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will include half the greater fphere, if its centre be 
affumed near the centre of the greater fphere, and a 
fphere of twelve times this radius will include half 
the greater fphere, if the point be affumed almofl in 
the furface of it. 
If we afiiime the flars belonging to our own fyflem 
to be about 1000 ; fince they are in all refpedts fimilar 
to the Sun (excepting perhaps fuch amongfl them as 
are liable to frequent changes), and we have nothing 
to determine us to one magnitude rather than another, 
we may mofl reafonably fuppofe the magnitude of the 
Sun to be a medium amongft the whole number.. 
Upon this fuppofition, he will probably rank only 
with the flars of the fourth magnitude; and his light 
therefore, if he was removed to the medium diftance 
of the other flars (viz. a diftance equal to the radius 
of the fphere, that would include half the flars of 
our own fyflem) would hardly, I think, exceed a 
200th part of the light of Sirius ; and confequently, 
if the parallax of Sirius would be about one fecond, 
if he was of the fame fizeand native brightnefs with 
the Sun, it will be an equal chance, that the parallax 
of one half of the flars, belonging to this fyflem, is 
not lefs than one fecond divided by the fquare root of 
200 , that is a little more than \ r " ; and it will like- 
wife be an equal chance, that the parallax of no one 
amongfl them exceeds between 9 and 12 times that 
quantity, or a little more than two thirds of a 
fecond. 
If, inflead of 1000 flars, we fuppofe the whole 
number, belonging to this fyflem, to be only about 
350, the Sun will then, if he is of a medium fize 
amongfl them, rank probably with the flars of the 
third 
