But many centuries elapsed before its power was applied to any useful purpose; indeed, as suggested, there is reason for supposing that this science was misapplied by the priests, and used as a means of deceiving the people by inducing them to believe it to be a miraculous power granted only to the professors of the craft of idolatry. “A fire,” says Hero (experiment No. 70), “having been kindled on a transparent altar, figures will appear to dance” on a drum driven round by steam, “emitting sounds similar to those of a stringed instrument,”[9] which, according to Pausanias, “resemble the snapping of the strings of a harp;” thus, while delighting the young people of those days, as the ornaments in churches now do, these experiments became instruments of make-belief in the hands of the priests, who propounded as strange theories about their supernatural powers as the so-called philosophers of our own days still do, when they attempt to deal with the unrevealed mysteries of creation and of a still more mysterious hereafter.[10] [Sidenote: Revival of learning.] Although the Romans did nothing towards applying the knowledge of the power of steam to useful purposes, and little enough generally for the mechanical arts, the true value of the works of Hero and of the older mechanicians came to be appreciated in the dawn which succeeded the darkness of the Middle Ages. Then the youths of a generation, which had cast aside many of the superstitions of the ancients, and had found in the doctrines of Christianity a wider and nobler field for their genius and aspirations, began to study how the power Hero had described could be best applied for the benefit and happiness of mankind. Then, indeed, was the advent of an era wherein the foundation was laid of a fabric which, though slow in its erection, and not yet completed, is destined to eclipse all the other works of man. There can be, therefore, no subject affecting the transitory interests of the human race more worthy of the pen of the historian than the development of the power and usefulness of steam traced from that remote period to our own time, when we see in every quarter of the civilised world this power compassing land and ocean, affording profitable employment to myriads of the human race, and giving to the people of every nation and tongue rapid and easy intercourse. [Sidenote: Robertus Valturius, 1472.] “Although an old work on China,” remarks Mr. MacGregor,[11] “contains a sketch of a vessel moved by four paddle-wheels, and used perhaps in the seventh century, the earliest distinct notice of this means of propulsion appears to be by Robertus Valturius in A.D. 1472, who gives several woodcuts representing paddle-wheels,”[12] one of which is as follows. [Illustration]