Our nineteenth century is the age of tools. They grow out of our structure. “Man is the metre of all things,” said Aristotle; “the hand is the instrument of instruments, and the mind is the form of forms.” The human body is the magazine of inventions, the patent-office, where are the models from which every hint was taken. All the tools and engines on earth are only extensions of its limbs and senses. One definition of man is “an intelligence served by organs.” Machines can only second, not supply, his unaided senses. The body is a metre. The eye appreciates finer differences than art can expose. The apprentice clings to his foot-rule, a practised mechanic will measure by his thumb and his arm with equal precision; and a good surveyor will pace sixteen rods more accurately than another man can measure them by tape. The sympathy of eye and hand by which an Indian or a practised slinger hits his mark with a stone, or a wood-chopper or a carpenter swings his axe to a hair-line on his log, are examples; and there is no sense or organ which is not capable of exquisite performance. Men love to wonder, and that is the seed of our science; and such is the mechanical determination of our age, and so recent are our best contrivances, that use has not dulled our joy and pride in them; and we pity our fathers for dying before steam and galvanism, sulphuric ether and ocean telegraphs, photograph and spectroscope arrived, as cheated out of half their human estate. These arts open great gates of a future, promising to make the world plastic and to lift human life out of its beggary to a godlike ease and power. Our century, to be sure, had inherited a tolerable apparatus. We had the compass, the printing-press, watches, the spiral spring, the barometer, the telescope. Yet so many inventions have been added, that life seems almost made over new; and as Leibnitz said of Newton, “that if he reckoned all that had been done by mathematicians from the beginning of the world down to Newton, and what had been done by him, his would be the better half,” so one might say that the inventions of the last fifty years counterpoise those of the fifty centuries before them. For the vast production and manifold application of iron is new; and our common and indispensable utensils of house and farm are new; the sewing-machine, the power-loom, the McCormick reaper, the mowing-machines, gas-light, lucifer-matches, and the immense productions of the laboratory, are new in this century, and one franc’s worth of coal does the work of a laborer for twenty days.