CH. III. HIERO'S CROWN. 



23 



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 workmen 

 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 if it had been pure gold. Archimedes, puzzling 

 over this problem, went to his bath, which was filled to the 

 brim with water. As he stepped in he saw the water, which 

 his body displaced, pouring over the edge of the bath, and 

 to the astonishment of his servants he sprang out of the water 

 and ran home through the streets of Syracuse almost naked, 

 Qxymg Eureka ! Eureka! (' I have found it, I have found it.') 

 What had he found? He had discovered that any 

 solid body put into a vessel of water displaces its own bulk 

 of water, and therefore, if the sides of the vessel are high 

 enough to prevent it running over, the water will rise to a 

 certain height. He now got one ball of gold and another of 

 silver, each weighing exactly the same as the crown. Of 

 course the balls were not the same size, because silver is 

 lighter than gold, and so it takes more of it to make the 

 same weight. He first put the gold ball into a basin of 

 water, and marked on the side of the vessel the height to 

 which the water rose. Next, taking out the gold, he put in 

 the silver ball, which, though it weighed the same, yet, being 

 larger, made the water rise higher ; and this height he also 

 marked. Lastly, he took out the silver ball and put in the 

 crown. Now, if the crown had been pure gold, the water 

 would have risen only up to the mark of the gold ball, but 

 it rose higher and stood between the gold and silver mark, 

 showing that silver had been mixed with it, making it more 

 bulky. This was the first attempt to measure the specific 



