Whilst wood was extensively used for Swords, the Age of Stone supplied few. The broad and leaf-shaped silex-flakes, dignified by the name of Swords, are only daggers and long knives. The fracture of flint is uncertain, even when freshly quarried.[136] The workmen would easily chip and flake it to form scrapers, axes, spear-heads, and arrow-piles; but after a certain length, from eight to nine inches, the splinters would be heavy, brittle, and unwieldy. Obsidian, like silex, would make daggers rather than swords. Such are the stone dirk and cutlass in the Kensington Museum. Several European museums preserve these flat, leaf-shaped knives of the dark cherty flint found in Egypt. The British Museum contains a polished stone knife broken at the handle, which bears upon it in hieroglyphics the name of ‘Ptahmes (Ptah-son), an officer.’ There is also an Egyptian dagger, of flint from the Hay Collection, still mounted in its original wooden handle apparently by a central tang, and with remains of its skin sheath.[137] The Jews, who borrowed circumcision from the Egyptians, used stone knives (τὰς μαχαίρας τὰς πετρίνας). Atys, says Ovid, mutilated himself with a sharp stone,— Ille etiam saxo corpus laniavit acuto; and the Romans sacrificed pigs with flints. Several undated poniards in our collections are remarkable: for instance, the English daggers of black and white flint, rare in Scotland and unknown in Ireland; (_a_) the Iberian or Spanish blade in the Christy Collection, five and a half inches long, and found at Gibraltar; the Tizcuco blade of chalcedony, eight inches long (_ibid._); (_b_) the Danish dagger in the Copenhagen Museum, thirteen and a half inches long (the rounded handle makes it a ‘marvel of workmanship’); and (_c_) the flint hatchet-sabre of the same collection, fifteen and a half inches in length. It is a mystery how the minute and delicate ornamentation, the even fluting like ripple marks, on these Danish flint-daggers was produced. [Illustration: FIG. 58.—FRAGMENTS OF STONE KNIVES FROM SHETLAND.] [Illustration: FIG. 59.—FLINT DAGGERS. _a._ Iberian or Spanish Blade (Christy Collection); _b._ Danish Flint Dagger; _c._ Danish Flint Hatchet Sabre.] A better substance than flint was found in the compact sandstone and in granitic serpentine, so called because that rock resembles a snake’s skin. It is easily worked, while it is harder than the common serpentine. A dagger or knife found beside a stone cist in Perthshire is described as a natural formation of mica-schiste.