of great weight, and in those the value of which depends more upon the material than upon the labour expended on it.  Most of the metallic ores being exceedingly heavy, and being mixed up with large quantities of weighty and useless materials, must be smelted at no great distance from the spot which affords them:  fuel and power are the requisites for reducing them; and any considerable fall of water in the vicinity will naturally be resorted to for aid in the coarser exertions of physical force; for pounding the ore, for blowing the furnaces, or for hammering and rolling out the iron.  There are indeed peculiar circumstances which will modify this.  Iron, coal, and limestone, commonly occur in the same tracts; but the union of the fuel in the same locality with the ore does not exist with respect to other metals.  The tracts generally the most productive of metallic ores are, geologically speaking, different from those affording coal:  thus in Cornwall there are veins of copper and of tin, but no beds of coal.  The copper ore, which requires a very large quantity of fuel for its reduction, is sent by sea to the coalfields of Wales, and is smelted at Swansea; whilst the vessels which convey it, take back coals to work the steam-engines for draining the mines, and to smelt the tin, which requires for that purpose a much smaller quantity of fuel than copper.

278.  Rivers passing through districts rich in coal and metals, will form the first highroads for the conveyance of weighty produce to stations in which other conveniences present themselves for the further application of human skill.  Canals will succeed, or lend their aid to these; and the yet unexhausted applications of steam and of gas, hold out a hope of attaining almost the same advantages for countries to which nature seemed for ever to have denied them.  Manufactures, commerce, and civilization, always follow the line of new and cheap communications.  Twenty years ago, the Mississippi poured the vast volume of its waters in lavish profusion through thousands of miles of countries, which scarcely supported a few wandering and uncivilized tribes of Indians.  The power of the stream seemed to set at defiance the efforts of man to ascend its course; and, as if to render the task still more hopeless, large trees, torn from the surrounding forests, were planted like stakes in its bottom, forming in some places barriers, in others the nucleus of banks; and accumulating in the same spot, which but for accident would have been free from both, the difficulties and dangers of shoals and of rocks.  Four months of incessant toil could scarcely convey a small bark with its worn-out crew two thousand miles up this stream.  The same voyage is now performed in fifteen days by large vessels impelled by steam, carrying hundreds of passengers enjoying all the comforts and luxuries of civilized life.  Instead of the hut of the Indian, and the far more unfrequent log house of the thinly scattered settlers—­villages, towns, and cities, have arisen on its banks; and the same engine which stems the force of these powerful waters, will probably tear from their bottom the obstructions which have hitherto impeded and rendered dangerous their navigation.(1*)