Sir D. Brewster on the Theory of Accidental Colours. 435 



squared differences, does not a natural passage to the former 

 lie through 11 functions of the squared differences ? 



In other words, may not the quantities S SPD (/zj Zrg... ^„), 

 &c., serve as natural and valuable intermediaries between the 

 coefficients of an equation involving simple quantities and the 

 coefficients of the equation involving the squares of their dif- 

 ferences ? 



P.S. In the next part I trust to be able to present the 

 readers of this Magazine with Ql direct and symmetrical method 

 of eliminating any number of unknown quantities between 

 any number of equations of any degree, by a newly invented 

 process of symbolical multi{)lication, and the use of compound 

 symbols of notation. 



I must not omit to state that the constituents of multiplica- 

 tion \ and \j.f explained in Cor. 2. to Theorem (3.) are equal 

 to the expressions /h-^ . kc^^ ... ^'^-r-iA 



\ -h k I 



"tn—r ••• "-m 



and its analogue respectively. 



University College, London, October 15, 1839. 

 [To be continued.] 



LXIV. Observations on Professor Plateau's Defence of his 

 Theory of accidental Colours. By Sir David Brewster, 

 K.H., V.P.R.S. Ed.''' 



IN the Numbers of this Journal for May and June last. Pro- 

 fessor Plateau has published an elaborate defence of his 

 " Theory of accidental Colours," against certain observations 

 ^ which have been made upon it in England. The authors to 

 whose observations he replies are an anonymous vvriter in the 

 Edinburgh Review f find myself; and as I have no hesita- 

 tion in acknowledging that I am the anonymous reviewer, 

 I feel myself bound to bear the whole burden of examining the 

 able defence which Professor Plateau has now made. Having 

 the honour of being personally acquainted with this distin- 

 guished individual, and admiring his character as well as his 

 talents, I regret that my opinion should have been placed in 

 collision with his ; but from the temperate and truly philoso- 

 phical manner in which he has conducted the discussion, and 

 which in so far as the first of these qualities is concerned I 

 shall not fail to imitate, I trust the interests of science and of 



* Communicated by the Author, 

 t April 1834, p. 160. 

 2 F2 



