326 METALLIC OXIDES. 



ration has been carefully examined by Davy, Berzelius,, 

 and others. It is always resolved into ammonia and 

 mercury ; and, although the latter chemist is strongly 

 inclined to regard it as affording evidence of the com- 

 pound nature of nitrogen, and he has, indeed, proposed 

 the name nitricum for its hypothetical base, yet, to the 

 present time, we have no satisfactory explanation of this 

 apparent metallization of ammonia. 



No attempt will be made to describe the various ele- 

 mentary substances which come under the class of 

 metallic bodies, much less to enumerate their combina- 

 tions. Many of the metals, as silver and copper, are 

 found sometimes in a native state, or nearly pure ; but, 

 for the most part, they exist, in nature, in combination 

 with oxygen or sulphur ; gold furnishing a remarkable 

 exception. They are occasionally found combined with 

 other bodies, as oxidized carbon, phosphorus, chlorine, 

 &c. -, but these cases are by no means so common. 

 Those substances called metals are generally found em- 

 bedded in the rocks, or deposited in fissures formed 

 through them; but it is one of the great discoveries of 

 modern science, that those rocks themselves are metallic 

 oxides. With metals we generally associate the idea of 

 great density ; but potassium and sodium, the metallic 

 bases of potash and soda, are lighter than water, and 

 they consequently float upon that fluid. We learn, 

 therefore, from the researches of science, that the crust 

 of this earth is composed entirely of metals, combined 

 with gaseous elements ; and there is reason for believing 

 that one, or perhaps two, of the gases we have already 

 named are also of a metallic character. Strange as it 

 may appear, there is nothing, as will be seen on atten- 

 tive consideration, irrational in this idea. Many of the 

 metals proper, under the influence of such heat as we 

 can, by artificial means, command, are dissipated in va- 

 pour, and may be maintained in this state perfectly invi- 

 sible. Indeed, the transparent space above the surface 



