INFLUENCE OF THE PTOLEMAIC EPOCH. 543 



inculcated in the Alexandrian Museum;* and this science 

 comprehended in the advanced stages of its development pure 

 mathematics, mechanics, and astronomy. In Plato's high 

 appreciation of mathematical development of thought, as well 

 as in Aristotle's morphological views which embraced all 

 organisms, we discover the germs of the subsequent advances 

 of physical science. They became the guiding stars which led 

 the human mind through the bewildering fanaticism of the 

 dark ages, and prevented the utter destruction of a sound and 

 scientific manifestation of mental vigour. 



The mathematician and astronomer, Eratosthenes of Gyrene, 

 the most celebrated of the Alexandrian librarians, employed 

 the materials at his command to compose a system of universal 

 geography. He freed geography from mythical legends, and, 

 although himself occupied with chronology and history, 

 separated geographical descriptions from that admixture of 

 historical elements with which it had previously been not un- 

 gracefully embodied. The absence of these elements was, 

 however, satisfactorily compensated for by the introduction of 

 mathematical considerations on the articulation and expansion 

 of continents ; by geognostic conjectures regarding the connec- 

 tion of mountain chains, the action of clouds, and the former 

 submersion of lands, which still bear all the traces of having 

 constituted a dried portion of the sea's bottom. Favourable 

 to the oceanic sluice-theory of Strabo of Lanrpsacus, the Alex- 

 andrian librarian was led, by the belief of the former swelling 

 of the Euxine, the penetration of the Dardanelles, and the 

 consequent opening of the Pillars of Hercules, to an important 

 investigation of the problem of the equal level of the whole 

 " external sea f surrounding all continents." An additional 

 proof of this philosopher's power of generalising views is 

 afforded by his assertions that the whole continent of Asia is 

 traversed by a continually connected mountain chain, running 



* Fries, Geschichte der Philosophie, bd. ii. s. 5; and the same 

 author's Lehrbuch der Naturlehre, th. i. s. 42. Compare also the con- 

 siderations on the influence which Plato exercised on the foundation of the 

 experimental Sciences by the application of mathematics, in Brandis, 

 Geschichte der griechiscli-romisclien Philosophie, th. ii. abth. i. s. 276. 



t On the physical and geognostical opinions of Eratosthenes, see 

 Strabo, lib. i. pp. 49-56, lib. ii. p. 108. 



