. A dictionary of arts, manufactures and mines : containing a clear exposition of their principles and practice. the same thing is sometimes done with therich ores, whose lighter parts might otherwise be lost. Most usually, especially for ores of lead, silver, copper, &c., the trough of the stamperis placed in the middle of a current of water, of greater or less force: which, sweepingoff the pounded substances, deposites them at a greater or less distance onwards, in theorder of the size and richness of the grain ; constituting a first washing, as they escapefrom beneath the pestles. In the dr
. A dictionary of arts, manufactures and mines : containing a clear exposition of their principles and practice. the same thing is sometimes done with therich ores, whose lighter parts might otherwise be lost. Most usually, especially for ores of lead, silver, copper, &c., the trough of the stamperis placed in the middle of a current of water, of greater or less force: which, sweepingoff the pounded substances, deposites them at a greater or less distance onwards, in theorder of the size and richness of the grain ; constituting a first washing, as they escapefrom beneath the pestles. In the dry stamping, the fineness of the powder depends on the weight of the pestles,the height of their fall, and the period of their action upon the ore; but in the stampersexposed to a stream of water, the retention of the matters in the trough is longer orshorter, according to the facility given for their escape. Sometimes these matters flowout of the chest over its edges, and the height of the line they must surmount has aninfluence on the size of the grain; at other ? mes, the water and the pounded mat^. 820 METALLURGY. which it carries off, are made to pass through a grating, causing a kind of sifting at thesame time. There are, however, some differences in the results of these two , the quantity of water that traverses the trough, as well as its velocity, has aninfluence on the discharge of the pounded matters, and consequently on the products ofthe stampers. The size of the particles of the pounded ore being different, according to the variablehardness of the matters which compose them, suggests the means of classing them, anddistributing them nearly in the order of their size and specific gravity, by making thewater, as it escapes from the stamping trough, circulate in a system of canals called alabyrinth, where it deposites successively, in proportion as it loses its velocity, the earthyand metallic matters it had floated along. These metalliferous portions, esp
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Keywords: ., bookcentury1800, bookdecade1840, booksubje, booksubjecttechnology
