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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