Eratosthenes has been called a poet, and Se slier, in his commentary on Ilanilius, givea some fragments of a poem attributed to him, entitled 'Hennes, or de Zonis,' one of which is a description of the terrestrial Zones: it is not improbable that these are authentic; the chroniclers as well as philosophers of all nations, in a state of incipient civilisation, have called in the aid of metre to popularise their labours. Eratos thenes is therefore entitled to the name of a versifier rather than a poet, like his precursor Manetho, who wrote 'AvereSecrearocci (effects or influences), a mixture of astrology and astronomy; one of whose lines, containing the names of tho sun and planets, may be taken as a specimen : Zsirr "Apes Ticupie Mire Iiporos"Hhoos The wretched doggrel arising from forcing names, scientific terms, and reasonings into verse, may be judged by some ridiculous productions of the kind in our own language.
That Eratosthenes was an excellent geometer we cannot doubt, from his still extant solution of the problem of two mean proportionals, preserved by Theon, and a lost treatise quoted by De Loris ad Medietates,' on which Montucla has offered some conjectures, ' Histoire des Math.; an. vii., p. 280.
Eratosthenes appears to have been one of the first who attempted to form a system of geography. His work on this subject, entitled Geographica ' (rsoripassocii), was divided into throe books. The first book contained a history of geography, a critical notice of the autho rities used by him, and the elements of physical geography. The second book treated of mathematical geography, and contained the method above explained, by which he determined the earth's circum ference. The third book contained the political or historical geography, arranged according to the three great divisions of the known globe, Europe, Asia, and Libya. The whole work was accompanied with a map of the known world. The geography of Eratosthenes is lost ; the fragments which remain have been chiefly preserved by Strobe, who was doubtless much indebted to him.
Eratosthenes also busied himself with chronology. The reader will find some remarks on his Greek chronology in Clinton', 'Faati Hellenici ; and on his list of Theban kings, by It. Bask, in his little
work on the ancient Egyptian chronology, German translation, Altona, 1830.
The properties of numbers attracted the attention of philosophers from the earliest period, and Eratosthenea also distinguished himself in this branch by a work which he denominated K4KKWOY, Cribrnm,' or ' Sieve,' the object of which is to separate prime from composite numbers, a curious memoir on which was published by Horsley iu the Philosophical Transactions,' 1772. The principle of the method ia to reject all the multiples of the primes, tabulating first all the odd numbers; the multiples of 3 will be found with intervals of two places, of 5 with intervals of 4, and by placing a mark over each such multiple, none but prime numbers will remain after this shifting. The same method, which is indeed iodirect, but comparatively rapid in application, has been employed by Ladislaus Chernac, in forming a table of primes from 1 to 1,020,000, iu a treatise published in 1811 : the following example will explaiu the method : . . . . .
3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41 , 43, 45, 47, 49.
By actually trying this method it will be seen how readily the composite numbers aro marked out, and we may terminate the operation when our commencing number exceeds a third of the last number in the table.
Eratosthenes arrived at the age of eighty years, and ultimately becoming weary of life, died by voluntary starvation. (Suidas, 'Eratosthenes) Montucla, with his usual naivet6, says it would have been more philosophical to await death "de pied fenne." (Montucla, Histoire des Math., p. 239 ; Delembre, Hut. de 1' Astro nomic Ancienne, p. 86 i • Lalande, Astron. art.; Sententice Cr. et Lat. in Poetis Redulphi li'intertoni, Cambridge,1700; Fraymenta Gr. et Let., by Shaubach, Gottingen; Aratus, Oxford edition, 1672; lioraley, Tr acts and Nceioir in Phil. Trans., 1772; Catasteritmi, Heyne; Crawls's' drills, by L. Chernao; (7rographicoruin Fragmenta, 1787; Eutocius, Commentary on Archimedes. The edition of the Fragments of Eratoethenes, by Bernhardy (Berlin, 1822, 8vo), does not contain the Catasterismi: See CLEOMEDES.)