( 604 ) 
confirm’d it. And if in his own Experiment he had 
looked at the painted Spetfrum fucceffively holding 
the refra&ing Angle of the Priftn upwards, and then 
downwards with the fame Inclination (or, what is 
ealier, turned the Spettrum upfide down, the Priftn 
remaining fix’d) he would have feen his Speftrum 
Shorter in one Cafe than in the other. 
“ That Sir I faac Newton's 8th Experiment of P. f. 
« B. II. (in which the prifmatick red and blue falling 
“ fucceffively on the fame Place of a Book, have 
« a different Focus in projecting their Image through a 
“ Lens ) is inconclufive j and rejeCts Richterus ' s 
« Anfwer, viz. That the Colours reflected from the 
« Book, as it has a rough Surface, fall always with 
« the fame Inclination upon the Lens , in what - 
« ever Direftion they came from the Trifm to the 
« B 00 k adding, That he had acquainted 
“ Richterus, that permanent Colours enlighten’d by 
“ direCt Light in any different Inclination, always fell 
* upon the Lens with the fame Inclination ; but ap- 
parent Colours, which were produced by RefraCtion 
“ with a Prifin, differed from permanent Colours in 
« their Incidence: But that Richterus had purpofely 
concealed it.” 
N.B. It is not likely he would have concealed it, ifit 
had been true. 
“ That Monfieur Marriotte ' s Experiments difprove 
<* the different Refrangibility of Colours”; though, if 
he had read with Attention and Impartiality the Ac- 
count of the Experiments which I made before the 
Royal Society by their Order on that Occafion (pPhil. 
Tranf. Numb. 348.) he might have been convinced 
as well as feveral Gentlemen of the French Royal 
2 Academy , 
