4 66 Sir W. Herschel’s astronomical observations 
generally contracted ; a globular cluster is reduced to a 
cometic appearance ; to an ill defined star surrounded by 
nebulosity, and to a mere small star with rather a larger 
diameter than stars of the same size generally have. In 
consequence of these considerations, it seems to be highly 
probable that some of the cometic, many of the planetary, 
and a considerable number of the stellar nebulae, are clusters 
of stars in disguise, on account of their being so deeply 
immersed in space, that none of the gaging powers of our 
telescopes have hitherto been able to reach them. The dis- 
tance of objects of the same appearances, but which are of a 
nebulous origin, on the contrary, must be so much less than 
that of the former, that their profundity in space may proba- 
bly not exceed the 900th order. 
VII. Of the extent of the power of our telescopes to reach into space, 
when they are directed to ambiguous celestial objects. 
The method of equalising the light of stars on which the 
gaging power of telescopes has been established, may also be 
applied to give us an estimate of the extent of their power 
to reach ambiguous celestial objects. 
When the united light of a cluster of stars is visible to the 
eye, there will then be a certain maximum of distance to 
which the same cluster might be removed so as still to 
remain visible in a telescope of a given space-penetrating 
power; and if the distance of this cluster can be ascertained 
by the gaging power of any instrument that will just show 
the stars of it, the order of the profundity at which the cluster 
could still be seen as an ambiguous object, may be ascertained 
