THE ALEXANDRIAN PERIOD 81 



tion, containing some new additions, reveals an 

 imitator who is unfamiliar with experiments and 

 technique. The instructions given for the construction 

 of a troupe of performing automata on a larger scale 

 than that of Philo suffers from the same defect : the 

 author, for example, forgets to describe the motive 

 power which puts the whole in motion. 1 These latter 

 writings were, however, much appreciated both by the 

 Arabs and the savants of the Renaissance ; they gave 

 rise to the construction of many garden fountains with 

 figures moving automatically, which excited the 

 admiration of visitors. The old clock of Strasbourg 

 with its moving figures is a direct descendant of the 

 Automata of Hero. The Mechanics, of which we only 

 possess the Arabic version, is less defective : it explains, 

 in accord with Archimedes, the principles of statics 

 and the parallelogram of forces, and describes the use 

 of the toothed wheel, the lever, the tackle, the wedge, 

 and the screw. Hero has also devoted a work to the 

 study of the crane, and the problem of Archimedes : to 

 move a given weight with a given force. Despite its 

 defects, his work remains one of our chief authorities on 

 the history of Greek mechanics. 



2. GEOGRAPHY AND ASTRONOMY 



The interest in geography awakened by the conquests 

 of Alexander the Great, far from declining, continued 

 and developed thanks to the fostering care of the 

 Seleucids and the Ptolemies. The progress of mathe- 

 matics, also, had a favourable influence on the 

 development of this science, which, from the purely 

 descriptive stage, grew more and more systematic and 

 accurate. 



Eratosthenes of Cyrene (275-194 B.C.), the learned 

 librarian of Alexandria, must be regarded as the creator 

 of geography as a science. His history of geography 

 1 15 Heiberg, Natuvwiss., p. 79 et seq. 



