( 6*7 ) 
fiC fle&ion of all Sort9 of Rays ro the Eye, look 
“ white and bright. And every where between p 
c< and C, by reafon of the Tranlmiflion of many 
Ra^s of either Sort, look more pale, oblcure and 
“ dark. But at r, and in other Places between p 
“ and t, where all the more refrangible Rays are re- 
“ fl^ed to the Eye, and many of the lefs refrangi- 
“ gible are tranfmitted, the Excefs of the molt re- 
“ frangible in the reflected Light will tinge that Light 
“ with their Colour, which is violet and blue, this 
“ happens by taking the Line CprtB any where 
« between the Ends of the Priftn H G and E I. 
If this needs any farther Explanation, let us fup- 
pofe CAB the Se&ion of the Prifm in Fig. zo 
transferred to Fig. 21. at AC B. If R 0 be a red 
Ray inclined to a Perpendicular to A B in an Angle 
of more than 41 or 42 Degrees, it will at its Emer- 
son under the Surface ABbe turned into the Curve 
onmi , and fo go up again to the Eye at E ; but a- 
nothcr red Ray coming in the Diredion r^makino- 
an Angle with the Perpendicular fufficiently lefs, vviU 
after its Emerfion at be only bent fo much as 
to be turned out of the Way, and refra&ed to y, in 
an Angle of Rcfra&ion agreeable to the Refrangibi- 
lity of red Light. But V m a violet Ray with the 
fame Inclination as the lad red one r n fhall not be 
refraded, but turned up in the Curve m i P, and fo 
go to the Eye at E. Another violet Ray \m making 
an Angle fomething lefs with the Perpendicular, will 
pals through the Glafs, and be refra&ed in the Line 
m S. Upon this Account all that Part of the Bafe 
of the Prifm ( of which A B is the Se&ion ) between 
A and p will be dark or faint, all that Part between P 
rs ^ ^ t 
