366 NINETEENTH CENTURY. FT. in. 



into more than one substance. So he heated some pure 

 potash in a spoon until it was quite liquid, and fastening 

 the two ends of the spoon to the wires of a battery, he sent 

 an electric current through it. After a little while the potash 

 began to be agitated, and to rise up in bubbles, and then 

 there came to the surface beautiful silver-like globules, some 

 of which burst into flarne, while others remained covered 

 by a sort of white film. 



' Davy's delight,' writes his brother, ' when he saw the 

 minute shining globules like mercury burst through the 

 crust of potash and take fire as they reached the air, 

 was so great that he could not contain his joy he actually 

 bounded about the room in ecstatic delight.' It must indeed 

 have been a beautiful sight in itself ; but probably Davy's 

 excitement arose chiefly from the new truth he saw in it. 

 He had proved that potash was not a simple substance, 

 but contained something which had never before been 

 discovered. 



At first he had great difficulty in collecting the globules, 

 for they not only burst into flame when they met the air, but 

 even in water they took fire, joining themselves to the oxygen 

 and setting the hydrogen free. At last, however, he succeeded 

 in collecting them in rock oil, or naphtha, which contains no 

 oxygen. He was then able to examine them, and he found 

 they were composed of a metal hitherto quite unknown, to 

 which he gave the name of potassium. A few days later he 

 procured the metal sodium out of common soda by the same 

 process. 



This method of decomposing substances is called electro- 

 lysis, which means ' setting free by electricity.' Davy made 

 use of it to decompose many earths, such as lime, mag- 

 nesia, &c., and the great Swedish chemist, Berzelius (bom 



