478 Dr. Herschel's Catalogue 
often more considered than their contents. But here, in dividing 
the different parts of which the sidereal heavens are composed 
into proper classes, I shall have to examine the nature of the 
various celestial objects that have been hitherto discovered, in 
order to arrange them in a manner most conformable to their 
construction. This will bring on some extensive considerations, 
which would be too long for the compass of a single paper; I 
shall therefore now only give an enumeration of the species 
that offer themselves already to our view, and leave a particular 
examination of the separate divisions, for some early future 
occasions. 
In proceeding from the most simple to the more complex 
arrangements, several methods, taken from the known laws of 
gravitation, will be suggested, by which the various systems 
under consideration may be maintained ; but here also we shall 
confine ourselves to a general review of the subject, as obser- 
vation must furnish us first with the necessary data, to establish 
the application of any one of these methods on a proper 
foundation. 
ENUMERATION OF THE PARTS THAT ENTER INTO THE CONSTRUC- 
TION OF THE HEAVENS. 
I. Of insulated Stars. 
In beginning our proposed enumeration, it might be expected 
that the solar system would stand foremost in the list ; whereas, 
by treating of insulated stars, we seem, as it w r ere, to overlook one 
. of the great component parts of the universe. It will, however, 
soon appear that this very system, magnificent as it is, can only 
rank as a single individual belonging to the species which we 
are going to consider* 
