HERO, or HERON. There are two of this name, both writers on mechanical subject& Hero the elder was the pupil of Ctesibius, and lived at Alexandria about sm. 100. The country of the younger Here i e uncertain ; in a work attributed to him (on 'Geodesy ') he states that the precession of the equinoxes had produced seven degrees of effect since the time of Ptolemreus, so that he must have been about 500 years later than Ptolemrcus: he is generally placed under the reigt of Heraclius, A.D. 610.641.
Hero the elder must have enjoyed great reputation, since be b mentioned, by Gregory Nazianzen, with Euclid and Ptolemrcus : but in is now principally known by some fragments of his writings or mechanics, which are to be found in the Mathematicl Veteres, Paris, 1693; by the common pneumatic) experiment known as "Hero's fountain," in which a jet of water is supported by condensed air ; an by his mention of a machine, the motive-power of which is steam His extant writings are : 1. ' On the machine called the Chiroballiatra, vhich is in the 'Math. Vet.' already cited. 2. Barulcus; a treatise n the raising of heavy weights, which is mentioned by Pappus, and viiich was found by Golius in Arabic, but has not yet been printed. t. 'Belopceica,' a treatise on the manufacture of darts, published by 3aldi, with an account of Hero, at Augsburg, in 1616, and also in the Math. Vet.' 4. 'Pneumatics,' which contains the recently noticed lescription of a simple steam-engine, published by Commandine, Jrbino, 1575, and Amsterdam, 1680; and also in the 'Math. Vet.'
vith the additions of Aleotti, who had previously published an Italian version, Bologna, 1542, and Ferrara, 1589. 5. 'On the Construction if Automata,' which is in the 'Math. Vet.,' and was translated into Italian by Bernardino Baldi, with an account of the rise and progress A mechanics, Venice, 1589, 1601, 166L 6. 'On Dieptries,' a work taid by Lambecius to exist in manuscript in the Vienna library. ether works of Hero, now lost, are mentioned by Pappus, Eutocius, Efeliodorus of Larissa, &c., for which see Heilbronner, who is the authority for the preceding summary : (see also J. A. Schmidt, Heronis Alexandrini Vita Scripta et qumdam invents,' Helmstad. 1714, 4to.).
The writings of Hero the younger are : 1. a book 'On Machines of War,' edited in Latin by Barocius, Venice, 1572; together with, 2. a book of Geodesy,' a term then meaning practical geometry. 3. On the Attack and Defence of Towns,' printed in the 'Math. Vet.' 4. A book ' On Military Tactics,' said by Lambecius to exist in manuscript in the library at Vienna. 5. On the Terms of Geometry ;' printed st Strasbourg, 1571; and also edited by C. F. F. Hasenbalg, Stralsund, 1826, 4to, with notes. 6. Geometrical Extracts,' printed by the Benedictines in the first volume of the 'Analecta Grseca,' Paris, 1638, from a copious manuscript in the Royal Library at Paris. • 7. A Geometrical Manuscript, stated by Lambecius to be in the library at Vienna.
There was another Heron, the teacher of Proclus.