32 FARADAY 



does not) . All matter affects light more or less by what we 

 may consider as a kind of attraction, and I have arranged 

 (Fie. 18) a very simple experiment upon the floor of the 

 room for the purpose of illustrating this. I have put into 



FIG. 1 8 



that basin a few things which those who are in the body of 

 the theatre will not be able to see, and I am going to make 

 use of this power which matter possesses of attracting a 

 ray of light. If Mr. Anderson pours some water, gently 

 and steadily, into the basin, the water will attract the rays 

 of light downward, and the piece of silver and the sealing- 

 wax will appear to rise up into the sight of those who were 

 before not high enough to see over the side of the basin 

 to its bottom. [Mr. Anderson here poured water into the 

 basin, and upon the lecturer asking whether any body could 

 , see the silver and sealing-wax, he was answered by a general 

 1 affirmative,] Now I suppose that every body can see that 

 t they are not at all disturbed, while from the way they appear 

 to have risen up you would imagine the bottom of the basin 

 and the articles in it were two inches thick, although they 

 are only one of our small silver dishes and a piece of 

 sealing-wax which I have put there. The light which now 

 goes to you from that piece of silver was obstructed by the 

 edge of the basin when there was no water there, and you 

 were unable to see any thing of it; but when we poured 

 in water the rays were attracted down by it over the edge 

 of the basin, and you were thus enabled to see the articles 

 at the bottom. 



I have shown you this experiment first, so that you might 

 understand how glass attracts light, and might then see how 

 other substances like rock-salt and calcareous spar, mica, 

 HC VOL. xxx A 



