22 SCIENCE OF THE GREEKS. pt. I. 



the sun — the middle of the sun, the middle of the hole in the 

 shutter, and the middle of the spot of light, will all be in a 

 straight line. 



Archimedes, 287. — Another famous geometer, Archi- 

 medes of Syracuse, bom 287 B.C., lived about the same 

 time as Euclid. He studied for many years at Alexan- 

 dria, but afterwards returned to his native country. One 

 of the greatest discoveries made by Archimedes was that 

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

 and lay a ruler or any flat piece of wood or metal 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 and make the light end twice as long, because the 

 heavy end has twice the weight upon it. Put a three ounce, 

 and you must again lengthen the light end to three times the 

 length of the heavy one. You may go on doing this till the 

 heavy end is quite close to iho^ fulcrum or resting-point of the 

 ruler, and still the light w^eight 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 four-ounce. 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- 



