DIRECT STEREOSCOPIC PROJECTION.
In all the foregoing methods of stereo scopic projection, whether merely of still subjects or those of an animated nature, it has been shown that some kind of intermediate aids in the inspection of the projected pictures have to be used by the observer. Obviously these conditions dis count their value, inasmuch that the exhibitions must be limited to few persons or small audiences, to say nothing of the inconvenience to which the oh server is put. In view of these facts, a little reflection will show that what is needed is a method of stereoscopic pro jection that may be termed direct, not necessitating the use of any inter mediate agencies such as described above. There are many optical illusions which give rise to the sensation of relief that are not, however, stereoscopic pheno mena, scientifically speaking. When look
ing into the transparent mirror of plate glass used in the familiar illusion of Pepper's G host, one sees not only the real objects of furniture placed upon the stage, but a supplementary figure (the ghost) invested with roundness and relief, though the manner of its projection renders it more or less transparent. Pepper's Ghost effects derive their results from a combination of transmitted and reflected light, the transmitted light emanating from the real objects upon the stage, while the reflected light proceeds from i he surface of the leaning plate glass, and emanates from a brilliantly illuminated figure in white, concealed beneath the stage. This class of projection enables a large audience to see the results without intermediate aids, and while it is not