[ 2 3 8 ] 
only. In other inffinces we may perhaps judge in 
ibme degree of the native brightnefs of different 
liars with refpedl to one another by their colour; 
thofe, which afford the whited light, being probably 
the mod luminous a . 
3 We have at prefent no means of judging of the comparative 
brightnefs of the Sun and of the fixed ftars, in proportion to their 
refpedtive fizes, excepting from the comparifon of the Sun’s bright- 
nefs with that of our common fires; but the Sun’s light exceeds the 
light of our brightefl fires in fo very great a proportion, (viz. of fome 
thoufands to one) that we want ibme middle terms to be able to 
form any analogy, which might ferve to carry us farther. We 
find however in genera!, that thofe fires, which produce the 
whiteft light, are much the brighteft, and that the Sun, which 
produces a whiter light than any fires we commonly make, vaftly 
exceeds them all in brightnefs ; it is not therefore improbable, 
from this general analogy, that thofe ftars, which exceed the Sun 
in the whitenefs of their light, may alfo exceed him in their native 
brightnefs; now this is the cafe with regard to many of them; 
and, on the contrary, there are fome that are of a redder colour. 
If however it fhould hereafter be found, that any of the ftais 
have others revolving about them (for no fatellites fhining by a 
borrowed light could poflibly be vifibie), we fhould then hare the 
means of difeotering the proportion between the light of the 
Sun, and the light of thofe ftars, relatively to their refpedtive 
quantities of matter; for in this cafe, the times of the revolutions, 
and the greateft apparent elongations of thofe ftars, that revolved 
about the others as fatellites, being known, the relation between 
the apparent diameters and the denfities of the central ftars 
would be given, whatever was their diftance from us : and the 
adhial quantity of matter which they contained would be known, 
whenever their diftance was known, being greater or lefs in the 
proportion of the cube of that diftance. Hence, fuppofing them 
to be of the fame denfity with the Sun, the proportion of the 
brightnefs of their furfaccs, compared with that of the Sun, 
would be known from the comparifon of the whole of the light 
which we receive from them, with that which we receive from 
the Sun ; but, if they fhould happen to be either of greater or 
lefs denfity than the Sun, the whole of their light not being 
