ASTRONOMY. 
of the former, I have often feen double and treble nebu¬ 
la: varioufly arranged; large ones with fmall feeming at¬ 
tendants; narrow, but much extended lucid nebulae or 
bright dallies; fome of the fliape of a fan, refembling an 
elettric brufli i(Filing' from a lucid point; others of the co- 
metic fliape, with a feeming nucleus in the centre, or like 
cloudy liars, furrounded with a nebulous atmofphere: a 
different fort again contain a nebulofity of the milky kind, 
like that wonderful inexplicable phenomenon about 0 Ori- 
onis; while others fhine with a fainter mottled kind of 
light, which denotes their being refolvable into (tars. 
“ It is very probable that the great ftratum called the 
milky-way is that in which the fun is placed, though per¬ 
haps not in the very centre of its thicknefs. We gather 
this from the appearance of the galaxy, which feems to 
encompafs the whole heavens, as it certainly mud do if 
the fun is within the fame. For fuppofe a number of (tars 
arranged between two parallel planes, indefinitely extend¬ 
ed every way, but at a given conliderable diflance from 
one another, and calling this a fidereal ftratum, an eye 
placed fomewhere within it will fee all the ftars in the di¬ 
rection of the planes of the ftratum projected into a great 
circle, which will appear lucid on account of the accumu¬ 
lation of the ftars, while the reft of the heavens at the (ides 
will only feem to be fcattered over with conftellations, 
more or lefs crowded according to the diftance of the planes 
or number of ftars contained in the thicknefs or tides of 
the ftratum. 
“ Thus, in the annexed figure, an eye at S within the 
ftratum ab, will fee the ftars in the direction of its length 
a b, or height ed, with all thofe in the intermediate fitu- 
ation, projected into the lucid circle ABCD; while thofe 
in the fides me, nw, will be feen fcattered over the re¬ 
maining part of the heavens at MVNW. If the eye were 
placed fomewhere without the ftratum, at no very great 
diftance, the appearance of the ftars within it would aflume 
the form of one of the lcffcr circles of the fphere, which 
would be more or lefs contracted to the diftance of the 
eye; and, if tills diflance were exceedingly increafed, the 
whole ftratum might at laft be drawn together into a lucid 
fpot of any fliape, according to the petition, length, and 
height, of the ftratum. Let us now fuppofe, that a branch 
or (mailer ftratum ftiould run out from the former in a cer¬ 
tain direction, and let it alfo be contained between two pa¬ 
rallel planes extended indefinitely onwards, but fo that the 
eye may be placed in the great ftratum fomewhere before 
VoL. II. No. 75. 
the feparation, and not far ft‘om the place where the ftrata 
are (till united ; then will this fecond ftratum not be pro¬ 
jected into a bright circle like the former, but will be feen 
as a lucid branch proceeding from the firft, and returning 
to it again at a certain diftance lefs than a femicircle. Thus, 
in the fame figure, the ftars in the fmall ftratum pg, will 
be projected into a bright arch at PR, which, after its fe¬ 
paration from the circle CBD, unites with it again at P. 
“ What has been inftanced in parallel planes may eafily 
be applied to ftrata irregularly bounded, and running in 
various directions; for their projection will of confequerice 
vary according to the quantities of the variations in the 
ftrata, and the diftance of the eye from the fame. . And 
thus tiny kind of curvatures, as well as various degrees of 
brightnefs, may be produced in the projections. 
“ From appearances, then, as I obferved before, w'e may 
infer, that the Sun is molt likely placed in one of the great 
ftrata of the fixed ftars, and very probably not far from 
the place where fome fmaller ftratum branches out from 
it. Such a fuppofition will fatisfactorily, and with great 
fimplicity, account for all the phenomena of the milky- 
way ; which, according to this hypothefis, is no other than 
the appearance of the projection of the ftars contained in 
this ftratum and its fecondary branch. As a farther in¬ 
ducement to look on the galaxy in this point of view, let 
it be confldered, that we can no longer doubt of its whi- 
tifti appearance arifing from the mixed luftre of the num- 
berlefs ftars that cempofe it. Now', ftiould we fuppofe it 
to be an irregular ring of ftars, in the centre nearly of 
which we muft then fuppofe the Sun to be placed, it will 
appear not a little extraordinary, that the Sun, being a 
fixed ftar like thofe which compofe this imagined ring, 
fhould juft be in the centre of fuch a multitude of celeftial 
bodies, without any apparent reafon for this lingular dif- 
tinClion ; whereas, on our fuppofition, every ftar in this 
ftratum, not very near the termination of its length or 
height, will be fo placed-as alfo to have its own galaxy, 
with only fuch variations in the form and luftre of it as 
may arife from the particular fituation of each ftar. 
“ Various methods may be taken to obtain a knowledge 
of the Sun’s place in the fidereal ftratum, one of which I 
have put in practice : I call it gauging the heavens, or the 
Jlar-gauge. It confifts in repeatedly taking the number of 
ftars in ten fields of view of my refleftor very near each 
other; and, by adding their films, and cutting off one de¬ 
cimal on the right, a mean of the contents of the heavens 
in all the parts w hich are thus gauged are obtained. Thus 
it appears, that the number of ftars increafes very much 
as we approach the milky-way ; for, in the parallel from 
ninety-tw o to ninety-four degrees north polar diftance, and 
right afeenfion 15I1. 10', the ftar-gauge runs up from 9-4. 
ftars Ln the field to i8 - 6 in about an hour and an half; 
whereas in the parallel from feventy-eight to eighty de¬ 
grees north polar diftance, and R. A. 11, 12, 13, and 14, 
hours, it very feldom rifes above four. We are, however, 
to remember, that, with different inftruments, the account 
of the gauges will be very different, efpecially on our fup¬ 
pofition of the Sun in a ftratum of ftars. 
“ In my obfervations on nebulae, I found, that I gene¬ 
rally detected them in certain directions rather than in 
others: that thefpaccs preceding them were generally quite 
deprived of their ftars, fo as often to afford many fields 
without a fingle ftar in it: that the nebulae generally ap¬ 
peared fome time after among ftars of a certain confidera- 
ble (ize, and but feldom among very fmall ftars: that, 
when 1 came to one nebula, 1 generally found feveral more 
in the neighbourhood : that afterwards a conliderable time 
palfed before 1 came to another parcel. Thefe events be¬ 
ing often repeated in different altitudes of my telefcope, 
and fome of them at confiderable diftances from each other, 
it occurred to me that the intermediate fpaces between the 
fweeps might alfo contain nebulae ; and i fometimes found 
this to hold good. The w'ell-known nebula of Cancer, vi- 
fibie to the naked eye, is probably one belonging to a cer¬ 
tain ftratum, in which I fuppofe it to be fo placed as to 
4 T Ik 
