BOOK VIL
253
generally is ; I have written elsewhere of its nature88. First the gold is
rubbed on the touchstone, whether it contains silver or whether it is obtained
from the mines or from the smelting ; silver also is rubbed in the same
way. Then one of the needles, that we judge by its colour to be of similar
composition, is rubbed on the touchstone ; if this proves too pale, another
needle which has a stronger colour is rubbed on the touchstone ; and if this
proves too deep in colour, a third which has a little paler colour is used. For
this will show us how great a proportion of silver or copper, or silver and
copper together, is in the gold, or else how great a proportion of copper is in
silver.
These needles are of four kinds.39 The first kind are made of gold and
silver, the second of gold and copper, the third of gold, silver, and copper,
and the fourth of silver and copper. The first three kinds of needles are
used principally for testing gold, and the fourth for silver. Needles of this
kind are prepared in the following ways. The lesser weights correspond
proportionately to the larger weights, and both of them are used, not
only by mining people, but by coiners also. The needles are made in
accordance with the lesser weights, and each set corresponds to a bes,
which, in our own vocabulary, is called a mark. The bes, which is employed
by those who coin gold, is divided into twenty-four double sextulae, which
Hill's trans.) This humid " exudation of fine-grained stones in summer " would not sound
abnormal if it were called condensation. Pliny (xxxni, 43) says : " The mention of
" gold and silver should be accompanied by that of the stone called coticula. Formerly,
" according to Theophrastus, it was only to be found in the river Tmolus but now found in
" many parts, it was found in small pieces never over four inches long by two broad. That
" side which lay toward the sun is better than that toward the ground. Those experienced
" with the coticula when they rub ore (vena) with it, can at once say how much gold it contains,
" how much silver or copper. This method is so accurate that they do not mistake it to a
" scruple." This purported use for determining values of ore is of about Pliny's average
accuracy. The first detailed account of touchneedles and their manner of making, which we
have been able to find, is that of the Probierbüchlein (1527? see Appendix) where many of the
tables given by Agricola may be found.
ZiDe Natura Fossilium (p. 267) and De Ortu et Causis Subterraneorum (p. 59). The
author does not add any material mineralogica! information to the quotations from
Theophrastus and Pliny given above.
s*In these tables Agricola has simply adopted Roman names as equivalents of the
old German weights, but as they did not always approximate in proportions, he coined terms
such as " units of 4 siliquae," etc. It might seem more desirable to have introduced
the German terms into this text, but while it would apply in this instance, as we have
discussed on p. 259, the actual values of the Roman weights are very different from the
German, and as elsewhere in the book actual Roman weights are applied, we have considered it better to use the Latin terms consistently throughout. Further, the obsolete
German would be to most readers but little improvement upon the Latin. For convenience
of readers we set out the various scales as used by Agricola, together with the German :—
