428 THIRD REPORT — 1833. 



sixteenth century, and produces silver ores of superior quality. 

 The principal shaft is sunk about 6 feet deeper every year, by 

 which ground enough is drained for a regular extraction of the 

 ores. The mine is one of the oldest in Germany, and has al- 

 ways been profitable : it employs from 400 to 500 men. It is 

 the property of shareholders, who are very numerous, the in- 

 terest having been much subdivided in the course of time. 



The mine of Valenciana at Guanaxuato was one of the most 

 renowned in Mexico. It produced annually, about the end of 

 the last century, 360,000 ounces of silver, worth about £600,000 

 sterling, and then employed 3100 persons. The shaft referred 

 to in the section was commenced in 1791, the mine having been 

 long previously worked by other shafts : it had attained its pre- 

 sent depth in 1809, when the mine was stopped by the Revo- 

 lution. It is octagonal, and more than 30 feet in diameter, a 

 great part of its depth being walled with beautiful masonry, and 

 is probably the most magnificent work of the kind. The ex- 

 pense of forming this shaft is estimated by Humboldt at the 

 enormous sum of £220,000. The mine was so little troubled 

 with water that it was considered almost a dry one : during the 

 suspension of the works it, however, gradually filled. In 1825 

 one of the English companies undertook to drain it, which 

 was, after great labour and expense, accomplished ; but the 

 mine has not been sufficiently productive since to make it worth 

 while to continue the working. 



The Consolidated mines foi-m the most extensive concern in 

 Cornwall, embracing what were formerly several distinct mines, 

 which, as the name indicates, were connected in one under- 

 taking. 



This was arranged in 1818, and the mines which had remained 

 unwrought for many years were drained by very powerful steam- 

 engines, and were put into a state of active working. The ma- 

 nagement was confided to Mr. Taylor and the late Captain 

 William Davey : an outlay of £73,000 was incurred, which has 

 since been repaid with ample profit. The present produce is 

 20,000 tons of ore a-year, yielding about 1920 tons of fine cop- 

 per, being one seventh of the whole quantity raised in Great 

 Britain. The mines employ about 2400 persons, of whom about 

 1400 are miners working underground. The water raised to 

 the adit level is about 2000 gallons per minute : the height to 

 which this is lifted is more than 220 fathoms, or 1320 feet ; the 

 aggregate weight of the columns of water in the pumps being 

 512,000 pounds, or about 230 tons, and the whole is put in 

 motion by eight immense steam-engines, four of which are the 

 largest ever made. 



