Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/416

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there might be too great a quantity of fulphur adhering to the fand, tofufFer it to be turned into any metalline regulus by a long continuance in an open fire ; he mixed it with half its quantity of pot-afti, and toafted it in an open cru- cible about two hoars : after this the fait being waihed away with common water the fand was found to be much blacker than before, and about one fourth of it was now endued with a very powerful magnetic force.

"The fait has a great {hare in making this fand magnetic after burning j for a burning of it, without that admixture, is found to give it, indeed, fame power of this kind, but it is very little.

There is another matter, however, which being mixed with this fand, contributes yet greatly more to its virtue, this is black foap. This fand- being mixed with an equal quantity of black foap is to be put into a crucible, and placed in a gentle fire, where the foap will fwcll and bubble up ; as loon as this is over, and the moifture all evaporated, the fire is to be increafed, and the matter kept red hot, about half an hour, or a little longer than that ; then the crucible being taken out, and cooled, the remainder is to be wafhed, and this will be then a black powder ; every grain of which is magnet ical, and that very beautifully. If the operation be ever fo many times repeated on the fame fand, the power remains the fame in it, neither being increafed nor leffened by all the work.

A mixture of one third of this fand, one third of black foap, and one third of fait of tartar, treated in the fame manner as the former, feems to increafe the virtue of mag- netifm yet farther in the fand, than when treated with the foap alone ; beef fuet mixed with ih&fand gives it much of the magnetic virtue, after melting and burning it away en the fire j and common pitch treated in the fame manner with it, yet greatly increafes it. If it be too long kept over the fire, with any of thefe mixtures, the virtue decreafes, and if not long enough, it does not arife to its utmoft height; fo that experiments only can fettle the true degree of heat, neceflary to its greateft perfect ion. The greateft power that can be given to this fond, in this quality of magnetifm, is, however, to be given in the fol- lowing manner. Mix together equal parts of the fand, and of roiin, pitch, frankincenfe, and rape oil, put this into a crucible, and lute it well in all parts, then place it for an hour in a reverberatory furnace: when this is cooled, there Will be found black grains of the find, between black coals of the oily matter, which, when feparated, will leap up to the magnet, when held at fome diftance over them ; and ihew, in all refpe£ts, the ftrongeft magnetic virtue, that we know communicable to this fubltance.

It might appear, from this experiment, that the fand grew more fenfible of the magnet, as its particles more approach- ed to the nature of iteel ; but on making the trial by calcin- ing the fand with the ingredients ufed to turn iron into if eel, fuch as chimney foot, fea fait, powdered charcoal and allies, it acquired fome magnetic virtue indeed, but not nearly fo great as that given it by the latt procefs, or by the fimpiy mixing it with bluilh foap before the calcination. After thefe experiments, the queftion naturally occurs, of what can this fand be. It has been fuppofed by fome, to be the granulae or fragments of load-ftones, or the feparated particles, which when concreted into a mafs, afford the common magnet ; but this can by no means be the cafe, fince common load-ftones lofe of their force, by being cal- cined with the very ingredients which render this magnetic ; and indeed the phenomena it affords on experiments are fo very fincular, that it is not eafy to determine any thing about it.

There are fevcral parts of the world which afford thhfand, but with fome difference in the figure of its grains, and their magnetic virtue. Befide Perfia it is found on thefhores of Virginia ; another fort of it is found about Italy, and very common at Leghorn ; this is very magnetic. There are two forts of it found in the river Eber in Haffia, of which one is like the Italian, but the other confifts of large grains, almoft as big as hempfeed, but having very little virtue. A very ftrong fort is found in Dalmatia, near old Ragufa; and probably future enquiries will fhew, that there are yet many more kinds of it differing inftrength and iize. Phil. Tranf. N°432. p. 301. Sand %j, in the military art, are bags of earth or fand, con- taining about a cubical foot ; they are ufed for raifing para- pets in hafte, or to repair what is beaten down. They arc alfo of ufe when the ground is rocky, and affords no earth to cany on their approaches, becaufe they can eafily be brought from far off, and removed at will. The fmailer fand-bags hold about half a cubical foot of earth, and ferve to be placed upon the fuperior talus of the parapet, to cover thofe that are behind, who fire through theemhrailures, or intervals, which are left betwixt them. Sand #<?w/, a term ufed by the people of Suffolk, and fome other parts of England, to exprefs a mifchief to which they are fubjeiSt, by having their lands covered with vaft quan- tities of fund, rolling in upon them like a deluge of water.

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Mr. Wright, a fufferer by one of thefe deluger, gives a very good account of them in the Philofophical Ti an factions. In the neighbourhood of the plains, fubieci to this mifchief there are always hills which are made up of [and, and only covered with a thin turf. The plains thcmielves, which aie inevitably ruined by the deluge of this dry fort, are alfo fandy ; having only the fame fort of thin turf on them, though ca- pable of producing very good crops, and Handing all com- mon accidents.

Violent winds break through the turf that covers thefe hills, and then the fand lying loofe and naked, is foon carried down upon the plains, where it covers and buries the grafs, and in a very little time eats through the light turf, and mixing itfelf with the fand underneath, becomes one bed of this dry matter never to be covered with a turf again. A large body of fand being thus got together, nothing Hops its progrefs, but it at every ftonn rolls over more and more ground, fo that in a few years it extends itfelf a vaft way ; efpecially where the ground, over which it paffes, is of the fame fandy nature, and only covered with a thin turf. In fome parts of Suffolk the ground encourages this change fo greatly, that a bed of find broke loofe from a neighbour- ing hill, and covering only a few acres, perhaps eight or ten, will, before it has travelled four miles forward, which it does in a fmall courfe of years, deluge a thoufand acres. It travels down hill fatter than any way elfe, hut will not he ftopped by afcent, but will move up the fteepeft hill, only that it requires more time. The making of fences, in the common way, to keep it out is vain. It runs throuo-h the hedges, and flies over the tops of the banks ; and when it, reaches a village, in its courfe, will bury the cottages, unlefs preferved at more charge than they are worth. It will in a vety little time beat up to the eaves of a houfe, of the low kind, that are ufually built in country villages, and has often weight enough to break down walls in its paffa^e. The beft- way of flopping its progrefs is by hedges of furze, planted one over another as they become levelled ; thefe, if well kept up, will, by degrees, flop or divert the progrefs ; and fome who have tried this, with refolution, after they have had the find raifed twenty feet high, have found it flop its increafe; and then having manured this adventitious foil with dung, found it as good ground as that which made the furface before.

About Thetford the villages were wholly deftroyed by this about ninety years ago ; and the branch of the river Oufe, called then Thetford river, fo blocked up by it, that very fmall veffels only could go up it, where very large ones ufed before. The river has been of great fervice in flopping its progrefs into Norfolk, where otberwife its courfe would have carried it, and its vaft fpreading fideways in proportion of its going forward, would have made it bury vaft quantities of land in a very few years.

The moft probable conjecture, as to the caufe of this ft/range fort of deluge in thefe parts of England, is, that this por- tion of the county of Suffolk lies eail north eaft of a part of the great level of the. fens, and is by this expofed to verv impetuous winds, which acquire more than ordinary force', by their paffing through fo large a tract of country uninter- rupted i the ftorms feem to be one great caufe of the mif- chief, and the fandy nature of the foil the other. There are old ftories in the country, of fuits at law commenced among the farmers, for grounds blown out of the owner's pofleffion; but the people who gain this fort of wandering land are the greateft fufferers, A \\tt\e fand fprinkleJ by the winds over a tract of land, where there is a bed of fand under the turf, foon eats through that obftacle ; and what was at firft only a thin coat of find, becomes then a deep plain of it, capable of being blown away to the depth of eight, ten, twenty, or more feet, and is carried over every thing in its progrefs before the winds, when once ta- ken up by them. Phil. Tranf, N° 37. -

SAND-gavcI, a payment due to the lord of the manor of Rod- ley, in the county of Gloucefter, for liberty granted to the tenant to dig find, for their common ufe. Blount.

Sand-/(7Wj, a term ufed by our farmers to exprefs fuch grounds, as confift wholly of a pure {hcerfa?id. This is of different colours, as white, blackifh, reddifh, or yellowifh, and is very different in its nature, and in the fize of its particles, fome being harfher and fome milder, and fome very light, feeming only to be mere duft. The grey, black, and afh-coloured fmd-fonds are the worft of all, and generally are found on heaths and commons. Gra- velly lands approach much to the nature of thefe, and thofe which confift of largeft (tones, and are mixed with the harfheft_yW/.r, are of all the moft barren. The propereft plants for arable land, of this kind, are white ' oats, rye, black wheat, and rurneps. The natural produce, in weeds, is quick grafs, forrel, broom, furze, fern, and heath.

The beft manure for them is either marl, or fuch clay as will break wilh the frofts. Cow dung is alfo a good manure for thefe lands, and many ufe with fuccefs chalk, mud, and the half rotten ftraw from dunghils.

When