( 4 \9 ) 
en a white Sheet of Paper ; where it was obferveable, 
that when the red Half was diftin&ly painted on the 
white Paper (which was known by the Edges of the Image 
being regularly terminated) then the blue Half of the Image 
was confus’d : but if the white Paper was brought about 
two Inches nearer to the Lens, the Image of the blue Half 
became diftinct, and that of the red Half confus’d. 
I try’d the Experiment with a Paper colour’d half red 
and half blue, the red with Carmine and the blew with 
Smalt, making the Candle to enlighten the Paper ( the 
Room being other wife dark) and the Experiment fucceed- 
ed in the fame manner. The Experiment thus made is 
the fame that Sir Ifaac Newton gives an Account of. Book 
i* Part, i . Jheor. I. of his Optics. Only it is to be obferv’d 
that when the oblong Paper is coloured with red and blue 
from the Prifms, the focal place, where the red part of 
the Image is diftinct, is more diflant from the place where 
the blue part of the Tmage is diftinct, than when the Pa- 
per is colour’d with the Painter’s Powders, and much more 
vivid. 
The yth Figure (hews the Projection of the Paper 
ting’d with the Rays,* and Fig.S. the Projection of it when 
painted : where a black Thread is wrapp’d round the red - 
and the blue part, that the Diflinctnefs of the Image of 
the Thread may fhew when the red or when the blue 
part of the Image of the Paper is moll diftinct. 
N.B. When the Candle enlightens the painted Paper, 
fet an opaque Body as B between the Candle and Lens 
left the Image of the Candle being alfo projected fhould ■ 
difturb the Experiment. 
EXPERIMENT IV. 
Having made an Hole of^ Inch Diameter in the Win- 
dQW-ShutQf thedarkned Room, I fuffer’d a Sun-Beam to 
come 
