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SECT. V.

Containing one Chapter.

CHAP. XVIII.

Of the Changes on the terraqueous Globe, viz. of Water into Land, or Land into Water.

P ROPOSIT-ION I.

To enquire bow much of the Surface of the terraqueous Globe, the Earth and Water severally take tip.

IT is impossible to know this accurately, because we are ignorant of the Situation of the Earth and Ocean, about the North and South Pole, and because their Superficies are terminated by irregular and crooked Lines, not easily compu^ ted or measured. But so far as we can guesi, from a bare Inspection of the Globe, it seems that the Superficies of the Earth and Water are nearly equal; each taking up half of the Globe's Surface.

PROP OS IT 10 N II.

The Surfaces of the Earth and Waters, are not always equally extended, but sometimes more, and sometimes less; and what the one loses the other gains.

THE Sea frequently breaks in upon the Land in several Places and overflows it, or wastes it by degrees, and washes it awayby which means it's Superficies is enlarged according to the bigness of the Plane of Earth it overflows; such an Inundation happened of old in Thejsaly^ But the greatest that we know of have made no sensible Alteration in the Su face of the Globe, tho' it is possible that, some Time or other, there will happen such as may; as we shall shew in Proposition xviii.

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PROPOSITION III. v

To compute how much Earth and Water the terraqueous Globe contains.

TO find this accurately there ought to be known exactly the Surface of the Water•, and it's Depth in different Parts of the Sea, and also the Bulk of the subterraneous Waters. All which we are ignorant of, and have no method to find them •, and therefore are at a loss in finding the true quantity of either Earth or Water. We may form an Hypothesis, and take the Superficies of the Water for half the Superficies of the whole Globe, and also suppose the Sea to be a quarter or half a Mile deep, (one Place with another) not reckoning the Water in subterraneous Caverns.

THESE being granted, the quantity of Water is found thus: Take a quarter or half a Mile from the Semidiameter of the Earth, and find the Solidity of a Sphere, whose Semidiameter is equal to the Remainder. This Solidity being taken from the Solidity of the whole Globe, half the Remainder is the quantity of Water. This last being again substracted from the Solidity of the Globe, leaves the quantity of Earth, to which, for the Mountains, you must add a fourth or fifth Part of the Bulk of die Water, or even a half: yet

all all this is but guess-work, and not to be depended upon for* Truth.

PROPOSITION IV.

The Water may leave the Shore, and the Placet os the Earth which it covered before, for several Reasons; so that the dry Land may appear where it was Water or Sea before, and a new Plat es Earth may seem to be formed. ,

T R A C T S of Water are seven-fold; 1. The Ocean. 2. Bays. 3. Seas or Streights. 4. Rivers. 5. Lakes. 6. Ponds. 7. Bogs.

THAT Bogs or Marshes may be drained, either by letting off the Water, or drying it up by continual Fires, or by throwing dry Earth into them, none need doubt; for in several Places and Countries there are fertile Fields, where there were formerly nothing but Bogs and Marlhes; as in Westphalia, Gelderland, Brabant, Holland, Muscovy, &c. So the Peloponnesus in Greece was, in the Time of the Trojans, barren and marshy Ground, but was made fertile in Aristoll/% Time by draining it.

THE fame may be said of Pools and Ponds, which are not very different.

PROPOSITION V.

Rivers leave their Shores {or part of their Chanels) dry, and form new Parcels of Ground in many Places.

1. IF their Water bring down a great deal of Earth, Sand, and Gravel out of the high Places, and leave it upon the low, in process of Time these will become as high as the other, from 1 whence whence the Water flows: Or when they leave this Filth in a certain Place on one fide of the Chanel, it hems in and raises Part of the Chanel which becomes dry Land.

2. IF a River take another Course, made by Art, or Nature, or some violent Cause, as the Wind, or an Inundation, it leaVes it's former Chanel dry.

'3. IF the Fountains that feed a River are obstructed, or cease to send out their Waters, because of the Earth falling in, or by being stopped with1 Heaps of Sand driven in by the "Wind from the adjacent Places, the Chanel of that River becomes dry.

EXAM P L E S of Rivers, whose Qhanels are now dried up either wholly or in Part, are frequently met with among Authors; not of any great Rivers, but of those of the smaller sort, and some Branches of the great ones; thus that Branch of the Rhine, which formerly run by Leyden into the German Ocean, some Ages ago forsook it's Chanel, which is now dry Land, and stagnates between Ley den tniCatieic.

W E have also several Examples of Shores that have been left dry by Rivers .making themselves deeper and narrower Chanels than they used to run in; also of Rivers that are not navigable" now, which have been so formerly, their Chanels being made shallower", and, in process of Time, may be quite choaked up, as the Schelde, &c. Therefore the Rulers of Countries take care that the Sand-Banks, Filth, and Sediment,- be continually removed out of such Rivers, so that they may be kept open and navigable as much as-possible.' •'

BUT great Rivers are not dried up, or turned into dry Land in a great many Ages', or even Myriads of Ages, because a vast number of small J

ones

ones flowing from different Parts makeup their"Waters and feed them; so that if one or two of them be dried up, or change their Course, it will be a long time before such an Accident happen to them all. One single Sand-Bank indeed might perform Wonders, in choaking up the Passage of a River, and make it take a new Chanel, whereby the former is dried up; but the River itself continues to flow, because it's Fountains and Branches are not obstructed. Nevertheless it is certain, that neither the Nile, the Tanais, the Elbe, nor the Rhine, &c. did or will always flow in the fame Places, but their Chanels were formerly dry Land, and in future Ages will be so again.

P ROPOS ITION VI.

Lakes are dried up and turned into Earth.

IF the Lake be fed by Rivers flowing into it,-, the Change is made by turning the Rivers another Way, or by their ceasing to flow, together with Evaporation. If it receive it's Waters from the • Ocean or Sea by subterraneous Intercourses, these are to be stopped or diverted and so the Lake J. at first is changed into a Fen or Bog, and afterward into dry Ground. Aristotle (speaking of Lakes fed by Rivers) fays, it is certain that the' Force of the Water bringing Mud, or such like Matter, into any Lake, changes it into a Fen or Bog, and afterwards into dry Ground; for the Water stagnating, is in Time dried up. Thus, the Mud and Sand, which the many Rivers bring down into the Lake of the Mceotis, have made it, so shallow, that it will not admit such large Ships7 now, as sailed upon it about sixty Years ago. .

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