=338. The open-hearth (Siemens-Martin) process.=—Still another contribution to modern methods of steel manufacture, known as the “open-hearth,” or, from the names of its introducers, the Siemens-Martin process, has been of great importance since about 1870. The steel is made from ore or from a combination of different kinds of iron, and, by peculiar devices for economizing the heat of the furnace, the process may be continued so long and regulated so carefully that a product of high quality may be turned out at a moderate cost. The result of all these processes has been to change steel from a luxury to a necessity of modern life. Modern mild steel is 40 per cent stronger than iron, and is tough enough to be tied in a knot or punched in the shape of a bowl when cold. The increase in efficiency due to its substitution for iron in machinery, railroads, ships, and structural work is simply incalculable. =339. Development of the modern chemical industry.=—In detailing at such length as I have done the exploits of machinists in the past century, I may tempt the reader to undervalue the contributions of scientists. To guard against that error let us consider briefly the development of the chemical industry, which, like the iron industry, renders a service to modern civilization beyond any measure of dollars and cents. The Frenchman, Lavoisier, had established chemistry on a scientific basis before 1800, but industrial chemistry used still the primitive methods which had been employed for ages. Let us take, for instance, the single substance, carbonate of soda, of prime importance in industrial chemistry, for on it depend the various industries of glass, pottery, soap, photography, paper, etc. This substance was still obtained in the eighteenth century, by burning seaweed and seashore plants and treating their ashes; Spain had a considerable export of barilla, and owed to this product whatever success she attained in the soap manufacture. Leblanc emancipated the soda industry from kelp and barilla, by introducing the process based on sulphuric acid and salt; step by step improvements have been made since then. Sulphuric acid, discarded in the soda industry, has grown in importance notwithstanding; it is the controlling element in the manufacture of other acids, commercial fertilizers, alum, ether, glucose, etc., and in oil refining; and it is produced at a price and of a quality formerly unknown. The discovery of the anilin colors, in 1859, has revolutionized the art of dyeing. The chemist will make you, from coal tar, almost any color or shade desired. He will make you perfumes or flavors; and, if he has failed to construct quinine artificially, he has at least learned, in his attempts, to make substances such as antipyrin and phenacetin, of equal value for other purposes.