172 MOLECULAR POLARIZATIONS. 



they are electro-magnetically separated. Relying 

 on this law, Sir Humphrey Davy proceeded to 

 subject some dissolved potash in a saucer between 

 the two poles of a powerful voltaic battery, and 

 first revealed the surprising fact that this substance 

 is an oxide, or rust, of a shining metal resembling 

 silver. 1 



Followi-ng out this mode of detecting the exist- 

 ence of different kinds of molecules in various 

 compound substances, several important metals 

 were discovered ; now well known as calcium, 

 magnesium, aluminium, silicium, &c., the names 

 of these metals being borrowed from the names of 

 the compound substances from which they were 

 obtained. 



To designate the family relationships of certain 

 kinds of groupings of atoms into metallic mole- 

 cules, 



A CLASSIFICATION AND DESCRIPTIVE NOMENCLATURE 

 IS INTRODUCED. 



To distinguish the newly discovered metals 

 from the early known metals, a simple nomen- 

 clature is used, by giving to them the terminal 

 ium, as potassium, calcium, magnesium, alu- 

 minium, &c. The only non-metallic substance 

 having the terminal ium is selenium. 



1 The simple apparatus originally employed in making this memor- 

 able discovery, was courteously exhibited to the writer by his illustrious 

 successor) Professor Faraday, at the Royal Institution in London, in 

 1852, during an interesting visit to that temple, hallowed by many grand 

 discoveries in Physical Science. 



