of the Current, and the great Flakes of Ice which are commonly found in these Streights. Upon the northern Coast of America, the Pacific Ocean flows towards the Streights of Anian; there is alfo a Current from Japan towards China; and another from Eaft to Weft, thro' the Streights of Macaffer. In fhort, the whole Atlantic Ocean makes towards the Shores of America, and the Pacific from them, as is most remarkable about Cape Correntes, between Panama and Lima. PROPOSITION VIII. The Winds frequently change the general Motion of the Sea, especially thofe called Periodical Winds, or Monfoons, which we fhall treat of in Chapter xxi. BECAUSE these Winds blow most frequently from the North or South, or from other collateral Points, they must needs obftruct the general Motion of the Sea, which is from East to Weft, and cause it to turn afide, from the West, towards the North-Weft, or South-Weft. And even the constant, or Trade-Winds, which feldom blow directly from the Eaft, but from fome other collateral Points, change this general Motion of the Sea in many Places. Also the North Winds make a moft fenfible Difference in this general Motion in the northern Ocean, where thefe Currents are not ftrong, except in a few Places. PROPOSITION IX. The Caufe of this general Motion of the Sea from East to West is uncertain. THE SECT. IV. THE Ariftotelians (tho' neither they, nor their Mafter, nor any European Philofopher, had the leaft Notion of thefe Things, before the Portuguefe failed thro' the Ocean in the Torrid Zone) · fuppofe, that it is caufed by the Prime Motion of the Heavens, which is common not only to all the Stars, but even, in part, to the Air and Ocean; and by which they, and all things, are carried from Eaft to Weft. Some Copernicans (as Kepler, &c.) altho' they acknowledge the Moon, to be the prime caufe of this Motion, yet they make the Motion of the Earth not a little contribute to it, by reason that the Water, being not joined to the Earth, but contiguous only, cannot keep up with it's quick Motion towards the Eaft; but is retarded and left towards the Weft; and fo the Sea is not moved from one Part of the Earth to another, but the Earth leaves the Parts of the Sea one after another. OTHERS, who are fatisfied with neither of these Causes, have recourse to the Moon; which they will have to be the Governess of all Fluids, and therefore to draw the Ocean round with her from Eaft to Weft. If you ask, how she performs this? They Anfwer, it is, by an occult Quality, a certain Influence, a Sympathy, her Vicinity to the Earth, and fuch like. It is very probable indeed the Moon, fome way or other, caufes this Motion, because it is obferved to be much more violent at the New and Full Moon, than about the Quadratures, when it is, for the most Part, but fmall. THE ingenious des Cartes mechanically explains how the Moon may cause this Motion, both in the Water, and the Air. He fuppofes, according to his general Hypothefis, that there are an infinite number of Atoms, which revolve about the Earth, and fill up the Space be tween tween it and the Orbit of the Moon, fo as not to leave any Vacuum; this Space he calls the Earth's Vortex (b). Let FEHG (Fig. 22.) be the Earth, 2143 the Water, 6587 the Air, BADC the Vortex of the Earth, and B the Moon. Now, fays he, if there was no Moon in the Vortex BADC, it's Particles would without any Impediment revolve about the Center T; but fince the Moon is there, the Space, thro' which the celeftial Matter flows, is narroweft between B and T ; therefore this Matter flows fwifter between B and T, and by that means preffes both the Superficies of the Air at 6, and of the Water at 2, more than if the Moon had not been in the Diameter of the Vortex BD: and because both the Air and the Water are Fluids, and eafily give (b) The Flux and Reflux of the Sea, which des Cartes has endeavoured to explain, by an imaginary Plenum and Vortices, may be more easily and fully explained upon other Principles (as shall be shewn hereafter); for these are mere Fictions, and no way agreeable to Nature and Motion, as appears from the following Arguments. 1. If fome Vacuities were not supposed to be interfperfed among the Particles of Bodies, it would be very hard to conceive how Motion could be any way performed. For if we fuppofe every Place to be abfolutely full, a fmall Body cannot move ever fo little, without moving all the Bodies in the Univerfe, and whither, or to what Place they should move, when all Places are already full is not easy to conceive. And SECT. IV. way to Preffure, they ought to become lower under B, at 2, and higher under A, at 1. while the Earth is turned from E, by F, towards G, or from Weft to Eaft, the fwelling of the Water 412, and of the Air 856, which is now highest at E, moves by little and little to the weftward, and in fix Hours time is highest at the Part of the Earth H, and after twelve Hours at G. Hence it follows, that both the Water and the Air are perpetually moving from Eaft to Weft. Thus far des Cartes. The ftrefs of his Demonftration lies here; that the Earth EFGH, and Water 1234, are revolved round the Center T, together with the celeftial Matter in the Vortex, between BADC and 6587; but the Moon, being in B, makes the Space B6 narrower, whereby the celeftial Matter is fqueezed thro', and in it's Paffage preffes the Air and Water below B, at 6 and 2, towards 5 and 1, and while E paffes beneath B, it is preffed towards H and F, and fo round. Nor doth this celeftial Matter, ftrained between B and 6, rebound upward being fuppreffed, becaufe all things are full of Matter. And tho' it prefs the Air and Water from 62F not only towards the Weft E 15, but alfo towards the East 73G, yet becaufe the Parts between F and G, to the eastward, are, by degrees, removed from the Streight B6, and the Parts towards E, to the weftward, do more and more approach it, therefore this Force is chiefly received by thefe. BUT the following Particulars feem wanting in this ingenious Explanation. 1. IT fhould then follow, that the Sea would fettle when the Moon approached it, and rife in thofe Places that are diftant a Quadrant, or fix Hours, from it, viz. it would fall at 2, where the Moon is vertical, and rife at 6. But this is contrary to Experience; for at 2, under the the Moon, it rifes, and at 1 it falls. How this Abfurdity may be avoided, we fhall fhew in the following Propofition. 2. IT is not plainly thewed (des Cartes himself totally omitting it) why, when the celeftial Matter in the Streight B6 preffes the Air at 6, and the Water at 2, it is not equally moved towards G37, seeing that the Earth, and Air, and Water, are all carried that way, as well as the celestial Matter, which fhould therefore enforce the Air and Water rather towards the Eaft than the West. 3. THE Moon approaching any Sea, there fhould a stronger Wind blow from East to West than at other Times; but this feldom happens. 4. IT is more likely that the Sun fhould cause this Motion of the Air, and these conftant Winds, because in many Places they are obferved to blow fresher a little before, or about, Sun-rifing, when it is diftant a Quadrant from the Vertex of the Place (c). These things are worthy to be confidered in the aforefaid Explication, not to fay any thing for or against the Hypothefis itself. I very much doubt whether this Motion of the Sea has any relation to the general, or TradeWinds; because these Winds, in the Torrid Zone, are conftant; and therefore fhould cause the Motion of the Water to be conftant alfo (d). Indeed when the Wind blows harder the Motion is perceived to be greater; but this is no Argument that they have a Dependance, or proceed one from another. What hinders is, that there appears to be (c) See the Notes upon Chap. xxi. Prop. 2. below, where the Caufe of thefe TradeWinds is explained. (d) As periodical Currents are produced by the fhifting Winds or Monfoons: fo this con ftant one, without doubt, is ef- a Corre 1 |