40 ESSAYS AND OBSERVATIONS 



,S EC T;^-Y|I,i. 



Cbf2ccrmng' the Cdufe -of ihi '•diff&ent Refrangi- 

 ' 'hility of the Rays of ti^h K' 



■Tf^b. In order to account for the dijferent 

 teirangibility of the-dHfereatly-eoloured rays, 

 Sir Jfadc Newtcn -|- and feveral of his follow- 

 ei-s have fuppofed, that their particles ftre of 

 different magnitudes or denfities : bli^, if 

 there be any anaiogy between gravity and th^j 

 refraftive power.j it w'ill produce equal per-^; 

 pendicular velocities in all particles, whate^"' 

 ver their magnitude or denfity be ; and fo- 

 all forts of rays w^ould be flill equally re.-; 

 frangible. ,m ^lii ^'ol' 



37. It feems therefore a more probable 

 opinion, which others have advanced, that 

 the differently-coloured rays are proje(5ted 



with 



* Altho' the doflrine contained in this feflion has been 

 already publifhed in the Philofophical Tranfaflions for 1753, 

 (vid. vol. xlviii. part 1. p. 262, &c.) having been communi- 

 cated to the Royal Society, by the Author, in a letter to- 

 the Reverend Dr. James Bradley D. D. F. R. S. ; yet it 

 could not be omitted here, on account of its connexion with 

 feme of the queries that follow ; befides that it contains fe- 

 veral illurtrations not to be found in the Tranfaftions. 



f Nt"vjt, Opt. query 29, 



