The Optical Magic Lantern Journal (September 1893)

124 -The Optical Magic Lantern Journal and Photographic Enlarger. oxygen, so cold that when absolute alcohol is dropped into the liquid it freezes, and the solid drops rattle inside the liquid like marbles whenever the containing vessel is shaken. The plan he adopted is represented in the accompanying cut, in which diagram A is the electric lantern, me werescT! 8 B a double glass vessel, with an excessively high vacuum between the two glass surfaces ; the interior of the vessel D was filled with liquid oxygen, which liquid has a blue colour ; this brought the rays to a focus at C, and in that focus he set fire to brown paper. Without the vacuum between the two glass surfaces the outside of the vessel would have been covered with hoar frost from the condensed aqueous vapour of the air of the theatre. An ordinary vacuum, so-called, is useless for thepurpose. The vacuum he employed was much higher than that used in radiometers, and contained no trace of vapour of mercury. The great kindness of Professor Dewar in selecting brown paper for combustion will be noticed. Lord Rayleigh once did the same thing in the same place, by selecting burning brown paper to mark the track of a beam of light. He explained that when he was alone he used tobacco smoke for the purpose, but as some in the auditory might object to tobacco, he publicly burnt brown paper instead. The other feat in optical projection which attracted much attention was exhibited at one of the conversaziones of the Royal Society at Burlington House. It was Mr. Anderton’s -method, already described in these: pages, of obtaining stereoscopic effect in optical projection by means of polarised light and suitable appliances. A subsequent public criticisin suggested that some of the illusion of this was ‘spoiled by the surroundings of the screen being those of an ordinary hall, which detracted from the suggestion of reality, and that the effect might be enhanced if the screen were seen ‘through a kind of dark tunnel. The inventor, by his utterances, seemed to think that this point was directed against his invention in particular. It was, however, merely a suggestion for the improvement of all kinds of spectacular optical projections. Delicate little points like this receive the attention of the French, with their highly developed artistic perceptions, which is why Daguerre, when he was exhibiting his diorama in Paris, produced all the-effects at the end of a short black tunnel between the screen and the spectators. When he represented the mountain sliding down into the valley of Arth Goldau, the illusion would have been far less had there been a statue of Cupid, or any other adornment of a theatrical building, close to the edge of the screen. The arrangement of Mr. Anderton seems to be, perhaps, the best which has yet been presented to the public for exhibiting stereoscopic effects on a large scale, and by pushing it one step farther some highly sensational effects can be produced. Apparent motion, as in Mr. Muybridge’s effects, should be given to these great stereoscopic spectacular demonstrations. We are not aware that this has ever been attempted on a large scale, but it was done in rare instances Many years ago inside small hand stereoscopes, so that the principle is not altogether | new in relation to stereoscopy. Let us take, for instance, the scene with the prancing horses of life size shown at the Royal Society ; had those horses been seen going through all the movements of prancing in front of the spectators, it is easy to see what an effect it would have had on the imaginations of the observers. To achieve the result just stated seems to necessitate but the exercise of a little inventive ingenuity, and going to some cxpense in the first cost of apparatus. Farther off in the future, inventive skill may possibly present us with real instead of virtual optical images in the air, in connection with these demoibstrations, but that time is not yet, for practical attainment always follows slowly, and step by step, upon the heels of scientific ideas. The Crystal Palace Company has plenty of space before and behind screens for the production of new and old feats in optical projection, nor does it object to public attractions involving scarcely any expense but that of first cost. Would it not be eminently to its interest to try to bring new feats in optical projection prominently before the public, and to encourage all inventors in the particular field now under notice ? — 0:—— Striking Theatrical Lantern Effects. Now that the position of the lantern has so greatly changed for the better as a powerful educational instrument, a desire probably exists unong the members of the rising generation