[ .19 ] 



On the NUMBER of the PRIMITIVE COLORIFIC RAYS in 

 SOLAR LIGHT. By the Rev. MATTHEW YOUNG, D. D. 

 S. F. T. C. D. S5f M. R. I. A. 





X H E opinion that there are but three primitive colours has Read April 

 been maintained by M. du Fay, and after him by Father Caftell. '" ' 

 See Montucla, Vol. I. p. 630. ; but they and all others who hold 

 the fame dodrine, defend it merely on the principles of a painter, 

 who fhews how with thefe three colours on his pallet, he can 

 compound all others ; for with red and yellow he can form an 

 orange colour; with blue and yellow he forms green ; and witk 

 blue and red he forms indigo and violet ; and thus having com- 

 pounded the feven prifmatic colours, it is manifefl that all 

 other colours, with their different gradations, can be formed from 

 them likewife. But xhS.^ pharmaceutical argument is by no means 

 fufficient to fatisfy us as to the real compofition of folar light. 



" Light, in refradling, is decompofed into feven rays, red,. 

 '* orange, yellow, green, blue, indigo and violet. It has been. 



" fuppofed,'" 



