I have spoken of the use of wood-fuel in the early stages of iron manufacture in this country, followed by the adoption exclusively of coal and its products. Then, many years later, came the departure from this in the use of gas for fuel. The first use of this kind is said to date as far back as the eighth century, and modifications of the idea had been put in practice in this country, in which gas was first made from coal and then used as fuel. Then came "natural gas." This product has been known for many centuries. It was the "eternal" fuel of the Persian fire-worshippers, and has been used as fuel in China for ages. Its earliest use in this country was in 1827, when it was made to light the village of Fredonia, N. Y. Probably its first use for manufacturing purposes was by a man named Tompkins, who used it to heat salt-kettles in the Kenawha valley in 1842. Its next use for manufacturing purposes was made in a rolling mill in Armstrong county, Penn., in 1874, forty-seven years after it had been used at Fredonia, and twenty-nine years after it had been used to boil salt. Now the use of natural gas as manufacturing fuel is universal, not alone over the spot where the gas is found, but in localities hundreds of miles away. It is one of the strangest developments of modern scientific ingenuity. That enormous battery of boilers, which was one of the most imposing spectacles of the Columbian Exhibition of 1893, whose roar was like that of Niagara, was fed by invisible fuel that came silently in pipes from a state outside of that where the great fair was held. We are left to the conclusion that the making of the coal into gas at the mine, and the shipping of it to the place of consumption through pipes, is more certain of realization than were a hundred of the early problems of American progress that have now been successful for so long that the date of their beginning is almost forgotten. THE STEEL OF THE PRESENT.--The story of steel has now almost been told, in that general outline which is all that is possible without an extensive detail not interesting to the general reader. In it is included, of necessity, a resumé of the progress, from the earliest times in this country, of the great industry which is more indicative than any other of the material growth of a nation. I now come to that time when steel began to take the place that iron had always held in structural work of every class. The differences between this structural steel and that which men have known by the name exclusively from remote ages, I have so far indicated only by reference to the well-known qualities of the latter. It now remains to describe the first. In 1846 an American named William Kelley was the owner of an iron-works at Eddyville, Ky. It was an early era in American manufactures of all kinds, and the district was isolated, the town not having five hundred inhabitants, and the best mechanical appliances were remote.