Direct Stereoscopic Projection.—All the fore going systems may be termed indirect methods of stereoscopic projection, inasmuch that in every case the final results are observed after looking through coloured glasses, prisms, mirrors, shutters or other devices ; but as long as inter mediate agencies are necessary, stereoscopic relief upon the lantern screen will remain com mercially impracticable. The only systems of direct stereoscopic lantern and kinematograph projection have been evolved by Theodore Brown. One applies to ordinary lanterns and the other to the kinematograph. The former consists of a special carrier furnished with a plurality of glass slides or films carrying different sections of one subject in panoramic order and with varying speeds according to the supposed distance of each plane in the composition of the subject depicted. Remote mountains are depicted on one glass or rollable film ; the middle distant objects (ships) on a second one ; and foreground objects (trees, etc.) on a third. The mechanism of the carrier through which the three glasses are caused to slide hori zontally is such that the first has hardly any movement, the second moderate movement, and the third quick movement. On the screen, and before the mechanism is set working, the composition appears as an ordinary picture ; but on operating, and thus imparting the panoramic and varying movements, the observer at once perceives a depth of perspective, such as is apparent in any ordinary stereoscope. The
fast-moving foreground appears decidedly at a near plane, the sea and ships at a distance beyond the foreground, and, finally, the remote mountains at a great distance away. With this impression comes the sense of actual space between foreground and background. In com plicated subjects as many as six distinct layers of rollable films have been introduced.
In Brown's direct system as applied to kine matographs, there are four chief modes of pro cedure : (1) Placing the subject on a rotatable stand revolved synchronously with the working of the taking camera ; (2) Causing the camera to circumscribe the subject, by making the former travel round the subject at a speed regulated by the working of the camera ; (3) Using the camera on a special tripod head, designed to give an oscillation to the camera whilst in operation ; and (4) Taking the subject in a continuous panoramic direction, at a speed of operating according to the movement of the vehicle carrying the camera.