De Re Metallica Part 30

dwts.

gr.

per short ton.

1 _Scripulum_ 17.2 Per _Centumpondium_ 1 0 6 3 _Scripula_ = 1 _Drachma_ 51.5 " " 3 0 19 2 _Drachmae_ = 1 _Sicilicus_ 103.0 " " 6 1 15 4 _Sicilici_ = 1 _Uncia_ 412.2 " " 24 6 12 8 _Unciae_ = 1 _Bes_ 3297.6 " " 194 12 0

[28] The amalgamation of gold ores is fully discussed in note 12, p.

297.

[29] For discussion of the silver ores, see note 8, p. 108. _Rudis_ silver was a fairly pure silver mineral, the various coloured silvers were partly horn-silver and partly alteration products.

[30] It is difficult to see why copper scales (_squamae aeris_--copper oxide?) are added, unless it be to collect a small ratio of copper in the ore. This additional copper is not mentioned again, however. The whole of this statement is very confused.

[31] This old story runs that Hiero, King of Syracuse, asked Archimedes to tell him whether a crown made for him was pure gold or whether it contained some proportion of silver. Archimedes is said to have puzzled over it until he noticed the increase in water-level upon entering his bath. Whereupon he determined the matter by immersing bars of pure gold and pure silver, and thus determining the relative specific weights. The best ancient account of this affair is to be found in Vitruvius, IX, Preface. The story does not seem very probable, seeing that Theophrastus, who died the year Archimedes was born, described the touchstone in detail, and that it was of common knowledge among the Greeks before (see note 37). In any event, there is not sufficient evidence in this story on which to build the conclusion of Meyer (Hist.

of Chemistry, p. 14) and others, that, inasmuch as Archimedes was unable to solve the problem until his discovery of specific weights, therefore the Ancients could not part gold and silver. The probability that he did not want to injure the King's jewellery would show sufficient reason for his not parting these metals. It seems probable that the Ancients did part gold and silver by cementation. (See note on p. 458).

[32] The Alchemists (with whose works Agricola was familiar--_vide_ preface) were the inventors of nitric acid separation. (See note on p.

460).

[33] Parting gold and silver by nitric acid is more exhaustively discussed in Book X. and note 10, p. 443.

[34] The lesser weights, probably.

[35] Lead and Tin seem badly mixed in this paragraph.

[36] It is not clear what is added.

[37] HISTORICAL NOTE ON TOUCHSTONE. (_Coticula_.

_Interpretatio_,--_Goldstein_). Theophrastus is, we believe, the first to describe the touchstone, although it was generally known to the Greeks, as is evidenced by the metaphors of many of the poets,--Pindar, Theognis, Euripides, etc. The general knowledge of the const.i.tuents of alloys which is implied, raises the question as to whether the Greeks did not know a great deal more about parting metals, than has been attributed to them. Theophrastus says (78-80): "The nature of the stone which tries gold is also very wonderful, as it seems to have the same power with fire; which is also a test of that metal. Some people have for this reason questioned the truth of this power in the stone, but their doubts are ill-founded, for this trial is not of the same nature or made in the same manner as the other. The trial by fire is by the colour and by the quant.i.ty lost by it; but that by the stone is made only by rubbing the metal on it; the stone seeming to have the power to receive separately the distinct particles of different metals. It is said also that there is a much better kind of this stone now found out, than that which was formerly used; insomuch that it now serves not only for the trial of refined gold, but also of copper or silver coloured with gold; and shows how much of the adulterating matter by weight is mixed with gold; this has signs which it yields from the smallest weight of the adulterating matter, which is a grain, from thence a colybus, and thence a quadrans or semi-obolus, by which it is easy to distinguish if, and in what degree, that metal is adulterated. All these stones are found in the River Tmolus; their texture is smooth and like that of pebbles; their figure broad, not round; and their bigness twice that of the common larger sort of pebbles. In their use in the trial of metals there is a difference in power between their upper surface, which has lain toward the sun, and their under, which has been to the earth; the upper performing its office the more nicely; and this is consonant to reason, as the upper part is dryer; for the humidity of the other surface hinders its receiving so well the particles of metals; for the same reason also it does not perform its office as well in hot weather as in colder, for in the hot it emits a kind of humidity out of its substance, which runs all over it. This hinders the metalline particles from adhering perfectly, and makes mistakes in the trials. This exudation of a humid matter is also common to many other stones, among others, to those of which statues are made; and this has been looked on as peculiar to the statue." (Based on Hill's trans.) This humid "exudation of fine-grained stones in summer" would not sound abnormal if it were called condensation. Pliny (x.x.xIII, 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 touch-needles and their manner of making, which we have been able to find, is that of the _Probierbuchlein_ (1527?

see Appendix) where many of the tables given by Agricola may be found.

[38] _De Natura Fossilium_ (p. 267) and _De Ortu et Causis Subterraneorum_ (p. 59). The author does not add any material mineralogical information to the quotations from Theophrastus and Pliny given above.

[39] 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:--

ROMAN SCALE. OLD GERMAN SCALE.

6 _Siliquae_ = 1 _Scripulum_ 3 _Grenlin_ = 1 _Gran_ 4 _Scripula_ = 1 _s.e.xtula_ 4 _Gran_ = 1 _Krat_ 2 _s.e.xtulae_ = 1 _Duella_ 24 _Kratt_ = 1 _Mark_ 24 _Duellae_ = 1 _Bes_ or 24 _Grenlin_ = 1 "_Nummus_"

12 "_Nummi_" = 1 _Mark_

Also the following scales are applied to fineness by Agricola:--

3 _Scripula_ = 1 _Drachma_ 4 _Pfennige_ = 1 _Quintlein_ 2 _Drachmae_ = 1 _Sicilicus_ 4 _Quintlein_ = 1 _Loth_ 2 _Sicilici_ = 1 _Semuncia_ 16 _Loth_ = 1 _Mark_ 16 _Semunciae_ = 1 _Bes_

The term "_nummus_," a coin, given above and in the text, appears in the German translation as _pfennig_ as applied to both German scales, but as they are of different values, we have left Agricola's adaptation in one scale to avoid confusion. The Latin terms adopted by Agricola are given below, together with the German:--

Number in one Value in Roman Term. German Term. Mark or Bes. _Siliquae_.

_Siliqua_ 1152 1

"Unit of 4 _Siliquae_" _Grenlin_ 288 4

_Pfennig_ 256 --

_Scripulum_ _Scruple_ (?) 192 6

_Semi-s.e.xtula_ _Gran_ 96 12

_Drachma_ _Quintlein_ 64 18

_s.e.xtula_ _Halb Krat_ 48 24

_Sicilicus_ _Halb Loth_ 32 36

_Duella_ _Krat_ 24 48

_Semuncia_ _Loth_ 16 72

"_Unit of 5 Drachmae "_Nummus_" 12 96 & 1 Scripulum_"

_Uncia_ _Untzen_ 8 144

_Bes_ _Mark_ 1 1152

While the proportions in a _bes_ or _mark_ are the same in both scales, the actual weight values are vastly different--for instance, the _mark_ contained about 3609.6, and the _bes_ 3297 Troy Grains. Agricola also uses:

_Selibra_ _Halb-pfundt_ _Libra_ _Pfundt_ _Centumpondium_ _Centner_.

As the Roman _libra_ contains 12 _unciae_ and the German _pfundt_ 16 _untzen_, the actual weights of these latter quant.i.ties are still further apart--the former 4946 and the latter 7219 Troy grains.

[40] There are no tables in the Latin text, the whole having been written out _in extenso_, but they have now been arranged as above, as being in a much more convenient and expressive form.

[41] See note 39 above.

[42] See note 27, p. 242, for discussion of this "a.s.say ton"

arrangement.

[43] _Agrippinenses_ and _Antuerpiani_.

BOOK VIII.

Questions of a.s.saying were explained in the last Book, and I have now come to a greater task, that is, to the description of how we extract the metals. First of all I will explain the method of preparing the ore[1]; for since Nature usually creates metals in an impure state, mixed with earth, stones, and solidified juices, it is necessary to separate most of these impurities from the ores as far as can be, before they are smelted, and therefore I will now describe the methods by which the ores are sorted, broken with hammers, burnt, crushed with stamps, ground into powder, sifted, washed, roasted, and calcined[2].

I will start at the beginning with the first sort of work. Experienced miners, when they dig the ore, sort the metalliferous material from earth, stones, and solidified juices before it is taken from the shafts and tunnels, and they put the valuable metal in trays and the waste into buckets. But if some miner who is inexperienced in mining matters has omitted to do this, or even if some experienced miner, compelled by some unavoidable necessity, has been unable to do so, as soon as the material which has been dug out has been removed from the mine, all of it should be examined, and that part of the ore which is rich in metal sorted from that part of it which is devoid of metal, whether such part be earth, or solidified juices, or stones. To smelt waste together with an ore involves a loss, for some expenditure is thrown away, seeing that out of earth and stones only empty and useless slags are melted out, and further, the solidified juices also impede the smelting of the metals and cause loss. The rock which lies contiguous to rich ore should also be broken into small pieces, crushed, and washed, lest any of the mineral should be lost. When, either through ignorance or carelessness, the miners while excavating have mixed the ore with earth or broken rock, the work of sorting the crude metal or the best ore is done not only by men, but also by boys and women. They throw the mixed material upon a long table, beside which they sit for almost the whole day, and they sort out the ore; when it has been sorted out, they collect it in trays, and when collected they throw it into tubs, which are carried to the works in which the ores are smelted.

[Ill.u.s.tration 268 (Sorting Ore): A--Long table. B--Tray. C--Tub.]