C 258 ] 
to i; for removing Sirius to 57 times his prefent 
didance, his light would then be fainter than it is, 
in the proportion of 3249 to 1, that is, fainter than q 
of the Pleiades in the proportion of 32.49 to 1, fup- 
pofing v} of the Pleiades, as above, to afford us a 
hundredth part of the light of Sirius ; but the mag- 
nitude of liars, fuppofing them equally luminous and 
their didance to be given, is as the cube of the fquare 
root of their brightnefs; and therefore v\ of the Plei- 
ades, upon this fuppofition, mud be bigger than Sirius 
in the proportion of the cube of the fquare root of 
32. 49 (that is 185) to 1. 
But I mud obferve, that according to general (and, 
I believe, 1 may fay univerfal) analogy in all thofe 
nebulae, in which we difcover dars bigger than the 
red, thefe dars are placed towards the middle of 
their refpeCtive fydems, and, if therefore the fame 
thing obtains with regard to our own fydem, 
this will make >7 of the Pleiades dill fomething 
greater. 
If the didance of the Pleiades is greater than the 
mean didance of the dars of our own fydem, in the 
proportion of 57 to 1, it would be neceffary, in order 
to make dars, of the fame real magnitude amongd 
the Pleiades, equally vidble to us with thofe of our 
own fydem, to take in a pencil of rays of a greater 
diameter, than the pupil of the eye, in the fame pro- 
portion : this, after proper deductions for the lofs of 
light, could not well be effected by an objedt lens of 
lefs than two feet aperture. Now Dr. Hooke tells 
ns, in his Micrographia, that, with a telefcope of 
twelve feet length, he difeovered in the Pleiades 78 
