AND THE THEORY OF LIGHT. 37 



tally I had another opportunity of observing this pheno- 

 menon on a larger scale, at which two people were present 

 besides myself. In a court at a little distance two persons 

 were beating a red carpet ; the sun was shining at the 

 time. When the one struck it there was a large wave of 

 red; when the other struck it there was a large wave of 

 green. I examined the appearance very minutely, and 

 then desired those who were standing by me to observe, 

 and tell me what they saw. One said he saw nothing 

 remarkable, only the red carpet ; the other that he saw red 

 and green alternately. These observations being rather 

 difficult to repeat, I merely adduce them as additional 

 arguments in favour of the theory which I am attempting 

 to establish, and perhaps they may be of use to others 

 also. 



58. There is one experiment, however, which is uni- 

 versally admitted to have been performed with extreme 

 accuracy by one of the greatest philosophers of his age, 

 and which may be made available for our purpose. I refer 

 to Halley's celebrated diving-bell experiment. His atten- 

 tion, when under water, Avas directed to the colour of his 

 hand, and to that of the water below. The upper part of 

 his hand appeared red, the water and the lower part of 

 the hand green. Newton^s explanation of this is, that 

 water transmits the red, and reflects the green rays. 



It is difficult to understand this explanation, for to me 

 it appears that the light from both the upper and lower 

 part of the hand was reflected light. The upper part of 

 the hand reflected more of the subdued reddish light with 

 which he was surrounded ; the lower less, for it was in the 

 shade. In consequence of the depth of the water below, 

 few of the rays entering the water Avere reflected thence, 

 and the faint pulsation of reddish light alternating with 

 the darkness below, produced green, in a manner similar 

 to that in which we have seen the colour of the sky is 



