Those were the palmy days of the "trip hammer." Nasmyth was not born until 1808, and no machine inventor had yet come upon the scene. The steam-hammer that bears his name, which means a ponderous and powerful machine in which the hammer is lifted by the direct action of steam in a piston, the lower end of whose rod is the hammer-head, has done more for the development of the iron industry than any other mechanical invention. It was not actually used until 1842, or '43. It finally, with many improvements in detail, grew into a monster, the hammer-head, or "tup," being a mass of many tons. And they of modern times were not content merely to let this great mass fall. They let in steam above the piston, and jammed it down upon the mass of glowing metal, with a shock that jars the earth. The strange thing about this Titanic machine is that it can crack an egg, or flatten out a ton or more of glowing iron. Hundreds of the forgings of later times, such as the wrought iron or steel frames of locomotives, and the shafts of steamers, and the forged modern guns, could not be made by forging without this steam hammer. [Illustration: THE STEAM HAMMER.] 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. [Footnote: 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.