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era vast forests grew and died; and by a series of changes, chemical as well as mechanical, were turned into coal in its various forms. We may classify these in accordance with their carbon content, remembering that the series really begins with living wood containing about 50 per cent carbon and ends with the diamond which is practically pure carbon: Lignite, 67 per cent; cannel, 64 per cent; bituminous, 88 per cent, and anthracite, 93 per cent; to which we should add graphite, 95 per cent. That these have different properties and are valuable for various purposes is well known.

Coal was more or less known to the Romans and was slightly used by them as well as by the Chinese. It was mined in small quantities in England before the coming of the Saxons. Little attention was paid to it until the gradual decrease in the forested area by the ninth century. There is an English charter permitting the freemen of Newcastle to mine coal dating from 1239. Thereafter it came gradually into use but at the end of the sixteenth century two ships were able to keep the London market supplied. There was much opposition to its use on the ground of the smoke and dirt and at times it was prohibited particularly during the session of Parliament. In America bituminous coal was mined in Virginia about 1750 and at Pittsburgh in the following decade. Anthracite was discovered at Wilkesbarre in 1762 but was little used, as the people did not know how to burn it. It was used at Carlisle during the Revolution for the manufacture of firearms but as late as 1820 the Philadelphia market was satisfied with 365 tons from Lehigh.

The first coal product to be commercially used was illuminating gas which dates, as above indicated, from the end of the eighteenth century. In the process of manu

facture many other substances are given off which were wasted at first but which have now become very valuable. The first of these is crude tar; then by further distillation, naphtha, ammonia, benzene, vaseline, the heavy lubricating oils, paraffin, aniline and others. By different processes we get coke, soot and lampblack.

Natural petroleum was known at least five centuries before Christ and was used, it is believed, in keeping alight the sacred fires in the Persian temples. Marco Polo writUntil the discov

ing about A.D. 1260 mentions its use. ery of the oil wells of Pennsylvania it had little importance. So too asphalt seems to have been known and used in Egypt and Babylon but only recently, through the discoveries of the lakes in Trinidad and elsewhere, has it come into general use.

Now either directly from coal or from related substances come a considerable percentage of some of our most highly valued commodities. Aniline dyes which have made possible the colors of our clothing materials were developed after 1836 and became important by the middle of the century. Another product is carbolic acid.

Meantime coal, kerosene and gasolene furnish us with light for our houses and streets, with fuel for our engines and motors, with heat for our buildings; and have made possible a wonderful change in our daily life and industrial processes. Through their use we are able to make iron the basic material of our economic life.

The use of the sharp edge of shells or slices of stone as scrapers or knives marked a great advance. A new era dawned when man first discovered the softer metals, copper, lead and tin. The next stage is marked by the making of the alloys - brass and bronze. Relatively late, man began to forge tools of iron and really entered upon the metal stage. We should not forget that until the nineteenth century man depended upon the scanty supply of pure metal he could find. The ores which today form the basis of the iron industry were as meaningless to him as was the bog iron, so prized by the first whites in America, to the Indians. It is not an exaggeration today to say that our industry rests on iron foundations. But pure iron is rather soft and rusts badly, hence it is hard to preserve tools or keep sharp cutting edges. The next great step was the discovery of the art of making steel by mixing carbon with the iron. Even this could not be used in large quantities, because of its cost, until Bessemer invented his process in 1864. The cost of steel rails for the railways soon fell from $175 per ton to the neighborhood of $30. Today America produces 40 per cent of the steel of the world. But carbon steel has certain defects. It shows a crystalline structure and cracks rather easily. Now nickel steels are used for many purposes as they are harder and stronger and do not rust. Combined with chromium and molybdenum, steels are now made which resist such strong acids as hydrochloric or nitric, in some cases even aqua regia. Steels which remain hard at high temperatures are produced by alloys with chromium, tungsten and vanadium. Immense improvement in cutting tools has come through these new alloys. Safes are now made of these alloys which have not yielded to one and one-half hours' exposure to the intense heat of oxyhydrogen and oxyacetylene flames. These discoveries conditioned as they are upon the newer chemistry indicate that the possibilities of metallurgy are far from exhausted. It is a long journey from the fire-hardened stick, which was plow and hoe to the primitive agriculturist, to the iron plows, mowers and binders of today; but farming facture many other substances are given off which were wasted at first but which have now become very valuable. The first of these is crude tar; then by further distillation, naphtha, ammonia, benzene, vaseline, the heavy lubricating oils, paraffin, aniline and others. By different processes we get coke, soot and lampblack.

Natural petroleum was known at least five centuries before Christ and was used, it is believed, in keeping alight the sacred fires in the Persian temples. Marco Polo writing about A.D. 1260 mentions its use. Until the discovery of the oil wells of Pennsylvania it had little importance. So too asphalt seems to have been known and used in Egypt and Babylon but only recently, through the discoveries of the lakes in Trinidad and elsewhere, has it come into general use.

Now either directly from coal or from related substances come a considerable percentage of some of our most highly valued commodities. Aniline dyes which have made possible the colors of our clothing materials were developed after 1836 and became important by the middle of the century. Another product is carbolic acid.

Meantime coal, kerosene and gasolene furnish us with light for our houses and streets, with fuel for our engines and motors, with heat for our buildings; and have made possible a wonderful change in our daily life and industrial processes. Through their use we are able to make iron the basic material of our economic life.

The use of the sharp edge of shells or slices of stone as scrapers or knives marked a great advance. A new era dawned when man first discovered the softer metals, copper, lead and tin. The next stage is marked by the making of the alloys - brass and bronze. Relatively late, man began to forge tools of iron and really entered upon the metal stage. We should not forget that until the nineteenth century man depended upon the scanty supply of pure metal he could find. The ores which today form the basis of the iron industry were as meaningless to him as was the bog iron, so prized by the first whites in America, to the Indians. It is not an exaggeration today to say that our industry rests on iron foundations. But pure iron is rather soft and rusts badly, hence it is hard to preserve tools or keep sharp cutting edges. The next great step was the discovery of the art of making steel by mixing carbon with the iron. Even this could not be used in large quantities, because of its cost, until Bessemer invented his process in 1864. The cost of steel rails for the railways soon fell from $175 per ton to the neighborhood of $30. Today America produces 40 per cent of the steel of the world. But carbon steel has certain defects. It shows a crystalline structure and cracks rather easily. Now nickel steels are used for many purposes as they are harder and stronger and do not rust. Combined with chromium and molybdenum, steels are now made which resist such strong acids as hydrochloric or nitric, in some cases even aqua regia. Steels which remain hard at high temperatures are produced by alloys with chromium, tungsten and vanadium. Immense improvement in cutting tools has come through these new alloys. Safes are now made of these alloys which have not yielded to one and one-half hours' exposure to the intense heat of oxyhydrogen and oxyacetylene flames. These discoveries conditioned as they are upon the newer chemistry indicate that the possibilities of metallurgy are far from exhausted. It is a long journey from the fire-hardened stick, which was plow and hoe to the primitive agriculturist, to the iron plows, mowers and binders of today; but farming

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