faften'd in a Piece of Wood, being likewife placed in the Focus of a Glafs of twelve or thirteen Inches, the Rays struck against the loose End of it, and caused it to move backwards and forwards juft as if it had been thruft with a Stick..

Now this does undeniably prove a great Swiftness of Light; yet this amazing Course of it, as it furpaffes all Imagination, fo with many would it exceed all Appearance of Truth, were it not that the ten Years Obfervations made by Mr. Romer, upon the Eclipfes of Jupiter's Satellites, had put this Matter fo much out of Difpute and Doubt, that the greatest and most accurate Mathematicians have been forced to admit it upon the Strength of those Experiments.

It fhall fuffice here, that we may not fwell this Discourse too much, to produce only the Teftimony of Sir Ifaac Newton, tho' we could likewife add many others; these are the Words of that Gentleman in his Princ. Philof. p. 231. Prop. 96. Lib. 1. in the Scholium. For that Light is pushed on fucceffively, the Parts of it following each other, and that it paffes from the Sun to the Earth in the Space of ten Minutes (in the fecond Edition he has alter'd it to feven or eight Minutes) is now certain by the Appearances of Jupiter's Satellites, and confirmed by the Obfervations of feveral Aftronomers.

And when afterwards he published his Opticks, which are proved and illuftrated by a Number of wonderful Experiments, we find him speaking after this Manner, in the Eleventh Propofition of the Second Book of the Third Part, p. 236. The Light is tranfmitted in a certain Space of Time from the illuminating Body, and employs about feven or eight Minutes in its Course from the Sun to the Earth: Whereupon he adds the Proof, the first Words of which are, This was firft obferved by Romer, and afterwards by others, by Means of the Eclipfes of Jupiter's VOL. III. A a s Satellites:

Satellites: In his fecond Edition of his Opticks, he only allows about feven Minutes for this Paffage of the Light.

They that defire to fee this more largely proved, may confult Mr. Huygens, in his Treatife of Light; Mr. Whifton in his Pralect. Aftronom. and others. Besides, that the Impoffibility of the contrary Hypothefis has been already fhewn both by Newton and Huygens.

It is fufficient for us, fince we cannot here defcribe the Particularities of Aftronomy, to fhew that this has been proved to be an unconteftable and certain Argument, by the most accurate Inquirers into the Nature of Light, and that the boldest Atheists have no Reason to doubt thereof, unless they understand nothing of Mathematicks, or are ignorant of the latest Discoveries about the Properties of Light; or if they would be pleased to read the aforemention'd Aftronomical Lectures of Mr. Whifton, p. 229, and 230. where the Recti-linear Progreffive Motions of the little Particles of the Light are largely handled and proved beyond all doubt; and where he thews, according to the niceft Obfervations, that in half a quarter of an Hour's time, the Light paffes through all that Space that is between the Sun and the Earth. And this being allowed, let them reflect with themselves, whether it be credible, that it is by meer Chance, and without any Direction, that Bodies protruded with fuch an amazing Swiftnefs, can always obey fo many Laws without once varying in their unconceivable Progrefs, as it has been obferved with respect to Light upon fo many Occafions; of which more hereafter.

SECT.

SECT. XXI. What would be the Confequence, if the the Rays of Light fhould become a Solid Body, and the Parts thereof adhere to each other.

I SHALL here add, that I have been exceedingly affected with the Confideration of the dreadful Velocity of Light, as often as I thought that if once so many Particles thereof should adhere to each other, fo as to compofe a little Body, weighing no more than the tenth Part of a Grain, they would exert as great a Force by the Swiftnefs of their Motion in ftriking upon any Body upon the Earth, as a Bullet of twelve Pound Weight fhot out of a great Cannon.

Now that it is not impoffible that Light fhould become a folid Body, feems to be proved by that Matter which we at prefent call a Phosphorus, which feems to confift altogether, or for the moft part, of a combined Fire or Light; forafmuch as if we put the fame into Oyl of Cloves, the Light thereof cleaves to the Oyl, and caufes it to fhine, as is known to the Chymifts.

And now that no body may think fuch a dreadful Force improbable, which we fuppofe to be in the defcending Light, in the aforefaid Circumftances, let him fuppofe :

I. That Light paffes in half a Quarter of an Hour, or 450 Seconds from the Sun to the Earth, which has been fhewn above to amount to the Number of 78,463,128,000 French Fathoms.

II. It follows then, that this being divided by 450, the Light paffes thro' 174,362,506 thereof in one Second or Pulfe. Let us fuppofe it, for, the fake of a round Number, to be just 174,362,500.

III. Now a Twelve-pounder fhot out of a Cannon is found to advance in the fame time a hundred of thefe Fathoms:

IV. And

IV. And it is manifeft from the Laws of Mechanicks and the Doctrine of Percuffion, that the Force of Projectiles, with refpect to their Course and Percuffion, are in the fame Proportion to each other, as their Weights multiplied with the length of the Way which they make in the fame Time. Now for the fake of thofe that do not underftand Mathematicks, we fhall fpeak a little more plain, and fay; that a Bullet of fix Pound, which in a certain Time runs the Distance of 200 Fathom, has twice as much Force, as a Bullet of twelve Pound, that runs but 50 Fathoms in the fame Time; for 6 times 200 makes 1200, and 12 times 50 is but 600, or the half of 1200: After the fame manner, a Bullet of 12 Pound running 100 Fathom, in a certain Time, has as much Force as a Bullet of 6 Pound that

runs 200 Fathoms; of 3 Pounds and 400 Fathoms; of 2 Pounds and 600 Fathoms, in the fame Time, &c. forafmuch as the Weight of each of thefe Bullets being multiplied with the Way that they make in the fame Space of Time, does always produce the like Number of 1200.

V. From whence we may infer, That in cafe an Aggregate of Light by its Velocity, does a& with the fame Force as a Bullet of 12 Pounds; then in order to find out theWeight of the Light neceffary thereto, this Rule will have Place.

Wherefore, as the Length of the Way (or as 174,362,500 French Fathoms) which the Light goes in the Second of a Minute, is to the Length of the Way that fuch a Bullet runs in the fame time (or to 100 of fuch Fathoms ;) fo is the 12 Pound-weight of the Bullet to the Pounds, or rather to the Weight of this Body of Light, that has the fame Force.

VI. This Rule of Three being calculated, the Weight which the Light will have upon this Ocfion will be 174625 of a Pound.

X 2

And

And fuppofing a Pound, of 16 Ounces, to contain 7680 Grains, and thofe Ounces to be Troy-Weight, the Weight of this Body of Light will be 4162, or about of a Grain, as is faid before.

2160

17436259

SECT. XXII. Convictions from thence.

Now in order to be convinced not only of the Prefence, but likewise of the Neceffity of a Divine Direction, fince this dreadful Swiftnefs of Light is known, and fince we find by Experience, in thousands of Bodies, that Light will adhere to them, and become a folid Body, and they being kindled, it will appear again; let an unhappy Infidel once more ask himself, by what Law or Neceffity of Nature it happens, that this Light never comes to be turned into a little folid Body, whilft it is in the Sun, and fo defcend to us with its ufual Celerity; whereas Water is converted to Hail in the Air, and the Spots in the Sun feem to reprefent fuch a Cohesion of Parts. Certainly if Chance only had place here, we cannot give the leaft Reason why it fhould not fo happen, or why a dreadful Storm of thefe collected and compreffed Particles of Light, fhould not overfpread the whole Earth with utter Destruction in an Inftant.

SECT. XXIII. Light runs in ftrait Lines.

ONE of the Properties of Light is, its Motion in Right Lines,from whence, according to all Experiments, the Separation between Light and Darkness is juftly deduced, and fo likewife are the Shadows in Perspective.