ER'ATOS'THENES (Lat., from Gk. 'Eparo (c.275-195 D.c.). An eminent Greek as tronomer and geometer, who was the first to adopt the name philologist, `lover of learning.' Eratosthenes was born at Cyrene; for a time he enjoyed the teaching of Lysanias and Callima elms, and then went to Athens, where he heard the Stoic Ariston of Chios and the Academic .Ar cesilaus. Ptolemy Euergetes recalled him to Alexandria, and about me. 240 installed him as Callima•hus's successor in the office of librarian. At the age of eighty or upward, having become totally blind, he died of voluntary starvation. Eratostbenes's interests covered an enormous range. Ile wrote a commentary to Plato's Ti nUrnS, and also composed popular philosophical dialogues; in literary history lie produced a great work, On the Old Comedy, in at least twelve looks. His ehronob)gieai researehes also were important, while in the field of pune nvithematics he wrote fin the of the sphere and on a method of distinguishing prime and composite numbers. His astronomical views he set forth in part in the poems Hermes, Erigone, and prob ably info-inns. The extant work Katasterismai (KaruccrEpurnot), in which an account is given of the constellations in their relations to the popu lar mythology, is only a summary of a work by Eratosthenes which was apparently entitled The Catalogues, and in its present form has been worked over to follow the order of Aratus's Pha•omena.
It was, however, by his attempt to measure the size of the earth and by his geographical studies that Eratosthenes won most renown. He en deavored to determine the obliquity of the ecliptic Inv measuring the distance between the tropics; this he found to be 47° 42' 39", which gave 23' 51' 19.5" for the obliquity of the ecliptic. Con sidering the means of observation available and the state of knowledge at the time, the degree of error in his result—a trifle more than 23'—is re markably small. To measure the circumference of the earth he adopted the means employed at the present day. He found that the difference between Syene and Alexandria was one-fiftieth of a circumference, about 7° 13', and on this basis computed the circumference of the earth to be 250,000 stadia; as we do not know the length of the stadium Eratosthenes used as his unit we cannot determine the degree of error in his re sult. His greatest scientific publication was prob
ably his Geography (Peurypackfcct), in three books, the first scientific treatise on the subject which gave the history of the sciences and embodied the results of his own investigations. In his re searches Eratosthenes was greatly assisted by his patron, Ptolemy Euergetes, and he had the resources of the Alexandrian Library at his com mand. He was undoubtedly first among the Aiexandrians for great and wide learning, although in the special fields of poetry and philosophy others surpassed him. The extant fragments of his writings are collected and dis cussed in the following works: Bernhardy, Era tostheniea (Berlin, 1822) ; Stiehle, "Zu den Fragmenten des Eratosthenes," in Philologus, supplementary vol. ii. ((Bittingen, 1863) ; Berger, Die geographischen Pragmente des Era tosthenes (Leipzig. 1880) ; Hiller, Eratosthenis Carmintillt Reliquicr (Leipzig, 1872) ; Maass, "Eratosthenien," in Philologische Untersuchun gen, vol vi. edited by Kiossling and Wilamowitz M011endorff (Berlin, 1883) : Robert. Eratosthenis Catasterismorum Reliquiir (Berlin, 1878) ; Oli vieri, "Pseudo-Eratosthenis Catasterismi." in ilythographi iii. (Leipzig, 1897) : Susemih], Geschielf tc der griechis•hen Littcratnr in der .1lera»driner Zeit, vol. i. (Leipzig, 1892).
ERB, erp, WILHELM HEINRICH ( 1840-1. A German Douro-pathologist. Ile was horn at Winnweiler. Bavaria, and was educated at Ilea. Erlam-n. and Munch. After occupy " 1 le chair of special imthology and therapy at Leipzig, from 1s-..) to ISs:t. he was appointed to e sante di uriment at Ileidelberg, where he also mad, ;Iinie;.1 director. As tt specialist on pV :11.1 neuro-pathology he pub 1 the idiom works: Handbuch der i der prriphe rem le a er "(1 ed. Handbuch. der Krank ite 11 /1,3 R rick( and des rerlanyert en Marla 'd rd, 1875) : Handbuch der Elektro th rap 3d etl. 1886; Eng. trans. by L. Put :eel, ss31: I her di( yn tee re En I usieklung der :Nem n pa thologit (1880), and Dystrophia .11 uscu Loris Proyre ssira 11591).