THE WAVE THEOBY. 275 



cloud-particles. Now, the smaller the particles, the 

 wider are the coloured rings, and Young devised an 

 instrument, called the Eriometer, which enabled him 

 from the measurement of the rings to infer the size of 

 the particles. 1 Again, Kitter had discovered the ultra- 

 violet rays of the spectrum, while Wollaston had 

 noticed the darkening effect produced by these rays 

 when permitted to fall on paper, or leather, which had 

 been dipped in a solution of muriate of silver. Employ- 

 ing these invisible rays to produce invisible Newton's 

 rings, Young projected an image of the rings upon the 

 chemically-prepared paper. He thus obtained a dis- 

 tinct photographic image of the rings. This was one 

 of the earliest experiments wherein a true photographic 

 picture was produced. Young had little notion at the 

 time of the vast expansions which the art of photo- 

 graphy was subsequently to undergo. 



But Young was not permitted to pursue his great 

 researches in peace. The 4 Edinburgh Eeview ' had at 

 that time among its chief contributors a young man of 

 vast energy of brain and vast power of sarcasm, without 

 the commensurate sense of responsibility which might 

 have checked and guided his powers. His intellect was 

 not for a moment to be measured with that of Young ; 

 but as a writer appealing to a large class of the public, 

 he was, at that time, an athlete without a rival. He 

 afterwards became Lord Chancellor of England. Young, 

 it may be admitted, had given him some annoyance, 

 but his retaliation, if such it were, was out of all pro- 

 portion to Young's offence. Besides, whatever his per- 



1 In disorders of the eyes such particles sometimes escape into 

 the humours, and produce vivid colours. The enlargement of the 

 circles, which generally excites terror, is a good sign, as it indicatei 

 the increasing smallness of the particles by absorption. 



