NEWTON'S EXPERIMENTS ON DIFFRACTION. HI 



"about these matters, nor repeated some of those which I did try 

 "until I had satisfied myself about all their circumstances." I may 

 add that Newton's measures of the distances at which the first dark 

 bar was formed are so irreconcileable with those of his admirer Biot 

 that, referring to the avowal above-cited, I think no reliance ought to 

 be placed on the accuracy of his observations of diffraction. 



Since writing the above, I find that Biot has repeated the experi- 

 ment with the same result which I have obtained {Traite cle Physique, 

 Tom. IV. p. 749). He has not commented on or even mentioned 

 Newton's observation. 



G. B. AIRY. 



Observatory, 



May 6, 1833. 



p 2 



