George Westinghouse's father was superintendent of the Schenectady Agricultural Works, and it was there that the boy found his vocation. Before he was fifteen, he had modelled and built a steam engine, and followed that with a steel railroad frog, which was so great an improvement over the frogs then in use that it was soon widely adopted, and brought the young inventor both money and reputation. He moved to Pittsburgh, as the centre of the iron and steel business, and began the manufacture of his frogs there. One day he came across a newspaper account of the successful use of compressed air in the digging of the Mont Cenis tunnel, in Switzerland, and the thought occurred to him that perhaps a railroad train could be controlled by the same agency. He worked over the problem for a time, but when he mentioned his idea to his friends, they were inclined to think it absurd to suppose that a rubber-tube strung along under the cars could work the brakes effectively. However, Westinghouse was not discouraged, but continued to experiment, and the air-brake as we have it to-day was the result. * * * * * Which brings us to the most remarkable genius in the field of invention the world has ever known--the man who has made invention, as it were, a business, whose life has been devoted to rendering practical and useful the dreams of other men, who has reduced invention to a science--Thomas Alva Edison. There are some who are inclined to belittle Edison's achievements because some of the greatest of them have been founded upon the ideas of others. He is best known, for instance, as the inventor of the modern incandescent light; but the discovery that light may be obtained from wire heated to incandescence in a glass bulb from which the air has been exhausted, was made when Edison was only two years old. Experiments with this light were made by a dozen scientists, but it remained a mere laboratory curiosity until Edison took hold of it, and with a patience, ingenuity and fertility of resource, in which he stands alone, made it a practicable, efficient and convenient source of light. That the incandescent light, as it is known to-day, is his through and through cannot be questioned. It is as a scientific inventor that Edison likes to be known. He abhors the word discoverer, as applied to himself. "Discovery is not invention," he once said. "A discovery is more or less in the nature of an accident, while an invention is purely deductive. In my own case, but few, and those the least important, of my inventions, owed anything to accident. Most of them have been hammered out after long and patient labor, and are the result of countless experiments all directed toward attaining some well-defined object."