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primary planets; and of the primary planets, with respect to the Sun.

As to the Moon, the proposition is thus proved : the Moon's mean distance is 60 semidiameters of the Earth; her period, with regard to the fixed stars, is 27 days, 7 hours, 43 minutes; and the Earth's circumference 123,249,600 Paris feet. Now, supposing the Moon to have lost all her motion, and to be let drop to the Earth, with the power which retains her in her orbit, in the space of one minute she will fall 15 Paris feet; the arch she describes in her mean motion, at the distance of 60 diameters of the Earth, being the versed sign of 15 Paris feet. Hence, as the power, as it approaches the Earth, increases in a duplicate ratio of the distance in versely; so as at the surface of the Earth it is 60 × 60 greater than at the Moon; a body falling with that force in our region must, in a minute's time, describe the space of 60 × 60 X 15 Paris feet, or 15 Paris feet in the space of one second.

But this is the rate at which bodies fall by their gravity at the surface of our Earth; as Huygens has demonstrated by experiments with pendulums. Consequently, the power whereby the Moon is retained in her orbit, is the very same we call gravity; for, if they were different, a body, falling with both powers together, would descend with double the velocity, and in a second of time describe 30 feet.

As to the other secondary planets, their phenomena, with respect to their primary ,ones, being of the same kind with those of the Moon about the Earth, it is argued by analogy, that they depend on the same causes; it being a rule or axiom all philosophers agree to, that effects of the same kind have the same causes. Again, attraction is always mutual, i. c. the reaction is equal to the action: consequently the primary planets gravitate towards their secondary ones, the Earth towards the Moon, and the Sun towards them all. And this gravity, with regard to each several planet, is reciprocally as the square of its distance from the centre of gravity. See ATTRACTION,

&c.

IV. All bodies gravitate towards all the planets; and their weight towards any one planet, at equal distances from the centre of the planet, is proportional to the quantity of matter in each.

For the law of the descent of heavy bodies towards the Earth, setting aside their unequal retardation from the resistance of the

air, is this, that all bodies fall equal spaces in equal times; but the nature of gravity or weight, no doubt, is the same on the other planets as on the Earth.

Suppose, e. gr. such bodies raised to the surface of the Moon, and together with the Moon deprived at once of all progressive motion, and dropped towards the Earth: it is shewn, that in equal times they will describe equal spaces with the Moon; and therefore, that their quantity of matter is to that of the Moon, as their weights to its weight.

Add, that since Jupiter's satellites revolve in times that are in a sesquiplicate ratio of their distances from the centre of Jupiter, and consequently at equal distances from Jupiter, their accelerating gravities are equal; therefore, falling equal altitudes in equal times, they will describe equal spaces; just as in heavy bodies on our Earth. And the same argument will hold of the primary planets with regard to the Sun, and the powers whereby unequal bodies are equally accelerated are as the bodies, i. e. the weights are as the quantities of matter in the planets, and the weight of the primary and secondary planets towards the Sun, are as the quantities of matter in the planets and satellites.

And hence are several corollaries drawn relating to the weights of bodies on the surface of the Earth, magnetism, and the exist ence of a vacuum.

V. Gravity extends itself towards all bodies, and is in proportion to the quantity of matter in each.

That all planets gravitate towards each other has been already shewn; likewise, that the gravity towards any one, considered apart, is reciprocally as the squares of its distance from the centre of the planet; consequently, gravity is proportionable to the matter therein. Further, as all the parts of any planet, A, gravitate towards another planet, B; and the gravity of any part is to the gravity of the whole, as the matter of the part to the matter of the whole; and as reaction is equal to action: the planet B will gravitate towards all the parts of the planet A; and its gravity towards any part will be to its gravity towards the whole, as the matter of the part to the matter of the whole. Hence we derive the methods of finding and comparing weights of bodies towards different planets; of finding the quantity of matter in the several planets, and their densities; since the weights of equal bodies, revolving about planets, are as the

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diameter of their orbits directly, and as the squares of the periodical times inversely; and the weights at any distance from the centre of the planet are greater or less in a duplicate ratio of their distances inversely. And since the quantities of matter in the planets are as their powers at equal distances from their centres: and, lastly, since the weights of equal and homogeneous bodies towards homogeneous spheres are, at the surfaces of the spheres, as the diameters of those spheres; and consequently, the densities of heterogeneous bodies are as the weights at the diameters of the spheres.

VI. The common centre of gravity of the Sun, and all the planets is at rest; and the Sun, though always in motion, yet never recedes far from the common centre of all the planets.

For the matter in the Sun being to that in Jupiter as 105S to 1; and Jupiter's distance from the Sun to the semi-diameter of the Sun in a ratio somewhat bigger; the common centre of gravity of Jupiter and the Sun will be a point a little without the Sun's surface; and by the same means, the common centre of Saturn and the Sun will be a point a little within the Sun's surface; and the common centre of the Earth, and all the planets, will be scarce one diameter of the Sun distant from the centre thereof; but the centre is always at rest; therefore, thongh the Sun will have a motion this and that way, according to the various situations of the planets, yet it can never recede far from the centre, so that the common centre of gravity of the Earth, Sun, and Planets, may be esteemned the centre of the whole world. See Planet.

VII. The planets move in ellipses that have their foci in the centre of the Sun; and describe areas proportionable to their times. This we have already laid down à posteriori as a phenomenon; and now that the principle of the heavenly motions is shewn, we deduce it therefrom à priori. Thus, since the weights of the planets towards the Sun are reciprocally as the squares of their dis tances from the centre of the Sun; if the Sun were at rest, and the other planets did not act on each other, their orbits would be elliptical, having the Sun in the common umbilicus, and would describe areas proportionable to the times; but the mutual actions of the planets are very small, and may be well thrown aside.

Indeed, the action of Jupiter on Saturn is of some consequence; and hence, according to the different situation and distances

of those two planets, their orbits will be a little disturbed. The Earth's orbit too is sensibly disturbed by the action of the Moon; and the common centre of the two describes an ellipsis round the Sun placed in the umbilicus; and, with a radius drawn to the centre of the Sun, describes areas proportionable to the times. See EARTH, &c. VIII. The aphelia and nodes of the planets are at rest, excepting for some inconsiderable irregularities arising from the action of the revolving planets and comets. Conse. quently, as the fixed stars retain their position to the aphelia and nodes, they too are at rest.

IX. The axis, or polar diameter, of the planets is less than the equatorial diameter. The planets, had they no diurnal rotation, would be spheres, as having an equal gravity on every side: but by this rotation the parts receding from the axis endeavour to rise towards the equator, which, if the matter they consist of be fluid, will be affected very sensibly. Accordingly, Jupiter, whose density is found not much to exceed that of water on our globe, is observed by astronomers to be considerably less between the two poles than from east to west. And, on the same principle, unless our Earth were higher at the equator than towards the poles, the sea would rise under the equator, and overflow all near it. But this figure of the Earth Sir Isaac Newton proves likewise à posteriori, from the oscillations of pendulams being slower and smaller in the equinoctial, than in the polar parts of the globe. See EARTH.

X. All the Moon's motions, and all the inequalities of these motions, follow from these principles, e. gr. her unequal velocity, and that of her nodes and apogee in the syzygies and quadratures; the differences in her excentricity and her variation. See Moon.

XI. From the inequalities of the lunar motions, we can deduce the several inequa lities in the motions of the satellites.

XII. From these principles, particularly the action of the Sun and Moon upon the Earth, it follows, that we must have tides, or that the sea must swell and subside twice every day. See TIDES.

XIII. Hence, likewise, follows the whole theory of comets, as that they are above the region of the Moon, and in the planetary spaces; that they shine by the Sun's light, reflected from them; that they move in conic sections, whose umbilici are in the centre of the Sun; and, by radi drawn to

the Sun, describe areas proportional to the times; that the orbits, or trajectories, are very nearly parabola's; that their bodies are solid, compact, &c. like those of the planets, and must therefore acquire an immense heat in their perihelia; that their tails are exhalations arising from and encompassing them like atmospheres. See ASTRONOMY.

NEW trial, in law. Formerly the only remedy for a reversal of a verdict unduly given, was by writ of attaint; but this course is now justly exploded, and a new trial is granted upon application to the court from which the cause issued.

A new trial, in many cases, may be absolutely necessary. But it is not granted upon nice and formal objections, which do not go to the real merits; nor where the scales of evidence. hang nearly equal. It is generally upon some misdirection by the judge to the jury, in point of law, or where

NIC

a jury has found a verdict directly against
evidence; but where there has been evi-
dence as to the fact in doubt, on both sides,
granted where damages have been given
the court will not interfere. It is also
beyond the ordinary measure of justice;
and where the party has been surprised by
some evidence which he has subsequently
the means of answering, but had not at the
mages do not exceed 101.
trial. It is always refused where the da-

Nicander of Colophon, a genus of the De-
›NICANDRIA, in botany, so named from
candria Monogynia class and order. Essen-
four-parted; corolla one-petalled, ten-cleft;
tial character: calyx turbinate, coloured,
germ encircled with a membranaceous ring;
stigma peltate, orbicular, six-rayed; berry
seeded. There is one species, viz. N. amara,
roundish, six-grooved, three-celled, many-
a native of the large forest of Guiana.

C. WHITTINGHAM, Printer,

103, Goswell Street.

END OF VOL. IV.

.

ΑΜΡΗΙΒΙΑ.

Plate I.

[graphic]

Fig. 1. Draco volans: Alving Dragon Fig. 2.Lacerta alligator: Alligator Fig. 3 L.basilecus: Basilisk.
Fig.4.L.crva dilus crocodile.

London Published by Longman Hurst Rees & Orm Dec. 23.1808.

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