Camera Obscura. The simplest form of the Camera Obscura consists of a darkened room, with a round hole in the window-shutter, through which the light enters. Pictures of opposite objects will then be seen, inverted, on the wall, or on a white screen placed so as to receive the rays.

Camera Obscura 19Camera Obscura 20

We give here a very simple form of Camera, which our readers may easily construct. A B C D is a small rectangular box, closed on all sides, except the space E F G D, which is covered with a piece of ground glass. In the other end is a moveable tube, T, with a proper lens; and in the body, of the box is a mirror, E I II D, set to an angle of 45 deg. Upon this mirror the image of the object, P Q, falls, and is reflected upon the ground-glass plate.