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immense strata of fixed stars, of clusters of stars, and of nebule; till, going on with such interesting observations, he now perceives that all these appearauces must naturally arise from the confined situation in which we are placed. Confined it may justly be called, though in no less a space than what before appeared to be the whole region of the fixed stars, but which has now assumed the shape of a crookedly branching nebula; not, indeed, one of the least, but, perhaps, very far from being the most considerable of those numberless clusters that enter into the construction of the heavens.'

Dr. Herschel next proceeds to show that his theory is perfectly consistent with facts, and appears to be confirmed and established by a long and accurate series of observations; so that the assumed theoretical view just described, with all its consequential appearances, as seen by an eye inclosed in one of the nebulæ, is no other than a drawing from nature, in which the features of the original have been closely copied; and, says the author, 'I hope the resemblance will not be called a bad one, when it shall be considered how very limited must be the pencil of an inhabitant of so small and retired a portion of an indefinite system in attempting the picture of so unbounded an extent.'

Dr. Herschel, in this very curious paper, gives a table of what he calls gauges that have been taken. In the 1st column is the right assension, and in the 2d the north polar distance: in the 3d are the contents of the heavens, being the result of the gauges. The 4th shows from how many fields of view the gauges were deduced, and the 5th contains occasional remarks. Having next demonstrated the following problem as far as mathematical principles will apply, viz. that the stars being supposed to be nearly equally scattered, and their number, in a field of view of a known angular diameter, being given, to determine the length of the visual ray; he proceeds to show that

the stupendous sidereal system which we inhabit, this extensive stratum, and its secondary branch, consisting of many millions of stars, is, in all probability, a detached nebula. In order that the reader may perceive that the Doctor goes upon sure grounds, and that his facts are grounded upon an actual survey, he shews the length of his sounding line, as he calls it, that it may appear whether it was sufficiently long for the purpose. In the most crowded part of the milky way I have had fields of view that contained not less than 588 stars; and these were continued for many minutes ; so that, in one quarter of an hour's time, there passed no less than 116,000 through the field of my telescope.'

It may, he is aware, seem inaccurate to found an argument on the stars being equally scattered, when, in all probability, there may not be two of them in the heavens whose mutual distance shall be equal to that of any other two given stars. To this it is replied, that, when we take all the stars collectively, there will be a mean distance which may be assumed as the general one; and an argument founded on such a supposition will have in its favour the greatest probability of not being far short of the truth.

Dr. Herschel makes a distinction between a place crowded with stars, and a cluster, which he says may easily be perceived by the arrangement, as well as the size and mutual distance of the stars; for, in a cluster, they are generally not only resembling each other pretty nearly in size, but a certain uniformity of distance also takes place they are more and more accumulated towards the centre, and put on all the appearances which we should naturally expect from a number of them collected into a group at a certain distance from us. On the other hand, the rich parts of the milky way, as well as those in the distant broad part of the stratum, consist of a mixture of stars of all possible sizes, that are seemingly placed without any particular apparent order. Moreover, what would

produce the milky nebulosity alluded to, is the numberless stars, whose light reaches the eye. To make this appear, we must return to the naked eye, which can only see stars of the seventh magnitude so as to distinguish them; yet it is very evident that the united lustre of millions of stars, such as the nebula in Andromeda may be supposed to be, will reach our sight in the shape of a very small, faint nebulosity, since this nebula may easily be seen in a fine clear evening, and during the absence of the Moon. Dr. Herschel says, his telescope has not only a visual ray that will reach stars at 497 times the distance of Sirius, so as to distinguish them, but also a power of showing the united lustre of the accumulated stars that compose a milky nebulosity, at a distance far exceeding the former limits; so that it appears to the author highly probable that his telescope, not showing such a nebulosity in the milky way, goes already far beyond its extent, and consequently much more would a more powerful instrument remove all doubt on the subject, both by showing the stars in the continuation of the stratum, and by exposing a very strong milky nebulosity beyond them, that could no longer be mistaken for the dark ground of the heavens.

To these arguments, taken from observation, the doctor has added others drawn from analogy. Among the great number of nebula which he has seen, amounting to several hundreds, there are many which he thinks are equally extensive with that which we inhabit; and yet they are all separated from each other by very considerable intervals. Some, indeed, seem to be double and treble; but it may be supposed that there may still be some thinly scattered solitary stars in the large interstices of nebula, which, being situated so as to be equally attracted by the several clusters when they were forming, remain unassociated. And though, owing to their immense distance, we cannot expect to see these even with the best glasses, yet the number of them cannot probably be

very considerable in comparison with those that are already drawn into systems; which conjecture is confirmed in situations where the nebulæ are near enough to have their stars visible; for they are all insulated, and generally to be seen on a very clear and pure ground, without any star near them that might be supposed to belong to them. And though, says the author, I have often seen them in beds of stars, yet, from the size of these latter we may be certain that they were much nearer to us than those nebulæ, and doubtless belonged to our own system.'

[To be continued.]

Astronomical Occurrences.

THE Sun enters Sagittarius on the 22d November, at 9 m. after 9 in the morning; and on the 19th of this month there will be an eclipse of this luminary. Of the nature of eclipses, we, in the preceding volumes, have given popular and scientific accounts, to which we refer our readers; and shall only observe here, that the

Beginning of the eclipse will be 184 m. past 8 in the morning

Greatest obscuration

Visible conjunction

End of the eclipse

24

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The number of digits that will be eclipsed will be9° 23′ on north latitude. The Moon makes his first impression on the Sun's disk at 59° from his vertex on the right hand.

On the 5th, at 40 m. past 12 at night, Venus and the Herschel will be in conjunction; the latter being 53′ north. The greatest elongation of Mercury will be on the 10th. Jupiter will be in conjunction on the 13th, at 4 in the morning. Saturn will be in his quadratures at 6 in the morning of the 10th. Jupiter and Mercury will be in conjunction on the 28th, at past 12 at night.

ASTRONOMICAL OCCURRENCES.

TABLE

325

Of the Sun's Rising and Setting every fifth Day of the Month.

1, Sun rises 11 m. after 7 Sun sets 49 m. after 4

Friday
Wednesday 6,
Monday 11,
Saturday 16,
Thursday 21,
Tuesday. 26,

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Equation of Time.

[See January.]

m. S.

Nov. 1, from the time on the dial subtract 16 15

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The Moon is full on the 5th day of November, at 18 m. past 3 in the morning: she enters her last quarter on the 12th, at 8 m. past 7. The Moon is at change, or New Moon, on the 19th, at 23 m. after 10 in the morning; and she enters her first quarter at 6 m. past 5 on the 26th.

The eclipses of Jupiter's satellites are not visible this month, the planet being too near the Sun.

The Naturalist's Diary.

Languid the morning beam slants o'er the lea;
The hoary grass, crisp, crackles 'neath the tread.

ALTHOUGH November is usually dull and gloomy, yet there are some intervals of clear and pleasant weather: the mornings are, occasionally, sharp, but the hoarfrost is soon dissipated by the sun, and a fine open day follows.

The trees are now stripped of their foliage, and what is termed the fall of the leaf' takes place in

this month.

See T. T. for 1814, p. 301, and T. T. for 1815, p. 314.

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