relating to the Construction of the Heavens. 283 
No. 213 in the first class is “ A very brilliant and consider- 
' c ably large nebula, extended in a direction from south pre- 
■ ee ceding to north following. It seems to have three or four 
“ bright nuclei.” See fig. 5. 
From this construction of the nebula, we may draw some 
additional information concerning the point which was left 
undetermined in my last article ; for since there it was pro- 
posed as an alternative, that the nebulous matter might either 
be of a greater depth or more compressed in the brightest 
part of the nebula then under consideration, we have now an 
opportunity to examine the probability of each case. If here 
the appearance of several bright nuclei is to be explained by 
the depth of the nebulous matter, we must have recourse to 
three or four separate very slender and deep projections, all 
situated exactly in the line of sight ; but such a very uncom- 
mon arrangement of nebulous matter cannot pretend to pro- 
bability; whereas a moderate condensation, which may indeed 
be also accompanied with some little general swelling of the 
nebulous matter about the places which appear like nuclei, 
will satisfactorily account for their superior brightness. 
The same method of reasoning may be as successfully ap- 
plied to explain the number of unequally bright places in the 
diffused nebulosities which have been described in the 1st, 2d, 
and 3d articles. For instance, in the branching nebulosity 
V. 14, we find three or four places brighter than the rest — in 
the nebulosity No. 44 of the table we have places of different 
brightness. In the nebula of Orion, there are many parts 
that differ much in lustre ; and in V. 3 7 of the same article I 
found, by an observation in the year 1790, the same variety 
of appearance. In all these cases a proportional condensation 
O o 2 
