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J's latit. latit.

latit.

DECEMBER 1807.

' 8's h's 24's '8 q's

latit. declin. declin. declin. declin. declin

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O'

Q's

Clock D's

D's ('s

h's

24's

Q's

g's

2 9 26 12 21

D longitude. declin. aft. O long. latit. declin. long. longit. longit. longit. longit.

18 25 1621 s 4410

5310

24 16 16 8

56 4126 2 n 57 20 & 26 1611 9 8181035 2428167 8 3317 55 3 5318

2811 21 25

1314 53

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WHEN we reflect on the diurnal motion to which all the heavenly bodies are subject, we recognize the exist ence of a general cause that moves them, or which seems to move them round, the axis of the earth. If we consider that these bodies are insulated, with respect to each other, and placed at very different distances from the Earth; that the Sun and stars are at a much greater distance from it than the Moon, and that the variations in the apparent diameters of the planets indicate great alterations in their distances; and moreover that the comets traverse the heavens freely, and almost in all directions, it will be difficult to conceive that it is the same cause which impresses on all these bodies a common motion of rotation. But since the heavenly bodies present the same appearances to us, whether the firmament carries them round the earth, considered as immoveable, or whether the earth itself revolves into a contrary direction, it seems much more natural to admit this latter motion, and to regard that of the heavens as only appa

rent.

The earth is a globe not 8000 miles in diameter; but the diameter of the Sun is nearly 100 times larger. If its centre coincided with that of the earth, its volume would embrace not only the orbit of the Moon, but extend much more than as far again; from hence we may No. VII.

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GAOBO

judge of its immense magnitude: besides its distance from the earth is 95,000,000 of miles. Is it not then more natural to attribute to the globe that we inhabit a rotatory motion on its own axis, than to suppose a mass so enormous as the Sun is, such an extremely rapid motion as would be requisite to revolve in one day round the earth? Let us consider also what an immense power it would require to contain it, and to counteract its centrifugal force, that is to retain it in its orbit. Every one of the stars present to us similar difficulties, which are all removed by admitting the revolution of the earth on its supposed axis.

The pole of the equator seems to move closely round that of the ecliptic, from whence results the procession of the equinoxes.. If the earth is immoveable, the pole of the equator is equally so, since it corresponds to the same point of the terrestrial surface: the ecliptic therefore moves round these poles, and in this motion carries all the heavenly bodies along with it. Thus the whole system composed of so many heavenly bodies, differing from each other in their magnitudes, motions, and distances, would again be subject to a general motion, which disappears and is restored to a very simple law,. if we suppose the terrestrial axis to move round the poles of the ecliptic.

According to the true theory, we are but in a similar situation, on a large scale, of a spectator placed in a large ship that is in motion: we are carried on it is true with an immense velocity; which velocity is however common to every thing that surrounds us. The person on shipboard fancies himself at rest, and the shore, the hills, and all objects placed out of the vessel appear to him to move. But on comparing the extent of the shore and the heights perhaps of surrounding hills or mountains,

he begins to suspect that the apparent motion of these objects arises from the real motion of himself. The stars which fill as it were the celestial regions, are relatively to the earth what the shores and hills are to the vessel; and the same reasons which convince the navigator of the reality of his own motion, prove, or ought to prove to us the motion of the earth. It may be further observed, that in all the works of nature with which we are acquainted, the Creator appears to act by the shortest, easiest, and simplest means. Now if the earth be at rest and the stars move, the velocity of these latter must be immense, and yet all the purposes thereof might have been answered by a moderate motion of the earth alone.

It has been already stated in this work that the Moon's distance from the earth is 240,000 miles; of course, the length of the tract which it traverses, if it moves round the earth in 24 hours, is about 1,500,000, that is, at the rate of 62,500 miles in an hour, instead of 2290 miles, which is really the case, consequently in each second of time the Moon, known to be the swiftest of all the heavenly bodies, must move more than 17 miles. Again it has been stated that the mean solar distance from the earth is about 95,000,000 of miles; consequently the diurnal path of that luminary, if it revolve about our globe in 24 hours, must be 580,000,000; and therefore in a single second, the beat of a watch, he must move nearly 7,000 miles.

Upon the same principle, that is, supposing the earth to be the centre of the system, and not the Sun, the planet Mars in a second of time, must travel at the rate of more than 10,000 miles, Jupiter 36,000, and Saturn 62,000. And lastly, the fixed stars being yet more indefinitely remoter from the earth than the Sun or Saturn, their motions in or near the equator must be vastly swifter than his.

These arguments, and many others equally conclusive to the mathematician, though not so obvious to the general reader, are strengthened by analogy. A rotatory motion has been observed in several planets, and always from the west to the east, which is similar to that which the diurnal motion of the heavens seems to indicate in the earth. Jupiter, which is above a thousand times larger than the earth, moves unquestionably on its axis in less than twelve hours. An observer on its surface would see the heavens revolve round him in that time; yet we, as mere observers, know, in the case of Jupiter, that the motion of the heavens to that planet would be apparent, and not real. Is it not therefore reasonable to think, that it is the same with that we observe on the earth? What confirms this analogy is, that both the earth and Jupiter are flattened at the poles, which is no doubt occasioned by their rotatory motions about imaginary axes. This circumstance should, in theory, diminish the force of gravity at the equator,,and that this diminution does take place is proved by experiment. Hence every thing leads to the conclusion that the earth has a diurnal motion about its axis, and that the diurnal motion of the heavens which is produced by it, is merely an illusion; an illusion not unlike that which represents the heavens as a blue vault, to which all the stars are fixed, and the earth as a plane on which it rests.

In this month the Sun begins to decline in his meridian height; of course the day becomes shorter. The times of the Sun's rising and setting will be as follow:

Friday, 1st, Sun rises 45m. after 3, Sun sets 15m. after 8.

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Equation of Time.] The following table will shew

what is to be added to the apparent time as exhibited on

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