A HISTORY OF SCIENCE 



one can in imagination follow the flow of that por- 

 tion of water from spiral to spiral, the water always 

 running downward, of course, yet paradoxically being 

 lifted higher and higher towards the base of the cork- 

 screw, until finally it pours out (in the actual Archi- 

 medes' tube) at the top. There is another form of the 

 screw in which a revolving spiral blade operates with- 

 in a cylinder, but the principle is precisely the same. 

 With either form water may be lifted, by the mere 

 turning of the screw, to any desired height. The in- 

 genious mechanism excited the wonder of the contem- 

 poraries of Archimedes, as well it might. More efficient 

 devices have superseded it in modern times, but it 

 still excites the admiration of all who examine it, and 

 its effects seem as paradoxical as ever. 



Some other of the mechanisms of Archimedes have 

 been made known to successive generations of readers 

 through the pages of Polybius and Plutarch. These 

 are the devices through which Archimedes aided King 

 Hiero to ward off the attacks of the Roman general 

 Marcellus, who in the course of the second Punic war 

 laid siege to Syracuse. 



Plutarch, in his life of Marcellus, describes the Ro- 

 man's attack and Archimedes' defence in much detail. 

 Incidentally he tells us also how Archimedes came to 

 make the devices that rendered the siege so famous: 



"Marcellus himself, with threescore galleys of five 

 rowers at every bank, well armed and full of all sorts 

 of artillery and fireworks, did assault by sea, and rowed 

 hard to the wall, having made a great engine and de- 

 vice of battery, upon eight galleys chained together, 



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