Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/443

 SEA

When fait water freezes, it hath been thought to let fall all its fait ; the ice of fea water, and the water melted from it;, rafting frefh, and being good for boiling meat and peafe in. Captain Middleton, being in Hudfon's ftreights in July melted till he got forty quarts of water ; thefe he evapo- rated to drynefs, and out of that quantity had only fix ounces of fait, or about 1TT. Pn>^f. Tranf. N° 461- feci:. 13. The afcent of the 'fea water, for the formation of fprings by a fubterranean circulation of its water to their fources, has been a great objection with many againft the fyftem of their being formed of the fea ; but Dr. Plot has obferved, that there are many ways by which the water may afcend above its own level. 1- By the means of fubterranean heats. 2. By filtration. 3- By the unequal height of feveral feas. 4. By the diftance of the center of magnitude from the cen- ter of gravity in the terraqueous globe. The fuperficies of the Pacific fea is faid to be farther from the center of gravity, than the top of the higheft hill on the adverfe part of the globe. And 5. by the help of ftorms. ThR fea water actually afcends above its own level in com- ing into wells, whofe bottoms lie higher than the furface of the fea at high water mark. Plot, de Origine Font.
 * 738j took ice from under the furface of ttipfed, which he

General motion of the Sea. Mr. Daffie of Paris, in a work published about fixty years ago, has been at great pains to prove that the fea has a general motion, independent of winds and tides, and of more confequence in navigation than is ufually fuppofed. He affirms that this motion is from eaft to weft, inclining toward the north, when the fun has pafled the equinoctial northward, and that during the time the fun is in the northern figns ; but the contrary way, after the fun has pafTed the faid equinoctial fouthward ; add- ing, that when this general motion is changed, the diurnal flux is changed alfo : whence it happens, that in feveral places the tides come in during one part of the year, and go out during the other ; as on the coafts of Norway, in the Indies, at Goa, Cochinchina, &c. where, while the fun is in the fummer figns, the fea runs to the fhore, when in the winter figns, from it. On the moft fouthern coafts of Tonquin and China, for the fix fummer months, the diur- nal courfe runs from the north with the ocean ; but the fun having repafTed the line toward the fouth, the courfe declines alfo fouthward. Philof. Tranf. N° 135.

Bafon of the Sea, fundus maris, a term ufed by geographers, and other writers, to exprefs the bottom of the fea in general.

Our honourable Mr. Boyle is the firft who has written any thing on this part of the globe, and he has given us a treatife exprefsly upon it ; but this only gives an account of its irregularities, and unequal depths, and is founded on the obfervations communicated to him by mariners, and people of too little cur'iofity to be depended upon for great difco- veries.

The ingenious Count Marfigli has, fince his time, given us a much fuller account of this part of the globe, in a great part from his own experiments in many places, particularly along the coafts of Provence and Languedoc. The entire bafon of the fea is of fuch immenfe extent, and covered in many places with fuch an unfathomable depth of water, that it is not to be expected that it can be traced in every part ; but as the whole may be gueffed at, from fome part of it, and as its general figure is of no confequence in a fearch of this kind, the obfervations of this curious au- thor are of great value, in forming a judgment of the whole. Marfigli, Hift. de la Mer. p. 4.

- The materials, which compofe the bottom of the fea, may very rationally be fuppofed, in fome degree, to influence the tafte of its waters ; and Marfigli has made many expe- riments to prove, that foffile coal, and other bituminous fubftances, which are found in plenty at the bottom of the fea, may communicate in great part its bitternefs to it.

T We are not, however, to judge haftily, that there are not fo many beds of thefe at the bottom of the fea, as would be neceflary for fuch a purpofe, or to judge too haftily againft the exiftence of any other fubftances there, becaufe

- we do not find proofs of them by the plummet, which in founding brings up other fubftances, and not thefe ; for the true bottom of the fea is very often covered and obfeured from us by another accidental bottom, formed of various fubftances mingled together, and often covering it to a confi- derable depth.

The entire gulf of Lyons, fituated between Cape Quiez in Roufillon, and Cape Croifit in Provence, forms a bank above the furface of the water at the fhore, of the exact and peifeft figure of an arch ; and within this there is formed another fuch arch, making the bottom of the fea in that place for a very great way from fhore, which is of different depths in various places, but ufually between fixty and fe- venty fathom. See Shores.

It is a general rule among fuilors, and is found to hold true in a great many inftances, that the more the fhores of any place are Keep and high, forming perpendicular cliffs, the niore deep the fea is below; and that on the contrary/level

SEA

Mediterranean is generally allowed to be under the height of Malta. The obfervation of the ftrata of earth, and other foffils, on and near the fhores, may ferve to form a very good judgment, as to the materials which are- found in its bottom. The veins of fait and of bitumen doubtlefs run on the fame, and in the fame order in which we fee them at land ; and the ftrata of rocks, that ferve to fupport the earth of hills and elevated places on fhore, ferve alfo, in the fame continued chain, to fupport the immenfe quantity of water in the bafon of the fea. It is probable alfo that the veins of metals, and of other mineral fubftances, which are found in the neighbouring earth, are in the fame manner continued into the depths of the fea. The parti- cles of metals, in this cafe, are probably carried off into deep water, and funk among the fofter matter of the bottom, but fome of the lighter minerals feem to have given colour to thofe beautiful crufts, which are found upon many/is plants, and which lofe their luftre in the drying. The fubterranean rivers, and currents of water, make great changes in what would be the natural furface of the bottom of the fea, where they arife, each having a peculiar bafon of its own. We are informed by numerous inftances of fub- terranean currents, and as we fee them break out in rivers on the furface of the earth in fome parts, fo in others we may be well affured that they break up the bottom of the fea, and empty their frefh waters into the fait mafs. In this cafe, the rufhing up continually of fuch a body of water makes a roundifh cavity, and its running fome one way lengthens and carries on that cavity, till by degrees it is loft, as the frefh water by degrees becomes blended with the fait. Thus every river, that arifes in the bottom of the fea, alters the form of its furface, and makes a bafon for itfelf, in which it runs a confiderable way. Many feas near the fhore, and when the water is tolerably clear, fhew the traces of thefe currents to the naked eye from the furface, and the water taken up from them is found more or lefs frefh. Marfigli, Hift.de la Mer. p. 13. The coral fifheries have given us occafion to obferve, that, there are many, and thofe very large, caverns or hollows in the bottom of the fea, efpecially when it is rocky ; and that the like caverns are fometimes found in the perpendicular rocks, which form the fteep fides of thofe fifheries. Thefe caverns are often of great depths, as well as extent, and have fometimes wide mouths, equal to their largeft diameter in any part, but fometimes they have only narrow entrances into large and fpacious hollows. It is the common opini- on of the people about the place, that thefe caverns are pre- pared by nature for the circulating of the fea water ; but that operation, however neceflary, may be performed as well without, as with thefe caverns, and they feem in reality ta be only accidental.

We daily meet with immenfe hollows and caverns, natural- ly made in rocky mountains ; and as this part of the bot- tom of the fea is almoft all rock, and its fides of the fame nature, it is no wonder that the fame accidents fhould hap- pen, and like hollows be found, though with no particular intent of providence in their ufe. Nay there is this farther reafon to expefl them in the rocks buried under the fea than in thofe in hills, that the latter are in a ftate of reft and quiet, whereas the former are in continual reach of water, which will infmuate itfelf into every crack or crevice na- ture has left in them, and may be eafiiy fuppofed to have burrowed its way in a fmall hole made by nature, till it has formed of it a very large one.

It feems plain from the whole, that the bafon of the fea was at the creation, or at its fecond formation after the univer- sal deluge, covered with, or compofed of the fame fub- ftances, as the furface of the reft of the earth is, that is of rocks, clay and fand, and other fuch fubftances. The com- mon obfervations of feamen feem indeed to make againft this opinion, but they may be eafiiy folved, fo as not to • overthrow it. The plummet which they let down in found- ing, ufually brings up with it a matter compofed of mud, tartarous incruftations, or of dead weeds and broken ihells, or numbers of various bodies of this kind, cemented together into a firm mafs by fome fparry or tartarous matter, depo- sited from among the water, and agglutinating them toge- ther : thefe form an artificial bottom, covering the natural one; but it is eafy to fee, that fuch a cruft or coat as this muff needs have been formed over the true bottom, in places where numbers of animals and vegetables are produced, and decay again, and where the waters being at reft have time* to depofit their ftony matter, in the fame manner as the waters of feveral of our petrifying, or rather incruftating fprings do. And that thefe decayed fubftances, and this ftony matter, falling to the bottom together, and there lying un- dilfurbed, muff, ncceflaiily have formed jiift fuch a cruft 3s is found ; and the natural bottom of the fea, whether of ftone, of fand, or of clay, mull: be covered by fuch acci- dental concretions, and that probably to fuch a depth, that it is not eafy now to break through it* There are places however where, by fome accidents, this fort of adventitious cruft either has never been formed, or elfe has been removed. In thefe places we find the na- 2 C c c tural