MODERN HIGH FARMING. 



73 



there being many which, on account of their large percentage of 

 arsenic are looked upon with general disfavor. 



As Spain may be considered, not only the principal source of 

 present supply, but an inexhaustible field whence we may expect 

 to draw any quantity required during the next few centuries, we 

 shall devote ourselves to a short description of the Spanish mines, 

 regarding them as typical in all important points, of pyrites ore 

 deposits. 



They are situated in the mountainous regions of Andalusia, at a 

 distance of sixty or seventy miles from the port of Huelva, whence 

 they are principally shipped for their different destinations. The 

 surrounding rocks belong to the " lower Silurian " series, and are of 

 a schisty or slatey nature, intermixed here and there with green- 

 stone and felspatic rocks of various descriptions. 



The existence of these sulphurous copper ores has been known 

 from time immemorial, they having been exploited first by the 

 early Celts, then very extensively by the Phoenicians, and in due 

 course by the Romans, who worked them for upwards of three hun- 

 dred years, and left behind them traces of the gigantic nature of 

 their operations, which are still to be seen. 



When the Roman Empire had fallen, and while the Moors were 

 in possession of the country, the mines were abandoned, and indeed, 



