on the local arrangement of the celestial bodies in space. 309 
by which the degree of light of any given star may be ascer- 
tained, its distance will become a subject of calculation. But 
in order to draw valid consequences from experiments made 
upon the brightness of different stars, we shall be obliged to 
admit, that one with another the stars are of a certain physi- 
cal generic size and brightness, still allowing that all such 
deviations may exist, as generally take place among the indi- 
viduals belonging to the same species. 
There may be some difference in the intrinsic brightness 
of starlight : that of highly coloured stars may differ from 
the light of the bluish white ones ; but in remarkable cases 
allowances may be made. 
With regard to size, or diameter, we are perhaps more 
liable to error ; but the extensive catalogue which has already 
been consulted, contains not less than 14,144 stars of the 
seven magnitudes that have been adverted to ; it may there- 
fore be presumed that any star promiscuously chosen for an 
experiment, out of such a number, is not likely to differ much 
from a certain mean size of them all. 
At all events it will be certain that those stars the light of 
which we can experimentally prove to be , 
and ~ of the light of any certain star of the 1st magnitude, 
must be 2, 3, 4, 5, 6 , and 7 times as far from us as the standard 
star, provided the condition of the stars should come up to 
the supposed mean state of diameter and lustre of the stand- 
ard star, and of this, when many equalisations are made, 
there is at least a great probability in favour. 
V. Of the equalisation of starlight. 
In my sweeps of the heavens, the idea of ascertaining the 
