This characterization by Vitruvius of the writings of Ctesibius also applies with astonishing fitness to some of the works current under the name of Hero of Alexandria,[887] who is indeed in a Vienna manuscript of the Belopoiika spoken of as the disciple or follower of Ctesibius.[888] Hero, however, is not mentioned either by Vitruvius or Pliny, and it is now generally agreed as a result of recent studies that he belongs to the second century of our era.[889] His writings are objective and impersonal and tell us much less about himself than Vitruvius’s introductions to the ten books of De architectura. The similarity in content of his writings to those of the much earlier Ctesibius as well as the character of his terminology suggest that he stands at the end of a long development. He speaks of his own discoveries, but perhaps in the main simply continues and works over the previous principles and mechanisms of men like Ctesibius. As things stand, however, his works constitute our most important, and often our only, source for the history of exact science and of technology in antiquity.[890]
Medieval working over of the texts.
Not only does Hero seem to have been in large measure a compiler and continuer of previous science, his works also have evidently been worked over and added to in subsequent periods and bear marks of the Byzantine, Arabian, and medieval Latin periods as well as of the Hellenistic and Roman. Indeed Heiberg regards the Geometry and De stereometricis and De mensuris as later Byzantine collections which have perhaps made some use of the works of Hero, while the De geodaesia is an epitome of, or extract from, a pseudo-Heronic collection. The Catoptrica is known only from the Latin translation of 1269, probably by William of Moerbeke, and long known as Ptolemy on Mirrors. It appears, however, to be directly translated from the Greek and not from the Arabic. The Mechanics, on the other hand, is known only from the Arabic translation by Costa ben Luca. Of the Pneumatics we have Greek, Arabic, and Latin versions. It was apparently known to the author of the thirteenth century Summa philosophiae ascribed to Robert Grosseteste, since he speaks of the investigations of vacuums made by “Hero, that eminent philosopher, with the aid of water-clocks, siphons, and other instruments.”[891] Scholars are of the opinion that the Arabic adaptation, which is of popular character and limited to the entertaining side, comes closer to the original Greek version of Hero’s time than does the Latin version which devotes more attention to experimental physics. The Automatic Theater, for which there is the same chief manuscript as for the Pneumatics, also seems to have been worked over and added to a great deal.
Hero’s thaumaturgy.
From Vitruvius’s allusions to the works of Ctesibius and from a survey of those works current under Hero’s name which are chiefly concerned with mechanical contrivances and devices, the modern reader gets the impression that, aside from military engines and lifting appliances, the science of antiquity was applied largely to purposes of entertainment rather than practical usefulness. However, in Hero’s case at least there is something more than this. His apparatus and experiments are not intended so much to divert as to deceive the spectator, and not so much to amuse as to astound him. The mechanism is usually concealed; the cause acts indirectly, intermediately, or from a distance to produce an apparently marvelous result. It is a case of thaumaturgy, as Hero himself says,[892] of apparent magic. In fine, the experimental and applied scientist is largely interested in vying with the feats of the magicians or supplying the temples and altars of religion with pseudo-miracles.
Instances of experimental proof.
The introduction or proemium to the Pneumatics is rather more truly scientific and has been called an unusual instance in antiquity of the use as proof of purposive observation of nature and experiment. Thus the existence of air is demonstrated by the experiment of pressing an inverted vessel, kept carefully upright, into water, which will not enter the vessel because of the resistance offered by the air already within the vessel. Or the elasticity of air and the existence of empty spaces between its particles is shown by the experiment of blowing more air into a globe through a siphon, and then holding one’s finger over the orifice. As soon as the finger is removed the surplus air rushes out with a loud report. Along with such admirable experimental proof, however, the introduction contains some astonishingly erroneous assertions, such as that “slime and mud are transformations of water into earth,” and that air released from a vessel under water “is transformed so as to become water.” Hero believes that heat and light rays are particles of matter which penetrate the interstices between the particles composing air and water.
Magic jugs and drinking animals.
The Pneumatics consist of some seventy-eight theorems or experiments or tricks, call them what you will, which in different manuscripts and editions are variously grouped in a single book or two books. The same idea or method, however, is often repeated in the different chapters. Thus we encounter over half a dozen times the magic water-jar or drinking horn from which either wine or water or a mixture of both can be poured, or a choice of other liquids. And in all these cases the explanation of the trick is the same. When the air-hole in the top of the vessel is closed so that no air can enter, the liquid will not flow out through the narrow orifice in the bottom. Changes are rung on this principle by means of inner compartments and connecting tubes. Different kinds of siphons, the bent, the enclosed, and the uniform discharge, are described in the opening chapters and are utilized in working the ensuing wonders, such as statues of animals which drink water offered to them, inexhaustible goblets or those that will not overflow, and harmonious jars. By this last expression is meant pairs of vessels, secretly connected by tubes and so arranged that nothing will flow from one until the other is filled, when wine will pour from one jar and water from the other. Or when water is poured into one jar, wine or mixed wine and water flows from the other. Or, when water is drawn off from one jar, wine flows from the other. Other vessels are made to commence or cease to pour out wine or water, when a little water is poured in. Others will receive no more water once you have ceased pouring it in, no matter how little may have been poured in, or, when you cease for a moment to pour water in and then begin again, will not resume their outpour until half full. In another case the water will not flow out of a hole in the bottom of the vessel at all until the vessel is entirely filled. Others are made to flow by dropping a coin in a slot or working a lever, or turning a wheel. In the last case the vessel of water is concealed behind the entrance column of a temple. In one magic drinking horn the flow of water from the bottom is checked by putting a cover over the open top. When another pitcher is tipped up, the same amount of liquid will always flow out.
Various automatons and devices.