390 HISTORY OF OPTICS. 



why they were imperfect, namely, in consequence of 

 the different refraction of different colours, which 

 produces a chromatic aberration : and the theory 

 was confirmed by the circumstances of such imper- 

 fections. The false opinion of which we have 

 already spoken, that the dispersion must be the 

 same when the refraction is the same, led him to 

 believe that the imperfection was insurmountable, 

 that achromatic refraction could not be obtained : 

 and this view made him turn his attention to the 

 construction of reflecting instead of refracting tele- 

 scopes. But the rectification of Newton's errour 

 was a further confirmation of the general truth of 

 his principles in other respects ; and since that 

 time, the soundness of the Newtonian law of refrac- 

 tion has hardly been questioned among physical 

 philosophers. 



It has, however, in modern times, been very 

 vehemently controverted in a quarter from which 

 we might not readily have expected a detailed dis- 

 cussion on such a subject. The celebrated Gothe 

 has written a work on The Doctrine of Colours, 

 (Farbenlehre ; Tubingen, 1810,) one main purpose 

 of which is, to represent Newton's opinions and the 

 work in which they are formally published (his 

 Opticks,) as utterly false and mistaken, and capable 

 of being assented to only by the most blind and 

 obstinate prejudice. Those who are acquainted 

 with the extent to which such an opinion, promul- 

 gated by Gothe, was likely to be widely adopted in 



