alternate darken- ing and lighting of the screen, together with the “racing” of the slides across the screen in changing, so-called dissolving outfits are employed, by means of which each view is made to fade gradually and blend into the succeeding picture. This effect is very satisfactorily accomplished by combining two Model C Balopticons and fitting the lenses with our patent iris diaphragm dissolver. By means of simple connections the lanterns are mounted one above the other, so that the two fields are coincident upon the screen. The iris diaphragm dissolver consists of an iris diaphragm fitted to each lens, the two being jointly operated by a connecting rod which opens one diaphragm as the light is shut off by the other. The two Balopticons can be quickly put together or dismounted, so that the lanterns can be used separately in class rooms and combined for use in the auditorium. 29 Bausch & Lomb Op tical Company Specifications Base— Consists of metal feet on bottom of lamp house and front metal standard of one piece with front board, the whole carried on sliding rods; front standard- provided with elevating device for tilting instrument as desired. Lamp House— Two styles, small and large, both of sheet metal, fitted with our special, patent, light-tight ventilator and provided with two observation windows; small style measures 6/4 in. long, 11 in. high and 6 in. wide, asbes- tos lined; large style measures 13/4 in. long, 14 in. high and 7/4 in. wide, lio-ht-tight, constructed of double walls with air space between and provided with large light-tight door on the side— conforms to most rigorous re- quirements of Boards of Underwriters. Illuminant— Hand-feed arc lamp for direct or alternating current with adapters for small carbons, gas-fi'lled Mazda lamp, acetylene or oxhydrogen burner. Condensing System — Our regular double system in patent, ventilated mount; diameter, 4/4 in. * Slide Carrier— Our double carrier, No. 4430, with elevating device. Bellows — Mounted on metal frames which slide in metal ways, with extension sufficient for 18-inch focus lens. Projection Lens — Our Balo lens with rack and pinion adjustment. Dimensions — Length, extended, 27 in. without lens; height, 11 or 14 in. Weight — Alone, with small lamp house, 14 lbs.; in case, 24 lbs. Case— Regularly furnished only with small lamp house (see foot note under price list); of metal, neatly lacquered in black, measuring 22 M x 12 x 7 in. and provided with carrying strap. *The quick-changing slide carrier, No. 4449, giving a dissolving effect may be substi- tuted for $1.50 extra. We can supply to order carriers for small slides, so that one may use either the standard slide or the special small size now being offered. With Arc Lamp CodeWord Cat. No. Specifications Price Due CA 8q Model C Balopticon with small lamp house and 1 %-in. diam., 8-in. focus, projection lens . $30.00 CAL 8 q Same as above, but with large lamp house 37.50 Duenna CA 10q Model C Balopticon with small lamp house and l^j-in. diam., 10-in. focus, projection lens 30.00 Dumpling CALlOq Same as above, but with large lamp house 37.50 Duress CA 10 Model C Balopticon with small lamp house and 2%6-in. diam., 10-in. focus, projection lens 35.00 CAL 10 Same as above, but with large lamp house 42.50 Duet CA 12 Model C Balopticon with small lamp house and 2 /Win. diam., 12-in. focus, projection lens 35.00 CAL 12 Same as above, but with large lamp house 42.50 Dudgeon CA 15 Model C Balopticon with small lamp house and 2 %6-in. diam., 15-in. focus, projection lens 35.00 Durmast CAL 15 Same as above, but with large lamp house 42.50 Dubbeb CA 18 Model C Balopticon with small lamp house and 2 %6-in. diam., 18-in. focus, projection lens 35.00 Dubber CAL 18 Same as above, but with large lamp house — 42.50 A carrying case is not regularly supplied with the large lamp house. For those outfits we can supply one of lacquered metal for $2.50 additional. 30 Bausch & Lomb Optical Company With Mazda Lamp Code W ord Cat. No. Specifications Price Duram CM 10 Model C Balopticon with small lamp house, with 400-watt, 115-volt Mazda lamp with reflector and 2%8-in. diam. , 10-in. focus projection lens $37.00 Durban CM 12 Same as above, but with 12-in. focus lens 37.00 Durtwaun CM 15 Same as above, but with 15-in. focus lens 37.00 Durze CM 18 Same as above, but with 18-in. focus lens 37.00 CML 10 Model C Balopticon with large lamp house, 1000- watt, 115-volt Mazda lamp with glass reflector and 2%6-in- diam., 10-in focus projection lens . 52.50 Duse CML 12 Same as above, but with 12-in. focus lens 52.50 Duselic CML 15 Same as above, but with 15-ill. focus lens 52.50 Dusiship CML 18 Same as above, but with 18-in. focus lens 52.50 NOTE Any of the above outfits listed with the 400-watt Mazda lamp can be fitted with a 250-watt lamp if desired at a reduction in price of $2.00, and any of the outfits listed with the 1000 watt lamp can be fitted with the 500-watt lamp at a reduction in price of $5.00. If such substitution is to be made, specify definitely on order. For Mazda lamps on higher voltages we supply resistances (see “Accessories”). With Acetylene Burner Code Word Cat. No. Specifications Price • Duckhood CG 10 Model C Balopticon with small lamp house, double- jet acetylene burner with special glass reflector and 2 5 /ie-in. diam., 10-in. focus projection lens $33.00 Ducktneat CG 12 Same as above, but with 12-in. focus lens 33.00 Duckoy CG 15 Same as above, but with 15-in. focus lens 33.00 With Oxyhydrogen Burner Code Word Cat. No. Specifications Price Ducky CO 10 Model C Balopticon with small house, oxyhydrogen burner and 2 ,r ? / i6-in. diam., 10-in. focus projection lens $35.00 'Duddie CO 12 Same as above but with 12-in. focus lens 35.00 | Middle CO 15 Same as above but with 15-in. focus lens 35.00 NOTE Any of the above outfits can be fitted with a Water Cell for $5.00 extra. Double Dissolving Equipments A double dissolving equipment can be made up by combining two of any of the above models and adding the iris dissolver. The price is twice that of the single equipment, plus the price of the dissolver. In ordering use the catalog number or code word of the outfit desired, preceded by the word “ Double Code Word Cat. No. Specifications Price Deign 4490 Iris Dissolver ....■• $15.00 31 Bausch & Lomb Optical Company Attachments While the Model C Balopticon is primarily a lantern for slide projection, it can nevertheless be fitted with attachments for the projection of opaque objects, microscopical specimens or large transparent objects held in a horizontal plane. Attachment for Opaque Objects Figure 5 — Model C Attachment for Opaque Objects. The attachment for the projection of opaque objects, such as photographs, illustrations from text books, post cards, etc., Figure 5, can be very easily attached to the lamp house portion of the Model C Balopticon by means of the sliding ways on the front of the slide carrier support which regularly carries the rear end of the bellows. The front standard and rods are easily removed. If the apparatus is to be used at a comparatively short distance from the screen, the 12- inch focus lens of 2%6-inch diameter can be satisfactorily used, but for distances of 20 feet or more from the screen we recommend the use of the 4-inch diameter, 15 or 18-inch focus lens, since the illumination is increased according to the square of the diameter of the lens. The use of the attachment is recommended only when the apparatus can be placed at a comparatively short distance from the screen (25 feet) in a well darkened room and with an arc lamp operating on at least 25 amperes of current. Code Word Cat. No. Specifications Price Dusk 5080 Model C Attachment for Opaque Objects, with 2%8-in. diam. , 12-in. focus lens and reversing mirror $35.00 Dumose 5082 No. 5080, but with 4-in. diam., 15-in. focus lens 67.00 Durham 5084 No. 5080, but with 4-in. diam., 18-in. focus lens 67.00 32 Bausch & Lomb Optical Company Vertical Attachments An attachment that will be found of considerable value is the vertical attachment for the pro- jection of transparent objects held in a horizontal position, Figure 6. This attachment con- sists of a prism-shaped metal box with mirror which is attached to the fron£ of the slide carrier support. On the top of the box is a condens- er which serves as a stage upon which to place the objects to be projected. The lens used for lan- tern slide projection can be attached to the arm supported by the verti- cal rod, and a mirror attached to the hood of the lens directs the beam of light to the screen. This attachment will be found of parti- cular service in demonstrating var- ious phenomena in chemistry and Figure 6 — Vertical Attachment for Model C Balopticon. physics, such as crystallization, lines of magnetic force, etc, Code Word Cat No Specifications Price Drumlin 4376 Vertical Attachment for Model C Balopticon, consisting of mirror box, 4 1 %s-in. diam. condenser in mounting vertical rod with lens support and mirror for 1 diam. lens $10.00 Microscope Attachment Figure 7 — Simple Microscope Attachment. Teachers of biology will find much use for the simple microscope attachment, Figure 7, by means of which prepared slides of plant sections, parts of insects, etc., may be projected upon the screen. This attachment fits on the front standard in the same flange carrying the projection lens. Any regular microscope objec- tive of a power not higher than 16 mm can be used on this attachment with satisfactory results. Code Word Cat. No. Specifications Price Durity 4375 Simple Microscope with rack and pinion adjustment and substage condenser, but without objective $15.00 33 Bausch & Lomb Optical Company Special Portable Model G Outfits Figure 8— Special Portable Model C Balopticon CGT Mounted on Tripod. On account of its light weight and compactness and the ready interchange- ability of the different illuminants as required, the Model C is a favorite among institute and agricultural workers and traveling lecturers in general. As an aid to the convenient transportation of a complete outfit, we offer two styles of specially constructed carrying cases containing the complete equipment. The case shown in Figure 8 is of wood covered with leatheret and measures 29 Fz x 13/4 x 8FC inches. The cover is detachable and carries a metal plate to which the head of a camera tripod may be attached. This cover on a solid tripod forms a very convenient and substantial support for the lantern during operation. Space is provided in the case for a second type of illuminant and for a 10 cu. ft. acetylene gas tank, as well as for the tripod. The weight with two illuminants, tripod and tank is 40 pounds. The most compact outfit possible is illustrated in Figure 9. The case is of wood covered with leatheret and has hinged cover and metal corners. Space is provided for an extra illuminant, but not for tank or tripod. The case measures 21% x 12 x TA inches, and the complete outfit weighs only 22 pounds. 34 )--*+ Bausch & Lomb Optical Company Code Word Cat. No. Specifications Price Durtye CGT 10 Model C Balopticon with 2 5 A e-in. diam., 10-in. focus projection lens and acetylene burner fitted in special traveling case with detachable top to be used in connection with tripod for lantern support; tripod included; space provided for extra illuminant and acetylene gas tank, but not including tank . $45.00 Duroy CMT 10 Same as above, but with 400-watt, 115-volt Mazda lamp in place of acetylene burner 49.00 Durdenite CGMT10 Same as above, but with both acetylene burner and 400-watt, 115-volt Mazda lamp 55.75 Duran gite CGP 10 Model C Balopticon with 2%6-in. diam., 10-in. focus projection lens and acetylene burner in special portable case (see Figure 9) with space for extra illuminant ..... 40.50 Durauoatral CMP 10 Same as above, but with 400-watt, 115-volt Mazda lamp in place of acetylene burner 44.50 Durabl CGMP10 Same as above, but with both acetylene burner and 400-watt, 115-volt Mazda lamp . 51.25 Figure 9 — Special Portable Model C Balopticon CGP in Case. NOTE — We recommend that an extra Mazda lamp be included in traveling outfits equipped with this form of illuminant to guard against breakage or burning out. Space for this extra bulb is provided in both types of carrying case. The 400-watt Mazda lamp with clear globe is $5.00 net (see “Accessories”). The above outfits are listed with the 10-inch focus lens, which is the one generally required. The 12 or 15-inch focus lens can be supplied at the same price. If one of these is preferred, substitute “12” or “15” for the numeral “10” in the above catalog numbers. 35 Bausch & Lomb Optical Company Double Dissolving Model C Balopticon with Moving Picture Attachment Figure 10 — Double Dissolving Model C Balopticon with Power’s No. 6a Mechanism This is an ideal outfit for Y. M. C. A., church, school or college auditoriums, affording unusually attractive possibilities for entertainment and educational purposes. It permits one to combine regular dissolving views in lecture work with moving pictures in a very pleasing manner, since it provides for instant interchange betv een the two. Unlike other equipments of this character now on the market, there is no shifting of the lower lamp house when one wishes to change from lantern slides to moving pictures, or vice versa. The two Balopticons are securely mounted on a substantial baseboard in the manner illustrated above. The lamp house of the lower Balopticon is mounted in connection with the moving picture mechanism. The lantern slide section of this Balopticon is placed under that of the upper lantern and alongside the moving picture attachment. The dark chamber in front of the lamp house on the lower Balopticon contains a movable mirror which directs the light into the lantern slide section when projecting dissolving views. The upper Balopticon, of course, is used only for lantern slide projection. The projection lenses of this lantern and of the lower lantern slide section are equipped with our iris diaphragm dissolver, which automatically closes the dia- phragm of the upper lens as the light is admitted to the lower, and vice versa. The 36 Bausch & Lomb Optical Company mirror, which directs the light into the lantern slide section of the lower Balopticon, is controlled by the exterior lever, shown on top of the dark chamber (Figure 10). In order to change from one kind of projection to the other it is only necessary to shift this mirror, thus directing the beam of light either through the moving picture projection lens or over into the lantern slide section of the lower Balopticon, as desired. Another feature of these outfits lies in the fact that separate condensing systems are supplied for lantern slides and for moving pictures, suitable for their respective projection lenses. Because of this feature maximum efficiency is attained in both kinds of work. Any of the standard moving picture mechanisms (Edison, Powers or Simplex) are supplied with this outfit. All are fitted with the regular Bausch & Lomb projection lenses, which are of the highest quality. Both Balopticons are equipped with light-tight lamp houses with special ventilating device. We provide four strong legs, adjustable for height, which attach to the corners of the baseboard, giving a substantial stand to be raised, lowered or tilted as desired. Code Word Cat. No. Specifications Price Durenol 5210 Double Dissolving Model C Balopticon, complete with light-tight, specially ventilated lamp houses and 10, 12 or 15-inch focus, 2%6-in. diam. projection lenses, mounted on stand (Be sure to specify focus of projection lenses desired) ..... $175.00 Durn 5212 No. 5210 with Edison Type D Moving Picture Mechanism complete with magazine for 12-in. reels and with take-up device, automatic fire shutter and lens 347.00 Duroc 5214 No. 5210 with Power’s No. 6a Mechanism com- plete with 12-in. upper and lower film magazines with take-up device, automatic fire shutter and lens No. 5210 with Simplex Moving Picture Mechanism complete with 16-in. upper and lower film magazines, take-up device and 14-in. reels, automatic fire shutter and lens, and film rewinder 363.00 Duyong 5216 . 413.00 & We recommend with any of these outfits one of our adjustable rheostats for 15 to 25 amperes and one from 15 to 35 amperes, to be selected according to voltage available. 37 Bausch & Lomb Optical Company Model D Balopticon Figure 1 — Model D Balopticon with Small Lamp House. The Model D Balopticon is constructed on what is known as the optical bed type of construction. An accurately milled bed of lathe type is supported by feet at either end, those at the front being provided with leveling screws. To this optical bed the lamp house containing the arc and the standards supporting the different accessories are attached by means of clamping blocks. These stand- ards may be adjusted along the bed to any position, and the act of clamping fixes them rigidly in optical alignment. Science teachers have been quick to appreciate the refinements and conveniences of this Balopticon, and its optical bed affords convenient accommodation for the many accessories used in science laboratories. The Model D is equipped with the triple condensing system and a water cooling cell, which makes it the most perfect outfit for lantern slide projection. A combination of two of these instruments, equipped with our iris dissolver, makes an excellent double dissolving outfit for auditorium use (see Figure 2). The lanterns are readily separated for use in class rooms and laboratories. Two styles of lamp house are offered. The large, light-tight housing meets the most rigid requirements of the Boards of Underwriters. It is particu- larly recommended where a part of the audience is seated back of the lantern and for use with arcs of high amperage. This lamp house is well adapted to double dissolving outfits. The small lamp house is illustrated in Figure 1. Specifications Base — Consists of cast iron supports of 6-in. spread, front and back, supporting optical bed iyi in. in height; front support provided with elevating screws. Optical Bed Of lathe type, carefully planed, accommodating supports for differ- ent parts which may be adjusted as desired and rigidly clamped; measures 19/2 in. in length and accommodates projection lenses up to 15-in. focus; two models (see DA 18 and DAL 18 below) are furnished with 25-in. optical bed accommodating projection lenses up to 22-in. focus. 38 Bausch & Lomb Optical Company Lamp House — Two styles, small and large, both of sheet metal, fitted with our special, patent, light-tight ventilator and provided with two observation windows; small style measures 6)4 in. long, 11 in. high and 6 in. wide, asbes- tos lined; large style measures 13J4 in. long, 15 in. high and 7/4 in. wide, light-tight, constructed of double walls with air space between and provided with large light-tight door on the side — conforms to the most rigorous requirements of Boards of Underwriters. Illuminant — Hand-feed arc lamp for direct or alternating current. Condensing System — Our triple system in patent, ventilated mount; provided with water cooling cell; diameter, 4/4 in. * Slide Carrier — Our double carrier, No. 4430, with elevating device. Bellows — Mounted on metal frames which slide in metal ways. Projection Lens — Our Balo lens with rack and pinion adjustment. Dimensions — Length, extended, 32 in. without lens; height, 11 % in. or 15 in. Case — Regularly furnished only with small lamp house (see foot note under price list); strongly built of wood, measuring 33 x 13/4 x 8)4 in. and provided with iron handle; fitted with strong spring catches and locks. *The quick-changing slide carrier, No. 4449, giving a dissolving effect, may be sub- stituted for $1.50 extra. Code Word Cat. No. Specifications Price Daggle DA 10q Model D Balopticon as described with small lamp house and l|fj -in. diam., 10-in. focus projection lens $65.00 Darling DAL lOq Same as above, but with large lamp house 72.50 Deck DA 10 Model D Balopticon with small lamp house, 2%6- in. diam. , 10-in. focus projection lens 70.00 Dart DAL 10 Same as above, but with large lamp house 77.50 Deal DA 12 Model D Balopticon with small lamp house and 2%6-in. diam., 12-in. focus projection lens 70.00 Dask DAL 12 Same as above, but with large lamp house 77.50 Dealer DA 15 Model D Balopticon with small lamp house and 2%6-in. diam., 15-in. focus projection lens 70.00 Dantes DAL 15 Same as above, but with large lamp house 77.50 Damnous DA 18* Model D Balopticon with small lamp house, 25 in. optical bed and 2%e-in. diam., 18-in. focus projection lens ..... 73.50 Damourite DAL 18* Same as above, but with large lamp house 81.00 *The 25-inch optical bed supplied with this outfit will accommodate lenses up to 22 inches in focus. If 20 or 22-inch focus lenses are required, substitute “20” or “22” for the numeral “18” in the above catalog number. No additional charge is made for the longer focus. A carrying case is not regularly supplied with the large lamp house. For those outfits we can supply a special wooden case for $4.00 additional. If any of the above Balopticons is desired with some lamp other than the hand-feed arc, deduct the price of the latter, $10.00, and add price of illuminant desired (see “Accessories”). 39 Bausch & Lomb Optical Comp any Double Dissolving Equipments Figure 2— Double Dissolving Model D Balopticon. A double dissolving equipment can be made up by combining two of any ne of the above models and add.ng the iris dissolver. The price is twice that of the single equipment plus the price of the dissolver, indicated below. In ordering hT.^ ° r °' the “ D P« e d.d Code Word Cat. No. Specifications Price Deign 4490 Iris Dissolver . $15.00 Attachments The Model D Balopticon accommodates a variety of attachments which give n a wide range of usefulness in the class room and the laboratory. These attach- ments are: for the projection of opaque objects; of microscopic objects; of transparent subjects held in a horizontal position; projection of the spectrum and complementary colors; and a set of accessories for projecting on the screen experiments in chemistry and physics. Attachment for Projection of Opaque Objects attachment for the Projection of opaque objects is readily added to the Model D by clamping the accessory to the optical bed, first removing all the standards from the latter. It will be noted from the illustration, Figure 3 that the apparatus is set up with the back of the lamp house facing the screen. For this reason the light-tight lamp house is preferable, althoug either style, of course can he liseH. 40 Bausch & Lomb Optical C o m p a n y Figure 3 — Model D Attachment for Opaque Objects. Code Word Cat. No. Specifications Price buffet ' 4261 Attachment for Projection of Opaque Objects dulcimer with Model D Balopticon, with 2 5 /ie-in. diam., 12-in. focus projection lens and reversing mirror . $33.00 4263 Same as above, but with 4-in. diam., 15-in. focus ^ufrenite projection lens . . 65.00 4264 Same as above, but with 4-in. diam., 18-in. focus projection lens 65.00 Microscope Attachments Figure 4— Model D Balopticon with Medium Microscope. The Model D makes an excellent outfit for microscopical projection since it •^commodates either the Medium Microscope or the Large Projection Microscope (see Accessories”). The microscope is mounted on a hinged arm an d the lantern slide projection lens on a swinging arm so that either may be 'hstantly swung into the optical axis, thereby giving instant interchange between the two forms of projection. When the Balopticon is equipped with the Large Projection Microscope, aving special substage condensers for use with objectives of all powers, the est results are obtained by adding the Aspheric Condenser of 60 mm diameter, w hich is particularly designed for microscopical projection. To make its use convenient, two swinging arms, shown in Figure 5, are employed. The one next to e lamp house carries the aspheric condenser on one side and the regular lantern s 'de condenser on the other. The swinging arm on the lantern slide carrier support holds the third condenser of the triple system on one side and affords a j ear aperture on the other. When using the microscope, the lantern slide con- e nsers are swung out and only the aspheric condenser used. In this way the 41 Bausch & Lomb Optical Company Figure 5— Model D Balopticon with Swinging Arms, Aspheric Condenser and Large Microscope. very best illumination and definition are secured. No more than 5 amperes of current should be used with the aspheric condenser in position. Code Word Cat. No. r Specifications Price Dagonet 4250A Medium Microscope, including projection eyepiece (3X), substage condenser; mounted on swinging arm; without objectives ..... $45.00 Daker 4260 Substage Water Cell for above 5.00 Duper 4138 Large Projection Microscope. Horizontal Type, including projection eyepiece (3X), substage water cell, three substage condensers and triple revolving nosepiece; mounted on swinging arm; without pro- jection lens or objectives .... 100.00 Dungeon 4139 Same as above, but with 32, 16 and 8 mm objectives . 117.00 Dunter 4140 Same as No. 4139, but with large revolving plate to accommodate six objectives . 129.00 Dunstable 4144 Large Projection Microscope, Combined Hori- zontaland VerticalType, including projection eye- piece (3X), substage water cell, three substage con- densers, revolving plate and nosepiece for six objectives (no objectives), reversing mirror for low power objectives and a prism for use over eyepiece 160.00 Dunstical 4145 Same as above, but with 32, 16 and 8 mm achromatic objectives ...... 177.00 Dunted 4146 Same as above, but with 72, 48 and 32 mm Micro- Tessar, and 16, 8 and 4 mm achromatic objectives . 265.00 Dysuria 4306 Aspheric Condenser, 60 mm in.) diam. , in mounting. (Specify outfit on which it is to be used) . 10.00 Dysury 4320 Two Double Swinging Arms, one for carrying as- pheric condenser and two rear condensers of triple system; other, mounted on a slide carrier support, to carry third lens of triple system, also to afford clear aperture* When ordered separately .... When ordered with Balopticon 26.50 22.50 *In ordering Model D Balopticon with these two standards and aspheric condenser, give catalog number of the outfit desired and specify, “with standards No. 4320 and aspheric condenser No. 4306”. 42 Bausch & Lomb Optical Company Figure 6 — Vertical Attachment No. 4290 for Model D Balopticon. Vertical Attachments For the projection of transparent objects which must be maintained in the horizontal position two attachments are available. The one illustrated in Figure 6 is attached to the slide carrier support by removing the bellows and substituting in the sliding ways the prism-shaped metal box which contains a reflecting mirror. The vertical bed is attached to the slide carrier support by two strong screws. The front standard of the Balopticon carrying the pro- jection lens is removed and placed on the vertical bed together with a mirror which fits over the lens hood. The third condensing lens in mount is removed from the back of the slide carrier support and placed over the opening in the top of the prism box. It not only converges the light on the projection lens, but, the plane side of the condenser being uppermost, it serves as a stage, 4/4 inches in diameter, upon which the glass dishes, specimens, etc., to be projected are placed. The second type of vertical attach- ment, shown in Figure 7, is far more con- venient and affords a much wider range of usefulness because one can change instantly from projection with this attachment to the use of lantern slides, and vice versa. Consequently the attachment may be left in position on the lantern as long as any other work undertaken does not require the addi- tional space on the optical bed occupied by the vertical attachment. The instrument has a dark cham- ber supported by two standards which fit the optical bed and are provided with clamps. Within this dark chamber is the reflecting mirror, controlled by an exterior lever as shown in the illustra- tion. When the mirror is dropped to the 45° angle, it reflects the light up Figure 7— Vertical Attachment No. 4136B through the vertical attachment. When * or ® Balopticon. the mirror is turned up, it covers the condenser of this attachment, permitting an 43 Bausch & Lomb Optical Company uninterrupted passage of light through to the lantern slide projection lens. The attachment is provided, of course, with an individual condensing lens, which forms the third member of the triple system for vertical projection, and with a regular quality projection lens of ljHs-inch diameter, 10-inch focus. Code Word Cat. No. Specifications Price Dale 4290 Vertical Attachment, as described and illustrated in Figure 6 ..... $15.00 Dipody 4136B Vertical Attachment, including separate projection lens and condenser to permit instant interchange with lantern slide projection, as described and illustrated in Figure 7 42.00 Attachment for Projection of the Spectrum and Complementary Colors Figure 8 —Set of Accessories for Projecting Spectrum and Complementary Colors with Model D Balopticon. Figure 8 illustrates the Model D Balopticon equipped for projection of the spectrum and complementary colors. The bellows are removed and the standard, carrying an adjustable slit, attached to the lantern bed between the slide carrier support and the front standard. The accessory optical bed, carrying the rest of the accessories, is attached to the front of the regular optical bed. If the Balopti- con has the large lamp house, a set of revolving carbon holders, desirable in showing emission spectra, should be fitted to the arc lamp. Absorption and emission spectra only may be projected by using simply the adjustable slit and the prism placed before the projection lens. Code Word Cat. No. Specifications Price Daffodil 4154 Set of Accessories for projection of the spectrum and complementory colors, consisting of supple- mentary optical bed, adjustable slit and standard, carbon bisulphide prism, lenses, etc. $45.00 Dafish 4156 Pair of Special Carbon Holders with revolving plates carrying special electrodes for holding chemical salt (The following set of accessories is for projection of the spectrum only) 15.00 Daff 4150 Adjustable Slit ..... 7.00 Dudeen 4137 Standard for supporting the above 3.00 Deliberate 4446 Bottle Prism (for carbon bisulphide); width of face, 60 mm; height, 90 mm .... 6.00 Demy 4285 Prism Support for the above .... 3.00 44 Bausch & Lomb Optical Company Special Accessories for Projection of Chemical and Physical Demonstrations Figure 9— Accessories for Projecting Chemical and Physical Demonstrations with Model D Balopticon. In teaching chemistry and physics it is frequently desirable to project an experiment on the screen or to demonstrate various phenomena, such as electrolysis, precipitation, etc., before the entire class. This can best be done by placing the necessary cells, cylinders, thermometers, or whatever is required in the optical axis of a projection lantern. Since these pieces of apparatus are often of such size and shape that they cannot be adapted to the regular lantern, we supply special standards to support the lamp house and accessories of the Model D. These give almost unlimited space for the introduction of demonstration apparatus. One standard with a short section of optical bed supports the lamp house, water cell and slide carrier support. The other standard with a long section of optical bed supports the standard with projection lens. The apparatus used in the demonstration is supported between these two sections of optical bed upon the supports which are found in any labora- tory. The two standards with sections of optical bed are required in addition to the regular lantern bed. Code Word Cat. No. Specifications Price Dysluite Dyslysin 4158 4159 Standard with short section of optical bed Standard with 15-in. section of optical bed $7.50 8.50 45 Bausch & Lomb Optical Company Special Model D Balopticon for Large Plates For the benefit of those wishing to project plates larger than the standard size lantern slides we furnish the Model D Balopticon with 6-inch diametet condensing lenses in the regular triple system with patent, ventilated mount. It is particularly desirable for the projection of Lumiere autochrome plates, the binding of which generally leaves, even in the standard size plates, a larger opening than the ordinary lantern will cover fully. This outfit will project plates of any regular size up to 4 x 5 inches. It is supplied with two double slide carriers — one, our No. 4430, for standard size slides and the other for 4 x 5-inch plates. The latter is so constructed that one side will take the plate in a horizontal position and the other side in a vertical position. This will also be found a very attractive lantern for physicists who wish to have available an unusually large beam of light for projecting physical apparatus and the like. It can be very conveniently used for such work, since the bellows and different parts can be easi'y removed from the optical bed and other apparatus or materials adjusted as desired. To afford possibilities for a wide latitude of work this outfit is equipped with a 25-inch optical bed. Code Word Cat. No. Specifications Price Disbar DALS 15 Special Model D Balopticon, as described, without water cell and with 2%e-in. diam., 15-in. focus pro- jection lens ...... $125.00 (No carrying case is supplied with this outfit.) 46 Bausch & Lomb Optical Company Home Balopticon Figure 1— Home Balopticon, Simple Form for Projection of Opaque Objects Only- Interior View, Showing Reflecting Mirrors and Watch on Object Holder. This Balopticon has been designed to meet the popular demand for a really efficient, but inexpensive instrument, for the projection of post cards, photographs and similar objects in the home, the small classroom and the Sunday school room. It is meeting the popular demand in a most satisfactory manner and is also proving an excellent instrument for small schools that are unable to purchase more elaborate or expensive equipments. It is so simple in operation that any child can operate it, yet it far excells the ordinary post card projector in the quality of the picture produced, the illumination and its wide range of usefulness. The apparatus is made in two forms: for the projection of opaque objects only and in combination form for the projection of opaque objects and lantern slides as well. In the latter model the interchange between the projection of opaque objects and of lantern slides is instantaneous, being effected by simply turning a convenient lever on the outside of the dark chamber. This lever operates an in- terior shield which cuts off the light from the lens for either form of projection not desired at the time. One of the great advantages of this apparatus is that the object holder occu- pies a horizontal position against the floor of the dark chamber, rather than in the wall, as is the case with the ordinary post card projector. This permits solid objects of all kinds, such as coins, curios, etc., to be laid on the object holder and pro- jected on the screen, while any part of a magazine can be shown without trimming or in any way mutilating it. Further, this arrangement makes the changing of opaque specimens by the operator more convenient. A single interior mirror brings the image always into correct position, from left to right, on the screen, so that reading matter appears unreversed — another strong feature. The lenses are of achromatic construction, designed to give maximum illumination and a flat field. These lenses project a picture that is clearly defined to the extreme margin. The illumination is furnished by one of the new gas-filled Mazda lamps of 400-watt capacity. With this lamp and the use of a special, accurately corrected optical mirror, we are able to secure 47 Bausch & Lomb Optical Company Figure 2 — Combination Home Balopticon for the Projection of Both Opaque Objects and Lantern Slides. illumination exceeding considerably that obtained from a 5-ampere arc lamp. It can be attached to any convenient lamp socket, requires no rheostat and is entirely automatic. An aluminum screen, which greatly increases the brilliancy of the image, is included with each outfit. Specifications Base — Consists of front metal standard and metal feet at rear of dark chamber. Dark Chamber— Of sheet metal, 13>^x9^x7 in., light-tight and well ventilated; has convenient door on right side and opening in bottom, 5x5 Vz in., for pic- tures and objects; contains fixed mirror and adjustable shield, which is swung to horizontal position when lantern slides are projected. Illuminant 400-watt, gas-filled, Mazda stereopticon lamp mounted in connection with specially corrected glass reflector in compact metal casing attached to rear of lamp house; furnished with 15 feet of cord, plug and switch. Projection Lens — Achromatic construction, of 4-in. diameter, 13-in. focus; mounted in well constructed spiral focusing metal tube; gives image about 4 ft. wide at projection distance of 12 ft. Object Holder — Actuated by strong spring arm and always occupies horizontal position; supplied with two adjustable post card holders, with wooden mar- gins, light and conveniently manipulated. Screen — Aluminum coated, 54 in. square; mounted on plain roller. Lantern Slide Equipment — Attached to lantern body beneath large projection lens in combination model, BRMS; consists of double condensing system, double slide carrier, No. 4430, bellows and front standard carrying a smaller achromatic projection lens, in spiral focusing mount, which gives pictures from slides correspond ing in size to those from opaque obj ects ; front standard attached to sliding rods which aid in focusing; convenient lever shifts shield to change from one kind of projection to the other. Dimensions — Length (ready for operation) — simple model, 15 in., combination model, 24 in.; height, 15 in.; width, 7 in. 48 B a u s c h & Lomb Optical Company Code Word Cat. No. Specifications Price Darian BRM 13 Home Balopticon for projection of post cards, photo- graphs, etc., only, with 400-watt, 115-volt, gas-filled Mazda stereopticon lamp, connecting cord and plug and 4lTfoot square aluminum-coated screen $ 35.00 Daadic BRMS 13 Home Balopticon, CombinationModel, for lantern slides, as well as for post cards, etc., complete wuth lantern slide accessories, 400-watt, 115-volt, gas-filled, Mazda stereopticon lamp, connecting cord and plug and 4jTfoot square aluminum screen 45.00 Danalite 5333 Carrying Case ..... 2.50 NOTE — For classroom use, the 4^-foot screen may be considered too small, in which case we recommend the substitution of a 6x6-foot aluminum coated screen on spring roller, which may be secured with any of the above outfits for $6.00 extra. If the larger screen is desired, it should be so specified when ordering. For Mazda lamps on higher voltages we supply resistances (see “Accessories”). Special Equipment The Home Balopticon has been found very useful in Departments of English for projecting the compositions of students upon the screen, thus enabling the class as a whole to review and criticize them more readily. In order to pro- ject as much as possible of the entire composition at one time, we are prepared to supply the Home Balopticon on special order with an opening in the bottom of the dark chamber, 5% x 6 V 2 inches. This area permits the projection of an entire sheet of the composition paper generally used. The 5 Yv x 6 -inch area is the largest that can be projected with this apparatus, and we offer the suggestion that the compactness, simplicity and economy of the Home Balopticon, together with the excellent opportunities which it thus affords for criticism and class review, would many times offset any inconvenience occasioned by a necessitated change in size of composition paper. In order to project the large area with sharpness to the extreme edges, it is necessary to equip the instrument with one of our Balo projection lenses, which are of the highest quality. Code Word Cat. No. Specifications Price Dacelo BRM 15 Home Balopticon with special opening in dark cham- ber, 5}4 x 6, ’4 inches; with 15-in, focus Balo projection lens, 100-watt, 115-volt, gas-filled Mazda stereopticon lamp, connecting cord and plug and 8 x 8-foot alumi- num coated screen on spring roller; for projection of opaque objects only ..... $84.00 49 Bausch & Lo mb Optical C o m p a n y New Combined Balopticon with 1000- Watt Mazda Lamp Model CRM This new Balopticon is designed for the projection of opaque objects and lantern slides with instant interchange between the two forms. The instrument marks a new era in the projection of opaque objects on a large scale by reason of the adoption of an incandescent lamp as illuminant. It is the first apparatus of its kind upon the market and has proved remarkably popular from its introduction. This Combined Balopticon is fitted with a specially constructed, 1000- watt, gas-filled Mazda stereopticon lamp, which represents the highest development so far attained in this branch of illuminating engineering. Since, unlike the arc, the lamp is enclosed, it can be brought very close to the object without danger. By means of a mirror with very high optical corrections an unusually large percentage of the available spherical candle power is utilized. 50 Bausch Sc Lo m b Optical Co m pany Due to this special application of the llluminant it is possible to project an image of opaque objects with a brilliancy considerably exceeding that possible with a 35-ampere arc lamp on alternating current, and equaling that of a 20-ampere arc on direct current. The advantages of the new lamp are obvious. It operates on only 9 amperes of current, which means a considerable saving in current consumption and makes it available for use on many outlets which would not have the carrying capacity to supply the high power arc lamps. Furthermore, no rheostat is required. The most striking advantage, however, is that the lamp is entirely automatic, requiring no attention whatever. It works equally well on direct or alternating current, and the disagreeable noise so characteristic of the alternating current arc is absent. A final advantage is that the quality or color of the light is very pleasing to the eye and gives a better rendition of colors than that obtained with the alter- nating current arc. These lamps have no definite guarantee, but are rated to burn 200 hours. The saving in current and carbon consumption, however, is such that a new lamp could be purchased every 50 hours of use and the cost of operation would be less per hour than that for a 35-ampere arc lamp. In other words, the Mazda lamp, including renewals, costs about one-third as much to operate as an A. C. arc of equal power. This model, CRM, has been constructed especially for use with the new Mazda lamp, and the design is calculated to give the greatest possible efficiency. T. he lamp housing and the dark chamber have been brought together to allow the lamp to be placed as close to the object as possible. No condensers are used in illuminating the opaque object, but the specially corrected glass reflector placed back of the lamp directs the light upon the object in parallel rays. By means of special methods of ventilation the temperature of the outfit is kept sufficiently low so that there is positively no danger of scorching the specimen, neither does the apparatus become uncomfortably hot for operating. The instrument is constructed of heavy sheet metal by means of special forming tools, so that it has a pleasing appearance and the proper rigidity, at the same time being sufficiently light to make it readily portable from place to place. It is finished throughout in black enamel with a dull lustre, which is both service- able and appropriate in such an apparatus. The area of the opaque object that can regularly be projected is 6 x 6 inches but much larger objects can be placed in position and shifted about so as to project any portion desired. The specimen is held in position against the bott&m of the dark chamber by the object holder, which is actuated by a spring-arm. To facili- tate the rapid handling of small pictures, such as post cards, we supply two adjust- able carriers. The change from the projection of opaque objects to lantern slides, or vice versa, is made instantly by simply turning a convenient handle on the outside of the dark chamber. This handle operates a shield in the dark chamber, which cuts off the light from the projection lens for opaque objects, or from the lens for lantern slide projection, according to the form it is desired to use, no movement of the lamp being necessary. 51 B a u s c h & L o ni b Optica 1 Co m p a n y The lens for projecting the image of the opaque object is mounted on top of the dark chamber, together with a first-surface mirror which directs the light toward the screen and causes the picture to appear in correct position from left to right. The lens is either a 4-inch diameter, of 15 or 18 inches focus, or a 25-inch focus, with a diameter of 5 inches, the selection depending on the projection distance and the size of picture desired (see table, page 18). The mirror supplied with the 15 and 18-inch lenses is fixed above the lens in an adjustable mount, which permits the images from both opaque object and lantern slide to be brought into coincidence on the screen. The 25-inch lens is mounted in the horizontal position with the mirror behind it and enclosed in the mounting. No adjustment of the mirror is required with this lens. A lens is supplied for lantern slide projection which is of the proper focal length to give approximately the same size picture as that secured with the projection lens for opaque objects. For English Classes The projection lantern has recently been used to great advantage in English classes to project on the screen the students’ compositions. In this way the work can be read and criticized by the entire class. To meet such a requirement with this instrument we have cut the regular opening for opaque objects in a plate which can be taken out by removing four screws. An opening 6x7 inches is thus rendered available for projecting composition sheets. The plate is supplied in all instruments of this model and may be removed whenever the need arises. Since this lantern is also an excellent one for Departments of History and Language, as well as the auditorium, and is easily taken from one room to another, the instrument should find almost continuous use. Specifications Base — Consists of heavy sheet metal supports, front and rear, 10/4 in. wide, and carrying dark chamber at height of 5X in.; extreme length, 23 >4 in.; each foot is provided with screw hole for fastening Balopticon to table, if desired. Lamp House and Dark Chamber — One continuous with the other; measure 9/4 in. wide by 15 in. long; lamp house is 17 in. high; dark chamber, 12^-in.; light-tight and freely ventilated, constructed of double sheet metal walls, with an air space one inch in thickness between the two walls; roof of lamp house is fitted with our special, patented ventilator; dark chamber provided with large, light-tight door on side; convenient handle on outside of dark chamber at upper right corner controls shield by which light is cut off from opaque object lens or lantern slide lens, as desired. Illuminant — 1,000-watt, concentrated filament, gas-filled, Mazda stereopticon lamp, of special design; provided with ground and polished glass reflector, 8 in. in diam., corrected to throw a parallel beam of light upon the specimen. 52 Bausch & Lomb Optical Company Condensing System — Oar regular double system, consisting of two plano- convex lenses, 4 Vo. in. in diam., mounted at the front of the dark chamber, for lantern slide projection only. Object Holder — Square plate of sheet metal; held against opening in bottom of dark chamber by arm actuated by two strong springs; accommodates objects of varying thicknesses and automatically brings them into proper plane for pro- jection; opening in plate at bottom of dark chamber permits area, 6 in. square, to be projected; removal of plate gives 6 x 7-in. opening. *Slide Carrier — Our double carrier, No. 4430, with elevating device. Post Card Carrier — Fwo adjustable carriers with wooden frames, which slide in object holder. Projection Lenses Two of our new series of Balo lenses, especially corrected to give a brilliant, flat field with the Mazda lamp; provided with rack and pinion adjustment; of such relative foci as to project images of approximately equal size from opaque objects and lantern slides; lens for opaque objects fitted with first-surface mirror to direct light to screen and cause picture to appear in proper position from left to right. Dimensions — Length, rear of lamp house to front of lens for lantern slide pro- jection, 27 in.; height to top of mirror, 33 in. *The quick-changing slide carrier, No. 4449, giving a dissolving effect, may be sub- stituted for $1.50 extra. Codeword Cat. No. Specifications Price Dyester CRM 15 Combined Balopticon for projection of opaque objects and lantern slides, with 4-in. diam., 15-in. focus lens for opaque objects and 1 %-in. diam., 8-in. focus lens for lantern slides; 1000-watt Mazda stereopticon lamp $120.00 Dyete CRM 18 Same as above, but with 18-in. focus lens for opaque objects and 1%-in. diam., 10-in. focus lens for lantern slides . 120.00 Dyker . CRM 25 Same as above, but with 5-in. diam., 25-in. focus lens for opaque objects and 2% e -in. diam., 12-in. focus lens for lantern slides . , 200.00 N. B.— For those wishing to project autochrome slides with the above apparatus we recommend particularly the CRM-18 outfit, but with a special arrangement of the condensing system to increase the illumination and the substitution of a 2%e-in. diam., 10-in. focus pro- jection lens for the 1%-in. diam. lens regularly supplied. These changes will be made on special order at an extra charge of $10.00. 53 Bausch & Lomb Optical C o m p a n y Combined Balopticon with Arc Lamp Model CRA Figure 1 — Combined Balopticon with Lamp House Tilted for Projection of Opaque Illustrations and Objects. To those who have direct current and for some reason desire an arc lamp as illuminant, this model of the Combined Balopticon will appeal. If it is desired to use moving pictures, for instance, Model CRA with moving picture attachment, as described on a following page, makes an ideal equipment. The Combined Balopticon as here offered is designed along lines that have been found by experience to be most satisfactory from the standpoints of efficiency and convenient manipulation with this type of illuminant. When pro- jecting from opaque objects, the lamp house, with arc lamp and condensing system, is shifted to the inclined position, shown in Figure 1, so that the beam of light falls directly on the object, is collected by the projection lens and directed to the screen by the first-surface mirror above the lens. By this system a brilliant illumination is insured. In projecting lantern slides the lamp house is placed in the horizontal position, shown in Figure 2. The light from the condensing system in the front of the lamp house passes through the dark chamber in approximately parallel pencils to 54 Bausch & Lo m b Optical Co m pany Figure 2— Combined Balopticon in Position for Lantern Slide Projection, the condenser at D, immediately behind the slide carrier, E. This condenser properly illuminates the lantern slide, which is imaged on the screen by the lens, F. The change from the projection of opaque objects to that of lantern slides, then, means simply the shifting of the lamp house from the inclined to the horizontal position, and vice versa. It is very easily and quickly accomplished. This Balopticon is provided with a horizontal object holder for opaque objects, which is an advantage over a vertical holder since one can place on the horizontal holder objects which could not readily be placed in a vertical plane. A picture is obtained in correct position from left to right on the screen by the use of only one mirror, fitted over the projection lens for opaque objects. The area of the opaque object which may be projected is 5x5 inches. The object holder is so constructed that large illustrations can be shifted about to cover any position. For convenience in handling photographic prints and post cards two carriers are supplied with adjustable frames to take cards of varying widths. The projection lenses used are our Balo type, producing an extremely flat and sharply defined picture. The lens for the projection of opaque objects is of 4-inch diameter and either 15 or 18-inch focus, as may be required to give the size of picture desired at the given projection distance. The importance of 55 Bausch & Lomb Optical Company the large diameter is obvious when it is considered that the illumination a lens provides is directly proportional to the square of the ratio between its diameter and its focus. The lens for lantern slide projection is of 134-inch diameter and either 10 or 12-inch focus, as required to produce a picture from a lantern slide approximately equal in size to that projected from the opaque object. Both lenses are provided with a rack and pinion adjustment for focusing. For illuminant a 90-degree hand-feed arc lamp is provided, which can be used on either direct or alternating current. When using 25 to 35 amperes of electricity and operating on direct current, a picture up to 11 or 12 feet wide from an opaque object can be satisfactorily illuminated. With alternating current, a picture exceeding 8 or 9 feet wide should not be attempted. Specifications Base — Consists of heavy sheet metal supports, front and rear, 8 in. wide and carrying dark chamber at height of 9/4 in. Lamp House — Measures 1334 in. long, 15 in. high and 7/4 in. wide; light- tight and freely ventilated, constructed of double sheet metal walls, with an air space between the two walls and the roof fitted with our special patented ventilator; provided with large, light-tight spring door on the side and obser- vation windows on both sides; mounted between horizontal supports at front end and provided with handle at rear, permitting it to be easily tilted for por- jection of opaque objects and held rigidly in position by spring arm; conforms to the most rigorous requirements of Boards of Underwriters. Illuminant — Hand-feed arc lamp for direct or alternating current. Condensing System — Our regular triple system, with the two rear lenses mounted directly in front of the lamp house in our ventilated mount, giving a parallel beam of light in the dark chamber, and the front lens placed in front of the dark chamber immediately behind the slide carrier; diameter, 4/4 in. Dark Chamber — Of sheet metal, light-tight, measuring 12/4 x 11/4 x7 in.; has opening in bottom for projected objects 5 in. square; provided with hinged door and observation window on right side. Object Holder — Of square sheet metal mounted on arm controlled by two strong springs; will accommodate objects of varying thickness, and automat- ically bring object into proper plane of projection. *Slide Carrier— Our double carrier, No. 4430, with elevating device. Post Card Carrier — Two adjustable carriers with wooden backs and frame, which fit opaque object holder. *The quick-changing slide carrier, No. 4449, giving a dissolving effect, may be sub- stituted for $1.50 extra. 56 Bausch & Bomb Optical Company Projection Lenses — Two of our new Balo lenses with rack and pinion focusing adjustment, of such relative foci as to project images of approximately equal size from opaque objects and lantern slides; lens for opaque objects fitted with adjustable first surface mirror. Dimensions — Length, rear of lamp house to front of projection lens for lantern slides, 41 in.; height, 33 in. to top of mirror. Code Woid Cat. No. Specifications Price Daroga CRA15 Combined Balopticon for projection of opaque ob- jects and lantern slides with 4-in. diam., 15-in. focus lens for opaque projection; 1%-in. diam., 10- in. focus lens for lantern slide projection; first surface mirror for opaque projection, 90° hand-feed arc lamp; 2 post card holders ..... $120.00 Dardan CRA 18 Same as above, but with 4-in. diam., 18-in. focus projection lens for opaque objects and 12-in. focus lens for lantern slides 120.00 Combined Balopticon with Moving Picture Attachment A very desirable projection equipment for schools, churches, Y. M. C. A.’s, etc., is the Combined Balopticon with an attachment for moving pictures, illustrated in Figure 3. In order that instant change may be made from the projection of opaque objects or lantern slides to moving pictures and back again, we have designed a special stand with cross-rods upon which the Balopticon is mounted and moved from side to side. When moved to the right, it lines up with the moving picture mechanism, permanently mounted on the table top. The lens for lantern slide projection is carried by an arm extending from the side of the moving picture mechanism. When the Balopticon is moved to the left, it lines up with this lens and is in position for the projection of lantern slides and opaque objects. Any one of the three makes of motion picture mechanisms (Powers, Edison or Simplex) may be fitted. The price of a complete outfit is the price of the regular Combined Balopticon, plus the prices of the moving picture mechanism and the special stand to accom- modate the same. If it is desired to add the moving picture attachment to the Combined Balopticon after purchase, this may be done by returning the instrument to the factory for the special fittings required. 57 Bausch & Lomb Optical Co m pany Figure 3 Combined Balopticon, CRA, on Special Stand with Moving Picture Attachment. Code Word Cat. No. Specifications Price Dytane 4700 Powers No. 6a Mechanism complete with 12-in. upper and lower film magazine with take-up device, automatic fire shutter and lens $188.00 Dyte 4705 Edison Type D Mechanism complete with maga- zine for 12-in. reels and with take-up device, auto- matic fire shutter and lens 172.00 Dyspnea 4706 Edison Exhibition Mechanism in oak cabinet with upper and lower film magazines for 12-in. reels, automatic fire shutter and lens 130.00 Dysphagic 4707 Simplex Mechanism complete with 16-in. upper and lower film, magazines, take-up device and 14-in. reels, automatic fire shutter and lens, and film re- winder 238.00 Dynastidan 4715 Special Stand, arranged as shown in Figure 3, includ- ing knife switch and connecting wires 30.00 NOl E With all of the above mechanisms we supply one of our regular, high grade motion picture projection lenses. 58 Bausch & Lo m b Optic a 1 Company The Universal Balopticon Figure 1 — Universal Balopticon ERA 15 in Position for Lantern Slide Projection. The Universal Balopticon has proved very popular wherever a combination apparatus of extreme rigidity and general adaptability is desired. The base instru- ment projects lantern slides and opaque objects, up to 6 inches square. It is widely used in the science departments of colleges and high schools, however, because of the attachments it readily accommodates for the efficient projection of a wide range of subjects : microscopical objects, large, transparent objects held in a horizontal plane, the spectrum and complementary colors and physical or chemical phenomena. These attachments may be added at any time and are so arranged that instant interchange is provided between the different kinds of projection, the interchange between lantern slides and opaque objects being accomplished by raising or lowering the lamp house as required. In audition to these possibilities, an attachment for the projection of moving pictures may be added upon special order. Lantern Slide Projection For work with lantern slides the lamp house remains in the horizontal position, as shown in Figure 1. The projection lens for lantern slides is mounted on top of the dark chamber with the slide carrier support and the third lens of the triple con- densing system. The first two lenses of this system are mounted in the front of the lamp house to collect the rays proceeding from the arc. In the dark chamber is a mirror in mounting so inclined as to reflect the light coming from the arc lamp up to a second mirror parallel to the first and mounted back of the projection lens on top of the dark chamber. The second mirror directs the light through the slide and projection lens to the screen. The position of the tnirror in the dark chamber is indicated by the exterior lever over the door, this lever being used to shift the mirror when it is desired to change to microscopical projection. 59 Bausch & Lomb Optical Company " . It is sometimes desired to project lantern slides at a greater distance than is ■I mSm * possible with the regular 8 or 10-inch focus projection lens. For this reason we supply a set of accessories by means of which the projection lens for opaque objects, which is of 15 or 18-in. focus, may be utilized for the purpose. These accessories consist of a 4/4-inch condens- ing lens, which completes the triple system, a slide carrier support (the regular slide carrier being used), bellows and front standard to support the projection lens, Figure 2. The accessory optical bed is required to support the front standard carrying the lens. The mirror in the dark chamber is turned to the horizontal position, giving a direct path of light from arc lamp to screen. With this arrangement it is possible to project a distance of 75 or 80 feet, thus, with small additional expense, making the apparatus available for long distance lantern slide projection in large halls and auditoriums. Figure 2— Accessories for Projecting Lantern Slides with Long Focus Lenses. Projection of Opaque Objects Figure 3 — Universal Balopticon ERA 15 in Position for Projection of Opaque Objects. 60 Bausch 8c L omb Optical Company When projecting opaque objects, the maximum illumination obtainable from a single light source is obtained by direct lighting of the object without intermediate reflection and by decreasing the distance between specimen and illuminant. This is accomplished by tilting the lamp house as in Figure 3, the strong spring catch holding it in position. This throws the light directly down on the object, which is held against the opening in the floor of the dark chamber by the strong springs of the object holder. There is only one mirror reflection, that by which the light passing from the object through the projection lens is directed toward the screen. This reflection at the same time causes the image to appear in correct position, from left to right. This reflection is caused by the mirror in the dark chamber mounted on lower side of mirror carrier used in lantern slide projection. Vertical Attachment Figure 4 — Universal Balopticon, ERVA 15, Showing Vertical Attachment and Medium Microscope, 4250 U. With the addition of the vertical attachment organisms in water, physical, chemical and biological demonstrations, or any subjects which must be placed in a horizontal position, can be projected on the screen. This equipment, shown in Figure 4, is mounted on one end of a rectangular plate, which slides on metal rods over the opening in the top of the dark chamber. The mirror box and equipment for lantern slides is mounted on the other end of this plate, and to change from one to the other it is simply necessary to shift the plate by means of a convenient handle. The position of the movable mirror carrier within the dark chamber is the same for either lantern slide, opaque or ver- tical projection because of its two reflecting surfaces. 61 Bausch & Lomb Optic al Company The vertical equipment consists of a 4 V ? -inch plano-convex condensing lensr mounted in the sliding plate with the plane side up, to serve also as a stage for the subject, and a projection lens with reversing mirror carried above it on a vertical rod. Microscopical Projection For microscopical projection (Figure 4) provision is made for attaching a care- fully planed optical bed to the front of the base by means of a strong but con- venient set screw. The microscope with mounting is then attached to the bed in front of the large projection lens, which serves as a condenser. The movable mirror is raised to permit a free passage of light. If it is desired to change to the projection of opaque objects, the microscope can be quickly swung out of the path of light by means of a swinging arm. We list two microscopes for use on this Balopticon: our Medium Microscope, with simple substage condenser, and our Large Projection Microscope (Horizontal Type), with three substage condensers. The former is most efficient when used with medium power objectives, while the Large Microscope is equally efficient with all powers, low, medium and high. With either one there is supplied an ex- tension sleeve with supplementary condenser, which serves in connection with the projection lens for opaque objects as a substitute for the front lens of the triple condensing system. Spectroscopical Projection Figure 5— Accessories for Projecting Spectrum and Complementary Colors with Universal Balopticon. The apparatus for the projection of the spectrum and complementary colors, shown in Figure 5, consists of a supplementary bed, an adjustable slit, carbon bisulphide prism, holder to take deflecting wedges, and condensing and projecting lenses. An absorption spectrum is projected by placing the absorbing medium in the path of light before the slit, the emission spectra by introducing various chemi- cal salts into the arc. A pure spectrum will be obtained every time if the special revolving carbon holders are fitted to the arc lamp, permitting new carbons to be used with each salt introduced. 62 Bausch & Lomb Optical Company Accessories for Projection of Cells and Tubes Figure 6— Accessories for Projecting Cells and Tubes with Universal Balopticon. This set of accessories is designed for use in the chemical and physical laboratories for projecting any demonstrations which may be conducted with the aid of cells, test-tubes, thermometers, etc. It consists of a 4/4-inch condensing lens with adapter, which is substituted for the projection lens for opaque objects, a separate optical bed on support and a standard upon which is mounted the pro- jecting lens regularly used for lantern slides. The apparatus to be projected is carried directly in front of the condensing lens on one of the supports or standards to be found in every laboratory. With this arrangement unlimited space is provided for placing in position of cells, burrettes, cylinders, etc., as may be required for showing the phenomena desired. When this apparatus is to be used, a table with extra long top is required to accommodate the projection lens and its optical bed. For this purpose we recom- mend our Balopticon Table No. 4253B. (See "Accessories”.) In order that the image may not be inverted we recommend the use of the special erecting prism No. 4441, which fits over the front of the projecting lens. If one is satisfied with the smaller (3 -inch) beam of light obtained with the opaque object projection lens, this lens may be used and the cost of the extra condensing lens saved. Moving Picture Projection The special stand illustrated in Figure 7, permits the projection of moving pictures and affords instant interchange between this and the other forms of pro- jection. The Balopticon is carried on two lateral tracks upon which it can be moved from one side of the stand to the other. The supplementary optical bed, otherwise attached to the base of the instrument when it is desired to accommo- date a microscope or other attachments, is carried on supports beside the moving Picture mechanism. This bed carries all accessories regularly accommodated by the Universal. When changing from moving pictures to any other form of projection, the Balopticon is simply slid over until it lines with the supplementary optical bed, and vice versa. ->3 Bausch & Lomb Optical Company Figure 7 — Universal Balopticon on Special Stand with Moving Picture Attachment. 64 Bausch & Lomb Optical Company Specifications Base — Of cast iron, 25 in. in length; carried at height of 7 in. from table by two cast iron supports of 11-in. spread with elevating screws front and rear. Lamp House — Measures 13/£ in. long, 13/4 in. high and 7/4 in. wide; light- tight and freely ventilated, constructed of double sheet metal walls, with an air space between the two walls and the roof fitted with our special patented ventilator; provided with large, light-tight spring door on the side and obser- vation windows on both sides; mounted between uprights at front end and provided with handle at rear, permitting it to be easily tilted for opaque projec- tion and held rigidly in position by strong spring arm; conforms to the most rigorous requirements of Boards of Underwriters. Illuminant — Hand-feed arc lamp for direct or alternating current. Condensing System — Consists of two rear lenses of our triple system, 6-in. diameter, in ventilated mount direcdy in front of lamp house, rendering light approximately parallel in dark chamber, and a piano convex lens placed in front of the mirror box for lantern slide work, completing triple system. Object Holder — Round, of heavy metal, mounted on double arm with spring hinge at each end and handle at holder end; the whole adjustable for height on a grooved vertical standard and provided with set screw; will accommodate objects of widely varying thickness and size, the holder always remaining parallel to base and automatically bringing object into proper plane of projec- tion; dark curtain in front of opening prevents light from flooding room when object is being changed. Slide Carrier — Quick changing slide carrier so arranged that the slides can all be inserted from one side. Post Card Carrier — Two adjustable holders with wooden backs and frame which fits securely over opening in bottom of dark chamber. Projection Lenses — Two of our Standard lenses with rack and pinion focusing adjustment, that for lantern slides regularly of 8-inch focus, ljHs-in. diameter, and that for opaque work of 15-inch focus, 4-in. diameter; lenses of other foci may be substituted if so specified. Dimensions — Length over all, 38 in.; height, 24 in. Vertical Equipment — Regularly furnished with Universal Balopticon No. 4186 only, but can be ordered separately and easily added to No. 4185; consists of a rectangular metal plate, 6 % x 12 in., with circular opening at either end; over one end is mounted a piano convex condensing lens with plane side up, to complete triple condensing system for vertical projection and provide stage upon which to work; upright grooved standard near opening carries 10-in. focus, 1 ;14-in. diameter projection lens and mirror for vertical work; over other open- ing provision is made for mounting mirror box with lantern slide equipment; for quick transformation from one form of projection to the other entire plate slides on metal rods and is operated by convenient handle. 65 Bausch & Lomb Optical C o m p a n y Price List Code Word Cat. No. Specifications Price Durbar ERA 15 Universal Balopticon, complete for projection of lantern slides and opaque objects, as described, with 4-in. diam., 15-in. focus projection lens for opaque objects and 1%-in. diam., 8-in. focus projection lens for lantern slides ..... $160.00 Durant ERVA15 Same as above, but with Vertical Attachment, as described ...... 175.00 Durance ERA 18 ERA 15, but with 4-in. diam., 18-in. focus projection lens for opaque objects and 1%-in. diam., 10-in. focus projection lens for lantern slides 160.00 Duration ERVA18 ERA 18, but with Vertical Attachment, as described 175.00 Dzeggetai 4180 Set of Accessories for adapting opaque object projec- tion lens to lantern slide projection; consists of Ayi in. diameter plano-convex condensinglens in mounting slide carrier support, bellows and front standard (opti- cal bedNo.4141 must be used with this apparatus) 10.00 Durati Destinist 4459 250-watt gas-filled Mazda, bulb only . net 3.00 Destinate ' / 4466 400-watt Mazda Lamp with gas-filled globe, 3^ in. diam., with reflector; on support, with 15 feet of ex- tension cable and Hubbel plug . . 12.00*^-&? ^ Dancery 4479 400-watt gas-filled Mazda, bulb only . net 5.00 Destinably 4476 *1000-watt Mazda Lamp with clear, gas-filled globe, 5 in. diam., on support, with glass reflector, 4 feet of extension cable with separable connector and pass through switch ..... 20.00 Destinable 4478 *1000-watt gas-filled Mazda, bulb only . net 10.00 *On account of its size the 1000-watt lamp can only be used in the large, light-tight model lamp houses. Note: — We can supply 250 or 400-watt lamps with portion of globe silvered, if preferred, at $1.50 extra. The reflector and parts for attaching to any model B or C for use with clear globe may be secured at $1.50. Acetylene Lamp Acetylene is a convenient illuminant, as it is easily obtained or prepared and is portable. The illumination is sufficient for work at comparatively short distances. Our lamp has a powerful double jet, mounted in front of our patent, optical mirror of silvered glass, which concentrates and steadies the light, nearly doubling the illumination. For the best result obtainable with this lamp a 10-inch focus projection lens, of %6-inch diameter, giving 105 B a u s c h & Lomb Optical Company an image 6 feet wide at a distance of 20 feet, should be used. This burner consumes 1 /4 cubic feet of gas per hour. Code Word Cat. No. Specifications Price Dwarf 4467 Acetylene Lamp with rehector and 6 feet of rubber tubing ...... $8.00 Oxyhydrogen Burner The oxyhydrogen burner gives greater illumination than the acetylene, but is also somewhat more expensive to operate. Formerly a lime which had to be revolved was employed. In this new burner a pastil of special composition is used, producing a very white and satisfactory light. Code Word Cat. No. Specifications Price Dyad 4486 Oxyhydrogen Lamp on support with pastil, inter- changeable with the support of our hand-feed arc lamp $10.00 Rheostats We construct our rheostats to meet the strictest requirements of fireboards and under- writers and they have been approved by the National Board of Fire Underwriters’ Laboratory of Chicago. The wire in the resistance coils Figure 1 — 4jTAmpere Rheostat, has practically no temperature coefficient and No. 4452. W ill not deteriorate with frequent heating and cooling. The cases are of perforated metal thus providing for the freest possible air circulation among the coils. There are no exposed contact points, and every means of insuring safety has been taken advantage of. The coils in rheostats of 15 amperes capacity and over are wound on asbestos board strips to prevent sagging or possible contact between coils. The coils in the 4J4-ampere rheostats are carried on porcelain spools. The 4/4-ampere rheostats can be used satisfactorily with the electric wiring usually found in private houses, connecting with the ordinary lamp socket. Those of higher capacity generally require special wiring. When ordering be sure to specify voltage. 106 Bausch & Lomb Optic al Company Figure 2 15- Ampere Rheostat, No. 4450. Figure 3—15 to 35-Ampere Rheostat, No. 4456. Code Word Cat. No. Specifications Price Declension 4450 Fixed Form, 15 amperes, 110 volts $ 7.00 Decoct 4451 “ 15 amperes, 220 volts 18.00 Deco re 4452 “ amperes, 110 volts, with cord, plug and pass through switch 5.00 Decoy 4453 Fixed Form, 4 l / 2 amperes, 220 volts with cord, plug and pass through switch 7.00 Dearth 4453A Fixed Form, 4^ amperes, 110 and 220 volts, with cord, plug and pass through switch . 8.00 Deasil 4458 Adjustable Form, 5-10 and 15 amperes, 110 volts 12.00 Decree 4454 15 to 25 amperes, 110 volts 18.00 Decuman 4455 15 to 25 amperes, 220 volts 25.00 Duty 4456 15 to 35 amperes, 110 volts 27.00 Designer 4460 15 to 35 amperes, 220 volts 32.50 Resistance for Mazda Lamp on 220 Volts When the Mazda stereopticon lamps, which are of the 110-115 volt type, are to be used on a 220-volt circuit, a resistance must be introduced in series with the lamp. The proper resistance for the various wattages are listed below. Code Word Cat. No. Specifications Price Desolateness 4494 220-Volt Resistance for 250-watt lamp $ 5.00 Desolater 4496 u 400-watt lamp 6.50 Desolation 4498 “ 1000-watt lamp 12.00 107 Bausch & Lomb Optical Company Switches, Wire and Fuses All supply wires and fuses, of course, should have a carrying capacity conform- ing to the rheostat employed. Code Word Cat. No. Specifications Price Daisy 5168 Enclosed Knife Switch with 3 sections of wire for connecting with rheostat and lamp . $5.00 Dunny 5176 Approved Cartridge Fuses for 30 amperes, each .25 D argue 5177 Approved Cartridge Fuses for 40 amperes, each . .45 Dysnomy 5184 No. 14 Rubber Covered Portable Lamp Cord, for 10 amperes, per foot .... .04 Dunker 5179 Rubber Covered Twin Cable with No. 12 copper wire for 15 amperes, per foot .10 Duke 5180 Rubber Covered Twin Cable with No. 10 copper wire for 25 amperes, per foot .10 Dulia 5182 Rubber Covered Twin Cable with No. 8 copper wire for 35 amperes, per foot A2'/ 2 Carbons Codeword Cat. No. Specifications Price per 10 Defy Defix Defray Deft Defrn 4474 4470 4471 4472 4473 Cored Carbons, ^-inch diameter, 6 inches long . “ “ »/ 16 “ “ 6 “ “ “ %6 “ “ 6 “ “ “ 5/ u . “ “ 6 “ “ (( ({ 1^ (( (l fy a “ $0.60 .40 .38 .40 .38 Acetylene Tanks and Generator Code Word Cat. No. Specifications Price Despect Despeche Despight Deckle 4483 4447 4448 4485 10 cubic feet capacity .... net 30 “ “ “ . . . net 40 “ “ “ . . . net “Acetyjur” Generator $ 8.50 15.00 18.00 12.00 Oxyhydrogen Generator This generator is very simple to operate. Oxone and ether are used produc- ing oxygen and hydrogen which are mixed in the mixing chamber of the burner. Code Word Cat. No. Specifications Price Dunnage 4491 Economic Oxyhydrogen Generator $13.00 108 Bausch & L cf m b Optical Company Figure 1 — Large Projection Microscope, Horizontal Type. Large Projection Microscopes Horizontal Type Our Large Projection Microscope of the regular Horizontal Type, Figure 1, is carried on a swinging arm, as it has been in the past, so that quick interchange can be made between microscopical projection and that of lantern slides. The Substage Conden- sers — three in number — are adjustable for focus by rack and pinion. A condenser, 72 mm in diameter, is supplied for use with low power objectives, such as the 72, 48 and 32 mm Micro-Tessars. The 72 mm condenser works equally well with all three of these objectives, when the focal point is adjusted to meet a change of powers. For higher powers the instrument is equipped with two condensers of 0.50 and 0.85 N. A., respectively, the former for 16 and 8 mm objectives, the latter for 4 mm and shorter focus objectives. These two condensers are used in conjunction with the 72 mm condenser. They are mounted on a revolving nosepiece which can be swung to one side, thus giving quick interchange or permitting both to be turned away from the optical axis. I he stage of the microscope is provided with a U-shaped plate in which is inserted a water cell with an opening of 24 mm. This water cell is flush with the stage surface and consequently comes into direct contact with the slide, which it cools by absorption, thus allowing one to leave seasoned slides in position for any length of time without danger of melting the mounting medium. If desired, this water cell can be used with all objectives, from the 72 mm Micro-1 essar to the 3 mm objectives, although the opening is not large enough to permit the entire available field of the 32, 48 and 72 mm Micro-Tessars to be utilized. For this reason we supply a second U-shaped plate with aperture of 54 mm, which can be substituted for the other. This latter plate is, of course, without water cell, since none is required with low powers as the image of the arc does not fall near the object. The objectives are mounted on a regular triple nosepiece when the equipment consists of the usual microscope objectives, such as the 32, 16 and 8 mm; but if lower powers, such as the 48 and 72 mm Micro-Tessars, are to be used, we recommend that the microscope be equipped with the large revolving plate as shown in Figures 2 and 3, permitting instant interchange of six different objectives. The body tube is of large diameter (63 mm inside) to allow for the projec- tion of the full available field of the Micro-Tessars. Fitted to the outer end of the body tube is a revolving plate with two extension tubes for eyepieces and two other openings, the latter being 63 mm in diameter. In projecting with the Micro- 1 essar lenses the eyepiece should be turned aside and the light allowed to pass 109 Bausch & Lomb Optical Company through one of these large openings. The other opening is provided so that a mirror can be mounted on the plate for directing the light to the screen when using the vertical microscope, Figure 3, or when it is desired to direct the beam of light onto a drawing board. This mirror is used m connection with the Micro-Tessars only. The microscope is focused approximately by rack and pinion; fine focusing is accomplished by a side fine adjustment of our lever type, which eliminates any possibility of lost motion. Code Word Cat. No. Specifications Price Duper 4138 Large Projection Microscope, Horizontal Type, as described, including projection eyepiece (3X), substage water cell, three substage condensers and triple revolving nosepiece; mounted on swinging arm, without projection lens or objective . $100.00 Dungeon Dunter 4139 4140 Same as No. 4138, but with 32, 16 and 8 mm objectives Same as No. 4139, but with large revolving plate to accommodate six objectives .... 117.00 129.00 Combined Horizontal and Vertical Type To supply an apparatus with which microscopic objects can be projected while being held.in a horizonta 1 plane we have designed this new type of our Large Projection Microscope. Thus objects in liquid or substances in a more or less liquid state can be projected with the microscope in the vertical position, while objects which do not have to be held in a horizontal plane can be projected with the instrument swung into its horizontal position. The microscope itself is the same instrument as the one described under the Horizontal Type, but is mounted in connection with a small dark chamber. When the microscope is in the horizontal position, the light passes straight through this dark chamber to the microscope, Figure 2, but when the instrument is swung into the vertical position it draws out of the dark chamber the prism-shaped box upon which it stands, Figure 3. 110 Figure 2 — Large Projection Microscope, Combined Horizontal and Vertical Type, in Horizontal Position. Bausch & Lomb Optical Company A rectangular mirror, which is attached to the rear (base) end of the microscope by a hinge^ joint, lies on the bottom of the dark chamber when the instrument is in the horizontal position, but when the microscope is swung into the vertical position it draws the mirror up to an angle of 45°, where it forms the base (hypothenuse) of the prism-shaped box. The mount- ing of this mirror drops into a small slot and locks the microscope in the vertical position. The purpose of the mirror is, of course, to reflect the light up through the microscope when the latter is in the vertical position. h or the low power objectives a first surface mirror, two inches wide, directs the beam of light toward the screen. For the higher powers with which an eyepiece is used a small prism over the eyepiece takes the place of the first surface mirror. The prism is so mounted that it can be quickly swung out of the path of light when the instru- ment is returned to the horizontal position. The eyepieces with prism and first surface mirror are all carried on a revolving plate for quick interchange, as described under the Horizontal Type. The Combined Horizontal and Vertical Type of microscope is carried on two lateral rods which are fastened to a frame and rigidly clamped to the optical bed in front of the slide carrier support. A projection lens with adapter is also mounted on the two lateral rods side by side with the microscope attachment. The projection of microscope slides or lantern slides is accomplished by sliding one or the other attachment into position. Code Word Cat. No. Specifications Price Dunstable 4144 Large Projection Microscope, Combined Hori- zontal and Vertical Type, as described, with pro- jection eyepiece (3x), substage water cell, three substage condensers, revolving plate and nosepiece for six objectives (no objectives), reversing mirror for low power objectives and a prism for use over eyepiece $160.00 Dunstical 4145 No. 4144, but with 32, 16 and 8 mm objectives 177.00 Dunted 4146 No. 4144, but with 72, 48 and 32 mm Micro-Tessar, and 16, 8 and 4 mm achromatic objectives . 265.00 Ill Bausch & Lomb Optical Company Medium Microscope This is a compound microscope de- signed for use with our Model D, Universal and Convertible Balopticons. It has coarse and fine focusing adjust- ments, the former by diagonally cut rack and pinion with a long range and the latter by our lever type of adjust- ment. The stage measures 4/4 x 3^4 inches and gives a distance of 3/4 inches from its center to the base of the arm. It has a substage condenser with iris diaphragm, mounted in a threaded sleeve for focusing. A substage water cell can be fitted at extra cost as indicated in the price list. For use on the Universal Balopticon, the microscope is supplied in addition with a 424-inch diameter condensing lens which utilizes the beam from the large projection lens. Low power objectives, as well as high power, can be used on this microscope without eyepiece. The eyepiece tube is removable and the body tube is 2/4 inches in diameter, so that the entire available field of the Micro-Tessars is utilized. The instrument is finished in dull black. The microscope is mounted on a swinging arm by which it may be thrown out of the optical axis and permitting instantaneous interchange between micro- scopical and other forms of projection. In the case of the Convertible and Model D Balopticons, the microscope and lantern slide projection lens are mounted on this arm parfocally, so that one is swung out of the optical axis and the other swung in by the same movement, no adjustment of the light source or condensers being necessary. Code Worn Cat. No. Specifications Price Daisu 4250U Medium Microscope for Universal Balopticon, in- cluding projection eyepiece (3X), substage condenser mounted on swinging arm ; without objectives (optical bed No. 4141 must be ordered with this microscope) ..... $45.00 Dagonet 42S0A Same as above, but for Model D and Convertible Balopticons ...... 45.00 Daker 4260 Substage Water Cell for medium microscope 5.00 Durative 4141 Optical Bed, carefully planed, 15-in. long; attaches easily to front end of base of Universal Balopticon to accommodate microscope .... 5.00 112 Bausch & Lomb Optical Company Simple Microscope This is an efficient instrument for elementary work and is designed especially for the Model C Balopticon. It is intended for objectives of low power and has no eyepiece. The substage accord- ingly is fitted with a condenser for low power objectives, and the focusing adjustment is by diagonally cut rack and pinion only. The stage measures 90 x 80 mm and gives a distance of 42 mm from its center to the arm. The instrument is interchangeable with the projection lens and is finished in dull black to avoid reflections. Code Woid Cat. No. Specifications Price Durity 4375 | Projection Microscope for use on Model C, includ- ! ing substage condenser and 3 diaphragms for use in the slide carrier; no objective . . . i $15.00 Micro-Tessar Objectives The Micro-Tessars are constructed especially for projection and photomicro- graphic purposes after the formulae of the Tessar photographic anastigmats, and are capable of projecting a field approximately equal in diameter to their focal length. They are particularly desirable for projecting large sections. Code Word Cat. No. Equivalent Focus Price mm in. Dander 4401 72 V/i $32.00 Dane 4402 48 2 26.00 Dangle 4403 32 1 X 26.00 Achromatic Objectives The regular achromatic microscope objectives are recommended for powers of 16 mm e. f. and higher. These lenses are supplied in blackened mounts. Code Word Cat. No. Equivalent Focus mm in. Aubade 1009 32 IT $4.00 Aubin 1021 16 % 5.00 Auctary 1027 8 A 8.00 Audit 1029 4 A 8.00 Augite 1035 3 % 8.00 113 Bausch & Lomb Optical Company Projection Eyepieces use with the 16 mm objective and all Our projection eyepieces are of achro- matic construction and project an image superior in every way to those given by ordinary eyepieces. We recommend for >her powers. Code Word Cat. No. Specifications Price Deist Daalder 4400 4405 Projection Eyepiece, 3X . Projection Eyepiece, 5X $7.50 7.50 Reflecting Prism Codeword Cat. No. Specifications Price Calyptu 4551 Reflecting Prism, in mount fitting eyepiece tube $7.50 Attachable Mechanical Stage The mechanical stage enables one to examine a slide area con- veniently and accurately and to permanently locate special areas by means of the scale readings. The model offered attaches to the corners of any square micro- scope stage by means of an adjustable clamp. The move- ments are by rack and pinion, the adjustment heads being close together in fixed relative position. One scale reads 75 mm and the other 55 mm, the range available being dependent upon the size of the microscope stage. The scales of both move- ments are graduated in single millimeters with verniers reading to tenths. The main parts are lacquered black to avoid reflections. The scales are engraved on fine German silver. Code Word Cat. No. Specifications Price Amber 2116 Mechanical Stage, as described $16.00 114 Bausch & L o m b Optical Co m p a n y Microscope Accessories for Polarized Light For the projection of petrographical specimens, crystals, etc., we have designed a set of accessories for projection with either parallel or convergent polarized light. The accessories can be used with either the Horizontal or Combined Horizontal and Vertical Type of our Large Projection Microscope. This set of accessories is made up of the following: — Nicol prism polarizer in mounting to fit on the back of the substage condenser, and so mounted that there is no danger of overheating by the arc. Nicol prism analyzer in rotating mount which clamps over eyepiece of microscope and which can be thrown in or out of the optical axis. The mount- ing is provided with a slot for insertion of selenite plates, quartz wedges, etc. Supplementary draw tube which is attached to the revolving plate in place of one of the eyepiece adapters. This tube is required in the projection of interference figures to bring the Bertrand lens into correct position. 48 mm achromatic objective which is attached to above draw tube and serves as Bertrand lens in projection of interference figures. Substage condenser of high numerical aperture to be mounted on substage nosepiece in place of small condenser for projection of interference figures. An objective of correspondingly high numerical aperture, such as a 4 mm, must be used in this work. Circular revolving stage on plate to fit in microscope stage in place of plate carrying water cell. Code Word j Cat. No. Specifications Price Daan 4121 Nicol Prism Polarizer in mounting to fit on back of substage condenser $15.00 Dabld 4123 Nicol Prism Analyzer in rotating mount with clamp to fit over eyepiece; mounting is provided with slot for inserting quartz wedge, selenite plates, etc.; mounting carrying nicol prism can be swung out of Optical axis, if desired 15.00 Daboia 4125 Supplementary Draw Tube for Bertrand lens 3.00 Dabber 4127 Substage Condenser of high numerical aperture for projection of interference figures 5.00 Atypic 1005 48 mm objective for use as Bertrand lens; used on supplementary draw tube for projection of interference figures 4.00 Dumpish 4143 Plain Circular Revolving Stage on plate fitting in place of plate carrying water cell 15.00 Antefixa 1500 Selenite Plate, Red of 1st. Order 2.50 Antegrade 1502 Quartz Wedge, Order I-III . 5.50 Ante legal 1504 Quarter Undulation Mica Plate 2.25 115 Bausch & Lomb Optical Co m p a n y Vertical Attachments We provide several of these attachments for use with our different Balopticons. They afford a number of projection possibilities, permitting one to project large transparencies, liquids and other similar objects which must be placed in a hori- zontal position. The beam of light in each attachment is directed into a vertical course by a mirror placed at an angle of 45° within a dark chamber. A plano-convex con- densing lens is placed in a horizontal mounting on the top of this dark chamber. It serves as a stage upon which to work and focuses the light in the field of the vertical projection lens, which is carried upon an upright support or bed. A mirror above the projection lens directs the image toward the screen. The different attachments and the Balopticons for which they are designed are indicated in the price list below. Code Word Cat. No. Specifications Price Drumlin 4376 Vertical Attachment for Model C Balopticon, as described and illustrated, page 33 $10.00 Dale 4290 Vertical Attachment for Model D or Convertible Balopticon, with prism-shaped mirror box and station- ary mirror, as described and illustrated, page 43 15.00 Dipody 4136B Vertical Attachment for Model D Balopticon with front standard, and 1^-inch diameter, 10 in. focus projection lens, as described and illustrated, page 43 42.00 Ditty 4136C Vertical Attachment for Convertible Balopticon, as described and illustrated, page 76, consisting of dark chamber with two supports, adjustable interior mirror and sliding plate carrying 4 1 %2 in. diam. condenser in mount, l|f|-in. diam., 10-in. focus, projection lens with reversing mirror on vertical rod, permitting latter to be moved out of path of light from opaque projection lens. Accessories for projection of polarized light can be readily added 47.50 Dirl 4142 Special Vertical Attachment for Convertible Balopticon, as described and illustrated, page 74, consisting of dark chamber with interior adjustable mirror, 8-in. diam. condenser, 15-in. focus, 2%e-in. diam. projection lens on vertical support with swing- ing arm so lens can be swung out of path of light from opaque projection lens .... 50.00 Attachments for Projecting Opaque Objects The attachments for projecting opaque objects with the Models C and D Balopticons are listed herewith. These attachments are described and illustrated under the respective lanterns for which they are designed. 116 Bausch & Lomb Optical Company Code Word Cat. No. Specifications Price Dusk 5080 Attachment for projecting opaque objects with Model C Balopticon, with 2ii6-in. diam., 12-in. focus lens and reversing mirror .... $35.00 Dumose 5082 No. 5080 but with 4-in. diam., 15-in. focus lens 67.00 Durham 5084 No. 5080, 4-in. diam., 18-in. focus lens 67.00 Duffel 4261 Attachment for projecting opaque objects with Model D Balopticon, with 2%6 in. diam., 12-in. focus lens and reversing mirror ..... 33.00 Dulcimer 4263 No. 4261, but with 4-in. diam., 15-in. focus lens 65.00 Dufrenite 4264 No. 4261, but with 4-in. diam., 18 in. focus lens 65.00 Combined Polariscope and Vertical Attachment We have designed this attachment to provide for a quick interchange from pdariscopic to other forms of projection with the convenience characteristic of all of our projection apparatus. It permits practically instantaneous interchange between polariscopic, vertical and all other forms of projection. The attachment consists of a dark chamber, A, supported on the optical bed by two standards. The top of this dark chamber is fitted with a sliding plate upon which the vertical attachment, for projecting horizontally placed trans- parencies, and the polarizer are mounted side by side. The front of the chamber is provided with a plano-convex condensing lens and a slide carrier box, D, as well as means for attaching the bellows. Within the 117 Bausch & Lomb Optical Co m p a n y chamber is a swinging mirror which catches in any one of three positions as may be required for the method of projection being employed. The mirror is operated by a lever, E, at either side. Upon the slide on top of the dark chamber a Delezenne polarizer, F, is mounted in a metal box, on the front of which the quarter-wave mica plates for rotating the polarized beam are located at G. The size of the beam of light avail- able with this accurately constructed Delezenne polarizer is very large and of exceptional brilliancy, excelling that obtained with any other than very large and expensive nicol prisms. It illuminates an ample field. The stage, H, for objects, the objective, I, and analyzer, J, are mounted on supports, which are adjustable along the horizontal bed. The stage is 95 mm in diameter, is revolvable and has centering screws. It may also be removed and a revolving mechanical stage, furnished at an extra cost, substituted. Between the polar- izer and the stage is the mounting, K, for a highly convergent lens, while a similar mounting, L, is provided on the front of the stage for a highly divergent lens which is supplied with an iris diaphragm for controlling the size of the transmitted beam. These lenses are used when projecting with convergent polarized light, as m work with interference figures. The mountings include quick acting screws, which en- able the operator to turn either or both lenses out of the optical axis, when parallel polarized light is desired, and to focus. The objective is of 4-inch focus and, with a nicol prism, approximately 12 mm, is held in a tube which slides in a main tube. This in turn is mounted with a standard rack and pinion adjustment, M, thus affording a wide range for focusing. The analyzer may be revolved. This polariscope, giving a large, clear field upon the screen, offers means for extensively demonstrating the properties of parallel and convergent polarized light, with rock sections, crystals, etc. For vertical work it is only necessary to slide the plate over until the vertical attachment is in line with the opening in the roof of the dark chamber. The sliding plate is moved by means of the handle, N, and a stop insures its being brought into exact alignment. The interior mirror of the dark chamber must also be low- ered to its first or 45° position, to direct a beam of light directly upwards. The vertical attachment consists of a plano-convex condenser, O, which is mounted in the sliding plate with the plane side up, and thus serves also for a stage, 4/4 inches in diameter, upon which the glass dishes, specimens, etc., to be projec- ted, are placed. At one corner of the sliding plate is a vertical rod, B, which carries the projection lens and mirror by which the beam of light is directed to the screen. When projecting opaque objects the vertical attachment is withdrawn from the path of the large projection lens by means of the sliding plate, and the supports carrying the body tube and revolving stage of the polariscope are hinged so that they, too, can be turned away from the path of light. When projecting lantern slides or microscopic specimens the interior mirror is raised to its third position to 118 Bausch & L o m b Optical Co m p a n y permit the passage of the parallel beam of light straight through the dark chamber to the accessories for lantern slide or microscopical projection which are mounted on the optical bed in front of the dark chamber. This attachment, as described, is designed for use on the Convertible and Model D Balopticons. Code Word Cat. No. Specifications Trice Darkling 5525 Combined Polariscope and Vertical Attachment for the Convertible or Model D Balopticon, as de- scribed and illustrated .... $175.00 Dakotas 5530 Polariscope Attachment for Universal Balopticon as described, or for use with vertical attachment No. 4136 (dark chamber in either case should be returned to us for fitting) ..... 130.00 Dartrous 5525P Polariscope Attachment only 160.00 Apparatus for Projection of the Spectrum and Complementary Colors Figure 1— Showing Attachment Set Up on Either Model D or Convertible Balopticon. The projection of the spectrum and complementary colors is desirable in practically every physical or chemical department. We have designed for this work a set of accessories consisting of a supplementary bed attachable to any of our Balopticons fitted with the optical bed, an adjustable slit, carbon bisulphide prism and a set of lenses so that either the spectrum or complementary colors can be projected, as desired. Both absorption and emission spectra can be shown with this attachment, the former being demonstrated by simply placing the absorbing media in the path of light in the front of the slit, while the latter is shown by introducing various chemi- cal salts into the arc. When projecting the spectrum, the adjustable slit shown at the extreme left, Figure 1, is clamped to the optical bed of the Balopticon in front of the slide carrier. The projection lens of the lantern, which should have a focal length of not more than 8 or 10 inches, is mounted in front of the slit. The other accessories are carried on the supplementary bed, which is attached to the lantern bed. These accessories consists of a 60° bottle prism, which is filled with carbon bisulphide 11 ^ Bausch & Lomb Optical Company the iris diaphragm, which limits the area on the screen when projecting comple- mentary colors; the first lens which images the diaphragm upon the screen and also forms a small image of the spectrum in the plane of the slit on the vertical stage; vertical stage with horizontal slit and clips at the back for holding small refracting wedges; the second lens in hinged mount which projects a magnified image of the spectrum on the screen. For projecting complementary colors the vertical stage, Figure 2, has a verti- cal and cross slide with clips for holding small deflecting prisms, of which three are supplied of varying widths. By placing one of the deflecting prisms on this slide and moving it to any desired point a portion of the spectrum will be deflected, and there will be two images of the opening of the iris diaphragm upon the screen. One will represent that portion of the spectrum deflected by the prism, and the other will represent the remainder of the spectrum which passes through to the screen without refraction. Where the two circles overlap there will be clear, white light. This prism can be moved horizontally through the entire spectrum, deflect- ing any portion that may be desired. By putting in two prisms with the bases in opposite directions — that is, one facing downward and the other upward — three circles can be seen upon the screen. When showing complementary colors, the lens at the end of the supplement- ary bed should be turned out of the optical axis, the lens mount being hinged for this purpose. By turning this lens into the optical axis one can determine exactly what portion of the spectrum will be deflected by the prism. If one wishes to project absorption and emission spectra only, this can be done with the adjustable slit and the bottle prism, as indicated in the price list. Special Carbon Holders for Projecting Spectra of Chemical Salts The spectra of chemical salts are projected by intro- ducing the salt into the arc. If a pure spectrum is to be obtained the carbons must be changed with each new salt, but as this cannot be done conveniently with the ordinary lamp, we have de- vised a pair of Figure 2— Arc Lamp Showing Revolving Electrode Plates. special carbon holders with revolving electrode plates, which are attached to the lamp, as illustrated in Figure 2. There are five pairs of electrodes and the lower carbons are fitted with quartz cups in which the salts are placed. Thus a different cup is provided for each salt and the upper carbon changed, as well. The vapor of the salt becomes the light source and the characteristic spectrum, just as seen in the spectroscope, is projected on the screen. 120 Bausch & Lomb Optical Company Spectral Tube Holder for Projecting Spectra of Gases To show the spectra of gaseous elements it is necessary to use the transformer type of spectral tubes* in connection with a high voltage transformer or induction coil. The high voltage necessitates a special asbestos board holder for this tube to insulate it from the rest of the apparatus. The holder is illustrated in Figure 3. This holder is substituted for the ad- justable slit shown at the extreme left in Figure 1. A brass plate, secured to two posts by mille-' 1 nuts, holds the spectral tube in position. The plate has a slit which ful- fills the same function as the adjustable slit in Figure 1. Any good type of transformer or induction coil of about 10,000 volts capac- ity can be used for this work. Figure 3 *F. G. Nutting, Bulletin of the Bureau of Standards , Vol. IV. p, 511. Code Word Cat No. Specifications Price Daffodil 4154 Set of accessories for projection of the spectrum and complementary colors, with Model D and Convertible Balopticons, consisting of supplementary optical bed, adjustable slitand standard, carbon bisul- phide prism, lenses, etc. .... $45.00 Daffodiller 4154U Set of Accessories for projection of the spectrum and complementary colors, with Universal Bal- optieon, consisting of condensing lens in mount to fit front of dark chamber, supplementary optical bed, adjustable slit and standard, and front standard and front board with flange; carbon bisulphide prism, lenses, etc. ..... 50.00 Daffish 4156 Pair of Special Carbon Holders with revolving plates carrying special electrodes for holding chemical salts . .... 15.00 Dancli 4157 Spectral Tube Holder for projecting spectra of gases (The following set of accessories is for projection of the spectrum only) 10.00 Daff 4150 Adjustable Slit ..... 7.50 Dudeeti 4137 Standard for supporting the above 3.00 Deliberate 4446 Bottle Prism (for carbon bisulphide); width of face, 60 mm; height, 90 mm .... 6.00 Demy 4285 Prism Support for the above .... 3.00 121 Bausch & Lomb Optical Company- Adjustable Slit An adjustable slit is an indispensable attachment in spectrum experiments with light. We furnish the adjustable slit mounted on a blackened metal front board, which may be attached to the standard in such a way as to make the slit horizontal or vertical, as desired. The plates of the slit, which are of German silver, with edges carefully ground and polished, form two sides of a parallelogram. They are adjustable by means of a micrometer screw, with a pitch of .5 mm, and a spring, producing a very gradual movement. All the bearings and fittings, as well as the edges, are precisely made, giving unusually high grade results whenever this slit is used. Code Word Cat. No. Specifications Price Daff 4150 Adjustable Slit, as described above . . | $7.50 Prisms Code Word Cat. No. Specifications Price Deline 4442 Flint Glass Prism, 60°, l^-inch face $ 7.50 Despond 4443 Flint Glass Prism, 60°, 2-inch face 13.50 Deliberate 4446 Bottle Prism, of crystal glass; width of face, 60 mm; height, 90 mm; accurately ground glass stopper 6.00 Decide 4441 Trapezoidal Erecting Prism, in mount to fit over lJ4-in. diameter lens ..... 20.00 Prism Support This is a convenience in experiments with light, affording a support for the different prisms, etc. It has a regular standard with base block and clamp, which attaches directly to the optical bed and may be placed in any convenient position along it. It is of metal throughout. The top is circular, 75 mm in diameter, and is adjustable for height, a convenient clamping screw securing it in any desired position. Code Word Cat. No. Specifications Price Demy 4285 Prism Support, as described, for Model D, Universal or Convertible Balopticons .... $3.00 122 Bausch & Lomb Optic al Company Slide Carriers Figure 1— Rapid-Changing Slide Carrier, No. 4449. A satisfactory slide carrier, both con- venient and durable, is essential to a high grade projection apparatus. We supply several which have given such satisfaction. Particular attention is called to No. 4449, our new rapid-changing slide carrier, which is a double carrier operated entirely from one side. As a new slide is fed for- ward, the preceding slide is automatically returned, and a metal shield, which travels with the slide, obliterates all movement of the slide on the screen, so notice- able m ordinary double carriers and other types of slide changers. This approxi- mates a dissolving effect, thereby relieving all eyestrain. Two carriers, Nos. 4430 and 4432, are neatly finished wooden frames, provided with an automatic elevating device. This consists of loosely fitted metal pins beneath the center of the slides, which engage with an inclined plane at the end of the sliding Figure 2— Slide Carrier, No. 4430. movement, raising the slide so that it may be easily lifted out by its margin. No. 4430 is regularly supplied with our lantern slide equipments. An all-metal slide, No. 4435, is provided with an automatic centering device, which enables one to use slides of the English dimensions and the Standard American size in the same carrier. The measure- ments, which are given below, are outside dimensions and should not be confused with the size of the mats. We also make a convenient post card carrier for Figure 3 — Slide Carrier, No. 4435. our apparatus projecting opaque objects. Code Word Cat. No. Decapon 4430 Decalog 4432 Decamp 4435 Dunciad 4449 Dairy 5098 Dolly 5099 Specifications Slide Carrier, for two 3X x 4-inch slides with auto- matic elevating device Double Slide Carrier, for either 3X x 3 '/ or 3 V x 4-inch slides with automatic elevating device Slide. Carrier, all metal, with automatic centering device for slides x 3#, 3j( x4 and 3X x 4-/ inches . Rapid-Changing Slide Carrier , Post Card Carrier, holds cards and prints up to 5X inches square . Extra Holders for above, each Price $1.25 1.75 3.50 2.75 2.00 .75 Note— The semi-dissolving slide carrier, No. 4449, may be substituted on any equip ment regularly supplied with No. 4430 for $ 1.50 additional. 123 Bausch & Lomb Optical Co m p a n y Screens Ordinary sheeting, or common cloth, is too translucent to furnish a satisfactory screen for projection work. Our screens are all made of heavy cloth, specially prepared and as nearly opaque as possible. They are mounted on spring rollers. Code Word Cat. No. Specifications Price Dozzle 4420 Screen, 6 feet x 6 feet, each net $ 4.00 Deas 4421 CC 7 CC x 7 CC cc net 6.00 Deave 4422 «( 8 cc x 8 C C cc net 7.20 Debar 4423 CC 9 cc X 9 u cc net 12.00 Debate 4424 cc 8 cc x 10 cc c c net 13.50 Debel 4425 cc 10 cc x 10 C C It net 15.00 Deca 4426 CC 12 CC x 12 cc cc net 20.00 Larger sizes will be quoted upon request. Aluminum Screens These screens are made of heavy material with a metallic surface. They give a much more brilliant image than the ordinary screen and are recommended in all cases, but especially will their superiority be noted in projecting opaque objects, microscopic specimens and in all work requiring brilliant illumination. Owing to their narrower field, however, due to the high reflecting surface, they should be used only when the audience can be seated within an included angle of 60 degrees from the center of the screen. Code Word Cat. No. Size Price Code Word Cat. No. Size Price Demand Demark Deme 4420A 4421 A 4422A 6 x 6 ft. 7 x 7 ft. 8 x 8 ft. $10.00 net 14.00 net 18.00 net Demesne Demigod Demit 4423A 4425A 4426A 9 x 9 ft. 10 x 10 ft. 12 x 12 ft. $22.00 net 28.00 net 40.00 net Sateen Screens These screens are supplied for portable outfits. Sateen is as nearly opaque and highly reflecting a material as can be obtained, which at the same time is suitable for packing in a case. These screens are provided with eyelets for stretching and have reinforced borders. Code Word Cat. No. Specifications Price Deaco?i Deaconess Deaconry 4420S 4423S 4426S Screen, 6x6 feet .... net 9x9 feet .... net “ 12 x 12 feet .... net $ 3.50 8.50 14.00 124 Bausch Sc Lomb Optic al Company Screen Cases In order to provide a suitable casing in which to mount the screen and to protect it from dust we are offering a line of metal cases which are provided with brackets for holding the screen and with metal straps to support the casing. Code Word Cat. No. Specifications Damewort 4420C For 6 x 6-foot screen . net Damiana 4421 C “ 7 x 7-foot “ net Damianist 4422 C “ 8 x 8-foot “ . . net Dammar 4423 C “ 9 x 9-foot “ net Dammara 4425C “ 10 x 10-foot “ . net Damnify 4426 C “ 12 x 12-foot “ net Price $ 6.00 7.00 8.00 9.00 10.00 12.00 Balopticon Tables Figure 1— Balopticon Table, No. 4252, with No. 4456 Rheostat and No. 5168 Knife Switch. Our stands are constructed for rigidity and durability. They are of a con- venient height for operating the lanterns, and also of the proper height for clearing the heads of the audience. The tops are provided at the front with elevating screws operated by small cranks for tilting the lantern. The third stand 125 Bausch & Lomb Optical Co m p a n y ■ Figure 2 — Balopticon Table, No. 4253A, with No. 4456 Rheostat and No. 5168 Knife Switch. listed has castors on the two legs at the front, the legs at the back serving to keep the apparatus steady. The stand is easily moved by slightly lifting the legs at the back. No. 4256 is of metal throughout, finished in black enamel. No. 4253A has a heavy cast iron base and is provided with castors and leveling screws on all four feet. It is intended for large and heavy apparatus. Code Word Cat. No. Specifications Price Dunce 4256 Balopticon Table of metal, top 30 x 14 in. , $10.00 Dumpy 4258 Balopticon Table as above but with shelf for acces- sories *.•••• 12.00 Duel 4252 Balopticon Table of metal with wooden top, 32 x 16^ in. 16.00 Dupllcand 4253A Balopticon Table w ith strong cast iron base and frame and heavy 40 x 17-in. wooden top; space beneath for adding cabinet, if desired; provided with castors and leveling screws . 25.00 Duplicate | 4253B No. 4253A, but with top 46 x 16 in. 32.50 126 Bausch & Lomb Optical Company Index Page Accessories, Balopticon 97-126 Accessories, Microscope for Polarized Light 115 Accessories, Special for Chem. and Phys. Demonstrations 45 Accessories for Proj. of Cells and Tubes . 63 Achromatic Objectives 113 Acetylene Lamp 105 Acetylene Gas Tanks . 108 “Acetyjur” Generator 108 Adjustable Slit . . . 122 Aluminum Screens ApparatusforProjection 124 of Spectrum and Comp. Colors . 119 Apparatus, Simplified Micro-Projection . 83 Arc Lamp, Hand-Feed Arc Lamp, Hand-Feed 102 withMagneticCoils 103 Arc Lamp, Combined Automatic and Hand-Feed . 103 Aspheric Condenser . Attachable Mechanical 102 Stage 114 Attachments Combined Polariscope and Vertical . . . 117 Moving Picture 36,57, 63,78 Micro for Model C . 33 Micro for Model D . Opaque Objects, 41 Model C . . . 32,116 Opaque Objects, Model D . . . 41,116 Spectrum and Comple- mentary Colors . . 119 Vertical . . 33,43,61,116 Vertical Special . . 77 Balo Projection Lenses 17,100 Balopticons and Outfits Combined with Arc . 54 Combined with Mazda 50 Convertible .... 68 Double Dissolving 25,29,40 Double Dissolving Model C with Mov- ing Picture Attach- ment 36 Double Dissolving Page Special . 88 Home 47 Large Opaque . . . 86 Model B 21 Model BB .... 25-26 Model C . . . . 27 Model D . 38 Universal . . . . 59 B, Model Balopticon . B, Model Equipment 21 for Enlarging . BB, Model, Dissolving 24 Balopticon . 25-26 Balopticon Accessories 99-126 Balopticon Tables . . Bausch &Lomb Micro- 125 Tessar Objectives Branches and Foreign 113 Offices .... 2 C, Model Balopticon . Cameragraph, Nicholas 27 Power 92 Carbons 108 Carbon Holders, Special 120 Carriers, Slide . 123 Carrier, Post Card . 123 Cases, Screen Cells and Tubes, Pro- 125 jection of ... 63 Chemical Demonstration Spec. Accessories fo Combined Automatic and Hand-Feed Arc 45 Lamp .... Combined Balopticon, 103 CRA Combined Balopticon, 54 CRM . . . . Complementary Colors, 50 Projection of . . . Combined Polaiiscope and Vertical Attach- 15,119 ment 117 Condenser, Aspheric . 103 Condensing Lenses 101 Condensing Mount 19 Condensing Systems . 19 Construction, General 15 Convertible Balopticon 68 D, Model Balopticon . 38 Dissolver, Iris . . . 29,31 Page Double Condensing System .... 19 Double Dissolving Balopticons . . 29,36,40 Dissolving Outfit, Special 88 Edison Kinetoscope 90 Enlarging, Model B Equipment for 24 Eyepieces, Projection Microscope . . . 114 Foreign Offices and Branches .... 2 Fuses 108 Gas-filled MazdaLamps 104 Generator, “Acetyjur” 108 Generator, Oxyhydro- gen 108 Hand-Feed Arc Lamp 102 Hand-Feed Arc Lamp with Magnetic Coils 103 Historical Resume . . 6 Home Balopticon . . 47 Holders, Special Carbon 120 Holder, Spectral Tube 121 Illuminants .... 15 Acetylene Lamp . . 105 ArcLamp, Hand-Feed 102 Arc Lamp, Hand-Feed withMagneticCoils 103 Arc Lamp, Combined Automatic and Hand-Feed . . 103 Mazda Lamps, Gas- Filled .... 104 Oxyhydrogen Lamp 106 Illuminating System, Micro-Projection 11 Iris Dissolver 29,31 Kinetoscope, Edison . 90 Kcehler Illuminating System, Micro-Pro- jection 10 Lamps (see Illuminants) Lantern Slide Making, Model B Equip, for 24 Lantern Slide Projection 7 Large Balopticon for Opaque Objects . . 86 Large Microscopes . 109 Horizontal .... 109 (over) Bausch & Lomb Optical Company Index ( Continued .) Page Page Page Comb., Hor. & Vert. 110 Opaque Object Attachments Simplex Moving Pic- Lecturers’ Special Por- Model C . 32,116 ture Machine . 94 table Outfits, B & C 23,34 Model D . . . . 11,116 Slide Carriers 123 Lenses, Balo Projection 17,100 Opaque Objects, Pro- Slit, Adjustable . 122 Lenses, Condensing 101 jection of ... 7 Special Dissolving Ap- Magnification Tables Opaque Object Projec- paratus 88 Lantern Slide . 18 tion Tables . . . 18 Special Model D for Microscopical . . 12 Optical Projection . 6 Large Plates . . . 46 Opaque Objects . 18 Other Products . . . 129 Special Traveling Out- Mechanical Stage, At- Outfits, Suggested . 96-98 fits, B and C . 23,34 tachable .... 114 OxyhydrogenGenerator 108 Special Vertical Attach- Medium Microscope . 112 Oxyhydrogen Lamp . 106 ment 77 Microscope Accessories Physical Demon stra- Spectrum, Projection of 14,119 for Polarized Light . 115 tions, Special Acces- Stage, Attachable Me- Microscopical Projec- sories for .... 45 chanical .... 114 tion . .... 9 Polariscope . . . . 117 Substage Water Cell . 112 Micro - Projection Ap- Polarized Light, Pro- Suggested Outfits . 96-98 paratus, Simplified . 83 jection with 13 Support, Prism . 122 Microscopes, Projection Micro Accessories for 115 Switches 108 Large 109 Portable Outfits, Spe- Tables, Balopticon . 125 Medium .... 112 cial B & C ... 23,34 Tables, Projection Simple 113 Post Card Carrier . 123 Lantern Slide . 18 Microscope Objectives 113 Prisms 122 Microscopical . . 12 Micro - Tessar Objec- Prism, Reflecting . 114 Opaque Object . . 18 tives 113 Prism Support . . . 122 Terms 4 Model B Balopticon . 21 Projection Eyepieces . 114 Tessar, Micro - Objec- Model BB Balopticon 25-26 Projection Lenses, Balo 17,100 tives 113 Model C Balopticon . 27 Projection Microscopes Traveling Outfits, Spe- Model D Balopticon . 38 Large 109 cial, B and C . . . 23,34 Moving Picture Attachments Medium . . . . 112 Triple Condensing Sys- For Model C Dissolving 36 Simple 113 tern 19 For Combined, CR A 57 Projection, Optical 6 Universal Balopticon . 59 For Universal 63,67 Projection Tables . 18 Vertical Attachments . 116 For Convertible . 78,82 Reflecting Prism 114 For Model C . 33 Moving Picture Machines Resistance for Mazda For Model D . . 43 Edison 90 Lamp on 220 Volts . 107 For Universal . . 61 Nicholas Power . . 92 Rheostats 106 Vertical Museum Jars, Simplex 94 Screens 20 Projection with . 75 Museum Jars, Projec- White Opaque 124 Verdcaland Polariscope tion with .... 75 Aluminum . . 124 Attachment . . 117 N icholasPovrerCamera- Sateen 124 Wire 108 graph 92 Screen Cases .... 125 Objectives, Achromatic 113 Simplified Micro-Pro- Objectives, Micro- jection Apparatus 83 Tessar 113 Simple Microscope . 113 Other Produces We append a partial list of our other products of possible interest to the reader of this catalog. Astronomical Instruments Microscopes Bacteriological Apparatus Microtomes Centrifuges Ophthalmic Instruments Engineering Instruments Ophthalmic Lenses Electric Incubators Photographic Lenses and Shutters Field Glasses Photomicrographic Apparatus Haemacytometers Reading Glasses Laboratory Apparatus Magnifiers Searchlight Reflectors We shall be glad to furnish literature or information on any of the same upon request. . Research Council, UK |AHRC)and theSpanish