The practical imagination is no more foreign to inspiration than the esthetic imagination. The history of useful inventions is full of men who suffered privations, persecution, ruin; who fought to the bitter end against relatives and friends--drawn by the need of creating, fascinated not by the hope of future gain but by the idea of an imposed mission, of a destiny they had to fulfill. What more have poets and artists done? The fixed and irresistible idea has led more than one to a foreseen death, as in the discovery of explosives, the first attempts at lightning conductors, aeronautics, and many others. Thus, from a true intuition, primitive civilizations have put on a level great poets and great inventors, erected into divinities or demi-gods historical or legendary personages in whom the genius of discovery is personified:--among the Hindoos, Vicavakarma; among the Greeks, Hephaestos, Prometheus, Triptolemus, Daedalus and Icarus. The Chinese, despite their dry imagination, have done the same; and we find the same condition in Egypt, Assyria, and everywhere. Moreover, the practical and mechanical arts have passed through a first period of no-change, during which the artisan, subjected to fixed rules and an undisputed tradition, considers himself an instrument of divine revelation.[123] Little by little he has emerged from that theological age, to enter the humanistic age, when, being fully conscious of being the author of his work, he labors freely, changes and modifies according to his own inspiration. Mechanical and industrial imagination, like esthetic imagination, has its preparatory period, its zenith and decline: the periods of the precursors, of the great inventors, and of mere perfectors. At first a venture is made, effort is wasted with small result,--the man has come too early or lacks clear vision; then a great imaginative mind arises, blossoms; after him the work passes into the hands of _dii minores_, pupils or imitators, who add, abridge, modify: such is the order. The many-times written history of the application of steam, from the time of the eolipile of Hero of Alexandria to the heroic period of Newcomen and Watt, and the improvements made since their time, is one proof of the statement. Another example:--the machine for measuring duration is at first a simple clepsydra; then there are added marks indicating the subdivisions of time, then a water gauge causes a hand to move around a dial, then two hands for the hours and minutes; then comes a great moment--by the use of weights the clepsydra becomes a clock, at first massive and cumbersome, later lightened, becoming capable, with Tycho-Brahe, of marking seconds; and then another moment--Huyghens invents the spiral spring to replace the weights, and the clock, simplified and lightened, becomes the watch. _2. Special Characters_ The special characteristics of the mechanical imagination being the marks belonging to this type, we shall study them at greater length.