314 Dr. Herschei/s Astronomical Observations 
Number 97 of the Connoissance is “ A very bright, round 
sc nebula of about 3' in diameter ; it is nearly of equal light 
“ throughout, with an ill defined margin of no great extent.” 
IV. 13 is “ A pretty faint nebula of about T diameter ; it is 
4 ‘ perfectly round, and of an equal light throughout ; and the 
S( edges of it are pretty well defined.” Fig. 33. 
Admitting that these sixteen nebulae are globular collections 
of nebulous matter, they could not appear equally bright, if 
the nebulosity of which they are composed consisted only of 
a luminous substance perfectly penetrable to light; at least 
this could not happen unless a certain artificial condensation 
of it were introduced, which can have no pretension to pro- 
bability in its favour. Is it not rather to be supposed, that a 
certain high degree of condensation has already brought on a 
sufficient consolidation to prevent the penetration of light, 
which by this means is reduced to a superficial planetary 
appearance ? 
19. Of Nebula that draw progressively towards a Period offnal 
Condensation. 
In the course of the gradual condensation of the nebulous 
matter, it may be expected that a time must come when it can 
no longer he compressed, and the only cause which we may 
suppose to put an end to the compression is, when the con- 
solidated matter assumes hardness. It remains therefore to 
be examined, how far my observations will go to ascertain the 
intensity of its consolidation. 
The following two assortments contain seven nebulae, from 
I 
