Note 650 — BOOK XXXIII. THE NATURAL HISTORY OF METALS.647

“Æs;” by “æs” is here probably meant copper, as the author is speaking of what is dug out of the earth; it is more fully described in the first two Chapters of the next Book. According to the analysis of Klaproth, the æs of the ancients, when employed in works of art, cutting instruments, statues, vases, &c., was the “bronze” of the moderns, a mixture of copper and tin, in which the proportion of tin varied, from a little more than 2 to 1.14 per cent, according as the object was to procure a flexible or a hard substance. Agricola speaks of “æs” as synonymous with “cuprum,” and Pliny will be found several times in the present Book, speaking of “æs Cyprium,” meaning probably the finest kind of copper, and that without alloy.—B.