Then slowly came the period of all kinds of "machine tools." During the period briefly described above they could not make sheet metal. The rolling mill must have come, not only before the modern steam-boiler, but even before the modern plow could be made. Can the reader imagine a time in the United States when sheet metal could not be rolled, and even tin plates were not known? If so, he can instantly transport himself to the times of the wooden "trencher," and the "pewter" mug and pitcher, to the days when iron rails for tramways were unknown, and when even the "strap-iron," always necessary, was rudely and slowly hammered out on an anvil. [[13]]

[13.] About 1720, nails were the most needed of all the articles of a new country. Farmers made them for themselves, at home. The secret of how to roll out a sheet and split it into nail-rods was stolen from the one shop that knew how, at Milton, Mass., to give to another at Mlddleboro. The thief had the Biblical name of Hashay H. Thomas. He stole the secret while the hands of the Milton mill were gone to dinner, and served his country and broke up a small monopoly in so doing.

Shears came with the "rolls;" vast engines of gigantic biting capacity, that cut sheets of iron as a lady's scissors cut paper. This cut the squares of metal used for boiler plates, and the steam-engine having come, was turned to the manufacture of materials for its own construction. Others were able to bite off great bars.

The first mill in which iron was rolled in America, was built in 1817 near Connellsville, in Fayette county, Penn. Until 1844, the rolling mills of this country produced little more than bar-iron, hoops, and plates. All the early attempts at railroads used the "strap" rail; unless cast "fish-bellies" were used; which was flat bar-iron provided with counter sunk holes, in which to drive nails for holding the iron to long stringers of wood laid upon ties. When actual rail-making for railroads began, the rolling mill raised its powers to meet the emergency. The "T" rail, universally now used, was invented by Robert Stevens, president and chief engineer of the Camden and Amboy railroad, and the first of them were laid as track for that road in 1832. From this time until 1850, rolling mills for making "U" and "T" rails rapidly increased in number, but in that year all but two had ceased to be operated because of foreign competition.

During some five years previous to this writing a revolution has taken place in the construction of buildings which has resulted in what is known as the "sky-scraper." This was, in many respects, the most startling innovation of times that are startling in most other respects, and was begun in that metropolis of surprises and successes, the city of Chicago. This innovation was really such in the matter of using steel in the entire framing of a commercial building, but it was not the first use of metal as a building material. The first iron beams used in buildings were made in 1854, in a rolling mill at Trenton, N. J., and were used in the construction of the Cooper Institute, and the building of Harper & Brothers. For these special rolls, of a special invention, were made. These have now become obsolete, and a new arrangement is used for what are known as "structural shapes."

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.