Well's natural philosophy : for the use of schools, academies and privte students, introducing the latest results of scientific discovery and research ; arranged with special reference to the practical application of physical science to the arts and the experiences of everyday life ; with three hundred and seventy-five engravings (1873)
Wells, David A · New York : Ivison, Blakeman, Taylor and Co. · leaf 419
d sulphate of copper is formed. This, dissolving inthe liquid, maintains it at a constant strength. When the operator judgesthat the deposit on the medal is sufficiently thick, he removes it from thetrough, and detaches the coating. The deposit is prevented from adhering tothe medal by rubbing its… … In this way a most perfect reversed copy of the medal is obtained,—that ia,the elevations and depressions of the original are reversed in the copy. Toobtain a fac-simije of the original, the electrotype cast is subjected to a repe-tition of the process. In general, it is found more convenient to…
Physics · Science · Technology
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