ASTRONOMY. 
(Jars, fie perceive9 a few clutters of them in various parts 
of the heavens, and finds alio that there are a kind of ne¬ 
bulous patches: but llill-lvis views are not extended to 
reach lb far as to the end of the dratum in which he is li- 
tuated ; fo that he looks upon thefe patches as belonging 
to that fyftem which to hint feerns to comprehend every 
celeftial objeift. He now encreafes his power-of vifion ; 
and, applying himfelf to a clofer obfervation, finds that 
the milky-way is indeed no other titan a cotlettion of very 
fmal 1 liars. He perceives, that thofe objects which had 
been called nebula •, are evidently nothing but cluiters of 
liars. Their number increafes upon him; and when he 
refolves one nebula into liars, he difcovers ten new ones 
which he cannot refolve. He thdn forms the idea of im- 
ttienfe (hata of fixed liars, of chillers of liars, and of ne- 
bulae ; till, going on with fuch interelling obfervations, he 
now perceives, that all tiiele appearances mud naturally 
nrile from the confined fituation in which we are placed. 
Confined it may juftly be called, though in no lefs a fpace 
than what appeared before to be the whole region of the 
fixed liars, but which now has afiumed the lhape of a 
crookedly-branching nebula; not indeed one of the lead, 
-but perhaps very far from being the mod conliderable, of 
thole numberlefs chillers that enter into the conduction of 
the heavens. 
“ To thefe arguments vve may add the following con- 
fiderations drawn from analogy. Among the great num¬ 
ber of nebulae which 1 have feen, there are many which 
in all probability are equally extenfive with that which we 
inhabit; and yet they are all feparated from each other hy 
very conliderable intervals. Some, indeed, there are, that 
feem to bq double and treble ; and, though with mod of 
thefe it may be that they are at a very great didance from 
each other, yet we allow that fome conjunctions really are 
to be found ; but then thefe compound or double nebulas, 
which are thofe of the third and fourth forms, dill make 
a detached link in the great chain. It is alfo to be lup- 
pofed, that there may be fome thinly-fcattered folitarv 
liars between the large interdices of nebulas; which being 
fituated fo as to be nearly equally attracted by the feveral 
chillers when they were forming, remain unalfbciated : 
and, though we cannot expect to fee thofe dars on ac¬ 
count of their vad didance, yet we may well prefume that 
their number cannot be very conliderable in comparifon 
to thofe that are already drawn into lydems; which con¬ 
jecture is alfo abundantly confirmed in fituations where 
the nebulae are near enough to have their dars vifible ; 
for they are all infulated, and generally to be feen upon a 
very clear and pure ground, without any dar near that 
might be thought to belong to them. And, though I have 
©ften feen them in beds of liars, yet from the fize of thefe 
latter we may be certain, that they were much nearer to 
us than thofe nebulae, and belonged undoubtedly to our 
own fyllem.” 
Having thus determined that the vifible fydem of na¬ 
ture, by us called the univerfe, confiding of all the celedial 
bodies, and many more than can be feen by the naked eye, 
is only a group of dars or funs with their planets, condi- 
tuting one of thofe patches called a nebula , and perhaps 
not a ten-thoufandtli part of what is really the univerfe, 
Dr. Herfchel goes on to delineate the figure of tttis vad 
nebula, which lie is of opinion may now be done; and for 
this purpofe he gives a table, calculating the didance of 
the liars which form its extreme boundaries, or the length 
of the vifual ray in different parts, by the number of dars 
contained in the field of his telefcope at different times. 
He then proceeds to offer fome farther thoughts on the 
origin of tiie nebulous drata of the heavens ; in doing 
which he gives fome hints concerning the antiquity of 
them. “ If it were poflible, fays he, to didingb'ifh be¬ 
tween the parts of an indefinitely extended whole, the ne¬ 
bula we inhabit might be faid to be one that has fewer 
marks of antiquity than any of the red. To explain this 
idea perhaps more clearly, we fhould reeolledl, that the 
condenfation of cinders of dars has been aferibed to a gra- 
i 
dual approach; and whoever refle&s on the number of 
ages that mud have palled before fome of the cluders that 
are to be found in fny catalogue of them could be fo far 
condenled as vve find them at prefect, will not wonder if 
I alcribe a certain air of youth and vigour to many very 
regularly feattered regions of our fidereal dratum. There 
are, moreover, many places in it in which, if we may 
judge from appearances, there is the greated reafon to 
believe that the dars are drawing towards fecondary cen¬ 
tres, and will in time feparate into cinders, fo as to occa- 
fion many fubdivifions. Hence we may furmife, that, when 
a nebulous dratum confids chiefly of nebulx of the fird 
and fecond forms, it probably owes its origin to what may 
be called the decay of a great compound nebula of the 
third form; and that the fubdivifions which happened to 
it in length of time, occafioned all the (mall nebulx which 
fprung from it to lie in a certain range, according as they 
were detached from the primary one. In like manner 
our fydem, after numbers of ages, may very poflibly be¬ 
come divided, 1b as to give rile to a dratum of two or 
three hundred nebulas ; for it would not be difficult to 
point out fo many beginning or gathering cinders in it. 
This throws a conliderable light upon that remarkable 
coileclion of many hundreds of nebulx which are to be 
feen in what I have called the nebulous dratum in Coma 
Berenices. It appears from the extended and branching 
figure of our nebula, that there is room for the decom- 
poled fmall nebulas of a large reduced former great one 
to approach nearer to ns in the Tides than in any other 
‘parts. Nay, poflibly there might originally be another 
very large joining branch, which in time became fepara¬ 
ted by the condenlation of the liars : and this may be the 
reafon of the little remaining breadth of our fydem in that 
very place; for the nebulx of the dratum of the Coma 
are blighted and mod crowded jud oppolite to our fitua¬ 
tion, or in the pole of our fydem. As foon as this idea 
was fuggeded, I tried alfo the oppolite pole; where ac¬ 
cordingly I have met with a great number of nebulx, 
though under a much more feattered form. 
“ Some parts of our fydem indeed feem already to havs 
fudained greater ravages of time than others ; for indance, 
in the body of'the Scorpion is an opening or hole, which 
is probably owing to this caufe. It is at lead four degrees 
broad ; but its height I have not ascertained. It is re¬ 
markable, that the eighty Nebuleufe fans Etoiles of the Con- 
noijfance des Temps , which is one of the riched and mod 
compreffed cinders of fmall liars I remember to have feen, 
is fituated jud on the wed border of it, and would almoll 
authorife a fufpicion that the dars of which it is compo- 
fed were collected from that place, and had left the va¬ 
cancy. What adds not a little to this furmife is, that the 
fame phenomenon is once more repeated with the fourth 
duller of the Connoiffdnce des Temps ; which is alfo on the 
vvedern border of another vacancy, and lias moreover a 
fmall miniature cluder, or eafily refolvable nebula, of a- 
bout two minutes and half diameter north, following it at 
no very great dillance. 
“ There is a remarkable purity or clearnefs in the hea¬ 
vens when we look out of our dratum at the Tides ; that 
is, towards Leo, Virgo, and Coma Berenices, on one hand, 
and towards Cetus on the other ; whereas the ground of 
the heavens becomes troubled as we approach towards the 
length or height of it. Thefe troubled appearances are 
eafily to be explained by aferibing them to fome of the 
didant draggling dars that yield hardly light enough to be 
diftinguidied. And I have indeed often experienced this 
to be caufe, by examining thefe troubled (pots for a long 
while together, when at lad 1 generally perceived the dars 
which occafioned them. But when we look towards the 
poles of our fydem, where the vifual ray does not graze 
along the fide, the draggling dars will of courfe be very 
few in number; and therefore the ground of the heavens 
will affume that purity which I have always obferved to 
take place in thofe regions.” 
Though, in the above extrafts from Dr. Herfchel’s pa¬ 
pers, 
