American Edition of the British Encyclopedia; Or, Dictionary of Arts and Sciences; Comprising an Accurate and Popular View of the Present Improved State of Human Knowledge Volume 11
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1821 edition. Excerpt: ...size of a hair. Native silver, as we have observed, is seldom found pure, but is generally mixed with other metals; such as gold, copper, mercury, iron, lead, Sec. This last metal almost always contains a portion of silver, though frequently so small as not to be worth the expense of separating it. In the reign of Edward the First nearly 1G00 pounds weight of silver were obtained, in the course of three years, from a mine in Devonshire, which had been discovered about the year 900. The lead mines in Cardiganshire have, at different periods, afforded great quantities of silver. Sir Hugh Middleton is said to have cleared from them 2000 pounds in a month. The same mines yielded, about the year 1745, eighty ounces of silver out of every ton of lead. The lead ores from Bnmghill and Skekorn produced also a considerable quantity of silver. The lead only, in one of the smelting-houses at Holywell, in Flintshire, produced no less than, 31,521 ounces, or 3126$ pounds of silver, from the year 1754 to 1776. "There are some lead ores in this country," says Dr. Watson, " which, though very poor in lead, contain between three and four hundred ounces of silver in a ton of that metal. It is commonly observed, that the poorest lead-ores yield the most silver, so that a large quantity of silver is probably thrown away in England, from not having the poorest sort of lead-ores properly assayed." Silver in its mineral state occurs massive, disseminated, in blunt cornered pieces, in plates, and in membranes: it is said to occur also in Spanish America in rolled pieces. Its crystallizations are very various, as the cube, octahedron, prism, pyramidal, &c.: the crystals are small and microscopic. It is chiefly found in primitive earths, ...
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- 13 Sep 2013
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