thofe Bodies are greater or smaller. According to this Argument produced by moft, that all Effects are proportionable to their adequate Caufes: See Wallis Mechan. cap. 1. Prop. 7. So that if one certain Force caufes one Motion, the fame being doubled will caufe a double Motion, a triple Force, a triple Motion, and fo on.

And let him fuppofe, that if a Man in the beginning of the World, or four or five hundred Years ago, had laid a little round Marble upon a Table, and to put the fame in Motion had given it a Fillip with his Finger; the faid Marble, according to the abovemention'd Law of Nature, would (if no other Force had oppos'd its Motion) have moved to this very Minute with the fame Velocity in a Right-Line, and without ceafing, would have continued to run in the fame Line fuch a Length, as no Man could determine the end of.

He knows that this is no vain Opinion, but, as we have fully fhewn before, a Law of Nature really obtaining in moved Bodies, confirmed by very many Experiments, and upon which almoft the whole Science of Mechanics and Percuffions, particularly the Properties of accelerated and retarded Motion are founded; Examples of which may be met with in the Demonftrations of the two firft Propofitions of the Mechanics of Dr. Wallis.

And let him farther confider with himself, if no Divine and Incomprehenfible Power had place herein, which caufed the Continuation of this Motion, and which obliged all Bodies continually to obferve a Law, that otherwise was neither to be believed nor understood; whether he could imagine that the fmall and contemptible Force communicated by the Fillip of a Finger, could be the adequate Cause of fuch a Motion, by which this little Body can exceed in its Courfe all the Bounds

Bounds that he or any Man living is capable of prescribing to it, without any lofs of its Force and Velocity; and whether any one befides himfelf would fay, that this fo great an Effect can be accounted proportionable to fo mean a Caufe as the Fillip of a Finger; and if this does not fatisfie him, if he be a Mathematician, he must know firft, that no Body can be fo fmall, or move with fo little Force, but that ftriking against another, (which is at Reft, and has no Obftruction) how great foever this laft may be, it will move it, and caufe it to run forwards in a ftrait Line, fo that both of 'em will proceed with equal Swiftnefs; tho' fuch Swiftnefs will be fmaller than that which the firft moved Body was endowed with alone. (See befides, concerning this Matter, Wallis his Mechanics, Ch. XI. in the Scholium, Sec. II.)

So that from hence it follows, that when a little Body, not fo big as a Marble, but fo fmall even as the finest Grain of Sand, being protruded by the Fillip of a Finger, runs or strikes against another Body, which we will fuppofe to be as big as the whole Globe of the Earth, or if you will, thousands of times yet bigger (provided that neither of 'em be Elaftical, and confequently rebound from each other) this great Body will not only be protruded together with fuch a Grain of Sand according to a Right Line; but unless fome oppofing Force or Obstacle do intervene, and hinder the aforefaid Motion, the great Body, as well as the little Grain of Sand, will by the Force of this Fillip, continue to be moved according to the faid Line inceffantly; and if they were to meet in their Way with a hundred thousand of other Bodies, and each of them were a Million of times bigger than the Earth, they would carry them all along with 'em in Confequence of this small Force

Force, without any ones being able to determine how far.

Now that this, how wonderful foever it appears, is certainly true, no Mathematician cản deny; but let this Sceptical Philofopher, who hopes by the neceffary Deductions of one Law of Nature from another, to elude the Providence and Intervention of a God; I fay, let him fhew us from his Principles, whether he can any ways comprehend, not that fuch a Thing actually happens (for this the Mathematics will teach him) but how, and after what manner this Force of a little Grain of Sand fo moved does act; fo that any Percurffion thereof does not only protrude fuch unconceivable great Bodies with any Force, but likewife can continue the Motion of them without ceafing for thousands of Ages: And it has been long a queftion in Phyficks, How the Motion of one Body is communicated or transferr'd to another? which as far as I know, has never yet been rightly anfwered by any.

Then in cafe he could make no other Reply thereto, than that both the Communication and Continuation of Motion, is fomething which indeed he fees daily happening, and in the fame Cases; but that yet the most internal Effence of Motion is not fo well known to him, as that he fhould be able to fay, after what manner it paffes from one Body to another; and notwithstanding what is accounted the visible Caufe (as the Fillip, which in this Inftance produced fuch a Motion in the Sand) has long ceased to exift; yet the Effect may laft not only in its Form or Being, but likewife in the fame Force, fuch a Number of Years as no Man is able to determine; for to fhew the Greatness thereof, it is well known to thofe that understand Mathematicks, that according to this Law, a fix and thirty Pounder being protruded out of a Cannon

Cannon by the Force of the Gunpowder inflamed, would continue its Motion with the fame Strength and Swiftnefs for thousands of Years, unless hinder'd by fome other Force, notwithstanding that the Flame of the Gunpowder had ceafed long before: Will he not then even by this his own Anfwer be compelled to acknowledge, that here, as before in the Motion of the Body itself, there is likewise an incomprehenfible Power operating in the Communication and Continuation thereof ?

SECT. XV. The Reafons produced by fome for the Continuation of Motion, feems too weak.

I KNOW very well, that fome great Mathematicians who even confefs that they can fhew no Cause of this laft Phænomenon of Divine Power, which maintains every Thing in its Existence, and by Confequence likewife this Motion of a Bullet in its Continuation, to Illuftrate the Matter, affirm, that a Bullet being once put into Motion will always remain fo; juft as a Square, and a Globular Body will always retain the fame Figure; but I hope I fhall be excufed by them, if notwithftanding all the Efteem which I have for their Learning, I here add, that this Comparison, tho' produced with the beft Defign, which is to acknowledge God for the Caufe, feems to me fomewhat too weak, and not fufficiently Analogous and Proper: Since, Firft, tho' a Body being once turned from a Square into a Globular Figure, tho' it remains of itself Globular, yet the lafting Operation of the Globular Force does entirely cease: Whereas on the contrary, a Body that was once Still, and at Reft, being put into Motion, the lafting Operation of fuch moving Force will fully remain. Secondly, Since a Body cannot move of it felf, being according to the Description of

those

thofe Gentlemen a fluggish Lump of Matter, and all Motion feems to require a Force which continually produces it; forafmuch as we see fuch dreadful Strength and Violence exerted by a Body once moved (as for Inftance, by a Bullet hot out of a Cannon) which whilst it remained motionlefs, could not exert the leaft Force: So it feems to be a neceffary Confequence, that a Body that has continued already a thousand Years in Motion, fhould not retain the fame Motion for a thousand Years following, without a Power acting upon it, and producing farther Motion; whereas in order to retain a Circular Figure, there seems no farther Force to be neceffary, than that a Body fhould at first affume fuch a Figure.

Nor is this oppofed by any Mechanical Experiments or Rules; by which it plainly appears, that one Body running against and striking upon another, which other is at Reft, both of 'em will continue moving with equal Swiftness in a Right Line, till fome other Power fhall caufe a change therein; but it is not maintained nor demonstrated, that with the Continuation of this Motion the Power that protruded the Body, does not remain conftantly acting.

Now which foever of these be true, it is fure enough; 1. That this Communication and Continuation of Motion are both obfcure and entirely unconceivable, as to the manner of their Production. 2. That they are the Foundation of every Thing we are taught in Mechanics, and of all that happens in the World; infomuch, that nothing can fcarce appear plain either in Mechanics or Phyfics, to fuch who have not inquired into the Laws thereof.

SECT.