P'jrtable E!eBri-al M.'.chine. 507 



deep, made of half-inch board : upon the bottom of the box lies a pUte of glafs, alfo gj b/ 

 7^ inches, cemented to the wood at the four corners by common ek-ctrical cement ; this 

 plate is coated on both furfaces with tin-foil 7 inches by 5, as reprefentcd at Q^in figure ; 

 (except that the flips of tinfoil at H and I are palled or gummed upon the under fide only), 

 and is ufed as a fubftitute for a jar of 35 inches of coated furface, it being of no confe- 

 quence what the {hape of the glafs be, provided it have a proper quantity of coating. 

 M'E N is a cylinder of glafs of four inches diameter, the body of which is ',\ inches 

 long : at M and N are brafs or * boxen caps cemented as in other machines, upon the 

 fmall cylindrical ends of which the cylinder revolves bymeanjof a fimple winch C, which 

 may be taken off or put on at pleafure, either by fcre«ing, or by being inferted upon 

 a fquare flioulder. The central points of revoUuion of N and RI arc at about l\ Inches 

 from the top of the box, the firft inferted into a circular hole in one end of the box, and 

 the other let down in an open phce made down through the other, which has a detached 

 piece of fimilar wood to fit it, and to keep the cylinder in its place. L is the cuflilon, 

 and E the filk placed in the ufual way; D is a fcrew with a milled head, which, by the 

 adiftance of a tapped nut, placed fall in the infide of the box at 4 inches from the bot- 

 tom, prefles againft the elaftic part of thefupport of the cudiion which is hid from the eye : 

 this fupport, which may be of elaftic "wood, coated above D with tinfoil, or of any elaftic 

 metal, is fcrewcd faft to the back of the box near t\\Q. bottom in the infide. The chain at 

 D is hung on the fcrew at picafure, as the wood is found to be in a good or bad conducing 

 (late. 



F is a piece of light wood turned very fmooth in a lathe, and neatly covered with tinfoil, 

 its ends being rounded. This piece, which I (hall call the colleftor, is furniQied with about 

 a dozen fixed pins of brafs, projeding againft the fide of the cylinder, as reprefented in 

 the figure, as near as may be without touching it. The coUeftor is 6 inches long, and 

 fomewhat more than an inch in diameter, and is fupported by two folid glafs pieces, C C, 

 of an inch and three quarters in length, and nearly half an inch in diameter, cemented 

 into the fide of the box at 4§ inches from the bottom, and each at an inch from the end 

 of the colleftor : by this means the coUeiSar becomes ijifulated, and has a chain to be 

 hooked on an eye of wire fixed on any part thereof, fo as to fall occafionally upon the 

 upper infulatcd coating of the plate of glafs in the bottom of the box : the chain, however, 

 mull not be fo long as to extend beyond the coating by any motion of the box. 



B is a glafs tube | of about one-eighth of an inch bore, and about 3 or 3 ; inches long, with 

 a ring of brafs or horn, that has a male fcrew, cemented upon the middle of It, to fcrew 

 into another ring that has a female fcrew, and is cemented or otherwifc fattened into the 



into n 



■< When caps are made of wooil, they mud he turncU fo as to ajmit the glafi ixck of ihe c^liiuler i 

 fpacc or caviiy which it fli.nll nearly tit. By this difjidition, die gUfs is ceir.cnud to ihc ^vuod at both furfa'cci, 

 and the cap itfclf v. ill be ftroiiycr. VV. P. 



f Mr. Nicholfcn may have t ten aware, that j;la*-'uhes of a fmall boic, however thick, arc liable to be 

 broken by a (hock pilfing through them, when unguarded; and alfo that a lining of any kind will ufujlly 

 prevent fuch an cffcft. Mr. Fell of Ulverfion, in Lancalhirc, an txccllent cititrician, has tubes placed over 

 the wires of a very large battery, lined with paper or tinfoil, which do not break with a difchargc tliat melts 

 pretty thick brafs wire. The tuhc, arc uftd as a guard ag.iiiift any accidenial touch when the battery is 

 charged. W. I'. 



3 T 2 fri>nr 



