COMMERCE. 131 



authority on this subje6l. In his Treatise on the Art of re- 

 fining Metals, Don Alonzo Barba, re6tor of San Bernardo in 

 Potosi, makes the following observations : "It may be as- 

 serted without exaggeration, that many thousands of piastres 

 have been lost, as well in the extradlion of the metallic sub- 

 stance from the ores, the qualities and differences of which 

 have not been well understood ; as in the disproportionate 

 expenditure of quicksilver, of which upwards of two hundred 

 and thirty-four thousand seven hundred quintals have be6n 

 consumed, in the space of sixty-three years*, in the imperial 

 city of Potosi, Those who have been engaged in this pur- 

 suit, have, in the management of the ores, proceeded at ran- 

 dom, and without any fundamental rules, or certain infor- 

 mation relative to the silver they contained, and might be 

 made to yield.'* 



Notwithstanding the ignorance of mineralogy was attended 

 by such prejudicial consequences, it would be difficult to be- 

 lieve, that it 'reached the unfortunate extreme which is de- 

 scribed in an ancient and authentic document by Don Fran- 

 cisco Texada, intendant of the mine of Guadalcanal, dated 

 in 1607. Speaking of the produ6liveness of many of the ores 

 dug from the silver mines of Europe, each quintal of which 

 yielded fifteen, thirty, and even sixty marks of the pure me- 

 tallic substance, he adds as follows : ** In the celebrated 

 mountain of Potosi, which is now working, there is not a 

 greater produce than one ounce and a half of pure and limpid 

 silver, from each quintal of metallic earth, or stone, which is 

 extra6ted ; or, in other words, one thousand six hundred 



* The treatise from which this quotation is made, was published in 1637. 



s 2 ounces 



