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four-and-twenty beams, armed at their bottoms with iron ; 

 thefe, by a continual motion, beat and grind the ore, till 

 they reduce it to powder : during all this operation, the ore 

 is covered with water. There are four wheels ufcd to move 

 thefe beams, each wheel moving fix ; and the water, ai it 

 runs off, carrying fome of the metalline particles with it, is 

 received into feveral bafons, one placed behind another ; and 

 finally, after having paffed through them all, and depofited 

 fome fediment in each, it is let off mto a very large pit, of 

 almoft half an acre of ground ; in this it is fuffered to ftand 

 fo long, as to depofit all its fediment, of whatever kind, 

 and after this it is let out. This work is carried on day 

 and night, and the ore taken away, and replaced by more, 

 as often as occafion requires. That ore which lies next 

 the beams, where it was pounded, is always the cleanelt or 

 richell. 



When the filch is wathed as much as they can, a hundred 

 weight of it ufually contains about an ounce, or perhaps 

 but half an ounce of metal ; which is not all gold, for there 

 is always a mixture of gold and filver, but the gold is in the 

 largell quantity, and ufually is two-thirds of the mixture : 

 they then put the flich into a furnace with fome lime-llone, 

 and flaken, or the fcoria of former meltings, and run them 

 together. The firft melting produces a fubftance, called 

 lech ; this lech they burn with charcoal, to make it hghter, 

 to open its body, and render it porous, after which it is 

 called ro/l ; to this roll they add land in fuch quantity as 

 they find neceffary, and then melt it over again. 



They have at Cremnitz many other ways of reducing 

 gold out of its ore, but particularly one, in which they 

 employ no lead during the whole operation ; whereas, in 

 general, lead is always neceflary, after the before-mentioned 

 proceffes. See Gold. 



SLICKENBORCH, in Gfography, a town of Holland, 

 in the ftate of Friefeland, on the river Linde, at its union 

 with the Kuynder ; 28 miles S. of Le warden. 



SLICKENBURG, a fmall ifland near the N.W. coaft 

 of Borneo. N. lat. 3° 59'. E. long. 112° 31'. 



SLIDE-5i///, in /Igr'tcuUm-e, a fort of fledge contrived 

 in the form of a Itrong, oblong box, and fliod underneath 

 with ilrong, rough, thick pieces of timber. It is capable 

 of holding about three or four common wheel-barrows full 

 of earth or compoft. In Cornwall and other hilly diftrids, 

 it is found ufeful and convenient for drawing out dung and 

 other dreffings to fmall diftances from the large heaps depo- 

 fited in the fields or other places. They are ufed with one 

 or two oxen or horfes for the moft part. They have 

 fometimes alfo low wheels, when they are denominated 

 gurry butts in the above county. 



SLlVE-Raih, or Guard-Rails, in the conftrudlion of 

 Canals, are long pieces of timber fixed to piles or plugs in 

 the face of the walls of locks, bridges, tunnels, &c. gene- 

 rally a little above the furface of the water, to prevent 

 boats from ftriking and injuring the walls. 



SLIDING, in Mechanics, Superincejfus radens, is, when 

 the fame point of a body, moving along a furface, defcribes 

 a line on that furface. 



Such is the motion of a parallelepiped, protruding along 

 a plane. 



SLiDlNG-/?«/f , a mathematical inftrument, ferving to work 

 quettions in gauging, meafuring, &c. without the ufe of 

 compafies ; merely by the fliding of the parts of the in- 

 itrument one by another, the fines and divifions of which 

 give the anfwer, by infpedfion. 



This inftrument is varioufly contrived, and applied by 

 yaripus authors, particularly Everard, Coggefhall, Gunter, 



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Hunt, and Partridge ; but the moft ufual and ufeful ones 

 are thofe of Everard and Coggelhall ; the defcription and 

 ufes of which are 3=; follow. 



SLiDiNG-./?u/f, Everard's, is principally ufed in gauging ; 

 being ordinarily made of box, a foot long, an inch broad, 

 and xVths of an inch thick. It coiififts of three parts : 

 a rule, on each fide of which, a ^ and c d [Plate VII. Stir- 

 •veying. Jig. 4. ) is a groove, and two fmall icales, or fliding- 

 pieces, m, n, Aide in the grooves. Whei both thefe pieces 

 are drawn out to their full extent, the inftrument is three 

 feet long. 



On the firft broad face of the inftrument, ab, are four 

 lines of numbers ; for the properties, &c. of which, fee 

 Gunter's Line. The firll, marked A, confilling of two 

 radiufes numbered i, 2, 3, 4, 5, 6, 7, 8, 9, i ; and then 

 2, 3, 4, 5, &c. to 10. On this line are four brafs centre- 

 pins, two in each radius ; one in each of which is 

 marked M B, to fignify that the number it is fet againit, 

 2150.42, is the number of cubic inches in a malt-bu(hel ; 

 the other two are marked with A, to fignify that the num- 

 bers they are fet againft, viz. 282, are the cubic inches 

 in an ale-gallon. The fecond and third lines of numbers 

 are on the Hiding-pieces, and are exadlly the fame with the 

 firft. They are diltinguKhed by the letter B. Clofe to 

 the figure 7, in the firlt radius, is a dot, marked S /', fet 

 exactly over .707, denoting .707 to be the fide of a fquare 

 infcribed in a circle, whofe diameter is unity. Clofe to 

 9 is another dot, marked S e, fet over .886, which is the 

 fide of a fquare equal to the area of a circle, whofe diameter 

 is unity. Another dot, near W, is fet over 231, the num- 

 ber of cubic inches in a wine-gallon ; and another, near C, 

 is fet over 3.14, the circumference of a circle, whofe dia- 

 meter is unity. The fourth line of numbers, marked M D, 

 t9 fignify malt depth, is a broken line of two radiufes, num- 

 bered z, 10, 9, 8, 7, 6, 5, 4, 3, 2, I, 9, 8, 7, &c. the 

 number i being fet diredlly againft M B on the firft radius. 



On the fecond broad face, marked c d, are i. A line of 

 numbers of one radius, numbered i, 2, 3, &c. to 10, noted 

 by the letter D. On this are four centre-pins; the firft, 

 marked W G, is the gauge-point for a wine-gallon, i. e. the 

 diameter of a cylinder, whofe height is an inch, and content 

 231 cubic inches, or a wine-gallon, which is 17.15 inches : 

 the fecond centre-pin, A G, ftands at the g^uge-point for 

 an ale-gallon, which is 18.95 inches. The third, MS, 

 ftands at 46.3, the fide of a fquare, whofe content is equal 

 to the inches in a folid bufhel. Tiie fourth, M R, is the 

 gauge-point for a malt-buftiel, which is 52.32 inches. 

 2. Two fines of numbers on the fliding-piece, which are 

 exaftly the fame as thofe on the fliding-piece on the other 

 fide, called C. Clofe to the divifion 8 is a dot, marked c, 

 w-hich is fet to 795, the area of a circle, whofe circum- 

 ference is unity ; and another, marked d, ftands at .785, 

 the area of a circle, whofe diameter is unity. 3. Two 

 lines of fegments, each numbered i, 2, 3, to loo ; the firft, 

 for finding the ullage of a cafli, taken as the middle fruftum 

 of a fpherord, lying with its axis parallel to the horizon ; 

 and the other for finding the ullage of a cafk Handing. 



Again, on one of the narrow fides, noted e, are, i. A 

 fine of inches, numbered i, 2, 3, &c. to 12, each fub- 

 divided into ten equal parts. 2. A line, by which, with 

 that of inclies, we find a mean diameter for a cafk, in the 

 figure of the middle fruftum of a fpheroid : it is numbered 

 I, 2, 3, &c. to 7, and marked fpheroid. 3. A line for 

 finding the mean diameter of a calk, in the figure of the 

 middle Iruftum of a parabolic fpindle, which gangers call 

 the fecondary variety of cq/hs ; it is nunibcred 1, 2, 3, Sec. 

 and noted fecond variety. 4. A line, by which we find the. 



mean 



