SIMPLE EXPERIMENTS IN OPTICS. 



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lens. The i-oom is darkened, and the light coming from without is 

 brought to a focus on the inside of the flask. A hole has been made 

 through the glass, and as the water streams out the light is totally 



Fig. 8. The Fountain of Fire. 



reflected so as to illuminate the stream as it falls into the pail below. 

 Of this experiment the authors say : 



" How magical ! The curving stream of water is full of light, and appears 

 lilve a stream of molten iron. The spot where it falls seems touched with fire. 

 Put your finger in the stream of water, and it is brightly illuminated. Of 

 course, the water soon runs down, and the display stops. To prevent this, 

 bring water in a rubber tube from the water-pipes in the house, and then regu- 

 late the supply so that the receiver may be kepi full as fast as the water runs 

 out. 



" Place a piece of red glass behind the flask in the beam of sunlight, and the 

 stream of water will look like blood. Touch it, and the hand will be crimson, 

 and the scattered drops that fall in a shower into the tub will shine like drops 

 of red fire. Place a green or blue glass behind the flask, and the stream of 

 water will turn green or blue, and present a most singular appearance. Hold a 

 goblet in the stream, and it will overflow with liquid light. Flashes and sparkles 

 of fire will appear in it, and foam over the sides, shining with brilliant light. 



" This beautiful experiment is as interesting as it is strange and magical, and 

 it illustrates both refraction and total reflection. The flask makes a lens, and 

 the falling stream of water is lighted up by the cone of light that enters it at the 

 hole in the flask. Both the water and the light pass out of the hole together, 



