Biographical Memoir q/'Dr Thomas Young. 223 



awaken afresh public attention, which had been exhausted by so 

 many debates, nothing more was necessary than the high cele- 

 brity of two other members of the Royal Society, who now en- 

 tered the lists. The one was a well-known anatomist, and the 

 other the most celebrated artist of whom England can boast. 

 They combined their efforts for the purpose of establishing unal- 

 terably the form of the crystalline lens. The learned world would 

 not readily suspect that Sir E. Home and Ramsden together, 

 could make inaccurate experiments, or could be deceived in mi- 

 croscopic measurements. Young himself thought it impossible, 

 and therefore did not hesitate publicly to give up his theory. 

 This willingness to allow himself beaten, so rare in a young man 

 of twenty-five, is still rarer on the occasion of a first publication, 

 and was therefore almost an unexampled proof of modesty. 

 But, in truth, Young had nothing to retract. In 1800, after 

 withdrawing his disavowal, he propounded anew his theory of 

 the formation of the crystalline, in a paper to which, since, no 

 serious objection has been made. 



Nothing is more simple than his argument, and nothing more 

 ingenious than his experiments. Young first rejected the hypo- 

 thesis of a change in the curve of the cornea, by the assistance 

 of microscopic observations, which would have made the slightest 

 variations appreciable ; or, to express it otherwise, he placed the 

 eye in particular conditions, in which the change of the curve 

 could have no effect, — he plunged it in water, and proved that 

 then the power of seeing at different distances remained com- 

 plete. 



The second of these possible suppositions, that of an altera- 

 tion in the dimensions of the organ, is then" overturned by a se- 

 ries of objections and experiments, to which it would be difficult 

 not to yield. And thus the problem becomes irrevocably settled ; 

 for who, in truth, does not see that if, of three possible solutions 

 two have been rejected, the third becomes necessary, — that the 

 radius of the curve of the cornea, and the longitudinal diameter 

 of the eye, being unalterable, the shape of the crystalline itself 

 must necessarily change ? Young, however, did not stop there ; he 

 proved directly, by the minute phenomena of the disarrangement 

 of images, that the crystalline really changes its curve. He in- 

 vented, or at least improved, an instrument which might be used 



