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fresh Water: and we have {hewn that there is a different quantity of Salt in different Parts of the Sea; which must cause the Gravity of the Water to be unequal. But some Sea-Water may happen to taste more salt than others, and yet be not more weighty; because it perhaps contains a greater quantity of volatile Salt, which does rather diminish than increase it's Weight, tho' it make it more salt.

PROPOSITION XIII.

Sea-Wat er doth not so easily freeze as frejh; or a greater Degree of cold is required to congeal Sea-Wat ert than to congeal frejh.

EXPERIENCE shews this, contrary to the Opinion of the Peripatetics^ who mention that by how much Water is more pure, it is less liable to freeze, and that Sea-Water being more elementary than fresh will freeze the sooner; which is false.

BUT the Cause is, that in Salt there is a certain Spirit which resists Coagulation, and this being separated from it, will not congeal in the hardest Frost, as is well known to Chymists: for they frequently make use of this Spirit of Salt (i).

{/) The Particles of two different Bodies, which would be more at Rest when separate, when they are mixed are put into new Motions by Attraction, which acts upon them only when they approach one another; and causes them to meet and clash with great Violence, and to keep hot with the Mo

tion. So that Water mixed with Salt, is more in Motion than Water alone; and therefore the Particles of Sea-Water are not so easily congealed, or made to rest, as the Particles of fresh, which do not resist the cold with such violent Motions. See Newton's Optics. Pag. 355.

PROPROPOSITION XIV.

Why the Ocean is not enlarged when it receives so many Rivers.

THE Cause is; I. The Water returns from the Sea, thro' subterraneous Fissures to the Heads of the Rivers. 2. Plenty of Vapours are raised from the Ocean, a great Part of which being turned into Rain, fall partly into the Ocean, and partly on the dry Land (k).

PRO

{i) Since the Ocean constantly receives a prodigious quantity of Water, both from Rivers that exonerate themselves into it, and also from the Air, in Dew, Rain, and Snow, that fall; it is impossible but it sliould be enlarged, andencreafe to an immense Bulk, unless it be as much lessened some other way. And seeing there hath not been observed any such great increase in the Sea, and that the bounds of the Earth and Ocean are found to be in all Ages the fame, it remains that we inquire by what means the Ocean loses so much Water as it receives from Rain and Rivers flowing into it. There are two Hypotheses among Philosophers; one is, that the Water of the Sea is carried, by subterraneous Conduits to the Springs of Rivers, and, in it's draining thro' the Fissures, loses it's Saltness: the other is, that it happens by the Vapours that are drawn up from it's Surface- The former is now re

jected by most, it being difficult, if not impossible, to explain bow the Water of the Ocean, being more depressed than the very Mouths of the Rivers, can come up to their Springs, which are, for the most part, on very high Mountains; but in the latter Hypothesis we have no Occasion to explain this, neither to hinder the Growth of the Ocean, nor to supply the Springs with Water; both which may be more easily done by the Vapours, which we certainly know to be drawn up from the Surface of the Sea.

The quantity of Vapoun drawn up from the Sea was tried by Dr Hallty, who made the following Computation. Pbilof. Transaa. N° 189. Page 366.

By an Experiment made with great Care he found that Water, salted to the same Degree as is common Sea-Water, and heated to the fame Degree of Heat, which is observed to be that »f Air in our hottest Summers, PROPOSITION XV.

Some Parts of the Ocean differ in Colour from others,

W E observe that towards the North Pole, the Sea seems to be of a black Colour, and in the Torrid Zone of a dusky Colour, and in other Places of a green Colour. Upon the Coast of New Guinea,

the the Sea in some Parts appears white, and in others yellow: In Streights, or narrow Seas, it appears whitish. Upon the Coast of Congo, not far from Baya d'Alvaro, where the small River Gonzales falls into the Sea, the Water is of a reddish Colour which Tincture it receives from a red mineral Earth, thro' which the River flows. But the most famous for it's Colour is the Arabian Gulph, being therefore called the Red Sea. Some will have it to be only a bare Name, and taken from Erythrus, some time King on that Coast; others will have it to be called red from a certain Brightness peculiar to it, which is caused by the reflected Rays of the Sun (/). But the most probable Opinion, and which

mers, to exhale the thickness of a sixtieth Part of an Inch in two Hours. From whence it appears that a Bulk of Water a tenth Part of an Inch high will be exhaled into Vapours in twelve Hours.

So that if the Superficies of the whole Ocean, or a Part of it, as the Mediterranean Sea be known, it may also be known how much Water arises in Vapour from it every Day; supposing the Water to be equally hot with the Air in Summer.

"For from what hath been ** laid down, a Superficies of "ten square Inches emits daily ** a cubic Inch of Water; "one square Foot, half a "Pint; a Square whose sides *' are 4 Feet, one Gallon; a "square Mile, 6914 Tuns; "and one Degree square, (sup"posed consisting of 69 Evg"lijb Miles) 33 Millions of "Tuns."

This learned Gentleman estimates the Mediterranean to be about forty Degrees long, and four broad; allowances beWig made for the Places where it is broader by those where it is narrower, fg that it's whole

Superficies may be accounted cne hundred and sixty square Degrees; and consequently the whole Mediterranean must lose in Vapour, according to the forestated Proportion, in a Summer's Day, at least five thousand two hundred and eighty millions of Tuns. For what quantity of Water is licked off the Surface by the Winds, (which is even more sometimes than is exhaled by the Heat of the Sun) seems impossible to be reduced to any Rule.

It remains that we compare this quantity of Water with that which is carried daily into the Sea by the Rivers, which is very difficult to do, when we can neither measure the Breadth of the Chanels of these Rivers, nor the Velocity of the Currents. One thing is left, that a Comparison being made between these and the River Thames, and by supposing them rather greater than they are, we may have a greater quantity of Water than is really poured by them into the Mediterranean.

The Mediterranean receives these nine considerable Rivers; the Merits, the Rhone, the Tiber, the

the Po, the Danube, the Neijler, the Boryfthenes, the Tanais, and the Nikl all the rest being of no great Note. Eachof these Rivers, this ingenious Gentleman supposes to be ten times greater than the Thames, not that any of them is so great in Reality, but to comprehend with them all the small Rivulets that fall into the fame Sea.

He supposes the River Thames, at Kingston Bridge, w here the Flood seldom reaches to be in breadth about 100 Yards, and in depth 3; and the Water to run two Miles an Hour. If therefore the breadth of the Water, 100 Yards, be multiplied by 3, the depth, and the Product 300 square Yards by 48 Miles, or 84480 Yards, which the Water runs every Day, the product will be 25344000 cubic Yards of Water, or 20300000 Tuns that are carried every Day into the Sea.

Now if each of the aforesaid nine Rivers yield ten times us

much Water as the Thames; it will follow, that each of them carries every Day into the Sea 303 Millions of Tuns: and the whole nine, 1827 Millions of Tuns in a Day.

But this is but little more than one third of what is proved to be raised, in Vapour, out of the Mediterranean in twelve Hours time. Hence it appears that the Mediterranean is so far from increasing or overflowing by the Rivers running into it, that in a short Time it would rather be evaporated, and drawn out, unless the Vapours that it exhaled returned in Dew or Rain upon it.

Juries Appendix. (!) Some will have this to be the fame with Esau or Edom, who first inhabited Idumaa, a Country near the Arabian Gulph, from whence, fay they, it came to be called the Red-Sea, viz- from Edom, i. e. Rid.

is is confirmed by Experience, is, that it came to be so called from the red Sand that lies upon the Shore, and is often contrary to it's Nature, mixed with the Water by the vehement Flux and Reflux of the Sea, which is extraordinary in this Gulph; insomuch, that it tosses it to and again like Alhes, and keeps it from falling to die Bottom by it's violent Agitation. This is related by Sailors, who tell us, that it sometimes appears as red as Blood; but if it be kept in a Vessel without shaking, the red Sand will subside, and may be seen in the Bottom. It very often happens, that violent Storms blowing from the Red-Sea, towards Arabia or Africa, carry with them such Heaps of red Sand, as to cover whole Caravans, or Troops of Men and Beasts, whose Bodies in time are thus converted into true Mummy. There are other Opinions among Authors, about the Name of this Gulph, but they are all of no Weight, as appears from Experience.

WHETHER the fame or some other Cause, hath urged Mariners to call the Gulph of California or (yermejo) the Red-Sea, I have not yet found observed by Authors.

PROPOSITION XVI.

There are certain Peculiarities observed in some Parti of the Ocean.

THE Sea called by the Portuguese di Sargasso, begins about the Salt Islands, nor far from Cape Verd, and extends itself from the 20th Degr. of North Latitude, and to 34 Degr. South. It seems to be of a green Hue, tho' this be not it's proper Colour, but owing to a certain small leaved Herb, (not unlike Water-cresses) which we call the SeaLentile, or small leaved Parsley, but the Portuguese Sargasso. The Leaves of tliis Weed are so mutually

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