Conjlrudiion of the Heavens. 255 
faid to be one that has fewer marks of profound antiquity upon 
it than the reft. To explain this idea perhaps more clearly, we 
fhould recoiled that the condenfation of clufters of ftars has 
been afcribed to a gradual approach; and whoever refleds on 
the numbers of ages that muft have paft before fome of the 
clufters, that will be found in my intended catalogue of them, 
could be fo far condenfed as we find them at prefent, will not 
wonder if I afcribe a certain air of youth and vigour to many 
very regularly fcattered regions of our fidereal ftratum. There 
are moreover many places in it where there is the greateft 
reafon to believe that the ftars, if we may judge from ap- 
pearances, are now drawing towards various fecondary centers, 
and will in time feparate into different clufters, fo as to occa- 
fion many fub-divifions. Hence we may furmife that when a 
nebulous ftratum confifts chiefly of nebulae of the flrft and le- 
cond form, it probably owes its origin to what may be called 
the decay of a great compound nebula of the third form ; and 
that the fub-diviflons, which happened to it in length of time 
occafloned all the fmall nebulae which fprung from it to lie in a 
certain range, according as they were detached from the pri- 
mary one. In like manner our fyftem, after numbers of ao-es ? 
may very poffibly become divided 10 as to give rife to a ftratum 
of two or three hundred nebulas ; for it would not be difficult 
to point out fo many beginning or gathering clufters in it (/). 
This view oft the prefent fubjedt throws a conflderable flight 
upon the appearance of that remarkable colleftion of many 
(/) Mr. Mx c hell has alfo confidered the ftars as gathered together into 
groups (Phil. Tranf. vol. LVII, p. 249,); which idea agrees with the fub-divifion 
of our great fyftem here pointed out. He founds an elegant proof of this on 
the computation of probabilities, and mentions the Pleiades,, the Praftepe Cancri, 
and the nebula (or clufter of ftars) in the hilt of .PerWs fword, as initances. 
hundreds 
