PIN-HOLE FOCUS.
Make a pin-hole in a card, which hold between a candle and a piece of white paper, in a dark room, when an exact representation of the flame, but inverted, will be seen depicted upon the paper, and be enlarged as the paper is drawn from the hole; and if, in a dark room, a white screen or sheet of paper be extended at a few feet from a small round hole, an exact picture of all external objects, of their natural colours and forms, will be seen traced on the screen; moving objects being represented in motion, and stationary ones at rest.