THE ALEXANDRIAN PERIOD 79 



cannon, which were partly operated by compressed 

 air. His works were unfortunately lost, but we find 

 their essential features in the Mechanics published by 

 his immediate successor Philo of Byzantium, several 

 fragments of whose work have come down to us. 1 

 A general introduction prefaces this most important 

 work ; then comes the description of catapults, which 

 it has been possible to reconstruct in recent times by 

 the aid of the drawings which accompany the descrip- 

 tion. The accuracy and long range of these engines 

 were a revelation. 2 Reflections on the art of besieging 

 follow, then an accurate account of the theory of the 

 lever, further on a description of automata and 

 mechanical apparatus intended for use in theatres or 

 gardens, such as magic goblets, water-cans pouring 

 different liquids as desired, fountains with animals 

 drinking and birds singing, etc. Beside these there 

 were other more useful apparatus, such as for wash- 

 ing automatically the steps of the temples. The 

 mechanism of all these machines is based principally 

 on the action of levers and compressed air. 



Two centuries later Hero of Alexandria took up the 

 work begun by Ctesibius. He probably lived about 

 the end of the first century B.C., but the dates of his 

 life, death and works are very uncertain. 3 Although 

 Hero of Alexandria is more famous in history than 

 Ctesibius, his work is far from being of equal originality 

 and accuracy. 



From a mathematical point of view it consists of : 

 (1) An elementary geometry, with applications to 



1 A. de Rochas, La science des philosophes et I'art des thau- 

 maturges, Dorbon, Paris, p. 59. 



2 10 Diels, Antike, p. 92. 



3 J. L. Heiberg and P. Tannery place Hero in the second 

 century after Christ, but the majority of historians decide 

 in favour of the first century before the Christian Era (17 

 Loria, Sc. esatte, p. 583, and W. Schmidt in his introduction 

 to the works of Hero). 



