( <$lp ) 
(wot exactly in the fame Line, but) in a Line 
parallel to the Direction of the incident Ray: For 
Example, let the Ray R a ( not refracted at, becaule 
perpendicular to, the Surface C B ) emerge from the 
firft Prifm at a> in the Diredion a r ; its changed 
Direction at a will become a a, and at b> b b, or "ra- 
ther the Ray will be indexed in the Curve ab\ and 
at b getting out of the Power of the Attraction of the 
Surface A B, it will ( for the Reafons before given ) 
move in a ftraightLine from b to c , where it will be 
bent again the contrary Way in the Curve c d of the 
lame kind as a b, and laflly emerge in the Direction dd 
parallel to the firft Diredion R r. From hence it fol- 
lows, that when thePrifmsare brought fo near as to 
touch, their mutual Attractions deftroying each other, 
the Rays of Light will not be bent, but pafs through 
the two Prifms ( which in this Cafe perform the Of- 
fice of a Parallelopiped ) in the fame Direction with 
which they came into the firft Prifm, and confe- 
quently produce no Colours ; contrary to what is 
affirmed by Rizzetti ( Rage 78, 79, & c .) and 
when the Rays R a fall obliquely upon the Surface 
CB, the EfFed of their Refradion at their Immer- 
fion at S to produce Colours, is taken off by the 
Refradion which they fuffer at their Emerfion 
at z. 
Experiment VIL 
I took the Cube of Fig. 8, and looking oblique- 
ly through it at the Hole of the Window of my dark 
Chamber ( the Suu lhining or not Aiming) the Hole 
appeared entirely colourlefs, as did alib a Candle, 
Nnnn x both 
