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270. The Moon, however, necends and de scends five degrees in every revolution, so that in general the shadows pass under or over; but wher, the new or full moon take place at the very time she is passing the plane of the Earth's orbit, in ascending or descending, then the strik ing phenomena of an eclipse take place.

271. The shadow of the Earth, as seen on the Moon, demonstrates its rotundity; and the shadow of the Moon on the Earth, proves that it is nearer than the Sun; so the passing of the Moon over plancts and stars, called Occultations, proves that they are more distant than the Moon.

272. Occasionally, Venus and Mercury, the two planets nearer to the Sun than the Earth, pass over the surface of the Sun like black spots, called transits of Venus and Mercury.

This proves that those planets are nearer to the Earth than the Sun; and, by observing the progress of the transit at different parts of the Earth, we can obtain the measure of an angle, by which we can determine the exact distance of the Earth from the Sun.

273. Having ascertained, by means of the observation of a transit, the distance of the Earth from the Sun, the distances of all the other planets are determined by that law of nature, which exactly proportions the cubes of the distances of the plants, to the squares of their respective periodical revolutions,

274. Besides affording ns light, the Moon affects the waters, and causes high tides;

which obey her influence, as the seas pass beneath her. But as she moves forward in her orbit 12 or 13 degrees every day, and consequently passes over every sea 50 minutes later one day than the day before, so the time of high water is always 50 minutes later each following day.

Obs. I.-The tides, according to the theory of NEWTON, are caused by what he calls the attraction of the Moon and Sun. But, according to Phillips, they are phenomena of motion caused by the rotation or motion of the earth.

2. As such terms as attraction and repulsion ought not to be received as expressive of causes, we shall prefer the system which explains, or professes to explain, the causes, and omit that which, while it affects to describe the cause, in truth only defines the phenomena.

3.-If, says Sir R. Phillips, the Earth were composed of fixed matter only, there could be no tides; and if of fluid matter only, there could be no tides; because in neither case would there be any variable transfer of mo tion to the several parts: but as it is composed of fixed and of fluid matter, intercepting each other (as the two great continents intercepting the two great seas,) so a variable communication of motion arises between the fixed and fluid, and hence the tides of the seas.

4.-The tides, he says, are but oscillations of the great basins of the ocean, between the continents aud islands and rocks. The waters serve, in truth, as a species of balance-wheel, or pendulum, to the earth, each stroke being of six hours continuance, and its length from 30 to 50 miles, according to the velocity.

5. The connexion of the moon and the sun with the tides, he ascribes to the operation of the same uniform cause (that is of transferred motion,) on the whole, a uniform cause which operates on a system of bodies, pro ducing necessarily simultaneous effects.

275. The Sun and Moon concur in varying the motions; hence, we have high or spring tides, when their actions concur at the new and full moon; and low or neap tides, when the forces

act in opposite directions, as at the quarters; or when the moon is half way between the con junction and opposition.

Obs,-On small seas not readily communicating with others, and on which the rotary forces act generally, and produce but one wave, there is no appearance of tides.

276. All the terrestrial phenomena, and all the problems on the globes and maps, may be re duced to one general principle; that the Sun al ways illuminates one half of the earth, and that the other half is in darkness; and that, from every part of the earth, we always see one half of the heavens, the other half being invisible.

277. The circumference of the earth, the hea vens, and of all circles of the earth and heavens, is supposed to contain 360 equal parts or des grees; consequently, half a circle, or half the heavens, is 180 degrees, and a fourth 90 degrees. On the surface of the Earth, each degree is 694 miles but the actual size of a degree, as cars ried out to the heavens, is indefinite, because space is without bounds,

278, Hence, if the Sun illumines half the Earth, he illumines 180 degrees of the Earth; or 90 degrees every way, from the place over which he is vertical. Hence, also, it is 180 der grees from the north to the south pole; and po degrees from each pole is the middle of the Earth, called the Equator,

279. Hence, as half the heavens are always visible, 180 degrees are visible, and from the point over head, it will be 90 degrees to that Hue, while the earth and the heavens appear to

the eye to meet, called the Horizon. Hence, also, an inhabitant of the equator can see the stars as far as each pole; i. e. he can see 90 degrees each way.

280. The inhabitants of the poles can see the stars as far as the equator, and no further; i. e. they can see 90 degrees. When the Sun is vertical over the equator, he shines as far as each pole: because he shines 90 degrees from the place where he is vertical, or over head.

281. Also, when the Sun is vertical 10 degrees north of the equator, he shines 10 degrees beyond the north pole, and his rays do not reach the south pole by 10 degrees; and when he becomes vertical 234 degrees north of the equator, he shines 23 degrees beyond the north pole, and 23 degrees short of the south pole.

282. In its annual orbit, the Earth ascends 234 degrees above the level of the equator, and descends 234 degrees below. Hence, when it is at the highest point above, the Sun will be vertical over that part of the globe which is 231 below the equator, and when below, the contrary.

Obs. The terms above and below, up and down, relate merely to the feelings and sensations of human heings. In nature, there is no up or down, or above or be low. The earth is round, and all bodies fall towards its centre; because, according to Sir R. Phillips, they perform rotations inversely as their density, or seek to exhibit equal momenta in revolving with the mass.. All meu, and every thing called upright, stand in a straight line towards the centre of the earth; with the earth beneath their feet, and the heavens, which surround the earth, over their heads. We usually place the south pole downward, but the inhabitant of the south pole, likehim at the north pole, stands with his fact towards the centre

of the earth, both having the heavens over-head, The inhabitants of New South Wales are the Antipodes to us in Great Britain, standing with their feet towards ours, and their heads in opposite directions, each of them wondering how the other stands; but the earth is the centre or loadstone of all its inhabitants; and in nature up and down are merely relative terms,

a. It is usual for authors to talk about the Inclination of the axis to the orbit, its parallelism, &c. &8,; but as I consider the ascent and descent in the plane as inore simple, and more accordant with the phenomena, although it is a mere change of terms, I prefer my own explication to that generally adopted, particularly in aid of the tutor, if he should amuse his pupils by passing a globe round a candle, to show the change of the seasons, The idea of an inclination of the axis I consider a vulgar erFor. The moan ascends and descends in its orbit about bį degrees, but no one ever talked of the inclination of the moon's axis to the plane of its orbit!

3.-The obliquity of angle of the orbit diminishes at the rate of a minute in 110 years, and a degree in 6,600 years. Observ.tions were made in China 2,900 years co; by which it appears, that the obliquity was 23°, 51', but it is now only 232, 28',--a wonderful coinci. dence, and a proof, at once, of the diminution and the observation.

283. It must be evident, that during all the time the Sun is vertical north of the equator, he will shine as many degrees beyond the north pole as he is vertical north of the equator; and that, during all the time he is vertical to the south of the equator, he will constantly illumine as many degrees beyond the south pole,

Obs. -As it is minety degrees from the equator to each pole, and as the Sun shines ninety degrees from the part where he is vertical, he must of course shine as many degrees beyond either pole as he is degrees advanced towards it from the equator. If I can read an inscription ninety yards off, and I advance 23 nearer to it, it is evident I could read it if it were now placed 23 yards

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