172 ELEMENTARY GENERAL SCIENCE CHAP. 



just hidden by the edge of the basin. Get somebody to pour 

 water into the basin. You will now be able to see the coin 

 without any movement of your eye having taken place. 

 Evidently there has been some bending of the direction of the 

 light rays somewhere. 



In Fig. 83 let C be the position of the coin in which it is just 

 hidden, as far as the eye is concerned, by the edge of the empty 

 basin. If the rays from the coin C be continued in straight 

 lines these lines will evidently pass above the eye. Now when 

 the water is put in, these rays, which before miss the eye, are 

 refracted in passing out of the water and just enter the eye, 

 making the coin appear to be in the position C'. The right side 



FIG. 83. Coin Experiment to show Refraction. 



of the vessel, if continued upwards, represents the normal, and 

 evidently in passing out of water into air the light-waves are 

 bent away from the normal. 



EXPT. 168. Stretch a wire across the opening in the cap of 

 a lantern. Focus the shadow of the wire on a screen. Interpose 

 a strip of glass in front of the wire and tilt the strip. Notice 

 the displacement of part of the shadow. 



EXPT. 169. Place a glass cell before the lantern and focus 

 it on the screen. Let the surface of the water be visible. 

 Put a lump of ice on the water, and observe the streaky 

 appearance of the illuminated part of the screen. Add syrup, 

 alcohol, and hot water by a pipette. Notice similar effects. 



Pour the vapour of ether out of a bottle, and observe the 

 appearance on the screen. Examine the shadows of burning 



