PHYSICAL anp LITERARY. 59 
place in the time of emerfion, by a contra- 
ry fuccéflion of colours, beginning with red 
and ending in white. 
50. I this phenomenon flint be agu- 
ally perceived by aftronomers, we {hall 
have a fufficient direct proof of the ditte- 
rent velocities of the coloured rays; for I 
fee not to what other caufe the phaenome- 
non could be rationally afcribed: If it be 
not, we may conclude that the rays of all 
colours are emitted and reflected with one 
common velocity. 
Pome eek be Eke 
On the Imperfection of our Knowledge‘ concern= 
ing the Inflexions of Light, . 
51. Str Ifaac Newton went a very confi- 
derable length in examining the inflex- 
ions of light, as well as its reflexions and 
refractions; but did not bring his inquiry 
on this head toaconclufion, He tells us, 
that he intended once, if other bufinefs 
had not called him off, to have made more 
expe- 
