ILTo cover over both Ends of the Prifm with paper at fereral 
diftances from the middle ; or with moveable riDgSjto fee^how 
lhat will vary or divide the length of the figure^ icGfted upon 
ID the faid Theory. 
Ill* To move the Prifm fo , as the End may turn about the 
middle being fteady. 
I V.To move the prifm by (hoving 5t,tillfirft the one fidejthan 
the midle-j than the other fide pafs over the holcj obferving the 
fame Parallelifm. 
Tie Ohfsrvations^ made upon theft propofals. 
ISuppofe the dcfiga of the Propofer of thefe Experiments 
is, to have their events expreffed , with fuch obfervations 
as may occur coneeraing thera» f. Touching thc/r/?, I have 
obferv*d j that the Solar image falling on a paper placed at the 
focus of the Lens , was by the interpofed Pn(m drawn out in 
length proporcional to the Prifms reflexion or diftance from 
thsLt focus. And the chief obfervable here^ which I remem- 
ber, was, that the Streight edges of the oblong image were 
dittinfter than they would have been without the Lens. 
Confidering that the rays coming from the Planet l^enus are 
much lefs inclined one to another , than thofe ^ which come 
from theoppofite parts of the Suns difque, I once tryedan 
experiment or two with light. And to make it fufficient- 
ly ftrong, I found it neceflary to coUedit firft by a broad /ens^ 
and then interpofing a Prifm between the and its/ora/ ac 
fuch diftance, thatall the light might pafs through the Prifmj 
I found the focus, which before appeared like a lucid point, to 
be drawn out into a long fplendid line by the Prifms reflexion* 
1 have fometimes defigned to try^how a fixtiStar^feen throogh 
a long Telefcope, would appear by interpofing a Prifm be- 
tween the Telefcope and my eye* But by the appearance of 
Fenusy viewed with my naked eye through a Prifm^ I prelage 
the event. 
2. Concerning the/<?^W experiment,! have occafionaljy ob- 
ferved, that by covering both ends of the Prifm with Paper at 
feveral diftances from the midle^ the breadth of the Solar 
image will be increafed or diminiflied as much , as is the aper- 
ture 
