hood of knowledge, and we have noted the foundation of the British Royal Society, the Florentine Society, and their like as a consequence of this socializing of thought. These things were the roots of the mechanical revolution, and so long as the root of pure scientific inquiry lives, that revolution will progress. The mechanical revolution itself began, we may say, with the exhaustion of the wood supply for the ironworks of England. This led to the use of coal, the coal mine led to the simple pumping engine, the development of the pumping engine by Watt into a machine-driving engine led on to the locomotive and the steamship. This was the first phase of a great expansion in the use of steam. A second phase in the mechanical revolution began with the application of electrical science to practical problems and the development of electric lighting, power-transmission, and traction.
A third phase is to be distinguished when in the eighties a new type of engine came into use, an engine in which the expansive force of an explosive mixture replaced the expansive force of steam. The light, highly efficient engines that were thus made possible were applied to the automobile, and developed at last to reach such a pitch of lightness and efficiency as to render flight—long known to be possible—a practical achievement. A successful flying-machine—but not a machine large enough to take up a human body—was made by Professor Langley of the Smithsonian Institution of Washington as early as 1897. By 1909 the aeroplane was available for human locomotion. There had seemed to be a pause in the increase of human speed with the perfection of railways and automobile road traction, but with the flying-machine came fresh reductions in the effective distance between one point of the earth's surface and another. In the eighteenth century the distance from London to Edinburgh was an eight days' journey; in 1918 the British Civil Air Transport Commission reported that the journey from London to Melbourne, half-way round the earth, would probably, in a few years' time, be accomplished in that same period of eight days.
Too much stress must not be laid upon these striking reductions in the time distances of one place from another. They are merely one aspect of a much profounder and more momentous enlargement of human possibility. The science of agriculture and agri-
