The greatest of the world’s inventions appear to have had a very casual birth. So much an affair of chance has been their first manifestation, that science has not been called in aid; no law can be discerned which might govern the time and sequence of their coming; they seem to have been stumbled on, unpedigreed offspring of accident and time. A monk of Metz discovers gunpowder. “Surely,” says Fuller, “ingenuity may seem transposed, and to have crossed her hands, when about the same time a soldier found out printing.” “It should seem,” writes Lord Bacon, “that hitherto men are rather beholden to a wild goat for surgery, or to a nightingale for music, or to the ibis for some part of physic, or to the pot-lid that flew open for artillery, or generally to chance, or anything else, than to logic for the invention of the Arts and Sciences.” So it seemed. And in due time the legend of the pot-lid was woven round the unfortunate Marquis of Worcester, who, tradition had it, made the discovery of the steam engine by observation of the stew-pot in which, when confined a prisoner in the Tower, he was engaged in cooking his dinner. At a later date and in another form the story was connected with James Watt. In reality, the story of the discovery of the steam engine is far more inspiring. The history of the application of steam to human use is almost the history of science itself; the stages of its development are clearly marked for us; and the large succession of these stages, and the calibre of the minds which contributed to the achievement of the perfected steam engine, are some measure of the essential complexity of what is to-day regarded as a comparatively simple machine. For the steam engine was not the gift of any particular genius or generation; it did not leap from any one man’s brain. Some of the greatest names in the history of human knowledge can claim a share in its discovery. From philosopher to scientist, from scientist to engineer the grand idea was carried on, gradually taking more and more concrete form, until finally, in an age when by the diffusion of knowledge the labours of all three were for the first time co-ordinated, it was brought to maturity. A new force of nature was harnessed which wrought a revolution in the civilized world.