[817] Odyss. ix. 391.
[818] Ajax, 720.
[819] Exercitat. Plin. p. 763.
[820] Lib. xxxiv. 14, p. 666.
[821] Lib. xliv. p. 620.
[822] [There can be no question that the hardening or tempering effect produced by the sudden immersion of heated steel in fluids has no relation to the quality of the fluid, save as regards its conducting power of heat. The more suddenly the heat is abstracted from the metal, the greater is the amount of hardness and brittleness. Mercury has been found superior to any other fluid for this purpose, undoubtedly because it is so good a conductor of heat.]
[823] Le Vite de Pittori. Bologna, 1681, 4to, i. p. 11.
[824] Some account of this artist is given in J. C. Bulengeri de Pictura, lib. ii. cap. 7, in Gronovii Thesaurus Antiq. Græc. ix. p. 875. On the other hand, Sturm says, in that part of the Ritterplatzes which relates to architecture, p. 18: “An archduke at Florence discovered again the art of working porphyry, but suffered it to die with him in the year 1556.”
[825] Florillo Gesch. der Zeichnenden Künste, 8vo, i. p. 461.
[826] Art de convertir le Fer en Acier, p. 245.