Book I. late ingenious Author (f) faith, "Is as boundless " and unlimited as the Universe itself, or the Ex

panfum of all material Beings: The Vaftnefs of "which is fo great, that it exceeds the Comprehen"fions of Man's Understanding. Infomuch, that "very many have afferted it abfolutely infinite, and "without any Limits or Bounds.

And that this noble Creature of God is of this Extent, (g) is manifeft from our feeing fome of the fartheft diftant Objects, the Heavenly Bodies, fome

with

(f) Dr. Hook's Pofthumous Works. Lect. of Light, p. 76. (g) For the Proof of this vaft Extent of Light, I shall take the Computation of the fame great Man, pag. 77. If, faith he, we confider first, the waft Distance between us and the Sun, which from the best and latest Obfervations in Aftronomy, is judged to be about 10000 Diameters of the Earth, each of which is about 7925 English Miles; therefore the Sun's Distance is 7925000 Miles; and if we confider, that, according to the Obfervations, which I publifhed to prove the Motion of the Earth, [which were Obfervations of the Parallax of fome of the fix'd Stars in the Head of Draco, made in 1699,] the whole Diameter of the Orb, viz. 20000, made the Subtenfe but of one Minute to one of the fix'd Stars, which cannot therefore be lefs diftant than_3438 Diameters of this great Orb, and confequently 68760000 Diameters of the Earth: And if this Star be one of the neareft, and that the Stars that are of one Degree leffer in Magnitude (I mean not of the Second Magnitude, because there may be many Degrees between the first and fecond) be as much farther; and another Sort yet fmaller be three Times as far; and a Fourth four Times as far, and fo onward, pofibly to fome 100 Degrees of Magnitude, fuch be difcovered by longer and longer Telescopes, that they may be ico Times as far; then certainly this material Expansion, a Part of which we are, must be so great, that 'twill infinitely exceed our fhallow Conceptions to imagine. Now, by what I last mentioned, it is evident, that Light extends itself to the utmost imaginable Parts, and by the Help of Telescopes, we collect the Rays, and make them fenfible to the Eye, which are emitted from fome of the almost inconceivably remote Objects, &c.· Nor is it only

as may

the great Body of the Sun, or the vaft Bodies of the fix'd Stars, that are thus able to difperfe the Light thro' the vaft Expansum of the Universe; but the smallest Spark of a lucid Body must do the very fame Thing, even the smallest Globule ftruck from a Steel by a Flint, &c.

with our naked Eye, fome with the Help of Optical Inftruments, and others in all Probability farther and farther, with better and better Inftruments: And had we Inftruments of Power equivalent to the Extent of Light, the luminous Bodies of the utmost Parts of the Universe, would, for the fame Reason be visible too.

Now as Light is of greatest Use to impower us to fee Objects at all, fo the Extenfion thereof is no less useful to enable us to fee Objects afar off. By which Means we are afforded a Ken of those many glorious Works of the infinite Creator, visible in the Heavens, and can improve them to fome of the nobleft Sciences, and moft excellent Ufes of our own Globe.

T

CHA P. V.

Of Gravity.

HE laft Thing fubfervient to our Globe, that I shall take Notice of, is Gravity (a); or, that Tendency which Bodies have to the Centre of the Earth.

In

(a) That there is fuch a Thing as Gravity, is manifest from its Effects here upon Earth; and that the heavenly Bodies attract or gravitate to one another, when placed at due Diftances, is made highly probable by Sir Ifaac Newton. This at tractive, or gravitating Power, I take to be congenial to Matter, and imprinted on all the Matter of the Universe by the Creator's Fiat at the Creation. What the Cause of it is, the Newtonian Philofophy doth not pretend to determine for want of Phænomena, upon which Foundation it is that that Philo fophy is grounded, and not upon chimerical and uncertain Hypothefes: But whatever the Caufe is, that Cause penetrates even to the Centres of the Sun and Planets, without any Diminution of its Virtue; and it acteth not according to the Superficies of Bodies (as Mechanical Caufes do) but in Proportion to the Quantity of their folid Matter: And lastly, it acteth all round it at immenfe Diflances, decreafing in duplicate Proportion to those

Diftan.

In my Aftro-Theology, Book 6. Chap. 2. I have fhewn of what abfolute Neceffity, and what a

noble

Diflances, as Sir Ifaac Newton faith, Princip. pag. ult. What ufeful Deductions, and what a rational Philofophy, have been drawn from hence, may be seen in the fame Book.

This Attraction, or Gravity, as its Force is in a certain Proportion, fo makes the Defcent of Bodies to be at a certain Rate. And was it not for the Refistance of the Medium, all Bodies would defcend to the Earth at the fame Rate ; the lighteft Down, as fwiftly as the heavieft Mineral: As is manifelt in the Air-Pump, in which the lighteft Feather, Duft, &c. and a piece of Lead, drop down feemingly in the fame Time, from the Top to the Bottom of a tall exhaufted Receiver.

The Rate of the Defcent of heavy Bodies, according to Galileo, Mr. Huygens, and Dr. Halley (after them) is 16 Feet one Inch in one Second of Time; and in more Seconds, as the Squares of thofe Times. But in fome accurate Experiments made in St. Paul's Dome, June 9, 1710. at the Height of 220 Feet, the Defcent was fcarcely 14 Feet in the firft Second. The Experimennts were made in the Prefence of fome very confiderable Members of the Royal Society, by Mr. Hawksbee, their Operator, with Glafs, hollow Balls, fome empty, fome filled with Quick-filver the Barometer at 297, the Thermometer 60 Degrees above Freezing. The Weight of the Balls, their Diameters, and Time of the Descent is in this Table.

The Reason why the heavy full Balls fell in half the Time of the hollow Ones, was the Refiftance of the Air: Which Refiftance is very ingenioufly and accurately affign'd by Dr. Wallis, in Philof. Tranf. No 186. And the Caufe of the Refiftance of all Fluids, (as Sir Ifaac Newton, Opt. Q. 20.) is partly from the Friction of the Parts of the Fluid, partly from the Inertia thereof. The Refiftance of a spherical Rody meets with from Friction, is as the right Angle under the Diameter,

and

noble Contrivance this of Gravity is, for keeping the feveral Globes of the Universe from shattering to Pieces, as they evidently muft do in a little Time, by their fwift Rotation round their own Axes (b). The Terraqueous Globe particularly, which circumvolves at the rate of above 1000 Miles an Hour (c), would

and the Velocity of the moving Body: And the Refiftance from the Vis Inertia, is as the Square of that Product.

For a farther Account of the Properties and Proportions, &c. of Gravity in the Fall or Projection of Bodies, I fhall refer to the larger Accounts of Galilæus, Torricellius, Huygens, Sir Ifaac Newton, &c. or to the fhofter Accounts of Dr. Halley, in Philofoph. Tranfact, abridged by Mr. Lovuthorp, Vol. I. p. 561. or Dr. Clarke in his Notes on Robault, Phyf. 2. c. 28. Sect. 13, 16. And for the Refiftance of Fluids, I refer to Dr. Wallis, before-cited, and the A&t. Erudit. Lipf. May 1693. where there is a Way to find the Force of Mediums upon Bodies of different Figures.

(6) That the Heavenly Bodies move round their own Axis, is, beyond all Doubt, manifeft to our Eye, in fome of them, from the Spots vifible on them. The Spots on the Sun (eafily visible with an ordinary Glafs) do manifeft him to revolve round his own Axis in about 25 Days and quarter. The Spots on Jupiter and Mars prove those two Planets to revolve alfo from East to Weft, as Dr. Hook difcovered in 1664, and 1665. And Venus alfo (altho' near the ftrong Rays of the Sun) hath, from fome Spots, been discovered by Mr. Caffini, in 1666. and 1667, to have a manifeft Rotation. Vide Lowthorp's Abridg. ol. I. p. 382, and 423, 425. And fuch Uniformity hath the Creator obferv'd in the Works of Nature, that what is obferTable in one, is generally to be found in all others of the fame Kind. So that fince 'tis manifeft the Sun, and three of his Planets whirl round, it is very reasonable to conclude all the reft do so too; yea, every Globe of the Universe.

(c) The Earth's Circumference being 25031 Miles and half, (according to Book II. Chap. 2. Note (a) if we divide that into 24 Hours, we shall find the Motion of the Earth to be near 1043 Miles in an Hour. Which, by the by, is a far more reasonable and lefs rapid Rate, than that of the Sun would be, if we fuppofe the Earth to ftand still, and the Sun to move round the Earth. For according to the Proportions in Note (e) of the preceding Chapter, the Circumference of the Magnus Orbis is 540686225 English Miles, which divided by 24 Hours, gives 22528364 Miles in an Hour. But what is

Book I. would by the centrifugal Force of that Motion, be foon diffipated and fpirtled into the circumambient Space, was it not kept together by this noble Contrivance of the Creator, this natural inherent Power, namely, the Power of Attraction or Gravity.

And as by this Power our Globe is defended against Diffipation, fo all its Parts are kept in their proper Place and Order. All material Things do naturally gravitate thereto, and unite themfeves therewith, and so preserve its Bulk intire (d). And the fleeting Waters, the most unruly of all its Parts, do by this Means keep their conftant Equipoife in the Globe (e), and remain in that Place which, the Pfalmift faith, God had founded for them; a Bound be had fet, which they might not pafs; that they turn not again to cover the Earth, Pfal. civ. 8, 9. So, that even in a natural Way, by vertue of this excellent Contrivance of the Creator, the Obfervation of the Pfalmift is perpetually fulfilled, Pfal. Ixxxix. 9. Thou ruleft the raging of the Sea; when the Waves thereof arife, thou ftilleft them.

To thefe, and an hundred other Ufes of Gravity that I might have named, I shall only just mention another Thing owing to it, and that is Le

vity,

this to the Rapidity of the fix'd Stars, if we fuppofe them, not the Earth, to move? Which is a good Argument for the Earth's Motion.

(d) Nihil majus, quàm quòd ita ftabilis eft Mundus, atque ita cohæret ad permanendum, ut nihil nè excogitari quidem poffit aptius. Omnes enim partes ejus undique medium locum capeffentes, nituntur æqualiter: maximè autem corpora inter fe juncta permanent, cùm quodam quafi vinculo circumdata colligantur: quod fa cit ea natura, quæ per omnem mundum omnia Mente, & Ratione conficiens, funditur, & ad medium rapit, & convertit extrema. Cic. de Nat. Deor. 1. 2. c. 45.

(e) Eâdem ratione Mare, cùm fupra terram fit, medium tamen terræ locum expetens, conglobatur undique æqualiter, neque redundat, unquam, neque effunditur. Id. paulo poft.

(f) That