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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