. The American encyclopædia of commerce, manufactures, commercial law, and finance. t to be coated. — the solutionthus becoming weaker as it loses its copper, buthaving its strength renewed by consumption offresh crystals of blue vitriol. To avoid the com-plete incrustation of the metal or other object, onesiile of it is coated with varnish or some other pro-tective medium, so that the deposition of coppertakes place only on such parts as are deposit may be easily removed when suffi-ciently thick, and will be found to present anexact counterpart of the original, every raisedline be
. The American encyclopædia of commerce, manufactures, commercial law, and finance. t to be coated. — the solutionthus becoming weaker as it loses its copper, buthaving its strength renewed by consumption offresh crystals of blue vitriol. To avoid the com-plete incrustation of the metal or other object, onesiile of it is coated with varnish or some other pro-tective medium, so that the deposition of coppertakes place only on such parts as are deposit may be easily removed when suffi-ciently thick, and will be found to present anexact counterpart of the original, every raisedline being represented by a corresponding depres-sion. To obtain a facsimile of the original it istherrfore necessary to treat this matrix in thesame way that the original was treated, and thissecond deposit will of course present the naturalrelief. Another method consists in taking a mouldof the original coin in fusible metal, and then de-positing copper upon this die, so as to obtain atonce a direct copy of the original. Considerableextension was given to the process by the discov-. o. A constant battery cell. 6. Decomposition cell: a cubical vessel made of wood or earth-enware, and filled witU a niisture ofl part of dilute sulphuricacid (1 acid -f- 9 water), and 2 parts of saturated solution ofsulphate of copper by measure. CfC,e. Moulds suspended to the brass rod ( /), and connectedwith the zine or positive element of the battery (a), by meansof the screw (5). d, d. Pieces of sheet copper suspended on the brass rod (A),and connected with the zinc end of the battery, by means ofthe screw (i), employed to keep up the strength of the cupre-ous solution in the decomposition cell. ery, apparenly trivial, made in 1840, that an elec-tro-deposit of metal could be formed upon almostany material if its surface was rendered a conduc-tor of electricity bj- a thin coating of graphite or black lead. Instead, therefore, of copying acoin in fusible metal, or indeed in any
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