Page:Popular Science Monthly Volume 78.djvu/306

296 Thus chemists and chemical engineers have answered the demand of the hour. With the boundless atmospheric nitrogen and with water power, the development of which has scarcely begun, man need never fear an insufficient nitrogenous food supply.

We are inclined to lament because of the extent to which some of our limited natural resources, such as iron, are being drawn upon. But if we compare the condition of the people of the United States now with that at the time when these resources were comparatively untouched we must admit that their use has added immensely to human comfort and progress, and that this increased comfort could have been gained in no other manner. In addition we must consider that, although much material is being used, the processes of putting it upon the market are gaining immensely in economy of operation through the studies of scientific men, and that much that we were in the habit of discarding is now used repeatedly. So that the total amounts taken from their terrestrial storehouses does not fairly represent the loss to humanity.

For instance, since the time of Tubal Cain until about the end of the fifteenth century iron ores were reduced in a crude forge where the yield ran from 100 to 300 pounds per charge—far less than a ton per day. Compare the continuous process of the modern blast-furnace producing 75,000 or more tons annually and think how many conveniences we should be deprived of if we were still limited to the primitive methods. Compare also the price per ton of pig iron from the old and the present processes and no doubt will remain that wastefulness is relatively immensely less in the iron industry now than then. Nor is iron once used discarded, but it is worked over into new forms and employed for other purposes.

Previous to 1856 the only means of producing steel was to laboriously remove the carbon from the pig iron in the puddling furnace, roll the iron into bars, slowly add the requisite carbon again by heating the two together for days, and melting or hammering to get a homogeneous product. But in 1856 Henry Bessemer announced his process for making steel from pig iron in one operation, a process so simple that we please ourselves by thinking that we might have invented it if it had not previously been done. Bessemer found it necessary only to burn out from the molten crude iron the impurities, carbon and silicon, by a blast of air forced into the bottom of his crucible, just as we stimulate the burning of fuel in our fireplaces by the use of a bellows. No fuel was added as the heat from the burning impurities was adequate to keep the mass melted until the change was complete. To the purified iron thus obtained he added the requisite amount of carbon and, in half an hour, had a dozen tons of steel. The price of steel rails before and after the Bessemer process came into vogue is a testimony not only to the knowledge of the metallurgist, but to the saving in time, labor