74 MODERN HIGH FARMING. 



were left unworked, until about the middle of the last century, 

 when an enterprising Swede endeavored to turn them to account. 



The want, however, of sufficient skill and capital, combined 

 with the difficulties of transport and the political troubles, which 

 never ceased to convulse the country, caused all attempts to end 

 in failure, until in 1873 the Spanish government decided to dispose 

 of the properties by selling them to the company known as the 

 Rio Tinto, limited. 



The pyrites deposits are somewhat irregular and occur in lenticu- 

 lar shaped masses. There are three important lodes the South, the 

 Dionisio and the North ; the mineral resources of all three being so 

 immense as to be considered by the best authorities inexhaustible. 



The principal opening is that existing in the South lode, which is 

 1,500 yards long, 100 yards deep and 200 yards in breadth, and an- 

 nually yields about 700, OCO tons of ore, the composition of which is 

 shown in our analytical table as Spanish No. 2. 



Before this great lode could be worked, it was found necessary to 

 remove nearly four million tons of earth, or overburden. 



Beneath this immense bed of ore, which some engineers have es- 

 timated as containing about 200 million tons, are extensi\e under- 

 ground workings reached by a tunnel already nearly 1,000 yards in 

 length. When this tunnel attains a length of about three miles, it 

 will connect and open out the Dionisio lode, upon which a shaft 

 has already been sunk in the centre. 



The great value of these sulphur ores is not confined to the manu- 

 facture of sulphuric acid, but, by the development of certain chemi- 

 cal bye-processes, has assumed considerable importance in the pro- 

 duction of the precious metals ; thus, from Hie enormous amount of 

 pyrites she annually consumes, Great Britain extracts in addition to 

 the acid, about 18,000 tons of pure copper, 300,000 ounces of silver, 

 1,800 ounces of Gold and over 400, OCO tons of iron ore. 



