Buffon (‘Hist. Nat.’ article ‘Cuivre’) believed in the ‘lost art.’ Rossignol[163] (pp. 237–242) has treated of the _trempe_ (διά τινος βαφῆς) _que les anciens donnèrent au cuivre_; and relates that the chemist Geoffrey, employed by the Comte de Caylus, succeeded in hardening copper and in giving it the finest edge; but the secret was not divulged. Mongez, the Academician, held that copper was indurated by immersion and by gradual air-cooling, but that _la trempe_ would soften it.[164] In 1862 David Wilson, following Proclus and Tzetzes, declares the process of hardening and tempering copper so as to give it the edge of iron or steel, a ‘lost art.’ Markham[165] supposes that the old Peruvians hardened their copper with tin or silica; and he erroneously believes that tin is scarcely found in that section of South America. Modern archæological discovery has suggested that in many parts of the world we must intercalate an age of virgin Copper between the so-called Stone and Bronze Periods. The first metal, as far as we know, was the stream-gold, washed by the Egyptians; and, as Champollion proved, the hieroglyphic sign for Núb (gold) is a bowl with a straining-cloth dripping water.[166] The fable of glass-discovery by the Sidonians on the sands of the Belus,[167] a tale which has _le charme des origines_, explains, I have said, how a bit of metalliferous stone, accidentally thrown upon the fire in a savage hut, would suggest one of the most progressive of the arts. And soon the ‘featherless biped,’ like the Mulciber and the Mammon of Milton— Ransack’d the centre, and with impious hands Rifled the bowels of their mother earth For treasures better hid. The greater antiquity of copper in Southern Europe was distinctly affirmed, as has been seen, by the Ancients. The use of sheeting, or plating, on wood or stone was known as long ago as the days of Hesiod (B.C. 880–850?): Τοῖς δ’ ἦν χάλκεα μὲν τεύχεα, χάλκεοι δέ τε οἶκοι, Χαλκῷ δ’ εἰργάζοντο, μέλας δ’ οὐκ ἔσκε σίδερος.—_Erga_, 149. Copper for armour and arms had they, eke Copper their houses, Copper they wrought their works when naught was known of black iron.[168] Copper sheets[169] were also used for flooring, as we learn from the χάλκεος οὐδός (Copper threshold) of Sophocles (‘Œdip. Col.’); and the treasury-room of Delphi, as opposed to the λάϊνος οὐδός (stone threshold). So in the Palace of Alcinous (‘Odys.’ vii. 75) the walls and threshold were copper, the pillars and lintels were silver, and the doors and dogs of gold. The same practice was continued in the Bronze Period, as Dr. Schliemann proved when exploring the Thalamos attached to the Treasury of Minyas at Orchomenus. Nebuchadnezzar, in the ‘Standard Inscription,’ declares that he plated with copper the folding-doors and the pillars of the Babylon rampart, and it is suspected that gold and silver sheeted the fourth and seventh stages of the Temple of Belus, _vulgò_ the Tower of Babel.