The History of Chemistry. Thomas Thomson

and gold approached each other nearer in value among the ancients than at present: an ounce of fine gold was worth from ten to twelve ounces of fine silver, the variation depending upon the accidental relation of the supply of both metals. But after the discovery of America, the quantity of silver found in that continent, especially in Mexico, was so great, compared with that of the gold found, that silver became considerably cheaper; so that an ounce of fine gold came to be equivalent to about fourteen ounces and a half of fine silver. Of course these relative values have fluctuated a little according to the abundance of the supply of silver. Though the revolution in the Spanish American colonies has considerably diminished the supply of silver from the mines, that deficiency seems to have been supplied by other ways, and thus the relative proportion between the value of gold and silver has continued nearly unaltered.

      3. That copper must have been known in the earliest ages of society, is sufficiently evident. It occurs frequently native, and could not fail to attract the attention of mankind, from its colour, weight, and malleability. It would not be difficult to fuse it even in the rudest ages: and when melted into masses, as it is malleable and ductile, it would not require much skill to convert it into useful and ornamental utensils. The Hebrew word תשחנ (nechooshat) translated brass, obviously means copper. We have the authority of the Book of Genesis to satisfy us that copper was known before the flood, and probably as early as either silver or gold.

      “And Zillah, she also bore Tubal-cain, an instructor of every artificer in brass (copper) and iron.”31

      The word copper occurs in many other passages of the writings of Moses.32 That the Hebrew word translated brass must have meant copper is obvious, from the following passage: “Out of whose hills thou mayest dig brass.”33 Brass does not exist in the earth, nor any ore of it, it is always made artificially; it must therefore have been copper, or an ore of copper, that was alluded to by Moses.

      Copper must have been discovered and brought into common use long before iron or steel; for Homer represents his heroes of the Trojan war as armed with swords, &c. of copper. Copper itself is too soft to be made into cutting instruments; but the addition of a little tin gives it the requisite hardness. Now we learn from the analyses of Klaproth, that the copper swords of the ancients were actually hardened by the addition of tin.34

      Copper was the metal in common use in the early part of the Roman commonwealth. Romulus coined copper money alone. Numa established a college of workers in copper (ærariorum fabrum).35

      The Latin word æs sometimes signifies copper, and sometimes brass. It is plain from what Pliny says on the subject, that he did not know the difference between copper and brass; he says, that an ore of æs occurs in Cyprus, called chalcitis, where æs was first discovered. Here æs obviously means copper. In another place he says, that æs is obtained from a mineral called cadmia. Now from the account of cadmia by Pliny and Dioscorides, there cannot be a doubt that it is the ore to which the moderns have given the name of calamine, by means of which brass is made. It is sometimes a silicate and sometimes a carbonate of zinc; for both of these ores are confounded together under the name of cadmia, and both are employed in the manufacture of brass.

      Solinus says, that æs was first made at Chalcis, a town in Eubœa. Hence the Greek name, χαλκος (chalkos), by which copper was distinguished.

      The proper name for brass, by which is meant an alloy of copper and zinc, was aurichalcum, or golden, or yellow copper. Pliny says, that long before his time, the ore of aurichalcum was exhausted, so that no more of that beautiful alloy was made. Are we to conclude from this, that there once existed an ore consisting of calamine and ore of copper, mixed or united together? After the exhaustion of the aurichalcum mine, the salustianum became the most famous; but it soon gave place to the livianum, a copper-mine in Gaul, named after Livia, the wife of Augustus. Both these mines were exhausted in the time of Pliny. The æs marianum, or copper of Cordova, was the most celebrated in his time. This last æs, he says, absorbs most cadmia, and acquires the greatest resemblance to aurichalcum. We see from this, that in Pliny’s time brass was made artificially, and by a process similar to that still followed by the moderns.

      The most celebrated alloy of copper among the ancients, was the æs corinthium, or Corinthian copper, formed accidentally, as Pliny informs us, during the burning of Corinth by Mummius in the year 608, after the building of Rome, or one hundred and forty-five years before the commencement of the Christian era. There were four kinds of it, of which Pliny gives the following description; not, however, very intelligible: 1. White. It resembled silver much in its lustre, and contained an excess of that metal. 2. Red. In this kind there is an excess of gold. 3. In the third kind, gold, silver, and copper are mixed in equal proportions. 4. The fourth kind is called hepatizon, from its having a liver colour. It is this colour which gives it its value.36

      Copper was put by the ancients to almost all the uses to which it is put by the moderns. One of the great sources of consumption was bronze statues, which were first introduced into Rome after the conquest of Asia Minor. Before that time, the statues of the Romans were made of wood or stoneware. Pliny gives various formulas for making bronze for statues. Of these it may be worth while to put down the most material.

      1. To new copper add a third part of old copper. To every hundred pounds of this mixture, twelve pounds and a half of tin37 are added, and the whole melted together.

      2. Another kind of bronze for statues was formed, by melting together 100lbs. copper, 10lbs. lead, 5lbs. tin.

      3. Their copper-pots for boiling consisted of 100lbs. of copper, melted with three or four pounds of tin.

      The four celebrated statues of horses which, during the reign of Theodosius II. were transported from Chio to Constantinople; and, when Constantinople was taken and plundered by the Crusaders and Venetians in 1204, were sent by Martin Zeno and set up by the doge, Peter Ziani, in the portal of St. Mark; were in 1798, transported by the French to Paris; and finally, after the overthrow of Buonaparte, and the restoration of the Bourbons in 1815, returned to Venice and placed upon their ancient pedestals. The metal of which these horses had been made was examined by Klaproth, and found by him composed of Copper, 993 Tin, 7 1000 38

      Klaproth also analyzed an ancient bronze statue in one of the German cabinets, and found it composed of Copper, 916 Tin, 75 Lead, 97 1000 39

      Several other old brass and bronze pieces of metal, very ancient, but found in Germany, were also analyzed by Klaproth. The result of his analyses was as follows:

      The metal of which the altar of Krodo was made consisted of Copper, 69 Zinc, 18 Lead, 13 100 40

      The emperor’s chair, which had in the eleventh century been transported from Harzburg to Goslar, where it still remains, was found to be composed of Copper, 92·5 Tin, 5·0 Lead, 2·5 100 41

      Another piece of metal, which enclosed the high altar in a church in Germany, was composed of Copper, 75·0 Tin, 12·5 Lead, 12·5 100 42

      These analyses, though none of them corresponds exactly with the proportions given by Pliny, confirms sufficiently his general statement, that the bronze of the ancients employed for statues was copper, alloyed with lead and tin.

      Some of the bronze statues cast by the ancients were of enormous dimensions, and show decisively the great progress which had been made by them in the art of working and casting metals. The addition of the lead and tin would not only add greatly to the hardness of the alloy, but would at the same time render it more easily fusible. The bronze statue of Apollo, placed in the capitol at the time of Pliny, was forty-five feet high, and cost 500 talents, equivalent to about £50,000 of our money. It was brought from Apollonia, in Pontus, by Lucullus. The famous statue of the sun at Rhodes was the work of Chares, a disciple of Lysippus; it was ninety feet high, was twelve years in making, and cost 300 talents (about £30,000). It was made out of the engines of war left by Demetrius when he raised the siege of Rhodes. After standing fifty-six years, it was overthrown by an earthquake. It lay on the ground 900 years, and was sold by Mauvia, king of the Saracens, to a merchant, who loaded 900 camels