( ) 
Academy, who had feen Monfieur Marriotte make his 
Experiment?, and acknowledged themfelves fatisfied 
when they faw me repeat thofe of Sir Ifaac in the 
Year 1715'. 
“ That in the firft Experiment of Sir Ifaac (Book I. 
<c Part II.) He never could deftroy any one Colour, the 
“ reft remaining; and that. with a larger Obftacle 
“ he could deftroy the yellow and blue, but not the 
“ yellow c m<S. green — could bring the green, not the 
<c yellow , to be next to the Shadow and could leave 
<c the green only remaining, but not theyellow.” This 
is an.eafie Experiment ^ but Inaccuracy and a very bad 
Prifm, and Prejudice towards an Hypothecs, or againft 
an Adverfary, may miflead a Man ftrangeiy. 
<c That when the Colours produced by the Prifm, 
and afterwards united by the Lens, produce white 
“ upon a Paper in the Focus, no Inclination of the 
“ Paper will tinge the white Spot with Colours”. 
“ That a yellow Paper in the blue Light appears 
“ green , as does alfo a blue Paper in the yellow 
“ Light.”- But not when the Room is well darken’d, 
and the Light homogeneal. 
rt That Sir Ifaac Newton afferts falfly, that Light 
« immerging into a Parallelipiped, and then emerging 
« out of it, produces no Colours.” 
“ That the 6th Experiment of Part I. Book I. of 
“ Sir Ifaac is true 5, but no different Refrangibiiity of 
u Rays is prov’d by it, though the Colours coming 
“ fucceffivety from the firft Prifm to the fecond with 
the fame Incidence, are carried to different Heights 
“ by the laft Prifm.” Now the Confequence is fo 
plain here, that this is, after my Lord Bacon's Man- 
ner, called an Exferimentum Crucis. 
I fhould 
