Nor have such discoveries been confined to the so-called precious metals. The advance of North American civilisation towards the head waters of the Missouri has made known abundant mines of lead, which the cost of transport chiefly prevents as yet from seriously competing with European produce along the Atlantic border. The joint march of Canada and the United States along the shores of Lake Superior, has laid open veins of copper of inexhaustible magnitude—on a scale, we may say, in size and richness commensurate with the other great natural features of the American continent;—while, of coal and ironstone, the Central States of the Union are so full, that imagination itself cannot conceive a time when they shall cease to be sufficient for the wants of the whole civilised world. Men untrained themselves to observe, and ignorant that it is intellectual knowledge which opens and guides the eye, affect to wonder—often, indeed, do seriously wonder—that gold so plentifully scattered over the surface of a country as it is said to be in California and Australia, or sprinkling with its yellow sheen thick veins of snowy quartz, should, for a time so comparatively long, have escaped observation. “What surprises me,” says Captain Sutter, in whose mill-race the gold was first discovered, “is, that this country should have been visited by so many scientific men, and that not one of them should have ever stumbled upon these treasures; that scores of keen-eyed trappers should have crossed the valley in every direction, and tribes of Indians have dwelt in it for centuries, and yet this gold should never have been discovered. I myself have passed the very spot above a hundred times during the last ten years, but was just as blind as the rest of them, so I must not wonder at the discovery not having been made earlier.”[3] Such seeming blindness, indeed, is not really a matter of surprise. The ability to observe is an intellectual gift no less than the ability to reason; and, like the latter talent, the former also must be trained. It must be taught where to look, and what to look for; what the signs are of the presence of the thing we wish to find, and where they are likely to be met with.