But in this chapter I am not going to deal with smoke; neither with the grain that feeds nations, nor the lumber that builds their homes. They will be described in their time. The backbone of American manufacturing industry--the mainspring of our commercial prestige abroad--is iron; and it is this iron, gathered in the one-time wildernesses of the Northland and brought down a thousand miles by ship, that stands largely for the greatness of the Lakes to-day. “Gold is precious, but iron is priceless,” said Andrew Carnegie. “The wheels of progress may run without the gleam of yellow metal, but never without our ugly ore.” And the Lake country, or three little patches of it, produce each year nearly a half of the earth’s total supply of iron. Farmers in the wake of their ploughshares, our millions of workers in metal, and our other millions whose fingers daily touch the chill of iron have never dreamed of this. Few of them know that eight hundred great vessels are engaged solely in the iron ore traffic; that in a single trip this immense fleet can transport more than three million tons, and that in 1907, they brought to the foundries of the East and South over forty-one million tons. If every man, woman, and child, savage or civilised, that inhabits this earth of ours were to receive equal portions of this one product carried by Lake vessels in 1907, each person’s share would be forty pounds! And still the world is crying for iron. There is not enough to supply the demand, and there never will be. The iron ore traffic of the Lakes has doubled during the last six years; it will double again during the next ten--and iron will still be the most precious thing on earth.