Note 864 — Chapter IV · INDUSTRY: SMITHS, CUTLERS, ARMOURERS, THE ART OF MINING, CHARCOAL-MAKING, ETC.
Reading edition
The hardness, however, would appear to have been produced partly by the interfusion of different metals, partly by the liquid in which the implements were quenched. Ulloa, Mémoires Philosophiques, &c., t. ii. p. 90. 94. Observations, p. 468. Cf. Voyages, t. i. p. 384.