The Camera Obscura.
This is a very pleasing and instructive optical apparatus, and may be purchased for a small sum. But it may be easily made by the young optician. Procure an oblong box, about two feet long, twelve inches wide, and eight high. In one end of this a tube must be fitted containing a lens, and be made to slide backward and forward, so as to suit the focus. Within the box should be a plain mirror, reclining backward from the tube at an angle of forty-five degrees. At the top of the box is a square of unpolished glass, upon which, from beneath, the picture will be thrown, and may be seen by raising the lid. To use the camera, place the tube with the lens on it opposite to the object, and having adjusted the focus, the image will be thrown upon the ground glass, as above stated, where it may be easily copied by a pencil or in colors.