1803. ] 
that three ftars may be preferved in a per- 
manent connection, by revolving in pro- 
per orbits about a common center of mo- 
tion. Having demonftrated the. faa, he 
fays, ** If we admit of triple flars, we 
can have no reafon to cppofe more com- 
plicated conneétions.”” And to form an 
idea how the laws of gravitation may ealily 
fupport fuch fyftems, he adjoins fome 
figures, with proper defcriptions. 
Inanfwering the objection which may be 
made, that pofiibly ai] this fort of reafon- 
ing may be ufélefs and fanciful, he fays, 
*¢ Such combinations as I have mentioned 
are not the inventions of fancy: they have 
an aétual exiftence, and J could point 
them out by thoufands. ‘There is not a 
fingle night when, in pafling aver the 
zones of the heavens, by {weeping, I 
do not meet with numerous collections of 
double, triple, quadruple, quintuple, and 
multiple ftars, apparently infulated from 
other groups, and probably joined in fome 
fmail fidereal fyftem of their own. 
In treating—IV. Of cLUSTERING 
STARS, and the MILKY-WAY, Dr. Her- 
fchel fays, that the flars of which the 
milky-way 1s compofed, are very unequal- 
ly {cattered, and fhew evident marks of 
cluftering together into many feparate al- 
lotments. Thus in the fpace bétween 8 
and y Cygni, the ftars are feen cluftering 
together towards two different regions ; 
and, taking the average breadth in this 
{pace of about five degrees, it contains 
more than 331,000 ftars, and, admitting 
them to be cluttering two different ways, 
there will be 165,000 for each cluftering 
collection; this name the milky appear- 
ances certainly deferve, as they are brighter 
about the middle, and fainter near their 
undefined borders; and that the brightnefs 
of the milky-way arifes only from ttars, is 
evident, fince their compreffion increales 
in proportion to the brightnefs of the 
milky-way. 
From cluftering-ftars there is but a 
fhort tranfition to Groups of sTaRs, 
which is Dr. Herchel’s Vth divilion.s A 
group 1s a collection of clofely, and almoft 
eyaally, compreffed ftars, of any ficure or 
outline, fufficiently feparated from neigh- 
bouring ftars to thew that it makes a pe- 
culiar fyftem of its own. 
VI. Of cLusTerRs of sTaRs, which 
are the moit magnificent objeéts to be feen 
in the heavens :—their form is generally 
round, aod the compreffion of the ftars 
fhews a gradual, and pretty fidden accu- 
‘mulation towards a center, the exiltence 
Proceedings of Learned Socteties, 
359 
of which cannot be doubted, either in a 
ftate of real folidity, or in that of an 
empty fpace, poffefled of an hypothetical 
force, arifing from the joint exertion of 
-the numerous ftars that enter into the com- 
pofition of the clufter. 
NéeuLa@, the VIIth divifion, which, 
on account of their great diltance, can 
only be feen by inftruments of great {pace- 
penetrating power. Thefe Dr. Her{chel 
thinks may beall refolved intothe three laft | 
mentioned fpecies, which at certain im- 
menfe diftances will put on the appearance 
of nebula. Nebulze are objects that may 
be perceived at the greateft diftance, but 
only with a telefcope of great power, 
which, fays the aftronomer, has not only 
a power of penetrating into {pace, but a 
power alfo of penetrating into time paft. 
‘To explain this, we are reminded, that, 
when we look upon Sirius, the rays that 
enter the eye cannot have been lefs than 
fix years and four months and a half com- 
ing from that ftar to the obferver.— 
‘¢ Hence it follows, that when we fee an 
objeét of the calculated diftance at which 
one of thefe remote nebule may be per- 
ceived, the rays of light which convey its 
image to the eye, muft have been more 
than xineteen hundred and ten thoufand 
years on their way; and that confequently 
fo many years ago this object mutt al- 
ready have had an exiftence in the fidereal 
heavens, in order to fend out thofe rays 
by which we now perceive it. 
VIII. Of srars wiTH BURS. Thelfe 
may be a real clufter of ftars, the whole 
light of which is gathered fo nearly into 
one point, as to leave but juft enough of 
the light of the clufter vifible to produce 
the appearance of burs. 
IX..The phenomenon of MILKY ffr- 
BULOSITY is probably of two kinds, one 
of them deceptive, namely, fuch as arifes 
from widely extended regions of clofely 
connected cluftering ftars, contiguous to 
each other, like the colleétions that con- 
ftruct our milky-way. The other, being 
real, and poffibly at no very great dif- 
tance from us; but of its nature Dr. 
Herfchel does not prefume to fpeak. 
X. The nature of NEBULGUS STARS is 
enveloped in much obicurity, and will pro- 
bably, according to our aftronomer, re- 
quire ages of obfervations before we can 
form a proper eftimate of their condition. 
There is,no doubt of the ftarry nature, of 
the central point; but the great diltance 
of fuch ftars renders the real extent of 
the furrounding nebulofity a furprizing 
‘s phencmenon 
