ONE:Primarily, power is a product of heat; and wherever force and motion exist, they can be traced to heat as the generating element: whether the medium through which the power is [30] obtained be by the expansion of water or gases, the gravity of water, or the force of wind, heat will always be found as the prime source. So also will the phenomenon of expansion be found a constant principle of developing power, as will again be pointed out. As steam-engines constitute a large share of the machinery commonly met with, and as a class of machinery naturally engrosses attention in proportion, the study of mechanics generally begins with steam-engines, or steam machinery, as it may be called.
TWO:In the last chapter we considered the philosophy of Plato chiefly under its critical and negative aspects. We saw how it was exclusively from that side that he at first apprehended and enlarged the dialectic of Socrates, how deeply his scepticism was coloured by the religious reaction of the age, and how he attempted, out of his masters mouth, to overturn the positive teaching of the master himself. We saw how, in the Protagoras, he sketched a theory of ethics, which was no sooner completed than it became the starting-point of a still more extended and arduous enquiry. We followed the widening horizon of his speculations until they embraced the whole contemporary life of Hellas, and involved it in a common condemnation as either hopelessly corrupt, or containing within itself the seeds of corruption. We then saw how, by a farther generalisation, he was led to look for the sources of error in the laws of mans sensuous nature and of the phenomenal world with which it holds communion; how, moreover, under the guidance of suggestions coming both from within and from without, he reverted to the earlier schools of Greek thought, and brought their results into parallelism with the main lines of Socratic dialectic. And finally, we watched him planting a firm foothold on the basis of mathematical demonstration; seeking in the very constitution of the soul itself for a derivation of the truths which sensuous experience could not impart, and winning back from215 a more profoundly reasoned religion the hope, the self-confidence, the assurance of perfect knowledge, which had been formerly surrendered in deference to the demands of a merely external and traditional faith. That God alone is wise, and by consequence alone good, might still remain a fixed principle with Plato; but it ceased to operate as a restraint on human aspiration when he had come to recognise an essential unity among all forms of conscious life, which, though it might be clouded and forgotten, could never be entirely effaced. And when Plato tells us, at the close of his career, that God, far more than any individual man, is the measure of all things,133 who can doubt that he had already learned to identify the human and divine essences in the common notion of a universal soul?
