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Knight's Mechanical Encyclopedia (ed. Knight) 3 1 Browse Search
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Knight's Mechanical Encyclopedia (ed. Knight), S. (search)
the matrixes thus formed; in the same year Jacobi, of Dorpat, in Russia, made casts by electro deposit, which caused him to be put in charge of the work of gilding the dome of St. Isaac, at St. Petersburg. Electrotyping originated with Mr. Joseph A. Adams, a woodengraver, of New York, who made casts (1839-41) from woodcuts, some engravings being printed from electrotype-plates in the latter year. Many improvements in detail have been added since in the processes as well as the appliances. nd when this shell is sufficiently thick it is taken from the bath, the wax removed, the shell trimmed, the back tinned, straightened, backed with an alloy of type-metal, then shaved to a thickness, and mounted on a block to make it type-high. Adams's process consists in adding finely pulverized tin to the graphite for facing the wax mold: the effect in the sulphateof-copper bath is to cause a rapid deposition of copper by the substitution of copper for the tin, the latter being seized by th