( *» 4 .) 
brought up to the Eye at E, which confequently muft 
fee a round Part of the Paper at k y juft as big as the 
Place of Contact, which appears like an Hole $ or as if 
the two Priftns being changed to a Parallelopiped, were 
covered with a dark Paper that had only afmallHole 
in it. 
But to make this more evident, efpecially to fuch as 
are not well acquainted with Sir Ifaac Newton's Op* 
ticks, 1 beg Leave to explain the Manner of the bend* 
ing of the Rays where they are refraded or refleded. 
Of the Bending of the Rays in their Refratfion. 
Let DD (Fig iz) reprefent a denfe Medium (as 
Glafs) whole Surface is GG, and A A a rare 
Medium (as Air). Now let us fuppofe a Power to extend 
all over the Surface G G, ading from A A towards 
D D in Lines perpendicular to the Surface G G, 
very ftrong in Contad, but infenhble at a very 
fmall Diftance from the faid Surface, which we will 
call th z Attraction of the Surface G G, without confi- 
dering whether it be any real Virtue in the faid Surface, 
or the Adion of a Medium impelling towards it. Let 
Lines n, u, 3 3, fuch as exprefsthe Lines in which the 
Attradion exerts it felf, and the LineM M (extremely 
near to G G) the Limits of the Attradion, beyond which 
it cannot affed a Ray of Light. Let the Ray of Light 
R a moving from a rare Medium into a Denfe in the 
Diredion R r, come towards the Surface G G in fuch 
an Angle that it may be refraded. When the Ray 
comes to a , by the Attradion at a it will be aded upon 
* in 
0 
