HERON. he wrote commentaries on Deinarchus, Herodotus. Thucydides, and Xenophon ; a work entitled A'l h 'Afi^jwiS Si/ca£ KfKpiixevwv 'OvofiaTav, in three books ; an epitome of the history of Heracleides ; and a work on the ancient orators, entitled Uepl Tuiv Apxai<>iv 'Ft}t6pwv koI rwu Aoywu oTs iuiKT]- aav irpds dW-^Kovs dycavi^Sfievoi. There are no data for determining when he lived. (Fabric. Bibl. Grace, vol. iv. p. 239 ; Vossius, De Hist. Graec. p. 452, ed. Westermann.) 2. A grammarian, a native of Ephesus, quoted frequently by Athenaeus (ii. p. 52 b, iii. p. 76 a, p. Ill c, &c.), and in the scholia on ApoUonius Rho- dius(i. 769, iii. 2). Others of this name, not worth inserting, will be found mentioned in Fabricius (L c). [C. P. M.] HERON {"Hpwv). I. Of Alexandria, is called by Heron the younger {de Mach. 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 no- tices. The common pneumatic experiment, called Hero's fountairiy in which a jet of water is main- tained 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 engiiie, 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 Barkers 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 Avery, one of which, of six horse power, is, or lately was, at work near Edinburgh.* 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 modemes," (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 men- tioned. The remaining works, or rather fragments, of Heron of Alexandria, are as follows : — 1. XeipoSaWiffTpas KaTaaKevri Koi a-vfifHTpla, de Constrttctione et Mensura Manvhalistae. First pub- lished (Gr.) by Baldi at the end of the third work presently noted. Also (Gr. Lat.) by Thevenot, Boivin, and Lahire, in the " Veteram mathemati- corum Athenaei, Apollodori, Philonis, Heronis et aliorum Opera," Paris, 1693, fol. 2. Barulcus sive de Oneribtis traJiendis Libri tres, a treatisq brought by J. Golius from the East in Arabic, not yet trans- lated or published {Ephemerid. Litter. Gotting. ann. 1785, p. 625, &c. cited by Fabricius). 3. BeAo- HERON. 437
- 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. TTOit/ca, BeXoiroiTjKa, or {Eutoc. in Arch, de Sph. et Cyiiyid.) BeKo-7roir}TLKd, 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. MatJiemat. &c. above mentioned. 4. rii/eu^oTt/ca, 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. MatJiemat. &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 Ita- lian translation, by Alessandro Giorgi, of Urbino, 1592, 4to., and by J. B. Porta, Naples, 1605, 4to. There is a Gennan translation by Agathus Carlo, with an appendix by Solomon de Cans, Bamberg, 1687, 4to., Frankfort, 1688, 4to. 5. Uepl avTo- /uoTOTroiTjTi/f&i/, de Automatorum Fabrica Libri duo. Translated into Italian by B. Baldi. Venice, 1 589, 1601, 1661, 4to.: also (Gr. Lat.) in the Veter. Matliemat, &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 : — Tot irepl idpo(TKoirei£u^ by Proclus, Pappus, and Heron himself ; MTjxai'i'ca^ Iffoyooyai., hy Eutocius, Pappus, and Heron him- self ; Ilepi jLterpiKccv, by Eutocius ; Hepl TpoxtwSiwi', by Pappus ; and a work Uepl ^vyiwv^ is mentioned by Pappus, and has been supposed to be by Heron. (Fabric. Bibl. Graec. vol. iv. p. 234 ; Murhard's Catalogue ; Heilbronner, Hist. Matlies. Univ. ; Montucla, Hist, des Mathtm. 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 men- tioned by Eutocius as the commentator on the arith- metic 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 de- grees 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 bellicis, 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 hav- ing been written by Heron ; but we suspect that he supposed it to be attributed to Heron of Alex- andria. 3. De Obsidione repellenda^ oTrcoy xpi^ riiv TTJs TToXiopKovixefT^s irSXews (TTpaTrjyov irpds rrjp troKiopKiav dvTirdaa-eadui, published (Gr.) in the Veter. Mathemat. Opera, &c. mentioned in the life of Heron of Alexandria. 4. Ilap^KSoKaX eK rwv arparTiyiKUV irapaTd^ewv, &c. This exists only in manuscript. 5. 'Ek t<Sv tou "Hpwvos irepl rdov TTJs FidOfiCTpias KoL ^Tep^wfurpias dvoudrcov, pub- FF 3
