Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/415

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nia, but not known elfewhere. Hi IPs Hift. ofEoff. p. 568. It is remarkable 'that find, though it appear a very hard, denfe, and indifl'oluble body, yet is contained invifibly in the brine, or fait water of our fait fprings ; and even on the fhooting of the fait, after evaporation, there (till remain the particles of it in the clear pellucid fait } and this, though wholly foluble in water, yet when a brine, made by fuel a folution, is boiled, depofits as much of the fand as the com- mon brine of the pits, or fea water.

Dr. Plot, who was very curious to know the true hiltory of this lingular effect, procured experiments to be made in the following manner. Eight folds of fine Holland, and as many of much finer cambrick, were put together, and a quantity of the brine of the Staffordfhire fait pits being itrained through this, there was nothing feparated from it but a final! quantity of black duff, which feemed to have fallen in by accident, and which was not at all Wkcfand; yet on evaporating this brine, it was found to contain no lefs than one fourth part as much fand as fait. The quantity of brine yielding a bufhel of fait, yielding alfo a peck of fund.

Some have fuppofed from thefe, and the like obfervations, that the find was generated during the time of the boiling of the liquor, but the more careful examiners think other- •wife; it appearing to them, that the particles of this fand may be fecn in the brine, by the help of a microfcope, be- fore the boiling, inform of rectangular oblong plates, fbme nearly fquare ; thefe were fo fmall, as readily to pafs the ftra'iner with the water ; and appearing as numerous in it after, as before the {training, fhew that they are no more to be kept, but by fuch means, than the fait. The pores of the fineft (trainers, examined by the micro- fcope, appear twenty times bigger than thefe plates, or par- ticles of the fand, and therefore it is not to be wondered at, that they let them through. There requires, therefore, no more to the formation of the fand, than the coalefcing of feveral of thefe particles info one larger granule, and fo on ; and this is very likely to be done by means of the evapora- tion of a part of the fluid which kept them feparate, and of the motion given to them in boiling, which naturally and neceflarily brought them into the fpheres of their own mutual attractions, at a time when their attraction with the fluid they fwam in, was alfo much diminifhed with its quantity. This attraction feems even evidently to increafe between the particles, as the water becomes evaporated, and when finally the fait is drawn from it, and it is exa- mined as it drops from the bafkets, in which the fait is put to drain ; it is feen to contain more numerous particles of this fandy matter than before ; and thefe are found to co- alefce into yet larger concretions, by degrees, as the re- mainder of the fluid evaporates from them on the glafs. The particles of this ftony matter, when once thus united, are no more to be feparated by water, nor is the matter any longer foluble in that fluid. The common fpar found in form of ftalactites and incruftations on the roofs, walls, and floors of old caverns, fhews that it was once diffulvcd in water, and by that means brought to thofe places, and made into thofe forms j and it mould (texn, that thhjand, as it is called, was only this fort of fpar, which is contained more or lefs in all water ; and which, on the evaporating of that water and reparation of the fait, which might help in making the water a mcnflruum proper for the retaining it, fhoots out into its own natural concretions ; for the figure of thefe thin plates "is the true and natural thin parallellopiped or rhomboidal figure of the fmaller concretions of that matter, and even of thofe pieces into which it falls on breaking. Phil. Tranf. N° 145-

Sand feems to have been the firft fubftance added to proper falts for the making of glafs. Jofephus, Tacitus, Strabo, Pliny, Agricola, fcfe. all mention this, and tell us of the itores, from which the find for this ufe was brought, being inexhauftible.

Later ages have found that ftones which have cryfta! for their balls make a finer glafs than fand, of this kind are flints, &c. but thefe all are fo expenfive in their prepara- tion, that fand is ftill ufed in much greater abundance than any other ingredient. All the preparation it requires, is, that it be well warned before it is ufed ; which much of what is ufed is found ready to their hands, being brought from the fhores and beds of rivers.

Our glafs-houfes, in London, ufe for their white glafs the common white fand ufed in writing, and have it from Maid- ftone in Kent in vaft quantities. For their green glafs they ufe a common coarfe and greenifh looking fund, of which there are vaft ftrata at Woolwich. Merret's Notes on Neri, p. 260.

Common find is a very good addition by way of manure to all forts of clay lands, it warms them, and makes them more open and Ioofe. The beft fand for the farmers ufe is that which is wafhed by rains from roads, or hills, or that which is taken from the beds of rivers ; the common fand that is dug in pits never anfwers nearly fo well. Sand mixed with dung is much better than laid on alone : and a very fine manure is made by covering the bottom of fheep Sufpl. Vol. II.

folds with feveral loads of fand every week, which are to be taken away, and laid on cold ft iff lands, impregnated a= they are with the dung and the urine of the fheep, Eefide clay land there is another fort of ground very im- proveable by fand ; this is that fort of black foggy land on which bufhes and fedge grow naturally, and which they cut into turff, in fome places. Six hundred load of fand being laid upon an acre of this land, according to the Chefhire meafure, which is near double the ftatute acre, meliorate it fo much, that without plowing, it will yield good crops of oats or tares, though before it would have produced fcarce any thing. If after this crop is taken off, the laud be wed dunged, and laid down for grafs, it will yield a laroe crop of fweet hay.

Once landing this land will improve it for a vaft: number of years, and it will yield two crops of hay in the year, if there be weather to make it in. Some land in Chefhire has been, by this means, rendered of twelve times its former value to the owner. The bogs of Ireland, when drained, have been rendered very fruitful land, by mixing fand in this manner among the earth, of which they confift. Add to this, that in all thefe boggy lands, the burning them, or firing their own turff upon them, is alio a great advan- tage. The common peat, or turff afhes, mixed with the find for thefe purpofes, add greatly to its virtue. Sea fand, which is thrown up in creeks and other places, is by much the richeft of all find for manuring the earth, partly its faltnefs, and partly the fat and unctuous filth that is mixed among it give it this great virtue. In the weftem parts of England, that lie upon the fea coafts, they make very great advantages of it. The fragments of fea {hells alfo, which are always in great abundance in this find, add to its virtues; and it is always the more efteemed by the farmers, the more of thefe fragments there are anions it. The fea fand ufed as manure in different parts of the king- dom is of three kinds : that about Plymouth, and on other of the fouthern coafts, is of a blue grey colour like afhes, which is probably owing to thefhells of mufeles, and other fifh of that or the like colour, being broken and mixed among it in great quantity. Weft ward, near the land'.s end, the fea fand is very white, and about the ifles of Scilly it is very glittering, with fmall particles of talc ; on the coafts of the north fea the fand Is yellowifh, brown, or reddifh, and contains fo great a quantity of fragments of cockle (hells, that it feems to be chiefly compofed of them. That fea fand is accounted beft, which is of a reddifh colour : the next in value to this is the bluifh, and the white is the worft of all.

Sea fand is beft when taken up from under the water, or from find banks, which are covered by every tide. The fmall grimed fand is moft fudden in its operation, and is therefore beft for the tenant who is only to take three or four crops ; but the coarfe or large grained fand is much better for the landlord, as the good it docs lafts many years.

Where the fand is dredged out of the fea, it is ufually twice as dear as where it is taken from the find banks. When the land has been well manured with the laro-e fand, they take four crops of corn from it, and then lay it down for pafture for fix or feven years before they plow it again. The grafs is fo good, that they commonly mow it for hay the firft year ; it always abounds very much with the white flowered clover. If the grafs grows but fhort, it is the farmer's intereft to feed his cattle upon it, and it will turn to as good account this way, being very fweet and rich, and making the cattle fat, and the cows yield a very large quantity of milk. Mortimer 's Hufbandry. LidianSATsD. The uibfhuce, commonly called Indian fand, is famous fpr anfwering to the magnet. It is brought into feveral parts of Europe, and is laid to be gathered on the fea fhore in Perfia. After it is gathered, it is boded in water to wafli away the fea fait and other impurities it may contain. After this o- peration, it is dried and fent abroad in form of a black powder, confuting of grains of different fizes. Some of thefe grains arc very rough in every part of their furface, and others have one fide only rough, the others perfectly fmooth and gloffy. Their figure is very irregidar, and refembles that of the grains of common find only ; the grains of this Indian fand are ufually fmaller than thofe of our com inonfauds. Thefe little lumps have neither taftc nor fmell, and are fo friable, that they are eaiily reduced to an impalpable powder by rubbing. Some of the particles are ftrongly attracted by the loadftone, and others are fo inactive as to be fcarce at all affected by it. Thofe particles, which are of the deepefl dufky black, are moft of all affected by the loadftone ; thofe which are not affected by it, feem rather of the colour of lead, of a bluifh black and mining ; thefe are in the greatefr. quantity, and the others are felected from among thefe by the loadftone. Phil. Tranf. N D 432. p. 298. Mufchenbroek confulcring that fome of the particles of this find had fo frrong a magnetic virtue, and others fcarce an-' at all, was tempted to try whether it might not be poflible to increafe the like virtue in thefe laft, and after fome trials he found a way to fucceed in this attempt ; fufpecting, that T t t there