We have already seen that the ancients had attained some degree of perfection in the construction of automata, or pieces of mechanism which imitated the movements of man and the lower animals. The tripods, which Homer[31] mentions as having been constructed by Vulcan for the banqueting-hall of the gods, advanced of their own accord to the table, and again returned to their place. Self-moving tripods are mentioned by Aristotle; and Philostratus informs us, in his life of Apollonius, that this philosopher saw and admired similar pieces of mechanism among the sages of India. [31] Iliad, lib. xviii., 373-378. Dædalus enjoys also the reputation of having constructed machines that imitated the motions of the human body. Some of his statues are said to have moved about spontaneously; and Plato, Aristotle, and others have related that it was necessary to tie them, in order to prevent them from running away. Aristotle speaks of a wooden Venus, which moved about in consequence of quicksilver being poured into its interior; but Callistratus, the tutor of Demosthenes, states, with some probability, that the statues of Dædalus received their motion from the mechanical powers. Beckmann is of opinion that the statues of Dædalus differed only from those of the early Greeks and Egyptians in having their eyes open and their feet and hands free, and that the reclining posture of some, and the attitude of others, “as if ready to walk,” gave rise to the exaggeration that they possessed the power of locomotion. This opinion, however, cannot be maintained with any show of reason; for if we apply such a principle in one case, we must apply it in all, and the mind would be left in a state of utter scepticism respecting the inventions of ancient times. We are informed by Aulus Gellius, on the authority of Favorinus, that Archytas of Tarentum, who flourished about four hundred years before Christ, constructed a wooden pigeon that was capable of flying. Favorinus relates that, when it had once alighted, it could not again resume its flight; and Aulus Gellius adds, that it was suspended by balancing, and animated by a concealed aura, or spirit. Among the earliest pieces of modern mechanism was the curious water-clock presented to Charlemagne by the Kaliph Haroun al Raschid. In the dial-plate there were twelve small windows corresponding with the divisions of the hours. The hours were indicated by the opening of the windows, which let out little metallic balls, which struck the hour by falling upon a brazen bell. The doors continued open till twelve o’clock, when twelve little knights, mounted on horseback, came out at the same instant, and after parading round the dial, shut all the windows and returned to their apartments.[32] [32] Annales Loisiliani, anno 807.