LXXIV. The Satellites of Jupiter do, by Rays drawn to the Center of Jupiter, defcribe Areas proportional to the Times: And their periodic Times are in the fefqui-alteral Proportiof their Distances from the Center of their Primary.

LXXV. The Satellites of Saturn do, by Rays drawn to the Center of Saturn, defcribe Areas proportional to the Times: And their periodic Times are in the fefqui-alteral Proportion of their Distances from the Center of their Primary.

LXXVI. The Force whereby the Primary Planets are perpetually drawn back from right Lines, and retain'd in their Orbs, does refpect the Sun; and is as the Squares of the Diftances from the Center of the Sun reciprocally.

LXXVII. The Force wherewith the Satellites of Jupiter and Saturn are perpetually drawn back from right Lines, and retain'd in their Orbs, refpect the Centers of Jupiter and Saturn refpectively; and is as the Squares of the Distances from thofe Centers reciprocally.

LXXVIII. The Force wherewith the Moon is perpetually drawn back from a Rectilinear Motion, and retain'd in its Orb, respects the Center of the Earth; and is as the Squares of the feveral Distances from the fame Center reciprocally.

PART

PART II.

A particular Account of the Syftem of the Universe.

T

HE Sun, that immenfe and amazing Globe of Fire, the Fountain of all the Light and Heat of the whole Planetary and Cometary World, is in Diameter 763 000 Miles, in Surface it contains 1,813.200,000.000 Square Miles, and in Solidity 23.000,000.000,000 000 Cubical Ones, in Magnitude 9c0.000, and in Quantity of Matter 230.000 Times as great as the Earth, tho' only a Quarter fo Denfe; and all Bodies weigh 24 Times as much on its Surface, as on the Surface of the Earth. It is fituate near the Center of Gravity of the whole System, and revolves in about 25 Days and a half round its own Axis. It has frequently Spots, and fometimes brighter Parts feen upon its Surface, of vaft Dimenfions; as if they were great burning Vulcanes, fometimes clouded with Smoke, and fometimes clear. Its Heat, on its own Surface

is above 11000 Times as Intense as that on the Earth. All the Planets and Comets gravitate to the Sun in a duplicate reciprocal Proportion of their Distances from it, and are thereby retained in their feveral Orbits. Their Periodical Times are in a fefquiplicate or fefquialteral proportion to their Distances; that is, the Triplicate or Cubes of the Distances, are as the Duplicate or Squares of the periodical Times; and that to the greatest Exactnefs poffible; which equally obtains in the fecondary Planets, with regard to their primary Ones alfo; and is the fundamental Law of the entire System.

Mercury is the nearest to the Sun of all the known Planets. Its utmoft Elongation from it, to an Eye on the Earth is but 28 Degrees, fo that it is but rarely feen by us. This Planet is in Diameter 4.248 Miles, in Surface it contains 55,000.000 of fquare Miles; and in Solidity 39.000,000.000 of Cubical Ones,& is 32,000.000 Miles diftant from the Sun, and describes a very Eccentrical Ellipfis about it in less than 3 Months, or in 88 Days. The Eccentricity of its Orbit is of its mean Distance from the Sun and by its Pofition must appear thro' a Telescope with Phafes like thofe of the Moon.No fecondary Planets have yet been obferved about it, nor any Diurnal Rotation. It enjoys above 6 Times as much Light and Heat from the Sun, as doth the Earth; and it appears very rarely like a Spot in the Disk of the Sun, in its Retrograde Conjunctions, when it paffes between the Sun.

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and Earth.

Venus is fomewhat higher in the System, and fo has its utmost Elongation 45 Degrees. It is a larger Planet than Mercury, and comes fome

times much nearer to us. It is our Morning and Evening Star by turns, and is the Brighteft of the Heavenly Bodies to us, next the Moon, as cafting a visible Shadow in the Dark, and fometimes appearing in the very Day-time also. It is in Diameter 7.900 Miles; in Surface it contains 2.000,000.000 of Square Miles; and in Solid it is 264.000,000.000 of Cubical Ones and is diftant 59,000.000 from the Sun, and defcribes its Ellipfis about it in 7 Months and a half, or 225 Days. The Eccentricity of its Orbit is but of its mean Distance from the Sun. It moft plainly thro' the Tellescope appears with Phases, and Horned like the Moon. No fecondary Planets have yet been discovered about it, yet has it a Diurnal Revolution on its own Axis in 23 Hours. It receives almoft double the Light and Heat from the Sun which the Earth does; and appears very rarely as a Spot in the Sun also.

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The Earth is the next Planet to Venus, and has the Moon for its fecondary Planet; the common Center of whofe Gravity describes an Ellipfis about the Sun in one Year, or 365 Days. and a Quarter, nearly, the Eccentricity of its Orbit is of its mean Distance from the Sun, in Surface it contains 200,000.000 of Square Miles, and in Solidity 266.000,000.000 of Cubical Ones, and is in Diameter 7.970 Miles. and is diftant from the Sun 81,000.000 Miles. This Annual Motion is perform'd in the Ecliptick, and is directed, as is that of all the Planets, primary and fecondary, from Weft to Eaft, or according to the Order of the Signs, and therefore caufes the Sun to have an apparent Annual Motion the fame way, and in the

fame

fame Plain; but as ftill in the oppofite Point of the Ecliptick. It has alfo a Diurnal Rotation upon its own Axis from Weft to Eat in 24 Hours, and fo occafions an apparent Motion of all the Heavenly Bodies from East to West in the fame time. The Axis of the Diurnal Motion is 23 Degrees and one half, oblique to that of the Ecliptick, which occafions the Varieties of Spring, Summer, Autumn, and Winter. It is in Figure an Oblate Spheroid, as having the Diameter of its Equator about 62 Miles longer than its Axis, on Account of the Elevation of the Equatorial and Depreffion of the Polar Regions, occafion'd by the centrifugal Force of the Diurnal Motion.

Mars is ftill higher in the System, and looks more red and fiery than the rest of the Planets. It takes a larger Circuit than the Earth, and fo comes to its Conjunction, Quadratures and Oppofition; and in fome Degree imitates the Phafes of the Moon, being fometimes only Gib bous, tho' it cannot be at all Horned like the other. This Planet defcribes its Ellipfis about the Sun in lefs than 2 Years, or in 687 Days. The Eccentricity of its Orbit is of its mean Distance from the Sun; it is in Diameter 4444 Miles; in Surface it contains 60,000.000 of Square Miles; and in Solidity 44.000,000.000 of Cubical Ones; and is diftant from the Sun 123,000.000 Miles; it has no fecondary Planet that can be seen, but revolves about its own Axis in 24 Hours and 40 Minutes. The Quantity of Light and Heat it enjoys from the Sun is between one half and one third of what the Earth receives from it. It alfo appears to us upon the Earth to be fometimes Direct, fomes C

times