Stories of Useful Inventions. Forman Samuel Eagle
their furnaces to a height of twenty or thirty feet. About this time also a better and a stronger blast was invented. Water-power instead of hand-power began to be used for operating the bellows. In some cases wooden bellows – great wooden pistons working in tubs – were substituted for the old bellows of leather. By the end of the sixteenth century so many improvements had been made upon the primitive forge that it no longer resembled the forge of ancient times. So the new forge received a new name and was called a blast furnace.10 You should observe, however, that the blast furnace was simply the old forge built with a large closed furnace and provided with a more powerful blast.
The invention of the blast furnace marked the beginning of a new era in the history of iron making. In the first place there was produced in the blast furnace a kind of iron that was entirely different from that which was produced in the primitive forge. In the primitive forge there was made a lump of practically pure unmelted iron, known as wrought iron. In the blast furnace there was produced a somewhat impure grade of melted iron, known as cast iron, or pig11 iron. In the second place, the blast furnace produced iron in quantities vastly greater than it was ever produced by the old forge. In the blast furnace more iron could be made in a day than could be made by the forge in a month. In some of the early blast furnaces a thousand pounds of iron could be made at one melting and we read of one early furnace that produced 150 tons of iron in a year.
FIG. 7. – MAKING CHARCOAL.
But even with the blast furnace it was still difficult to make enough iron to supply the ever-increasing demands of the industrial world. In the sixteenth and seventeenth centuries machinery was brought into use more than ever before and of course more iron was needed for the construction of the machines. There was ore enough for all the iron that was needed but it was difficult to get fuel enough to smelt the ore. Charcoal was still used as the fuel for smelting (Fig. 7), and in order to get wood for the charcoal great inroads were made upon the forests. In England in the early part of the eighteenth century Parliament had to put a check upon the manufacture of iron in certain counties in order to save the forests of those counties from utter destruction. It then became plain that if iron making were to be continued on a large scale a new kind of fuel would have to be used in the furnaces. So men set their wits to work to find a new kind of fuel. As far back as 1619 Dud Dudley in the county of Warwick, England, undertook to use ordinary soft coal in his furnaces but his experiment was not very successful or very profitable. More than a century after this an English ironmaker named Abraham Darby began (in 1735) to use charred coal in his blast furnaces, and his experiments were successful. Here was the new fuel which was so badly needed. Charred coal is simply coke and coke could be had in abundance. So the new fuel was soon used in all parts of England and by the end of the eighteenth century coke was driving charcoal out of blast furnaces (Fig. 8).
FIG. 8. – A PITTSBURGH COKE OVEN.
FIG. 9. – A MODERN BLAST FURNACE.
About the time the use of coke for smelting became general, an Englishman named Neilson brought about another great change in the process of iron making. Before Neilson's time the blast driven into the furnace had always been one of cold air. Neilson learned that if the air before entering the furnace were heated to a temperature of 600 degrees it would melt twice the amount of ore and thus produce twice the amount of iron without any increase in the amount of fuel. So he invented (in 1828) a hot blast for the blast furnace (Fig. 9). With the use of coke and with the hot blast the production of iron increased enormously. But there was need for all the iron that could be made. Indeed it seems that the world can never get too much iron. About the time the hot blast was invented iron chains instead of ropes began to be used for holding anchors, iron plows began to be made in great numbers (p. 83), iron pipes instead of hollow wooden logs began to be used as water-mains in cities, and iron rails began to be used on railroads. To supply iron for all these purposes kept ironmakers busy enough, even though they burned coke in their furnaces and made use of the hot air blast.
But ironmakers were soon to become busier than ever before. About the middle of the nineteenth century Sir Henry Bessemer invented a new process of making steel. Steel is only iron mixed with a small amount of carbon. Ironmakers have known how to make steel – and good steel, too – for thousands of years, but before the days of Bessemer the process had always been slow and tedious, and the cost of steel had always been very great. Bessemer undertook to make steel in large quantities and at low prices. In his experiments amid showers of molten metal he often risked his life, but his perseverance and courage were rewarded. By 1858 he had invented a process by which tons of molten iron could be run into a furnace and in a few minutes be converted into a fine quality of steel. This invention of Bessemer was the last great step in the history of the forge.
From copyright stereograph by Underwood & Underwood, N. Y.
FIG. 10. – GREAT STEEL RAIL PASSING THROUGH ROLLER STEEL MILL.
Now that steel could be made in great quantities and at a low cost it was put to uses never dreamed of in former times. Soon the railroad rail was made of steel (Fig. 10), bridges were made of steel, ships of war were plated with steel. Then ocean grayhounds and battleships were made of steel, still later steel freight cars and steel passenger coaches were introduced, while in our own time we see vast quantities of steel used in the building of houses. So while the invention of Bessemer marked the last step in the history of the forge it also marked the ending of the Age of Iron and the beginning of the wonderful age in which we live – the Age of Steel.
THE STEAM-ENGINE
We have now traced the steps by which man mastered the art of kindling a fire quickly and easily and have followed the progress that has been made in the most common uses of fire. But the story of a most important use of fire remains to be told, the story of its use in doing man's work. How important this use is, how much of the world's work is done through the agency of fire, a little reflection will make plain. Fire makes steam and what does steam do? Its services are so many you could hardly name all of them. The great and many services of steam are made possible by the fire-engine, or steam-engine, and the story of this wonderful invention will now be told.
FIG. 1. – FIRST EXPERIMENTS WITH STEAM.
That steam has the power to move things must have been learned almost as soon as fire was used to boil water. Heat water until it boils and the steam that is formed is bound to move something unless it is allowed to escape freely. It will burst the vessel if an outlet is not provided. That is why a spout has been placed on the tea-kettle. Where there is cooking, steam is abundant and the first experiments in steam were doubtless made in the kitchen (Fig. 1). It has been said that the idea of the steam-engine first occurred to Adam as he watched his wife's kettle boil.
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