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he' wrote commentaries on Deinarchus, Herodotus. Thucydides, and Xenophon; a work entitled At fv 'AQrfvais Sf/ccu KeKpinivav 'Overdrew, in three books ; an epitome of the history of Heracleides ; and a work on the ancient orators, entitled Tlepl T<av ^Apxalw 'PrjTSpow Kal twv &6y<av ots evfari-go.v irpos oAA7JA.ous dfywvi£6fji.€voi. There are no data for determining when he lived. (Fabric. Bibl. Grace, vol. iv. p. 239; Vossius, De Hist. Grace, p. 452, ed. Westermann.)
Others of this name, not worth inserting, will be found mentioned in Fabricius (L c.). [C. P. M.]
HERON fHpcor). 1. Of Alexandria, is called by Heron the younger (de Mack. Bell. c. 23, Fabr.) a pupil of Ctesibius, and he lived in the reigns of the Ptolemies Philadelphus and Euergetes (b. c. 284—221.) Of his life nothing is known; on his mechanical inventions we have but some scanty parts of his own writings, and some scattered notices. The common pneumatic experiment, called Hero's fountain, in which a jet of water is maintained by condensed air, has given a certain popular celebrity to his name. This has been increased by the discovery in his writings of a steam engine, that is, of an engine in which motion is produced by steam, and which must always be a part of the history of that agent. This engine acts precisely on the principle of what is called Barker's Mill : a boiler with arms having lateral orifices is capable of revolving round a vertical axis ; the steam issues from the lateral orifices, and the uncompensated pressure upon the parts opposite to the orifices turns the boiler in the direction opposite to that of the issue of the steam. It is nearly the machine afterwards introduced by A very, one of which, of six horse power, is, or lately was, at work near Edinburgh.'3'' Heron's engine is described in his pneumatics presently mentioned ; as also a double forcing pump used for a fire engine, and various other applications of the elasticity of air and steam. It is, however, but recently, that the remarkable claims of Heron to success in such investigations have received any marked notice. In the " Origine des Decouvertes attributes aux modernes," (3rd edition, 1796), by M. Dutensf, who tries, with great learning, to make the best possible case for the ancients, the name of Heron is not even mentioned.
The remaining works, or rather fragments, of .Heron of Alexandria, are as follows :— ' 1. X€ipo€a\\i(rrpas KaraffKevf) Kal ffvfJLfjLerpla, de Constructions et Mensura Manubalistae. First published (Gr.) by Baldi at the end of the third work presently noted. Also (Gr. Lat.) by Thevenot, Boivin, and Lahire, in the " Veterum mathemati-corum Athenaei, Apollodori, Philonis, Heronis et aliorum Opera," Paris, 1693, fol. 2. Barulcus sive de Oneribus traJiendis Libri ires, a treatise brought by J. Golius from the East in Arabic, not yet translated or published (Ephemerid. Litter. Gotting. ann. 1785, p. 625, &c. cited by Fabricius). 3. BeAo-
* So says the translator of Arago's Eloge of Watt, and he adds that it is in pretty general use in Scotland.
'+ This work is very valuable, from its giving at length, every passage to which reference is made.
HERON. . 437
or (Eutoc. in Arch, de Sph. et Cylind.) BeAoironjTi/ce«, on the manufacture of darts. Edited by Bernardino Baldi (Gr. Lat.) with notes, and a life of Heron, Augsburg, 1616, 4to. ; also in the Veter. Matftemat. &c. above mentioned. 4. Hv€v}jua,rtKOL^ or Spiritalia, the most celebrated of his works. Edited by Commandine (Lat.) with notes, Urbino, 1575, 4to., Amsterdam, 1680, 4to., and Paris, 1683, 4to. It is also (Gr. Lat.) in the Veter. Maihemat. &c. above mentioned. It first appeared, however, in an Italian translation by Bernardo Aleotti, Bologna, 1547, 4to., Ferrara, 1589, 4to. ; and there is also (Murhard) an Italian translation, by Alessandro Giorgi, of Urbino, 1592, 4to., and by J. B. Porta, Naples, 1605, 4to. There is a German translation by Agathus Cario, with an appendix by Solomon de Caus, Bamberg, 1687, 4to., Frankfort, 1688, 4to. 5. Ilepl ai5<ro-luaTOTroiTjTiKtof, de Automatorum Fabrica Libri duo. Translated into Italian by B. Baldi. Venice, 1589, 1601, 1661, 4to.: also (Gr. Lat.) in the Veter. MatJiemat., &c. above mentioned. A fragment on dioptrics (Gr.) exists in manuscript, and two Latin fragments on military machines are given by Baldi at the end of the work on darts. The following lost works are mentioned:— Ta irepl tidpoarKOTreitoi', by Proclus, Pappus, and Heron himself ; M^xcm/cal ttroycoyat, by Eutocius, Pappus, and Heron himself ; Ilepl juerpi/cwy, by Eutocius ; Hep! Tpoxw8/c3i/, by Pappus ; and a work IXcpi £Vyi«i/, is mentioned by Pappus, and has been supposed to be by Heron. (Fabric. Bibl. Graec. vol. iv. p. 234 ; Murhard's Catalogue; Heilbronner, Hist. Matties, Univ.; Montucla, Hist, des Mathein. vol. i.)
2. The teacher of Proclus, of whom nothing more is known. Fabricius (Bibl. Graec. vol. iv. p. 239) takes this to be the Heron who is mentioned by Eutocius as the commentator on the arithmetic of Nicomachus.
3. The younger, so called because we have not even an adjective of place to distinguish him from Heron of Alexandria, is supposed to have lived under Heraclius (a. d. 610—641). In his own work on Geodesy (a term used in the sense of practical geometry), he says that in his own time the stars had altered their longitudes by seven degrees since the time of Ptolemy: from which the above date must have been framed. But if he spoke, as is likely enough, from Ptolemy's value of the precession of the equinoxes, without observing the stars himself, he must have been about two hundred years later. He was a Christian.
The writings attributed to Heron the younger are, 1. De Machinis betticis, published (Lat.) by Barocius, Venice, 1572, 4to. There is one Greek manuscript at Bologna. 2. Geodaesia, published (Lat.) with the above by Barocius. Montucla notices this as the first treatise in which the mode of finding the area of a triangle by means of its sides occurs. Savile, who had a manuscript of this treatise, rejects with scorn the idea of its having been written by Heron ; but we suspect that he supposed it to be attributed to Heron of Alexandria. 3. De Obsidione repellenda, oirws XP$ fbv rfjs TToAtopKOVjUej'rjs TnJAews ffrpwrtiybv irpos ti)j» iroXiopKiav avnrdffffeffQai, published (Gr.) in the Veter. Mathemat. Opera, &c. mentioned in the life of Heron of Alexandria. 4. IIap€K§o\al e/c rwv ffrparriyiK&v irapardl-ewv, &c. This exists only in manuscript. 5. *E« t&v rod "Hpwvos irepl t&v Kal "%T€p€(0fji€Tptas oj'oittfrcw, pub-
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