METALS. 



We come now to treat of the last division of the 

 metallic substances ; those which, remaining in the 

 air in the metallic state, have received the name 

 particularly of metals. 



Those metals whose combinations with oxygen 

 form alkalies, as potassium, sodium, and lithium, as 

 also those whose oxides form earths, as calcium, 

 magnesium, barium, strontium, silicium, alumium, 

 yttrium, glucinum, zirconium, and thorinum, have 

 been already mentioned incidentally, in speaking of 

 the alkalies and earths to which they give rise. But 

 we shall now enumerate the general properties of 

 this important class of bodies, including the above 

 mentioned. 



The metals are distinguished from all other sub- 

 stances by certain properties, particularly a pecu- 

 liar lustre ; and most of them have great weight, or 

 specific gravity. 



Several of them have been known to part of the 

 world in very ancient times, while some savages in 

 the present day are totally unacquainted with their 

 use : but a considerable number of the metallic sub- 

 stances have been discovered only lately. The 

 metals are so important in many mechanic arts, 

 that mankind could never have attained their pre- 

 sent state of civilisation without them. 



Metals are, in general, solid bodies at the usual 

 temperature : one only, mercury, is fluid. 



They are opaque in the mass in its usual state ; 

 but gold, when beat into very thin leaves, transmits 

 a faint greenish light, when held between the eye 

 and the direct rays of the sun. 



