Shall devote a chapter to the stereograph and its philosophy;in this I shall simply give plain instructions for taking the stereoscopic negative by the wet collodion process.
In the ordinary stereoscopic negative, as in every negative, the pictures are laterally inverted, and when printed, this inversion is corrected only for each picture individually, for the right-side picture is still inverted and in the place of the left-side picture. In consequence of this, the printed stereographs have to be cut apart, and mounted so that the right-hand photograph is placed on the right side, and the left hand photograph on the left side. When taking pictures of still life, as also others, where the living objects are not in motion, it is very easy to manage matters so as to invert the photographs on the negative. The method is as follows: Take a large-sized camera-stand, allowing sufficient space for the camera to slide laterally. Placing the camera in the right-hand corner, focus the left-hand lens. Next slide the camera gently, or lift it up and place it in the left corner, and focus the right-hand lens. The space between the centers of the two pictures thus focussed must be about two inches and three quarters. Whilst the camera is in this position on the left side, insert the sensitized plate, take out the slide, uncover the right-side cap for a second or two, and take this picture. Then close up the lens, lift up the camera gently and place it on the right side. In this position uncover the left-side lens for the same length of time. In this way, and in the space of ten seconds or so, the two pictures can be taken in a proper condition for printing so as to produce a non-inverted stereograph. For such work it would be no difficult task to contrive a slide by which a single lens would be all-sufficient; that is, when the camera is on the left side, the lens must slide to the right side, and vice versa on the right side.
As soon as the negative is this taken, it has to be developed before it gets dry. The development and fixing can be performed in a dark tent specially arranged for such purposes. Various contrivances have been adopted in landscape photography for these operations. For my own part I consider a simple hand-cart, with iron rods from corner to corner diagonally, in the form of semi-ellipses, and covered with a balloon-shaped tent, a very practical accommodation. But each successful photographer is somewhat of a genius, and can easily arrange a dark chamber according to his own taste and materials on hand.
Negatives thus taken and fixed are placed carefully away in slides where they can not be injured during transportation home. In the evening, or the next day, or at any convenient time, the negatives are examined; if clear, transparent in the lights, and sufficiently intense in the shades, they are varnished. On the contrary, if the opacity of the shadows is not deep enough, although the appropriate gradation exists between the lights and shades, it will then be deemed necessary to proceed to intensification. Previously the edges of the negatives must be varnished to the depth of one tenth of an inch upon the collodion, to prevent its peeling off during the operation. This is effected by dipping the quill end of a feather into the varnish, and then running along the edge of the collodion and of the glass, with this portion of the feather slightly inclined, so that the varnish does not drop oil; a sufficient quantity is attracted upon the collodion as you proceed. After this put the negatives aside, that the varnish may become thoroughly dry and hard. As soon as it is dry, immerse the plates in rain-water, and allow diem to remain there for about a quarter of an hour, by which time the collodion film will have become saturated iv with this fluid.