for ascertaining the distances of clusters of stars, &c. 467 
by the space-penetrating power of the telescope through 
which it is observed. But as the aggregate brightness of the 
stars depends entirely on their number and arrangement, this 
method can only be used with clusters of stars that have been 
actually observed. 
The 35th of the connoissance, for instance, being visible to 
the eye as a small cloudiness, its profundity in space was, by 
an observation of the 7 feet telescope, shown probably not to 
exceed the 144th order ; then, as the stars that enter into the 
composition of this cluster are of such an arrangement that 
their united lustre may be seen by the eye at the distance of 
the 144th order, the 10 feet telescope, by which this cluster 
was viewed, having a power of penetrating into space 28.67 
times that of the eye, would be able to show this cluster as a 
small cloudiness, if it were removed to the distance of the 
4128th order. The 20 feet Newtonian telescope, in which it 
was also observed, having a space-penetrating power 61.16 
times that of the eye, would still be sufficient to discover it as 
an ambiguous object, if it were removed to the distance of 
the 8809th order. 
To investigate how far the 15th cluster, which is also 
visible to the eye, might be removed, so as still to be seen in 
the front view of the 20 feet telescope, we find, by inspecting 
the table in which the profundities are given, that the eye 
can reach it at the distance of the 243d order ; therefore this 
telescope, with a power 75.08 times that of the eye, would 
still be able to show it at the distance of the 18244th order, 
and being a globular cluster, its appearance would be that of 
a small star with rather a large diameter 
SF 
MDCCCXVIII. 
