THE MINERAL KINGDOM. 187 



fine wire, and beaten into leaves thinner than the 

 finest paper. A single ounce of gold may be 

 spread by the hammer over a surface of one hun- 

 dred and fifty square .feet, and yet remain quite 

 whole, without the least flaw or hole in it ; and 

 the same quantity may be drawn into a wire more 

 than a hundred miles long. All of them melt, 

 or are fused, by heat. 



The place from which metals are procured is 

 termed a mine : these often run to great distances 

 underground, and the miners are exposed to se- 

 rious danger at times, from want of a free circula- 

 tion of air. When the ore has been dug out and 

 brought to the surface, it has to be freed from the 

 impurities which are mixed with it : this is done 

 either by reducing it to a coarse powder, and then 

 washing it repeatedly, when the water carries off 

 the lighter particles, and leaves the metal behind ; 

 or it is roasted, that is, mixed with coal and burnt. 

 This removes most of the impurities, and it is then 

 smelted and made fit for use. 



No class of the productions of nature are more 

 useful to man than the metals. In all the arts of 

 life, and in all our manufactures, they are quite 

 indispensable : without them, indeed many of these 

 could never have been carried into effect. Every 

 implement requiring to be hard, durable, and flex- 

 ible, is made of metal. Vessels that have to 

 be exposed to the action of fire are made of the 

 same material, and every thing also used for cut- 

 ting, where a fine edge is necessary. 



