22 SCIENCE OF THE GREEKS. PT. I. 



Alexandria, but afterwards returned to his native country. 

 One of the greatest discoveries made by Archimedes was that 

 of the principle of the lever. If you place a book upright on 

 the table and lay a light ruler or flat piece of wood across 

 it, you will find there is one point at which the ruler will 

 balance. When you have balanced it, put an ounce weight 

 on each end and it will still balance at the same point, 

 which is called the fulcrum. But now change the ounce 

 at one end for a weight of two ounces ; that end will sink 

 at once, and to make it balance you will have to shift the 

 ruler till one end is longer than the other. You may go 

 on doing this by adding more weight to the heavy end till 

 that end is quite close to the fulcrum or resting-point of the 

 ruler, and still the light weight will balance the heavy one. 



This is the principle of the lever, and it is of great use 

 in lifting weights. A heavy block of stone which no set of 

 men could lift by taking hold of it may be easily raised by 

 fastening it to the short end of a lever, and then the weight 

 of the men at the end of the long arm will balance it, as 

 the one-ounce weight balances the heavier weights at the 

 other. Archimedes was so delighted when he made this 

 discovery that he is said to have exclaimed : ' Give me a 

 place on which to stand, and I will raise the world.' 



Another remarkable discovery made by Archimedes con- 

 cerns the weight of bodies immersed in water. Hiero, king 

 of Syracuse, had given a lump of gold to be made into a 

 crown, and when it came back he suspected that the work- 

 men had kept back some of the gold, and had made up the 

 weight by adding more than the right quantity of silver; 

 but he had no means of proving this, because they had 

 made it weigh as much as the gold which had been sent 

 Archimedes, puzzling over this problem, went to his bath. 

 As he stepped in he saw the water, which his body dis- 



