THREE:Power derived from water by means of wheels is due to the gravity of the water in descending from a higher to a lower level; but the question arises, What has heat to do with this? If heat is the source of power, and power a product of heat, there must be a connection somewhere between heat and the descent of the water. Water, in descending from one level to another, can give out no more power than was consumed in raising it to the higher level, and this power employed to raise the water is found to be heat. Water is evaporated by heat of the sun, expanded until it is lighter than the atmosphere, rises through the air, and by condensation falls in the form of rain over the earth's surface; then drains into the ocean through streams and rivers, to again resume its round by another course of evaporation, giving out in its descent power that we turn to useful account by means of water-wheels. This principle of evaporation is continually going on; the fall of rain is likewise quite constant, so that streams are maintained within a sufficient regularity to be available for operating machinery.The two elements of error and achievement are so intimately blended and mutually conditioned in the philosophy which we have been reviewing, that to decide on their respective importance is impossible without first deciding on a still larger questionthe value of systematic thought as such, and apart from its actual content. For Aristotle was perhaps the greatest master of systematisation that ever lived. The401 framework and language of science are still, to a great extent, what he made them; and it remains to be seen whether they will ever be completely remodelled. Yet even this gift has not been an unmixed benefit, for it was long used in the service of false doctrines, and it still induces critics to read into the Aristotelian forms truths which they do not really contain. Let us conclude by observing that of all the ancients, or even of all thinkers before the eighteenth century, there is none to whom the methods and results of modern science could so easily be explained. While finding that they reversed his own most cherished convictions on every point, he would still be prepared by his logical studies to appreciate the evidence on which they rest, and by his ardent love of truth to accept them without reserve. Most of all would he welcome our astronomy and our biology with wonder and delight, while viewing the development of modern machinery with much more qualified admiration, and the progress of democracy perhaps with suspicious fear. He who thought that the mind and body of an artisan were alike debased by the exercise of some simple handicraft under the pure bright sky of Greece, what would he have said to the effect wrought on human beings by the noisome, grinding, sunless, soulless drudgery of our factories and mines! How profoundly unfitted would he have deemed its victims to influence those political issues with which the interests of science are every day becoming more vitally connected! Yet slowly, perhaps, and unwillingly, he might be brought to perceive that our industry has been the indispensable basis of our knowledge, as supplying both the material means and the moral ends of its cultivation. He might also learn that there is an even closer relationship between the two: that while the supporters of privilege are leagued for the maintenance of superstition, the workers, and those who advocate their claims to political equality, are leagued for its restraint and overthrow. And if402 he still shrank back from the heat and smoke and turmoil amid which the genius of our age stands, like another Heracleitus, in feverish excitement, by the steam-furnace whence its powers of revolutionary transmutation are derived, we too might reapply the words of the old Ephesian prophet, bidding him enter boldly, for here also there are gods.
