To him also are to be attributed the endless screw, and a peculiar form of burning-mirror, by which, at the siege of Syracuse, it is said that he set the Roman fleet on fire.
ERATOSTHENES--APOLLONIUS--HIPPARCHUS.

Eratosthenes, who at one time had charge of the library, was the author of many important works.

Among them may be mentioned his determination of the interval between the tropics, and an attempt to ascertain the size of the earth.

He considered the articulation and expansion of continents, the position of mountain-chains, the action of clouds, the geological submersion of lands, the elevation of ancient sea-beds, the opening of the Dardanelles and the straits of Gibraltar, and the relations of the Euxine Sea.
He composed a complete system of the earth, in three books--physical, mathematical, historical--accompanied by a map of all the parts then known.

It is only of late years that the fragments remaining of his "Chronicles of the Theban Kings" have been justly appreciated.