A fresh phase in the history of invention opened 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 Institute 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, halfway round the earth, would probably in a few years’ time be accomplished in that same period of eight days. AN EARLY WEAVING MACHINE AN EARLY WEAVING MACHINE _From an engraving by W. Hincks in the British Museum_ 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 agricultural chemistry, for instance, made quite parallel advances during the nineteenth century. Men learnt so to fertilize the soil as to produce quadruple and quintuple the crops got from the same area in the seventeenth century. There was a still more extraordinary advance in medical science; the average duration of life rose, the daily efficiency increased, the waste of life through ill-health diminished. Now here altogether we have such a change in human life as to constitute a fresh phase of history. In a little more than a century this mechanical revolution has been brought about. In that time man made a stride in the material conditions of his life vaster than he had done during the whole long interval between the palæolithic stage and the age of cultivation, or between the days of Pepi in Egypt and those of George III. A new gigantic material framework for human affairs has come into existence. Clearly it demands great readjustments of our social, economical and political methods. But these readjustments have necessarily waited upon the development of the mechanical revolution, and they are still only in their opening stage to-day. LVIII THE INDUSTRIAL REVOLUTION