212 DEVELOPMENT AND PURPOSE CHAP. 



The shadoof was early in use, but the water wheel does not 

 seem to be verified before the Ptolemaic period. No siege 

 engines are shown in Egyptian monuments, but from the 

 eighth century we see towers raised against besieged cities. 



No epoch-making advance was effected in the industrial 

 arts by the Greeks or Romans. Yet Archimedes is credited 

 with the discovery of forty machines, including the com- 

 pound pulley, the screw pump, and the endless screw, while 

 the Romans had cause to remember his inventions in the 

 art of war. Hero of Alexandria was the first man of 

 eminence who systematically applied science to invention ; 

 but though he made the first steam engine, was familiar 

 with the expansion of air by heat, and constructed 

 mechanisms in which motion was produced thereby, his 

 contrivances were rather scientific toys than machines of 

 practical utility, and this side of his work was sterile till it 

 was taken up again in the Renaissance. Meanwhile the 

 mariner's compass was introduced into Europe from the 

 East it was known to the Chinese at least as early as the 

 second century B.C. and the possession of this guide made 

 long sea voyages possible, and led to the discovery of the 

 new world. Chemistry, originating as a practical art in 

 Egypt, had elaborated methods of experiment e.g. distil- 

 lation as a means of separating substances was known from 

 the fourth or fifth century A.D. Lastly, to mention only 

 one more point, clocks known to the Greeks in the shape 

 of the clepsydra and the sandglass had developed into 

 weight-driven machines needing only the experiments of 

 Huyghens with the pendulum to perfect them as time 

 measurers. Thus on the one side the more apparent natural 

 forces have been brought into the service of man, wind and 

 water are used to drive mills, animal strength is freely 

 utilised, rivers are canalised, land is irrigated, and fertility 

 maintained by some rotation of crops. On the other hand, 

 many artificial substances are empirically discovered and 

 brought into use from bronze to glass, and from iron to 

 the elixirs and potions of the older pharmacopoeia. All the 

 elementary machines, the wheel, pulley, lever and screw 

 are in use. 



Such, roughly, is the state of man's control over nature 



