Like many other geniuses who have lived before their time, Hero had his plagiarists, his devices having been adopted and described by later writers without one word of acknowledgment as to their authorship. From the middle to the end of the seventeenth century several books appeared which to a great extent were simply bad and erroneous copies of Hero’s inventions, and not even intelligently copied. Here for instance (Fig. 7) is a _facsimile_ of an illustration in a curious old book, “The Mysteries of Nature and Art,” by John Bate, published in 1635; this is poor Bate’s attempt to steal Hero’s device for the temple doors, showing an altogether impossible scheme. In the first place the doors could not open at all, for the ropes are so coiled as to neutralize each other’s action, and, secondly, the counterweight to the right has its cord simply looped round the spindle and therefore is absolutely useless; the accompanying description is even more absurd, for it explains the action of the apparatus as follows: “The fier on the Altar will cause the water to distill out of the Ball into the Bucket, which when (by reason of the water) it is become heavier than the waight, it will draw it up and so open the sayd gates or little doores.” [Illustration: Fig. 7.] Again, in one of Hero’s illustrations a revolving disc carrying little figures was made to rotate upon the reaction principle of his own Æolipile, or steam engine. By a little bit of bad perspective the ends of the cross tubes were shown as turning alternately up and down, and Bate not only repeats this error, but goes out of his way to point out that “in the middest” there must be “a hollow pipe spreading itself into foure severall branches at the bottom: _the ends of two of the branches must turn up and the ends of two must turn down_,” thus making any rotative action impossible. But Bate was not the only pirate of Hero’s work; a few years after Bate had written, that is, in 1659, there appeared another curious book by Isaak de Caus, upon Water Works,[5] and in that book we find our old friend the owl keeping the small birds in order, the only difference being that this is a more indulgent owl, or perhaps he is a teacher of singing, for in this case the birds sing while he is looking at them and cease the moment he turns his back. [Illustration: Fig. 8.] Another pretty conceit of Hero’s is shown in Fig. 8, in which there is a bird which not only makes a noise but at certain times will drink any liquid which is presented to it. The flow of water being intermittent, the cistern forming the pedestal is alternately filled and emptied. While it is being filled the air escapes through a whistle and causes the bird to sing, and when it is being emptied, by means of a siphon, a partial vacuum is produced and liquid presented to it is drawn up through the beak. [Illustration: Fig. 9.]