ftand night and day for feveral weeks, till their legs fwell, and many disorders come on them, which are not eafily got rid of. This has frequently happened to myself; and I have been more than once in danger of lofing a good horfe, by the confequences which have naturally enfued. Many methods have I tried for curing this disorder, if I may be permitted fo to call it, but ftill without fuccefs. I fome years ago, when I lived in Effex, applied to feveral horfedealers and grooms, but they could none of them inform me of any remedy. Chance at length, however, gave me that knowledge which I had been long in vain endeavouring to acquire; for dining about a month. ago at the house of a friend, there happened to be a gentleman in company who had lately been buying Tome horses of a noted dealer. As the converfation turned on horfes, this gentleman, whofe veracity I have the greatest reason to depend on, obferved, that when he was about buying his horfes, he afked the dealer whether they lay down in the ftable without trouble? to which he answered, that they did; but added, that it was a matter of no confequence, as, if they did not, they might, by a fimple method, be made to do it. When,' fays he, you have a mind to make a horfe lie down in the ftable, take a piece of ftrong packthread, or lay-cord, and tie it as tight round the horfe's tail as poffible, without breaking the skin, and as near as you can to the rump-bone: this,' adds he, will give him a pain in his back, and he will be glad to change his pofture to get eafe; and 6 when he finds he cannot in any other way procure it, he will lie down, which he will find the most eafy posture; and he will of course take a liking to it.' I was fo much pleafed with the fimplicity of this method, that I immediately thought of publishing it; thofe who entertain the leaft doubt of it, may easily try whether it anfwers in practice, without trouble, and, what is still better, without hazard or expence. A member of the Society of Arts. Experiments to ascertain the expence of burning chamber-oil in lamps, with wicks of various fizes. A 1000 Taper lamp, with eight threads of cotton in the wick, confumed in one hour 325 Oz. of fpermaceti oil, at two fhillings and fixpence per gallon; the expence of burning twelve hours is 4.57 farthings. N. B. This gives as good a light as the candles of eight and ten in the pound, in the next article marked *. This lamp feldom wants fnuffing, and cafts a fteady, ftrong light. A taper, chamber, or watch lamp, with four ordinary threads of cotton in the wick, confumes 1.664 oz. of fpermaceti oil in one hour: the oil at two thillings and fix-pence per gallon, the expence of burning twelve hours is 2.34 farthings. N. B. The above-mentioned taper lamps (which I efteem to be conftructed on the best principle of any, viz. on the afcent of fluids in capillary tubes) are made in great perfection by Mr. Naish, tin-plate worker, at the plume of feathers in Alderfgate-street, London. M 2 Experiments Experiments to determine the real and comparative expence of burning candles of different forts and fixes, as they are commonly made at Market-Harborough, in Leicestershire. Numb. of Weight of The time The time | The expence in candles one can- one can- that one twelve hours pound. will laft. are at 6 s. per dozen, which N. B. The time that one candle lafted was taken from an average of feveral trials in each fize. Ealy Eafy and fafe method of reftoring gold, when jullied, to its primitive luftre, without injuring the fineft ground it may happen to lie upon; from the Rev. Mr. Lewis's Philofophical Commerce of Arts. Τ HE bright deep yellow colour of gold, commonly diftinguished by its name, is one of the most obvious characters of this metal. Its colour and beauty are of great durability, being injured neither by air nor moisture, nor by any kind of exhalations that ufually float in the atmosphere; as may be obferved in the gildings of fome public edifices, which have refifted the weather, and the vapours of London and other populous cities, for half a century or more. In this property confifts great part of the excellence of this metal for ornamental and fome mechanic ufes: there is no other malleable metallic body fo little fufceptible of tarnish or difcoloration, or fo little difpofed to communicate any ftain to the matters which it lies in contact with. Tidee, As inftruments or ornaments of pure gold are liable to be fullied only from the fimple adhesion of extraneous substances; their beauty may be recovered, without any injury to the metal, however exquifitely figured, or without any abrafion of its furface, however thin and delicate, by means of certain liquids which diffolve the adhering foulnefs; a folution of foap, folution of fixt alkaline falts or alkaline ley, volatile alkaline fpirits, and rectified fpirit of wine. In the ufe of the alkaline liquors, fome caution is neceffary in regard to the veffels; thofe of fome metals being in certain circumftances corroded by them, fo as remarkably to difcolour the gold.. A gilt fnuff-box, boiled with foap-boilers ley in a tin pot, to clean it from fuch foulnefs as might adhere in the graved figures, and to prevent any deception which might hence arife in a hydroftatic examination of it, became foon of an ill colour, and at length appeared all over white, as if it had been tinned: fome pieces of ftandard gold, treated in the fame manner, underwent the fame change: and, on trying volatile alkaline fpirits, prepared with quick lime, the fame effect was produced more fpeedily. On boiling the pieces thus whitened, with fome of the fame kind of alkaline liquors, in a copper veffel, the extraneous coat difappeared, and the gold recovered its proper colour. For laces, embroideries, and gold thread woven in filks, the alkaline liquors are in no fhape to be used; for, while they clean the gold, they corrode the filk, and change or difcharge its colour. Soap alfo alters the fhade, and even the fpecies of certain colours. But fpirit of wine may be ufed without any danger of its injuring either the colour or quality of the subject, and in many cafes proves as effectual for reftoring the luftre of the gold, as the corrofive detergents. A rich brocade, flowered with a variety of colours, after being difagreeably tarnished, had the luftre of the gold perfectly restored by wathing it with a foft brufh dipt in warm fpirit of wine; and fome of the colours of the filk, which were likewife foiled, became at the fame time remarkably M 3 bright bright and lively. Spirit of wine feems to be the only material adapted to this intention; and probably the boafted fecret of certain artifts is no other than this fpirit difguifed among liquids, I do not know of any other, that is of fufficient activity to difcharge the foul matter, without being hurtful to the filk: as to powders, however fine, and however cautiously used, they fcratch and wear the gold, which here is only fuperficial and of extreme tenuity. But though fpirit of wine is the most innocent material that can be employed for this purpose, it is not in all cafes proper. The golden covering may be in fome parts worn off; or the bafe metal, with which it had been iniquitously alloyed, may be corroded by the air, fo as to leave the particles of the gold difunited; while the filver underneath, tarnished to a yellow hue, may continue a tolerable colour to the whole: in which cafes it is apparent, that the removal of the tarnish would be prejudicial to the colour, and make the lace or embroidery lefs like gold than it was before. A piece of old tarnifhed gold lace, cleaned by fpirit of wine, was deprived, with its tarnish, of the greater part of its golden hue, and looked now almost like filver lace. Though no one of the other metallic bodies fingly has any degree of the beautiful yellow colour which glows in gold, the true gold yellow may nevertheless be pretty nearly imitated by certain combinations of other metals, particularly of copper with zinc. But how nearly foever thefe compofitions ap. proach to gold in degree or fpecies of colour, they differ greatly in its durability; and their differences in other refpects are ftill more ftrongly marked, and of more eafy dif covery. Defcription of an engine, in which the centrifugal force is happily. applied to the raising of water; invented by Mr. Robert Erskine ; and from his defigns executed by Mr. Cole, mathematical inftrument maker, near Weftminster - bridge, Surry. TH HIS machine will be most easily understood from an account of the principles on which it is founded. Suppofe a tube, one part verti cal, and the other part horizontal, fufpended upon, and moveable round, an axis; and the upper aperture less than the lower aperture; let this tube be filled with water, and immerfed in water; the upper aperture being fhut by a valve opening, outwards; 'tis evident, the whole tube will remain full, though open at bottom, if the greatest height is not greater than that to which the air will fuftain a column of water. Again, fuppofe the tube turned round its axis, the water in the horizontal part will require a centrifugal force, which, fufficiently increased, muft overcome the preffure of the air on the valve, and be thrown out; and, fince the air cannot enter against a ftream of water, which has already overcome its preffure, the weight of the atmosphere on the water in the well muft neceffarily force it up, to fupply the place of what is ejected, Hence, Hence, in this machine, the water thrown out acts the part of a pifton on the column of water to be lifted. The horizontal part is called the ejected tube, or radius, and the mouth of it the aperture of ejection. In constructing this machine, there may be two or more ejecting tubes, provided the fum of the apertures of ejection be less than that of the bore of the tube through which the water 'afcends; and the higher the water is raifed, the larger must be the bore of the tube, in proportion to the apertures at which the water is difcharged, becaufe the velocity with which the atmosphere forces up the water through any tube, diminishes in a certain proportion the higher it is lifted. In fhips, the ejecting tubes may be immediately under the deck, moveable by a wheel and pinion, the frame-work to reit on the deck. In the largest machines, it will take up a space of about three feet fquare only. The space occupied by the ejecting tubes, fuppofing the cafe, which prevents the water from difperfing all round, to be upon the deck, need not exceed five feet diameter, and a foot deep, though the machine be made large enough to throw out three tons per minute; because it has been found by experiment, that an ejecting radius of only two feet is fufficient for a machine thirty feet high, being lately proved by a machine of that height, which threw out at the rate of a ton a minute, with fix ordinary hands not accuftomed to work at a winch. a flider, pulled up and pushed down by an iron rod which reaches the deck; the ufe of this is to ftop the bottom of the machine, when it is filled with water, by an aperture at the extremity of one of the ejecting tubes. At the bottom is likewife a valve, which anfwers the fame purpose with the flider in machines, where the required centrifugal force can immediately be given to the ejecting tubes. The valves on the apertures of ejection fhut of themselves by fprings, and open only when the centrifugal force overcomes the preffure of the air; the machine, once filled, remains full while worked, as long as there remains any water at the bottom to be raised. The joint by which the ejecting tubes have liberty to move, while the conveying tube is at reft, is contained in a cylindrical cup, immediately under the head, and the whole weight of the moveable part is fuitained on the extremity of the axis, which axis ends in a conical point, and terminates at the top of the fixed tube, refting in a focket, upon a fcrew; which fcrew and focket are fupported by three radii at the upper part of the conveying tube: the air is excluded by a collar of leather, which lies upon a flank of polished brafs; the leather is immoveable, being faftened to the cylindrical cup by a ring of brafs with fcrews paffing through both. Another brafs ring preffes with its weight (which is fometimes augmented by fprings) upon the inner circle of the leather, to keep it flat on the brafs flank, which, along with the head of the At the bottom of the machine is machine, moves below it. The |