Page:Prehistoric Times.djvu/91

Rh are absence of toughness, and the existence of a splintery conchoidal fracture almost as sharp as that of flint. . . . At the hornblendic extreme of the trap rocks we find the basalt, of which also celts were made; tough and heavy, the siliceous varieties having a splintery fracture, but never affording so cutting an edge as the former. . . . Intermediate in character between these two rocks we find all the varieties of felstone, slate, and porphyry streaked with hornblende, from which the great majority of the foregoing implements have been made."

It is very remarkable how carefully the best kinds of stone were selected, even when very rare. Of this the most interesting example is afforded by the axes, etc., of jade or nephrite, of jadeite and of saussurite. These minerals are very distinct chemically, but so similar in appearance that they can only be distinguished by analysis. Objects made from them, though far from common, are not very rare. M. Fischer gives the following table:—

Till 1884, no European locality of jade or nephrite was known, and though it has now been discovered in Silesia, and some few other places, they are very rare, and have not been found anywhere near Brittany.

Beads of Baltic amber are scattered over Central Europe. The same may be said of obsidian, for which there are only one or two sources. Another interesting case is afforded by the Pressigny flint implements (see page 81).

Again, beads of Callais, another mineral not known to occur in Europe, have been found in the tumuli of Brittany and some other parts of France.

Other facts of a similar nature are on record. Thus Messrs Squier and Davis tell us that in the tumuli of the Mississippi valley we find "side by side, in the same mounds, native copper from Lake Superior, mica from