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surrounding it, and distinctly visible in the general mass.'

Dr. Herschel, in a short time, with his superior instrument, discovered 466 new nebulæ and clusters of stars, none of which had ever been seen before by any person, and most of which were within the reach of his telescopes only. A remarkable circumstance attending the nebula and clusters of stars is, that they are arranged into strata, which seem to run on to a great length, and it is probable that they may surround the whole apparent sphere of the heavens, not unlike the milky way, which, the Doctor says, is unquestionably nothing but a stratum of fixed stars. As this latter immense starry bed is not of equal breadth or lustre in every part, nor runs on in one straight direction, but is curved, and even divided into two streams along a very considerable portion of space, it may be expected that there will be the greatest variety in the strata of the clusters of stars and nebulæ. One of these nebulous beds is so rich, that, in passing through a section of it, the Doctor, in a few minutes, detected no less than 31 nebulæ, all distinctly visible on a fine blue sky. Their situation, shape, and other circumstances, seemed to denote the greatest variety imaginable. In another stratum, or, perhaps, a different branch of the former, he saw double and treble nebulæ, variously arranged: large ones with small attendants; narrow, but much extended, lucid nebulæ or bright dashes, some of the shape of a fan, resembling an electric brush, issuing from a lucid point; others of the shape of a comet, with a seeming nucleus in the centre; or like cloudy stars, surrounded with a nebulous atmosphere. A different sort, again, contain a nebulosity of the milky kind, like a wonderful, and at that time denominated an inexplicable, phenomenon about Orionis; while others shine with a fainter, mottled kind of light, which denotes their being resolvable into stars.

It is very probable that the great stratum, called the milky way, is that in which the Sun is placed, though, perhaps, not in the very centre of its thickness. We gather this from the appearance of the galaxy, which seems to encompass the whole heavens, as it certainly must do if the Sun is within the same. For suppose a number of stars arranged between two parallel planes, indefinitely extended every way, but a considerable distance from each other, and call this a sidereal stratum, an eye placed somewhere within it will see all the stars in the direction of the planes of the stratum projected into a great circle, which will appear lucid on account of the accumulation of the stars; while the rest of the heavens, at the sides, will only seem to be scattered over with constellations, more or less crowded, according to the distance of the planes or number of stars contained in the thickness or sides of the stratum.' There may be a branch or smaller stratum run out from the former, in a certain direction, contained between two parallel planes extended indefinitely onwards, but so that the eye may be placed in the great stratum before the separation, and not far from the place in which 'the strata are still united. Then will this second stratum not be projected into a bright circle like the former, but will be seen as a lucid branch proceeding from the first, and returning to it again at a certain distance less than a semicircle. From all the appearances, Dr. Herschel infers that the Sun is most likely placed in one of the great strata of the fixed stars, and probably not far from the place where some smaller stratum branches out of it. Such a supposition will satisfactorily, and with great simplicity, account for all the phenomena of the milky way, which, according to this hypothesis, is no other than the appearance of the projection of the stars contained in this stratum and its secondary branch. As a farther inducement to look on the galaxy in this point of view, it must be considered that there re

mains no doubt whatever that the white appearance arises from the mixed lustre of the numberless stars that compose it. Now, supposing it to be an irregular ring of stars, in the centre, nearly, of which we must then suppose the Sun to be placed, it will appear not a little extraordinary that the Sun, being a fixed star like those which compose this imagined ring, should just be in the centre of such a multitude of celestial bodies, without any apparent reason for this singular distinction; whereas, on the supposition already assumed, every star in this stratum, not very near the termination of its length or height, will be so placed as also to have its own galaxy with only such variations in the form and lustre of it, as may arise from the particular situation of each star.

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Various methods,' says Dr. Herschel, may be pursued to come to a full knowledge of the Sun's place in the sidereal stratum, of which I shall only mention one as the most general and most proper for determining this important point, and which I have already begun to put in practice: I call it gauging the heavens, or a star-gauge. It consists in repeatedly taking the number of stars in ten fields of view of my reflector, very near each other, and, by adding their sums, and cutting off one decimal on the right, a mean content of the heavens, in all the parts which are thus gauged, is obtained. By way of example, I have joined a short table, extracted from the gauges contained in my journal; by which it appears, that the number of stars increases very fast as we approach the Via Lactea..

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Thus, in the parallel from 92° to 94° North Polar distance, and Right Ascension 15h 10, the stargauge runs up from 9.4 stars in the field to 18.6 in about an hour and a half; whereas, in the parallel from 78° to 80°, right ascension 11, 12, 13, and 14 hours, it very seldom rises above 4.'

The situation of the Sun will be obtained from considering in what manner the star-gauge agrees with the length of a ray revolving in several directions about an assumed point, and cut off by the bounds of the stratum. If the Sun should be placed in the great sidereal stratum of the milky way, and not far from the branching out of a secondary stratum, it will lead one to assume the cause of the probable motion of the solar system: for the very bright great node of the Via Lactis, or union of the two strata about Cepheus and Cassiopeia, and the Scorpion and Sagittarius, points out a conflux of stars manifestly quite sufficient to occasion a tendency towards that node in any star situated at no very great distance; and the secondary branch of the Galaxy, not being much less than a semicircle, seems to indicate such a situation of our solar system in the great undivided stratum as the most probable.

Dr. Herschel adds a few particulars with respect to the direction of some of the capital strata or their branches. The nebula Cancer, visible to the naked eye, is, he thinks, probably one belonging to a certain stratum, which he supposes to be so placed as to lie nearest us. It runs from ɛ Cancri towards the south, over a particular nebula, which is a very beautiful and pretty much compressed cluster of stars, readily seen by a good telescope, in which 200 stars have been seen at once in the field of view of Dr. Herschel's great reflector.

Another stratum which, perhaps, approaches nearer to the solar system than any of the rest, and whose situation is nearly at rectangles to the great sidereal stratum in which the Sun is placed, is that of Coma

Berenices; the Coma itself being one of the clusters in it. It has many capital nebulæ very near it; and, in all probability, this stratum runs on a very considerable way, through the Great Bear onwards to Cassiopeia; thence through the girdle of Andromeda and the Northern Fish, proceeding towards Cetus and the head of Centaurus. But though,' says Dr. Herschel, I have fully ascertained the existence and direction of this stratum for more than thirty degrees of a great circle, and found it almost every where equally rich in fine nebulæ, it still might be dangerous to proceed in more extensive conjectures, that have, as yet, no more than a precarious foundation.'

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Astronomical Occurrences.

THE Sun enters the sign Virgo on the 23d of October, at 49 m. past noon. On the 8th, Jupiter is in conjunction with a, the star being 31' south of the planet; and, on the 15th, Venus is in conjunction with the same star, the latter being 15' north of the planet. The planet Mercury will appear stationary on the 15th; and, on the 25th, at 11 at night, he will be in his inferior conjunction. Mars will be in conjunction on the 8th, at about 6 in the evening. Saturn will appear stationary on the 19th. The Moon will be in conjunction with the Herschel on the 23d, at 38 m. past 7 in the evening.

TABLE

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

the Month.

Tuesday, October 1, Sun rises 12 m. past 6

sets 48 m. past 5

Sunday,

Friday,

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31

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Wednesday,

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Monday,

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Saturday,
Thursday,

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9

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