2i 6 Dr. Hersc help's Catalogue of a fecond Thoufand' 
Taking it then for granted that the ftars which appear to he 
gathered together in a group are in reality thus accumulated, 
I proceed to prove alfo that they are nearly of an equal mag- 
nit udev 
The clufter itfelf, on account of the fmall angle it fubtend3 
to the eye, we muft fuppofe to be very far removed from us» 
For, were the ftars which compofe it at the fame diftance from 
one another as Sirius is from the fun ; and fuppofng the clutter 
to be feen under an angle of io minutes, and to contain 50 
ftars in one of its diameters, we fhould have the mean diftance 
of fuch ftars twelve feconds ; and therefore the diftance of 
the clufter from us about feventeen thoufand times greater than 
the diftance of Sirius. Now, fince the apparent magnitude of 
thefe ftars is equal, and their diftance from us is alfo equal, — 
becaufe we may fafely negledt the diameter of the clufter, 
which, if the center be feventeen thoufand times the diftance 
of Sirius from us,, will give us feventeen thoufand and twenty- 
five for the fartheft* and feventeen thoufand wanting twenty-five 
for the neareft ftar of the clufter; — it follows that we muft 
either give up the idea of a clufter, and recur to the above 
refuted fuppofition, or admit the equality of the ftars that 
compofe thefe clufters. It is to be remarked that we do not 
mean intirely to exclude all variety of fize ; for the very great 
diftance, and the confequent fmallnefs of the component 
cluftering ftars, will* not permit us to be extremely precife in 
the eftimation of their magnitudes ; though we have certainly 
feen enough, of them to know that they are contained within 
pretty narrow limits ; and do not, perhaps, exceed each other 
in magnitude more than in fome fuch proportion as one full- 
grown plant of a certain fpecies may exceed another full-grown 
plant of the fame fpecies, 
, . ‘ If; 
1 
