Page:The American Boy's Handy Book edition 1.djvu/379

All that is required for this apparatus is an ordinary wooden packing-box, A (Fig. 212), a kerosene hand-lamp, B, with an Argand burner, a small fish globe, C, and a burning-glass or magnifying glass (a common double or plano-convex lens), D. In one end of the box, A, cut a round hole, E, large enough to admit a portion of the globe, C, suspended within the box, A, with the lamp, B, close to it. The globe is filled with water, from which the air has been expelled by boiling.

Now moisten the surface of a piece of common window-glass with a strong solution of common table salt, dissolved in water, and place it vertically in a little stand made of wire, as shown at F, so that the light from the lamp, B, will be focused on it by the globe, which in this case answers as the condenser. The image of the glass will then be projected on the wall or screen of white cloth, G, providing the lens, D, is so placed in the path of the rays of light as to focus on the wall or screen. In a few minutes the salt solution on the surface of the glass, F, will begin to crystallize, and as each group of crystals takes beautiful forms, its image will be projected on the wall or screen, G, and will grow, as if by magic, into a beautiful forest of fern-like trees; it will continue to grow as long as there is any solution on the glass to crystallize. Then by adding a few drops of any transparent color to the water in the globe, the