In North America there are two great copper regions which supplied the whole continent[210]—Lake Superior and the lower Rio Grande. The former shows the first transitional steps from stone to metal. The ore occurs in the igneous and trappean rocks that wall in the vast fresh-water sea, and is found in solid blocks: one, fifty feet long, six feet deep, and six feet in average thickness, was estimated to weigh eighty tons. At Copper Harbour, Kawunam Point, a single vein yielded forty thousand pounds. The largest mass in the Minnesota Mine (Feb. 1857) occupied Mr. Petherick and forty men for twelve months: it was forty-five feet long, thirty-two feet broad (max.), and eight feet thick; containing over forty per cent. ore, and weighing four hundred and twenty to five hundred tons. Malleable and ductile, representing an average of 3·10 per cent. native silver, and with a specific gravity of 8·78 to 8·96, it required no crucible but Nature’s; it wanted only beating into shape, and it needed nothing of the skilled labour necessary for the ores of Cornwall and Devon, which contributed so largely to the wealth of Tyre. The workings are supposed to belong to the race conveniently called ‘Mound-builders,’ and to date from our second century, when the Damnonians of Cornwall were in a similar state of civilisation. ‘Cliff Mine’ supplied fine specimens of weapons and tools, arrow-piles and spear-heads, knives and three-sided blades like the old bayonet. The socket was formed by hammering flat the lower end, and by turning it over partially (without overlapping) at each side, so as to make a flange. Professor James D. Butler (‘Prehistoric Wisconsin’) facsimiles twenty-four copper implements. The ‘Indians’ called the metal Miskopewalik (red iron), opposed to black iron. As is also proved by the Brockville relics, the people had the art of hardening copper. The mines of the lower Rio Grande supplied Mexico with materials for arms and tools. According to Captain R. H. Bonnycastle,[211] the metal was found in New Mexico and in the volcanic rocks of Mechoacan (Valladolid, New Spain). Mexico, like Peru, used the crucible and added bronze to copper. The metals were under the god Quetzalcoatl, an Aztec Tubal Cain-ben-Lamech.