348 GREEK SCIENCE. 



that two bodies of equal magnitude, both heavier than the fluid in 

 which they are immersed, will lose equal parts of their weights ; and 

 that reciprocally, when the weights lost in the same fluid are equal, 

 the bodies are of equal magnitudes. The solution of the well-known 

 problem of Archimedes, relative to the crown of Hiero, king of Syra- 

 cuse, depends on the above principles. 

 Screw of Besides the theoretical principles of Hydrostatics, we owe also to 



Archimedes. , -, . -, .-, i j. ,1 . . i j v 



this philosopher, according to some authors, an ingenious hydraulic 

 engine, called, from the name of its supposed inventor, the screw of 

 Archimedes. It is employed in elevating water to small heights ; 

 and is very simple in its construction, and commodious in its appli- 

 cation. 



Diodorus asserts, that Archimedes invented this machine in his 

 voyage to Egypt, and that the Egyptians afterwards employed it for 

 the purpose of draining the marshes of that country ; but Vitruvius, 

 a contemporary of Diodorus, does not enumerate it amongst the dis- 

 coveries of Archimedes, of whom he was nevertheless a great admirer j 

 and Claudius Perrault, the translator and commentator of Vitruvius, 

 adds, that the use Diodorus gives to this machine, namely, that it was 

 employed to render Egypt habitable, by draining off the waters with 

 which it was formerly inundated, makes it highly probable that the 

 engine is of much earlier date than the time of the Syracusan philo- 

 sopher. If this conjecture have any foundation, let us not mix with 

 the legitimate claims of Archimedes, an invention which may be con- 

 tested with him : he is too rich in other respects to render important 

 the sacrifice of an equivocal right. 



ctesibiusand About a century after Archimedes, two mathematicians of the 

 Hero. Alexandrian school, viz. : Ctesibius, and Hero, his disciple, invented 



thl^ump the pump, the siphon, and the fountain of compression ; the latter of 

 and siphon. w hlch is to this day known under the appellation of Hero's fountain. 

 We owe more especially to Ctesibius, a machine of the same kind, 

 composed of a sucking and a forcing pump; so combined, that by their 

 alternate action, the water is drawn and forced into a tube placed 

 between them. The effects produced by these machines are in 

 truth highly curious and interesting, and doubtless must have ap- 

 peared very extraordinary to their original inventors, who, not know- 

 ing to what principle to attribute them, had recourse to their grand 

 scheme of occult qualities, so commodious for explaining all the 

 phenomena of nature. The water rose in the pumps, according 

 to these philosophers, because nature abhorred a vacuum, and 

 consequently the place abandoned by the piston was immediately 

 supplied by the water : we know not whether at that time philoso- 

 phers were aware of the limit to which the elevation of the water was 

 confined; but we do know, that when this was pointed out to the 

 great Galileo, the father of modern physics, he could only explain it 

 by stating, that nature's abhorrence of a vacuum only extended to 

 about thirty-three or thirty-four feet ! Such were the illustrations of 



