PHYSICAL ans LITERARY. 65, 
has advanced one ftep beyond them. ft 
is furprifing, that, before Sir Ifaac New- 
ton, the world continued fo long entirely 
ignorant of the true theory of light and 
colours ; 
- more diftant luminous object, fach as the window or the’ 
flame of 2 candle, may be feen by rays pafling near its’ 
edge : If another opaque body, nearer to the eye, be 
brought acrofs from the oppofite fide ; the edge of the’ 
firt body wil! feeny to fwell outwards and meet the lat- 
' ter, and, in doing fo, will intercept a portion of the lu- 
minous object that was feen betore. 
This phaenomenon has been rafhly afcribed to the in: 
Sexion of light, by fach as underftood not thoroughly the 
nature of inflexion, nor obferved accurately the circum. 
ftances of the fa@, 
Let AB reprefent the luminous objet (TAB, ili, Fins 
5.) to which the fight is directed, CD the more diftane 
opaque body, GH the nearer, and EF the diameter of 
the pupil; join ED, FD, EG, FG, and produce them till 
they mect AB in K, N, M, and L: It is plain, that the 
parts AN, MB of the luminous object cannot be feen, But, 
taking any point a between N and K, and drawing aDd; 
fince the portion dF of the pupil is filled with light flow. 
ing from that point, it muft be vifible: Any point 5 be- 
tween a and K mutt fil! fF a greater portion of the pupil, 
and therefore muft appear brighter. Again, any point ¢ 
between 4 and K mutt appear brighter than 4; becaufe it 
fills a greater portion gF with light. The point K itfelf, 
and every other poinc in the fpace KL, muf appear 
with 
