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270, The Moon, however, nocends and de sconde five degree in every revolution, so that in general the shadlows pass under or over; but wher, the new or full moon take place at the very time she is passing the plate of the Earth's orbit, in ascending or desending, 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 planets and stars, called Occulta tions, proves that they are more distant than the Moon,
272. Occasionally, Venne 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 Kun; 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 man
273. Having ascertained, by means of the observation of transit, the distance of the Earth froin the Sun, the distances of all the other planets are determined by that law of nuture, which exactly proportions the cubes of the distances of the plants, to the squares of their reaprocier periodi al rorolutions,
274. Besides affording on light, the Moon afforts ibe waters, mud causes bigh tides,
I 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, wbile it affects to de scribe 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 Auid matter only, there could be no tides; because ia peither case would there be any variable transfer of molion to the several parts : but as it is composed of fixed and of fluid matter, intercepting each other (as the two great continents intercepring the two great seas,) su a variable communication of motion arises hetween 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 strok being of six hours continuance, and its length from 90 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, producing necessarily simultaneous efiecis.
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
not in opposite direction, as at the quarters;
when the moon is bull way between the con, juuction and opposition.
Obs.:(n small gran not readily communicating with others, and on which the rotary forces act generally, hd produce but one wave, there lo ou appearance of tides,
276. All the terrestrial phenomena, and all the problems on the globes and maps, may be rm duced to one general principle; that the Sun al wayn 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 Venn, god of all circles of the earth and heavens, is supposed to contain 300 equal parts or les grees; consequently, half a circle, or half the henvenn, is 180 degrees, and a fourth po degrees. On the wurface of the Earth, each degree in 194 miles; but the actual size of a degree, as car ried out to fue heavens, is indefinite, because space is without bounds.
278. Heace, if the Sun illumines half the Earth, he illuminer 180 degrees of the Earth; or 90 degrees every way, from the place over which he is vertient. Hence, also, it is 180 der grees from the north to the south pole; and po degrees from eaoli pole in the middle of the Kartlı, called the Equator.
270. Hence, as half the heavens are always vinible, 180 degrees are visible, and from the point over head, it will be po degrees to that Har, while the carth and the heuvens appear to
the eye to meet, called the Horizon. Hence, alsó, an inhabitant of the equator can see the stars as far as each pole; i. e. he can see 90 degrees
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 vern tical over the equator, he shines as far as each pole: because he shines 90 degrees from the place where he is vertical, or over lead.
281. Also, when the Sun is vertical 10 degrees dorth 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 be becomes vertical 23 degrees north of the equator, he shines 234 degrees beyond the north pole, and 234 degrees short of the south pole.
282. In its annual orbit, the Earth ascende 284 degrees above the level of the equator, and descends 23}degrees below. Hence, when it is at the highest point above, the Suu 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, rethin late merely to the feelings and sensations of human hom ings. lo nature, there is no up or down, or above or more low. The carth is round, and all bodies fall towards its céotre ; because, according to Sir R. Phillips, they perform rotations inversely as their density, or scek to exhibit equal momenta in revolving with the mass.. AN meu, and every thing called upright, stand in a straight line towards the centre of the enti; with the rarth be. neath their feet, and the heavens, which surround the carth, over their heads. We usually place the south pola downward, but the inhabitant of the south pole, likehina at the north pole, stunds wila bid fet towards bly centru
of the earth, both having the heavens overhead, The inhabitants of New South Wales are the Antipodes to us in Great Britain, standing with their feet towards ours, and their head, in opposite directiona, each of thein won dering how the other standa ; but the earth is the centre or toadstone of all its inhabitants, and in nature up and down are merely relative terms,
9. It is usual for authors to talk about the inelination
consider the ascent and descent in the plane as inuresi, ple, and more accordant with the phenomena, although it is a mere change of terme, I prefer my own explicit tion to that generally adopted, particularly in aid of the tutor, if he should amuse his pupils by passing a slabe round a candle, to shew the change of the beasone, The idea of an inclination of the axis i consider a vulgar er Par. The moon ascends and descends in its artii abuut 53 degrees but no one ever talked of the inclination of the innan's axis in the plane of its orbit!
1.- The obliquity or angle of the orbit diminishes at the rate of a minute in 110 years, and a degree in 0,000 years. Observations were made in China 2,900 years ***0 by which it appears, that the obliquity was 2, 61', but it is gow only 23', 24',-wonderful coinei, deneer
, and a proof, at once, of the diminution and the observation.
203. It must be evident, that during all the time the sun is vertical north of the equator, het will shine as many degrees beyond the north pola as he is vertical north of the equator; and that, during all the time lie is vertical to the south of the equator, he will constantly illumine is many degrees beyond the south pole,
Ons -- As it is ninety degrees from the equator to each pole, and as the sun ohimea ninety degrees froin the paid where he is vertical, he most of course shine as many de. grees beyond either pole as he is degrees advanced to. wards it from the equator. If I can read an inseription nimely yarda nit, and I advance is nearer to it, it is evident i could read it if it were now placed 30 yards