Part 3 (1/2)

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 _pig_[11] iron. In the second place, the blast furnace produced iron in quant.i.ties 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.

[Ill.u.s.tration: 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 _c.o.ke_ and c.o.ke 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 c.o.ke was driving charcoal out of blast furnaces (Fig. 8).

About the time the use of c.o.ke 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 c.o.ke 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 c.o.ke in their furnaces and made use of the hot air blast.

[Ill.u.s.tration: FIG. 8.--A PITTSBURGH c.o.kE OVEN.]

[Ill.u.s.tration: FIG. 9.--A MODERN BLAST FURNACE.]

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 quant.i.ties 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.

[Ill.u.s.tration:

From copyright stereograph by Underwood & Underwood, N. Y.

FIG. 10.--GREAT STEEL RAIL Pa.s.sING THROUGH ROLLER STEEL MILL.]

Now that steel could be made in great quant.i.ties 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, s.h.i.+ps of war were plated with steel. Then ocean grayhounds and battles.h.i.+ps were made of steel, still later steel freight cars and steel pa.s.senger coaches were introduced, while in our own time we see vast quant.i.ties 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.

FOOTNOTES:

[8] J. R. Smith, ”The Story of Iron and Steel,” p. 3.

[9] From ”Five Black Arts,” p. 311.

[10] The old forge continued to be used by the side of the blast furnace for centuries, and of course where it was used it was still called a forge. Thus we are told that in Maryland in 1761, there were eight furnaces and ten forges. It is said that as late as twenty-five years ago in certain parts of the Appalachian regions the American mountaineer still worked the little primitive forge to make his iron.

[11] It was given the name of _pig_ iron because when the molten metal ran into the impressions made for it upon the sanded floor and cooled, it a.s.sumed a shape resembling a family of little pigs.

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.

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.

[Ill.u.s.tration: FIG. 1.--FIRST EXPERIMENTS WITH STEAM.]

Whatever may have happened in ancient kitchens, we are certain that there were no steam-engines until many centuries after Adam. The beginnings of this invention are not shrouded in so much mystery as are those of the match and the lamp and the forge. In giving an account of the steam-engine we can mention names and give dates from the very beginning of the story. We know what the first steam-engine was like and we know who made it and when and where it was made. It was made 120 B. C. by Hero, a philosopher of Alexandria in Egypt. It was like the one shown in Figure 2. The boy applies the fire to the steam-tight vessel _p_ and when steam is formed it pa.s.ses up through the tube _o_ and enters the globe which turns easily on the pivots. The steam, when it has filled the globe, rushes out of the short tubes _w_ and _z_ projecting from opposite sides of the globe and bent at the end in opposite directions. As it rushes out of the tubes the steam strikes against the air and the reaction causes the globe to revolve, just as in yards we sometimes see jets of water causing bent tubes to revolve. This was Hero's engine, the first steam-engine ever made.

[Ill.u.s.tration: FIG. 2.--HERO'S ENGINE, 120 B. C.]

Hero's engine was used only as a toy and it seems to represent all the ancients knew about the power of steam and all they did with it. It is not strange that they did not know more for there is no general rule by which discoveries are made. Sometimes even enlightened peoples have for centuries remained blind to the simplest principles of nature. The Greeks and Romans with all their culture and wisdom were ignorant of some of the plainest facts of science. It is a little strange, however, that after Hero's discovery was made known, men did not profit by it. It would seem that eager and persistent attempts would have been made at once to have steam do useful work, as well as furnish amus.e.m.e.nt. But such was not the case. Hero's countrymen paid but little attention to his invention and the steam-engine pa.s.sed almost completely out of men's minds and did not again attract attention for nearly seventeen hundred years.