Mr. J. Taylor's Led arcs on Metallurgy. 369 



Oxygen 

 Sulphur 

 Silex 



Carbonic acid 

 Arsenic acid 



Sulphuric acid 

 Muriatic acid 

 Phosphoric acid 

 Chromic acid 

 Molybdic acid 



Water Arsenic. 



The result of the natural combination of these substances 

 with metals is called an ore. 



Metallic ores are further compounded by including mixtures 

 of more than one metal, as in the case of yellow copper ore, 

 which contains both sulphuret of copper and of iron, — galena 

 or sulphuret of lead, which commonly contains silver, — and 

 anany ores which contain arsenic combined with other metals. 



Again : the metallic ores are much intermixed with earthy 

 substances of various kinds, which, though not in chemical 

 union, have often such an intimate mechanical union as to 

 filter their character, and add to tiie variety of their appearance 

 ^nd to the difficulty of extraction of the pure metal. 



Some of the compounds which have been before described 

 as the products of art, will appear again in the list of the ores ; 

 but generally speaking, owing to the circumstance of other 

 admixtures, or their having been formed in modes which art 

 cannot imitate, their external characters are different in the 

 one case from what they are in the otlier. 



One peculiarity which will strike us is the variety of form 

 and splendour of their crystals, each assuming a regularity in 

 their structure which forms an admirable guide by which their 

 nature may be detected ; and this circumstance has been used 

 as the foundation of a study that has rendered the greatest ser- 

 vices to mineralogy ; it has assumed the name of crystallo- 

 graphy, and should be attended to by all who intend to ac- 

 (juire a knowledge of the mineral kingdom. 



Besides the ores resulting from combinations such as have 

 been mentioned, certain metals are found in their pure or 

 malleable state, and we speak of them then as native metals : 

 such are 



Platijia, gold almost always. 



Silver, mercury, copper, antimony frequenriy. 



Arsenic, tellurium, bismuth, iron rarely. 



Taking then into account these and the compounded state 

 of the ores, it will appear that nature presents us witli the me- 

 tals under a great variety of form, exciting us to careful ex- 

 amination and diligent skill in their discovery, reduction, and 

 adaptation to our wants. It will hercalter be shown that the 

 art of reducing the metals, depends upon our power ol de- 



\o\. 61. No. 301. Ma>j 1823. 3 A slroyuig 



