PHYSICAL anv LITERARY. .- 67 
équality of Bradley’s aberration of light 
in fixed ftars of all magnitudes *? If this 
be fo, the comparative ftrength of diffe. 
rent lights, fuch as of the fun, moon, a 
candle, dc. may be eafily eftimated by 
finding the greateft diftances to which the 
fame opaque body is vifible when illumi- 
nated by each of them, or the limits be- 
yond which it is invifible to a given eye; 
for the denfities of the incident lights are 
nearly as the fquares of the diftances of 
thefe limits from the object ¢. Does not 
all light move with the fame velocity af- 
ter reflexion as before ; fince the angle of 
reflexion is always equal ta the angle of . 
incidence? - 
* Eames's Abridg. of tranfa&, yol. 6. p. 158. 
~ $ Let A and a (Tas, iii, fig. 6.) denote the faine or two 
equal bodies of the fame colour illuminated with different - 
lights, and B, 4, the limits. As we fuppofe the light re- 
ceived by the eye, at thefe points, is juit fufficient to affe& 
it fenfibly and no more, the two lights at thele different 
diftances muft be nearly of the fame denfity; taking 
therefore in AB a line A g equal to wd, the denficy of the 
light as g mult be, to the denfity ot the light at 4, near- 
ly as AB? to Ad? : And, it is evident, that thefe denfi- 
fities, at equal diftances, muft be as the whole quantities 
of light reflected; and thefe again very nearly as the 
whole quanties of light incident. 
