Page:Popular Science Monthly Volume 11.djvu/686

666 the light inside of the water. That this is so, may be proved by permitting the water to escape, when the light will be seen shining out of the hole horizontally into the room. Why, then, does it not shine out into the room while the water is escaping? When the stream of water is flowing out, it falls in a curve into the tub on the floor. The beam of light, passing out with the water, meets its curved surface at such an angle that it is totally reflected. This beam of reflection again meets the surface of the water, and is again totally reflected. In this manner it is reflected from side to side, again and again, till it reaches the tub, and there we see it shining brightly. It is a prisoner in the water, and follows it down into the tub. When you put your hand in the falling water, you see that it is lighted brightly, and yet the stream by comparison is rather dark. If it were pure distilled water it would hardly be visible. As it is full of floating specks and motes, each of these reflects light, and these cause the water to appear full of light.

"This fountain of fire is a charming experiment for a school, and its double lesson makes it as interesting as it is beautiful."

Prof. Mayer uses Lis flask-and-water lens, as illustrated in Fig, 9, to get a solar microscope, and so well does it succeed that it is doubtful if it can ever be excelled for combined cheapness and efficiency. With some blocks of wood, a twenty-five cent microscopic glass lens,



and a slide carrying a microscopic object, he gets very striking effects. Animalcules in water, and all sorts of transparent microscopic objects, can be projected upon a curtain by its aid, so that a large number of people can be entertained by observing the effects produced.

Fig. 10 shows how a common iron top, such as may be found in any toy-store, may be transmuted into a color-top. The shape of the handle is of no importance. By fastening disks of various colors, made of drawing-paper, around it, all sorts of chromatic changes may be studied. With red, green, and violet, white will appear by spinning the top. With one-quarter green and three-quarters red a deep