had been so great that the forests of England were being rapidly destroyed, and a series of experiments had developed the fact that by heating coal in a pit or oven, in a manner similar to that by which charcoal was produced from wood, the charred coal, called coke, could be used as a substitute for charcoal in iron furnaces. This substitute for charcoal did not come into use in the United States until much later, however, for the reason that the people of the eastern part of the United States were still anxious to get the timber off their lands to use them for agricultural purposes, and so were glad to turn it into charcoal and dispose of it to the iron furnaces at a low cost. In time, however, the supply of charcoal began to run low and the Americans began to cast about for a substitute. After a series of experiments it became evident that the anthracite coal of Pennsylvania could be used for iron smelting, as it was hard enough to bear the weight of the iron ore piled upon it, and also made a much more intense heat than did the bituminous coal which grew soft as it was heated and was useless in the furnace. By 1840 the making of pig iron with anthracite coal became an established industry and by 1854 the quantity of iron made by the use of anthracite was as great as that from charcoal, about 350,000 tons for each. But as the supply of anthracite was limited to a comparatively small area, those sections which had no anthracite and had run short of the timber supply for making charcoal began to cast about for a substitute, and hearing of the success of the English, with “charred coal,” or coke, began its use in the United States; and by 1856 there were more than a score of furnaces making pig iron by the use of coke. It was also found that if the air which was forced into the furnace was heated before entering a much more intense heat could be obtained and the use of the hot blast was soon established.
With iron being made by the use of anthracite coal and coke made from bituminous coal, the people began to realize
that the destruction of the forests to produce charcoal should not continue longer, and the making of charcoal iron rapidly decreased. Meantime the railways began to develop and were able to carry coal and coke to the places where the ore could be easily obtained, or to which it could be easily brought. Such a place was Pittsburg, for example. Iron ore was produced in certain parts of Pennsylvania and on the northern shores of the Great Lakes. Coal of a suitable quality for making excellent coke was produced at Connellsville, in western Pennsylvania. Limestone is required in great quantities in smelting iron ore, as the alkaline quality of the limestone neutralizes the acid of the waste matter forming a part of the iron ore and makes it melt at a lower temperature, the melted limestone also carrying off the impurities in the form of “slag,” and limestone was also plentiful near Pittsburg. Some of these materials could be floated down the rivers or on the Great Lakes, at least a part of the way from the place of production to the place at which they were combined, and for the remainder of the distance railways carried them over comparatively level or down-grade routes at small cost.
So, with the advent of the railway and the steamship the methods of iron making changed. The railway and the river or lake steamer could carry the finished product at such low cost that it was no longer necessary that each county should make its own iron, and more than that, they could carry the ore and the limestone and the coal or coke to any place convenient for assembling these necessary materials and distributing the finished product.
This combination of the raw materials and the manufacture of the iron in a few great establishments instead of many small ones encouraged the use of machinery in manufacturing. Machines were wanted for handling the ore, for handling the coal, for handling the limestone, for handling the molten material which issued from the furnace, and for turning it into the finished form, sometimes
accomplishing this without allowing the material to grow cold and harden at any point between the time it trickles from the blast furnace and its completion as a steel billet, a rail for the railway, or a roll of barbed wire for the ranchero of South America.
The iron as it leaves the blast furnace is not in a condition in which it can be used for manufacturing. It contains so much carbon and other impurities that it is brittle and breaks easily. This condition is similar to that of the “blooms,” or chunks of metal which came from the early furnaces and which had to be refined by laborious processes of reheating and hammering until the impurities were worked out.
Before the year 1800 it had occurred to somebody in England that if flames could be forced across the surface of the molten iron and the iron kept in a state of constant agitation the flames would burn out the carbon. This was accomplished by making an open hearth to contain the molten material and “puddling” the iron as the flames were forced across the surface. Then a series of grooved rollers was devised, between which pieces of partially cooled iron could be passed and repassed, and this machine process worked out the “slag” and other impurities which had been formerly worked out with hammers. This puddling and rolling began in England before the year 1800 and “the puddle and the grooved roll,” says J. Russell Smith, “closed the era of the blacksmith’s supremacy and opened the era of machine manufacture.” It was an adaptation of these methods and combination of them with the concentration of the material at convenient centers that proved the beginning of the machine-manufacturing methods in the United States at a considerably later period than in England.
The most notable step in developing the use of iron, however, was that by which it was quickly and cheaply turned into the reliable form known as “steel.” As already explained,
the iron when it leaves the blast furnace contains such quantities of carbon, silicon, sulphur, phosphorus, and other impurities that it is brittle and unreliable as to tensile strength, flexibility, or the qualities which make it available for edged tools. The puddling process already described deprived it of the carbon and sulphur, but left it too soft for immediate use. It required a small and fixed amount of carbon to give it the qualities of steel and this was replaced by reheating it in air-tight receptacles in combination with powdered charcoal. By this process steel was made, but it was a slow and expensive process. About the middle of the last century, William Kelly, of Pittsburg, conceived the idea that by forcing air through the molten iron as it came from the furnace the oxygen of the air would combine with the carbon of the iron and burn out the carbon, leaving the remainder pure iron. A series of experiments proved the accuracy of his theory, and he made steel by this process. About the same time Sir Henry Bessemer, of England, devised a similar process and it was put into practical operation in England and later in the United States. By this process, developed almost simultaneously in America and England by these two men, the transformation of iron into steel in a brief space of time and at a small cost was established, and the manufacture of steel developed with wonderful rapidity. The quantity of steel manufactured in the United States in 1870 was but 69,000 tons; in 1880, 1,247,000 tons; in 1890, 4,277,000 tons; in 1900, 10,188,000 tons; and in 1907, 23,363,000 tons. With this great development in manufacturing came a great development in the use of machinery for handling not only the finished steel itself but the pig iron from which it was manufactured, the iron ore from which it was produced and the coal and limestone used in its production. With this growing use of machinery in the manufacture and the great increase in the quantity used in the industries of the world have come the enlargement of