with glib readiness. But those who have looked at the history of the steam-engine know, of course, that there were steam-engines in abundance long before Watt's, and that Watt himself worked deliberately on the basis of Newcomen's model, Newcomen, in turn, had improved on Papin's invention, and Papin perhaps on De Caux's, and finally on Hero's. Now, nobody denies that Watt was a very great engineer; if he had never invented the double-acting engine at all, indeed, he would have been remembered among the mechanical geniuses of the world by his numerous other improvements and discoveries; but he was not so absolutely supreme and unique as the popular fancy has made him out to be. Indeed, taking into consideration the date of its construction, Newcomen's engine was a much more remarkable triumph of human ingenuity that James Watt's. But Watt introduced the final details which rendered steam a power in the world, and with him accordingly rest the popular suffrages as "the inventor of the steam-engine." Similarly, who invented the locomotive? George Stephenson, says everybody, as before. But those who have looked at the history of the locomotive know, of course, that both locomotives and railways existed in plenty before Stephenson's, and that the Rocket was merely the most successful competitor among many contemporary competitors for public favor. Nobody denies George Stephenson's marvelous native engineering abilities; on the whole, taking into consideration his humble beginnings, he seems to me more of a heaven-born genius in his own way than almost anybody else with whose history I am acquainted. But the work he did upon the locomotive was adaptive and developmental, not original and novel. The great invention did not spring in full panoply—like Athene from the head of Zeus—out of any one engineer's profound brain; it grew slowly, piece by piece, like everything else, from a hundred men's co-operating intelligences.
Like everything else, I say deliberately, for it is the same with every great invention. Look at the telegraph, so hotly debated between Morse and Wheatstone; look at the telephone, equally divided between Edison and Bell; look at photography, whose several stages owed so much successively to Wedgwood and Davy, to Niepce and Daguerre, to Talbot and to Archer. "Great discoveries," says Prof. Fiske, with evident wisdom, "must always be concerned with some problem of the time which many of the world's foremost minds are just then cudgeling their active brains about." It was so with the discovery of the differential calculus and of the planet Neptune; with the interpretation of the Egyptian hieroglyphics and of the cuneiform inscriptions; with the undulatory theory of light and the mechanical equivalent of heat; with the nebular hypothesis and with spectrum analysis. In some cases
