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To have correct ideas of the sensations arising from the appearances of the heavenly bodies, it should be observed that they become visible only by the luminous rays they transmit. When one of these bodies is observed, the rays proceeding from the opposite sides of its disk intersect each other in the eye of the observer, and form there a certain angle. It is the arc which measures this angle that determines the apparent diameter of the object. By this. means it is that the apparent magnitudes of the Sun, Moon, and planets, are measured; but as the fixed stars do not offer such a regular disk as to enable the eye to appreciate their contour, they appear only as brilliant points in the sky: they, however, retain constantly the same mutual arrangement and the same order, always rising and setting at the same points of the horizon, without any perceptible difference, except after long intervals of time. The planets are readily distinguished from the fixed stars by the want of permanency in their relative positions; for, though they rise and set like the stars, it may readily be perceived, after the lapse of a few days, that these positions have changed: they no longer appear to accompany the same stars, nor rise and set at the same points of the horizon.
Astronomy teaches that the Sun is the centre of the system to which our Earth belongs, and that he shines by his own light: the Moon, and all the planetary bodies, also belong to the same system, and revolve round him as their common centre. By the effects of this motion, in conjunction with their apparent magnitude, their distance from the Sun and the Earth are computed; but as the fixed stars are not included in this system, and are so remote that the rays proceeding from the opposite sides.of their disks do not form an angle at the eye of the observer that can be measured, neither their magnitudes nor distances can be made the subjects of calculation. Various circumstances, however, concur to prove
that the stars, like the Sun, shine by their own light, and their distance from the Earth is estimated by its velocity. Light moves at the rate of about twelve millions of miles a minute; and such is the amazing distance of the stars supposed to be, that it is three years in passing from the nearest of them to the Earth.
The light of the stars is, to the naked eye, generally white, being too faint to excite the idea of any particular colour; but when it is concentrated by large speculums, it appears of various hues. To the naked eye, indeed, some of the stars are a little redder than the others. All of them have more or less scintillation or twinkling in their appearance, the cause of which has not been fully ascertained; but it has been thought to be an effect of the atmosphere, as in some climates, where the air is remarkably pure and serene, the scintillation is greatly diminished. The number of stars that can be seen by the naked eye at once, is seldom much above a thousand, though, from their twinkling, and the indistinct manner in which they are viewed, they appear to be almost infinite. The whole number that can be embraced by the eye, taking in both hemispheres, is supposed to exceed 3000; but when they are views ed through high magnifying telescopes their number becomes so immensely increased, as to justify the conclusion of considering them almost, if not altogether, without limits. Dr. Herschel was of opinion that the Milky-way consists of an assemblage of stars too remote to be singly seen, but so closely disposed as to give a luminous appearance to that part of the heavens. On directing his large telescope to this part of the heavens, he has observed an immense number of stars pass the field of view in a few minutes. If the appearance of the heavens on a fine winter's night, when the sky is perfectly clear, justified the poet in representing the myriads of stars as baffling the utmost powers of calculation, how much
more the reality when viewed through the most perfect instrument which human skill and ingenuity has devised!
To count their numbers, were to count the sands
(To be continued.]
The Naturalist's Diary
For JULY 1823.
As loth to waken any singing bird. SUMMÉR may be said to begin with this month. How delightful to the admirer of Nature is a morning ramble at this season, before the heats of the day are felt! 'Do you know what you lose (we ask in the language of a popular modern writer')" by spending those hours in sleep which might be devoted to the most pleasing and most substantial enjoyment? · Only recollect the peculiar fascinations of the morning. Think upon the feelings which they are calculated to excite. Picture to yourself—(and if you imagine I have painted in too glowing colours, rise to-morrow and compare it with the reality, and if there be one tint too vivid, one touch too flattering, destroy the painting, and forget the artist,)-picture to yourself a summer morning. The Sun rising in all his native majesty, shedding his beams with a gentle influence, which, whilst it predicts their increasing power, teaches us to value their present mildness; every object, as it catches the first rays of “ the powerful king of day," appearing to smile at his approach; the lengthened shadows that shoot across the meadow, slowly dimi· Letters on Early Rising, 12mo, third edition. (Taylor and Hessey.)
nishing as he advances. The clouds, that seemed to check his early progress, gradually yielding to his growing might, and, “illumined with fluid gold,” disappearing amid “ the kindling azure.” The glistening dewdrops, “stars of morning," impearling every leaf. Vegetation clothed in a richer verdure, and the variegated flowers in livelier hues. The groves resounding with the melody of the feathered tribes, who appear susceptible of gratitude for the return of the opening day. Whilst every animal is in motion, and seems to feel a new satisfaction in the exercise of its active powers and the revival of its capacities for enjoyment.
Another modern author affords us the following accurate and beautiful picture of early morn. How delicious is the prime of the morning! It is to a summer's day what the spring is to the year, or childhood to human life. The dew hangs, like a blessing, on the glittering leaves; and the mists are rising from the grass, like the smoke of an acceptable sacrifice, steaming up to the heavens. Hark to those heifers cropping the crisp herbage. I know of no sound more purely pastoral: it is as refreshing to an ear sick of the talk of towns, as a draught of ice-cold water is to a parched palate! And how sweetly it meets and harmonises with the rich melody that comes down from yonder mounting lark! Here are no other sounds stirring ;-for the Sun has not yet awakened the breezes--the bee is still wrapped in its honey-heavy slumbers, and the “hum of men" is a thing of memory only:
To these descriptions we add a 'Sun-Rise,' from the pallet of that master-painter, Lord Byron :
The day at last bas broken. ...
Perinanent; so fleeting, we can scarcely call
Sardanapalus'. The numbers of our migrating visitors in the summer of 1821 were very small: most of our fruit devouring and insectivorous birds retire to warmer regions at the approach of winter, and return in the spring; hence we might suppose that their numbers would be annually nearly the same, by their 'not encountering the want and waste that winter occasions; but this is not the case: the numbers of our summer visitors are very uncertain, and they appear to incur so much loss and havock in their passage, or return, by adverse winds, birds of prey, and fatigue, that their scarcity, in some summers, is as manifest as their abundance is in others. Were it not for the constant provision of nature in confining the increase of its creatures, the labours of the agriculturist would often be ruined by their numbers. The scourges with which man is admonished or afflicted, are frequently formed of minute agents, as the worm, the slug, the insect, the mildew (a minute fungus): the havock that small birds make in our corn fields in some summers is deplorable! The increase of the common sparrow alone, without the restricting goodness of Him that careth for us,' would almost destroy our bread-corn! This bird will commonly hatch fifteen young in a season, and the first of these broods, themselves, become parents the same year : they are bold, rapacious birds, and, when driven away, return again to their plunder: but the eggs of the sparrow are taken by every bird's-nesting boy in the village; the young that are hatched, by flocking together, invite destruction; and the swarms of
* For some beautiful descriptions of Sun-rise, see our last volume, pp. 210, 211, 251.