ARCHIMEDES AND THE KING. 



to His Majesty, he had his doubts about the honesty of the goldsmith, and 



called to Archimedes to tell him whether or not the crown was of gold, pure 



and simple. Archimedes was puzzled, and 



went home deep in thought. Still con- 

 sidering the problem he went . to the bath, 



and in his abstraction filled it to the brim. 



Stepping in he spilt a considerable quantity 



of water, and at once the idea struck him 



that any body put into water would displace 



its own weight of the liquid. He did not 



wait to dress, but ran half-naked to the 



palace, crying out, " Eureka, Eureka ! I 



have found it, I have found it ! " What 



had he found ? He had solved the problem. 

 He got a lump of gold the same weight 



as the crown, and immersed it in water. He 



found it weighed nineteen times as much as 



its own bulk of water. But when he weighed *'* 7i.-Sectm of jug. 



the kings crown he found it displaced more water than the pure gold had 



done, and consequently it had been adulterated by a lighter metal. He 



assumed that the alloy was silver, and by immersing lumps of 



silver and gold of equal weight with the crown, and weighing 



the water that overflowed from each dip, he was able to tell the 



king how far he had been cheated by the goldsmith. 



It is by this method now that we can ascertain the specific 



gravity of bodies. One cubic inch of water weighs about half an 

 A ounce (or to be exact, 



2 5 2 2" grains). Take a 

 piece of lead and weigh 

 it in air ; it weighs, say, 

 eleven ounces. Then 

 weigh it in a vase of 

 water, and it will be 

 only ten ounces in 

 weight. So lead is 

 eleven times heavier 



Fig. 72. Weighing metal in water. t 



than water, or eleven 

 ounces of lead occupy the same space as one ounce of water. 



[The heavier a fluid is, or the greater its density, the greater 

 will be the weight it will support. Therefore we can ascertain 

 the purity or otherwise of certain liquids by using hydrometers, 

 etc., which will float higher or lower in different liquids, and Fig ^_HV? 

 being guaged at the standard of purity, we can ascertain (for drometer.. 

 instance) how much water is in the milk when supplied from the dairy.]- 



But to return to SPECIFIC GRAVITY, which means the " Comparative 



