106 A SHORT HISTORY OF SCIENCE 



visions and depravation) from matter ; so it was that mechanics came 

 to be separated from geometry, and, repudiated and neglected by 

 philosophers, took its place as a military art. 



One of his most famous inventions was the water-screw used 

 for irrigation, in Egypt, and for pumping. On occasion of diffi- 

 culty in the launching of a certain ship he successfully applied 

 a cogwheel apparatus with an endless screw. 



Archimedes . . . had stated that given the force, any given 

 weight might be moved, and even boasted, we are told, relying on 

 the strength of demonstration, that if there were another earth, by 

 going into it he could remove this. Hiero being struck with amaze- 

 ment at this, and entreating him to make good this problem by actual 

 experiment, and show some great weight moved by a small engine, 

 he fixed accordingly upon a ship of burden out of the king's arsenal, 

 which could not be drawn out of the dock without great labor and 

 many men ; and, loading her with many passengers and a full freight, 

 sitting himself the while far off with no great endeavor, but only 

 holding the head of the pulley in his hand and drawing the cords by 

 degrees, he drew the ship in a straight line, as smoothly and evenly, 

 as if she had been in the sea. The king, astonished at this, and con- 

 vinced of the power of the art, prevailed upon Archimedes to make 

 him engines accommodated to all the purposes, offensive and defensive, 

 of a siege . . . the apparatus was, in most opportune time, ready at 

 hand for the Syracusans, and with it also the engineer himself. 



Plutarch. 



In astronomy his orrery has been mentioned ; he also attempted 

 to determine the length of the year more closely. 



To the critical estimates already cited may be added as typical 

 of countless others : 



Whoever gets to the bottom of the works of Archimedes will 

 admire the discoveries of the moderns less. Leibnitz. 



His discoveries are forever memorable for their novelty and the 

 difficulty which they presented at that time, and because they are 

 the germ of a great part of those which have since been made, chiefly 

 in all branches of geometry which have for their object the measure- 



