i;o POPULAR LECTURES AND ADDRESSES. 



observation, which continually dilated itself till 

 it became sometimes more than one-half or 

 three-quarters of an inch in breadth before the 

 bubble broke. At first I thought there had 

 been no light reflected from the water in that 

 place, but observing it more curiously I saw 

 within it several smaller round spots, which 

 appeared much blacker and darker than the 

 rest, whereby I knew that there was some 

 reflection at the other places which were not 

 so dark as those spots. And by further trial I 

 found that I could see the images of some things 

 (as of a candle or the sun) very faintly reflected, 

 not only from the great black spot, but also 

 from the little darker spots which were within it. 



" Obs. 1 8. If the water was not very tenacious, 

 the black spots would break forth in the white 

 without any sensible intervention of the blue. 

 And sometimes they would break forth within the 

 precedent yellow, or red, or perhaps within the 

 blue of the second order, before the intermediate 

 colours had time to display themselves." 



Now I have a reason, an irrefragable reason, for 



