THE HAMILTON ASSOCIATION. 6 1 



changes, as is shown by the photographic art, but as to the extent to 

 which these enter into atmospheric bleaching I cannot at present say. 

 I might perhaps speculate as to the part taken by the rays of light in 

 the bleaching processes, but speculation in an experimental science, 

 such as chemistry is, had better not be attempted. I therefore close 

 with the suggestion that atmospheric bleaching is probably due in a 

 measure to the action both of ozone and of the sun's rays. 



