touched by the ftreight line E F in the point E, and if both the Ellipfe and Circle were turned round the Axis A B there would also be a Spheroid and a Sphere generated; both which would have the fane Plane touching them in the point E, because the periphery of a Circle whofe Radius is DE would be in both their furfaces, and the Ellipfis and Circle touch one another in the point E, that is, because the Horizons at E are fuppofed to be in the Plane which toucheth the Spheroid and Sphere in that point; both these Figures will have the fame Horizons. The fame thing is demonstrated of any other point.

As for his other thought, viz. That the Sea ought to be feventeen miles deeper at the Equator than at the Poles; he would have done well to have offered us fome of his abftrufe reasons why it ought to be fo, for a common Reader, that is not used to his profound way of thinking, cannot eafily perceive any, for he will not fuppofe without any arguments for it, that the Channel of the Sea is exactly of a Spherical furface, but rather think with the rest of mankind, that it is raised after the fame manner that the surface of the Sea is, and is further diftant from the Center at the Equator than at the Poles.

His next is a very ftrange thought about Rivers. For (fays he) if the Earth were of a broad Spheroidical Figure, and if we fhould fuppofe a Canal cut from the Equator

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to the Poles, it were a paradox to fay, that the water will not defcend from the Equator to the Poles; but it would be a greater to fuppofe, that Rivers would rife from thence to the Equator. Well, if this be a paradox, I hope he will thank me if I teach him how to folve it.

For the greater eafe and clearness, let us fuppofe the matter of the Earth first to have been fluid. If this matter had no Centrifugal force, it would fettle its felf into an uniform fmooth (tho' Spherical) furface; but the Earth being turn'd round its Axis, and all the parts of it by this rotation acquiring a Centrifugal force, and thofe at the Equator having a stronger force to recede from their Axis than thofe towards the Poles; it is evident, that the fluid at the Equator would rife no higher than that towards the Poles, and the fluid would fettle its felf into a broad Figure; as is here reprefented, [Fig. 16. Plate VIII.] where, EQ reprefents the Diameter of the Equator, PP its Axis.

Now this being the Figure which arifes from the force of Gravity joined with the Centrifugal force, it is evident, that as long as these two caufes continue to act, this Figure will remain the fame, and the fluid will not alter its pofition nor defcend from Æ to P; but that cause which firft brought it into fuch a pofture, will always preferve it in the fame. Or if we fhould fuppofe this Figure

alter'd

alter'd or chang'd by any external force, fo that the Diameter of the Equator was made fhorter; it is evident, that affoon as this external force is taken off, that the fluid being acted by the two already mentioned forces, will immediately restore its felf into its former natural figure; and the parts of the fluid will never come to an equilibrium one with another, till they fettle fo as that the Spheroid have the fame surface it had before.

Let us next fuppofe this fluid Spheroid to be chang'd into a folid one, all except one Channel extended from Æ to P, and as deep as you please: The fluid in this Channel having the fame forces to act upon it, according to the fame direction, and in the fame manner, will still keep the fame pofition, without ever changing its figure, and every part will remain in the fame place that it was in before; it being indifferent to the fluid in the Channel, EP whether the matter next it be fluid or not fluid, folid or not folid.

By this, I hope it will appear no paradox to fay, that if a Channel were cut from the Poles to the Equator, that the water would not run from thence down in this Channel to the Poles. I will next make it appear no paradox, to say, that water may be made to run from the Poles to the Equator. It is well known, that (whatever be the Figure of the Earth) water will not run from the Land to

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the Sea, except the Land be raised higher than the Sea, and be made to incline to it. Let us therefore fuppofe that BMNO Æ

Fig. 17. Plate VIII. were the surface of the Land raised higher than the Sea, but always inclining to it till it meets with it in Æ. It is plain, that whatever water is at B, will endeavour to approach to the furface PE as much as it can, and fettle it self there in its natural figure; and because the point M is nearer to the furface PE than B, the water must move from B to M, but the point N being nearer to the furface into which the water does naturally affect to fettle its felf: it is evident, that this water will likewise move from M to N; after the fame manner and upon the fame account, would the water move from N to O and from 0 to E, it ftill coming nearer to the furface upon which it would naturally fpread it felf, that is, it would move from the Poles to the Equator. Thus, I hope I have made it manifeft, that it is no great paradox to say, that the water will move from P to E or from the Poles to the Equator. I have infifted more largely upon this point, that it may appear more evident to the Defender; because it seems he cannot understand fuch reafonings, unless they are made very plain; for I had faid the fame things in the Examination tho' somewhat more obfcurely.

Before

Before I leave this fubject, I cannot but obferve, that tho' our Author perhaps is very well acquainted with the Antediluvian Geography and the rife of its Rivers, yet it feems that his skill is not very great in the modern. For he makes Nile in Africk to cross the line, whereas if he had confulted the modern Geographers and their obfervations, he had seen that the Nile rifes fome degrees on this fide of the line, as it is to be feen in Ludolphus's Map of Ethiopia.

After this fine difcourfe of our Authors about the ascending of Rivers towards the Equator, to conclude the argument he says, that if this difference of Pendulums were found, it will ftill bear a difpute from what Phyfical caufes it proceeds. He indeed may difpute it, and perhaps will never come to know it as long as he lives, but I believe very few elfe will ever doubt, but that it proceeds from a greater Gravity in the one. place than there is in the other; efpecially fince it can be prov'd from demonstrative principles, that if there be two Pendulums of equal lengths that perform their Vibrati ons in unequal times, that the Gravity where the fwifteft Pendulum Vibrates, is greater than where the floweft is. This I fay can be demonftrated from moft evident and Geometrical principles; and if the Defender does not understand them, it will be his wifeft courfe to fufpend his judgement till he has T 4

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