ted; its Rays would be lefs penetrant ; and Darknefs would with greater Difficulty and much Sluggifhnefs, be diffipated, efpecially by the fainter Lights of our fublunary, luminous Bodies. But paffing with fuch prodigious Velocity, with nearly the inftantaneous Swiftnefs of almoft Two hundred thoufand English Miles in one Second of Time, (e) or (which is the fame Thing) being but about seven or eight Minutes of an Hour in coming from the Sun to us, therefore with all Security and Speed, we receive the kindly Effects and Influences of that noble and useful Creature of God.

2. Another Thing of great Confideration about Light is, its vaft Expanfion, it's almoft incomprehenfible, and inconceivable Extenfion, which as a

(e) Mr. Romer's ingenious Hypothefis about the Velocity of Light, hath been established by the Royal Acamedy, and in the Obfervatory for eight Years, as our Phil. Trans. No. 136. obferve from the Journ. des Scavans; our most eminent Aftronomers alfo in England admit it: But Dr. Hook thinks with Monfieur Cartes, the Motion of Light Inftantaneous, Hook Poft. Works, pag. 77. And this he endeavours to explain, pag. 130, &c.

What Mr. Romer's Hypothefis is, may be feen in the Phil. Tranfact. before-cited: As alfo in the before commended Sir Ifaac Newton's Opticks: Light is propagated from luminous Bodies in time, and spends about seven or eight Minutes of an Hour in paffing from the Sun to the Earth. This was first obServed by Romer, and then by others, by means of the Eclipfes of the Satellites of Jupiter. For thefe Eclipfes, when the Earth is between the Sun and Jupiter, happen about feven or eight Minutes fooner than they ought to do by the Tables; and when the Earth is beyond the O, they happen about feven or eight Minutes later than they ought to do: The reafon being, that the Light of the Satellites hath farther to go in the latter Cafe than in the former, by the Diameter of the Earth's Orbit. Newt. Opt. L. 2. Part. 3. Prop. II.

Now forafmuch as the Distance between the Sun and the Earth (according to the Computations in my Aftro-Theology, B. 1. ch. 3. Note 2.) is 86051398 English Miles; therefore, at the rate of 7 Minutes, or 450 Seconds in paffing from the Sun, Light will be found to fly above 191225 Miles in one Second of Time.

late

late ingenious Author (f) faith, "Is as boundless "and unlimited as the Universe it felf, or the Ex"panfum of all material Beings: The vastnefs of "which is fo great, that it exceeds the Comprehen"fions of Man's Understanding. Infomuch that vecc ry 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

(f) Dr. Hook Poft. Works. Lect. of Light, pag. 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 vast 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 published to prove the Motion of the Earth, [which were Obfervations of the Parallax of fome of the fixt 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 fixt 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 fort yet (maller be three times as far; and a fourth four times as far, and so onward, poffibly to fome 100 Degrees of Magnitude, fuch as may be discovered by longer and longer Telescopes, that they may be 100 times as far; then certainly this material Expansion, a part of which we are, must be fo great, that 'twill infinitely exceed our fhallow Conception to imagine. Now, by what I last mentioned, it is evident that Light extends it self 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 the great Body of the Sun. or the vaft Bodies of the fixt Stars, that are thus able to difperfe their Light through the vast Expanfum of the Univerfe; 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 Univerfe, would for the fame Reafon be visible too.

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

СНАР. V.
Of Gravity.

HE laft Thing fubfervient to our Globe, that I fhall 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 manifeft 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 attractive 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 Philofophy is grounded, and not upon chimerical and uncertain Hypothefes But whatever the Caufe is, that Caufe penetrates even to the Centers of the Sun and Planets, without any Diminution of its Virtue; and it afteth 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 Distances, decreafing in duplicate proportion to those

Distances,

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

noble

Distances, as Sir Ifaac Newton faith, Princip. pag. ult. What ufeful Deductions, and what a rational Philofophy have been drawn from hence, may be feen 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 Refiftence of the Medium, all Bodies would defcend to the Earth at the fame rate; the lighteft Down, as fwiftly as the heaviest Mineral: As is manifeft 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 first Second. The Experiments 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 207, the Thermometer 60 Degrees above Freezing. The Weight of the Balls, their Diameters, and Time of the Defcent is in this Table.

The Reason why the heavy, full Balls fell in half the Time of the hollow ones, was the Refiftence of the Air: Which Refiftence is very ingenioufly and accurately affigned by Dr. Wallis, in Philof. Tranf. No. 186. And the caufe of the Refiftence 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 Refiftence a fpherical Body 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 Univerfe 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 Refiftence from the Vis Inertia, is as the Square of that Product.

For a farther Account of the Properties and Proportions, . of Gravity in the Fall or Projection of Bodies, I fhall refer to the larger Accounts of Galilaus, Torricellius, Huygens, Sir Ifaac Newton, &c. or to the shorter Accounts of Dr. Halley in Philof. Tranf. abridged by Mr. Lowtherp, Vol. I. p. 561. or Dr. Clarke in his Notes on Rohault, Phys. 2. c. 28. S.13, 16. And for the Refiftence of Fluids, I refer to Dr. Wallis before-cited, and the Act. Erudit. Lipf. May 1693. where there is a way to find the Force of Mediums upon Bo dies of different Figures.

(6) That the heavenly Bodies move round their own Axes, 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. The Spots on and prove thofe two Planets to revolve alfo from Eaft to Weft, as Dr. Hook difcover'd in 1664, and 1665. And alfo (although 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. V. Lowth. Abridg. Vol. 1. p. 382, and 423, 425. And fuch Uniformity hath the Creatør observ'd in the Works of Nature, that what is observable 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 fo too, yea, every Globe of the Universe.

(c) The Earth's Circumference being 25031 Miles, (according to Book II, Chap. 2. Note a.) if we divide that into 24 Hours, we fhall find the Motion of the Earth to be nearly 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 suppose the Earth to ftand ftill, 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