The speed of the exposure and the width of the opening B can be determined by making test strips. This can be done by setting the opening B to a certain width and turning the crank for 10 or 15 seconds and counting the number of revolutions. The proper exposure can be easily attained by this method.
An Emergency Clamp
While making an extra large guitar I did not have clamps large enough to hold the top and bottom onto the sides while gluing, so I fastened three pieces of wood together, each piece being about 1 by 2 in., as shown in the sketch. Then I bored holes in both top and bottom pieces and inserted a piece of soft wire in the form of a loop, which, when twisted, drew the ends of the clamp together.—Contributed by Geo. E. Walsh, Buffalo, N. Y.
While camping, remember a hot stone wrapped up makes an excellent substitute for a hot-water bag.
Home-Made Motion-Picture Camera and Projector In Three Parts—Part III
The Projector
The film positives are projected on a screen with the same kind of a lantern as is used for lantern slides, with the addition of the device for stepping the film through, one picture at a time, and flashing light on each picture as it remains stationary for an instant. The projector (Fig. 8) is composed of a lamp house, a condensing lens to make the beam of light converge upon the film for illuminating it evenly, a film-stepping device, and a projecting lens for throwing the enlarged picture of the illuminated film upon a screen.