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Smith, G. / The laboratory; or, School of arts: containing a large collection of valuable secrets, experiments, and manual operations in arts and manufactures, highly useful to gilders, jewellers, enamellers, goldsmiths, dyers, cutlers, pewterers, joiners, japanners, book-binders, plasterers, artists, and to the workers in metals in general; and in plaster of paris, wood, ivory, bone, horn, and other materials
(1799)
Part II. A variety of curious and valuable experiments on gold and silver; shewing the method of testing, refining, separating, allaying, and toughening those metals; together with other receipts, for gilding &c, pp. 69-112
Page 69
GOLR 4ND SILVER WORKS.
PART I.
A VARIETY OF
CURIOUS AND VALUABLE EXPERIMENTS
ON
GOLD AND SILVER;
&HEWING THE METHOD OF TESTING, REFINING, SEPARATING,
ALLAYING, ANiD TOUGHENING THOSE METALS; TOGETHER
WITH OTHER RECEIPTS, FOR GILDiNr, &.
P REVIOUS to entering upon the several detached re-
ceipts upon gold and silver, it may be proper to give
a brief sketch of metallurgy; or, in other words, "The
art of extracting and purifying of metals, in the great
way."
After trial has been made on a small scale (which is
called an Assay) that any particular mine is likely to be
profitable, the workmen proceed as follows: They dig a
perpendicular square pit, large enough to admit ladders,
whereby they may descend. Across the mouth of this pit,
which is called a shaft, an axis is usually laid, for the pur-
pose of raising buckets loaded- with the mineral ; , and
pumps are also placed, for carrying off the drainag% water.
If the depth of the mine be so great'as to exceed the due
proportion
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