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THE POPULAR SCIENCE MONTHLY 



the ligLt 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 reflec- 

 tion 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 doubt- 

 ful if it can ever be excelled for combined cheapness and efticiency. 

 With some blocks of wood, a twenty-five-cent microscopic glass lens, 



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Fig. 9. The Solab Microscope. 



and a slide carrying a microscopic object, he gets very striking 

 effects. Animalcules in water, and all sorts of transparent micro- 

 scopic 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 spin- 

 ning the top. With one-quarter green and three-quarters red a deep 



