To practically illustrate: In the front of camera (A) button ,a stereo negative, placing it upside down and film side in. Move the center portion with the lenses back from the negative, so that from the top of the lens to the negatiue will be twice the focal length of the lens in use. Clamp this section, and move the ground glass back until the distance from ground glass to stop i of lens equals twice the focus of lens in use. Adjust the ground glass until the image on the same is sharp, then tighten all clamp-screws.
A, Stereo negative. B, Hooded front, covering lenses. C, Mill-head for raising flap shutter. D, Screw for moving right-hand lens. E, Set-screw for vertical sliding-front. F, Ground glass. G, Holder. H, Door.
The diaphragm at back of camera gives the size of the two images, being 3f inches high by 3 inches wide. Inside the rear bellows is placed a bellow division separating the light from the two lenses. The sliding front of cam era carrying the negative should now be moved up or down in order to fix a base line for the picture, which will be an imaginary line drawn across the negative and passing through two sim ilar objects in the two halves of the negative. This settled, then, by means of the milled head screw, move the right-hand lens so as to bring some object, as a tree, corner of a house or fence, that it may be close to the side of diaphragm; then move the other lens so the same object will be j' of an inch from the other diaphragm.
These points settled, place a ground glass transparency plate, inches, in the holder, and adjust it to the camera. Place fairly small stops in the lenses; close the flap-shutter by means of the milled head (C), draw slide to holder, point camera to the sky; then raise the flap shutter, and give one, two or three seconds, according to circumstances. After developing, fixing, washing and drying, the face is covered with a thin piece of glass and the edges bound, when the transparency is ready for the stereoscope.
STILL.—An apparatus for distilling water or other liquids. A simple form is that shown in fig. 446.
The water or liquid to be distilled, is placed in a glass flask, the neck of which is connected with a long glass tube which is surrounded by an outer jacket of glass or tin through which cold, water must be continually kept flowing. This piece of apparatus is known as Liebig's Condenser. The end of the glass tube is placed within a flask known as a receiver because it receives the condensed liquid. The water in the retort. is heated with a Bunsen burner ; the steam given off passes through a con denser • it is then cooled and the distilled water is collected in the receiver. When large quantities are required the still is made of copper and the tube of tin made in a spiral form (see fig. 446).