Projection Apparatus (1917)

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