302 Dr. Herschel's Astronomical Observations 
“ and above 2' broad ; it is gradually a little brighter in the 
“ middle. Fig. 13. 
H. 549 is “ A very large and pretty bright nebula of an 
“ irregular figure ; it is a little brighter in the middle/' 
Fig. 14. 
II. 812 is “ A faint, small, round nebula ; it is very gradu. 
s< ally a little brighter in the middle, and the increase of 
brightness begins at a distance from the center/' Fig. 15. 
It is hardly necessary to say that the united testimony of 
so many objects can leave no doubt about the central seat of 
attraction, which in every instance of figure is pointed out to 
be in the middle. 
The only remark I have to make, relates to the exertion of 
the condensing power, which in the case of these nebulae ap- 
pears to have produced but a very moderate effect. This may 
be ascribed either to the unshapen mass of nebulous matter 
which would require much time before it could come to some 
central arrangement of form either in length, or in length and 
breadth, or lastly in all its three dimensions. It may also be 
ascribed to the small quantity of the preponderating central 
attractive matter ; or even to the shortness of its time of acting : 
for in this case millions of years, perhaps are but moments. 
20. Of Nebula which are gradually brighter in the middle . 
By the general description of a nebula, when it is said to be 
gradually brighter in the middle, we are to understand that its 
light was observed to be obviously brighter about the center 
than in other parts. Had the neb like of this class been only a 
little brighter, or had they been much brighter in the middle. 
