356 M. Amedee Burat on the 



large scale ; and the produce of the mines goes on continually 

 developing, in consequence of these operations, The cap- 

 tains of the mines in that district are unquestionably the 

 boldest practical men — the sterility of the affleuremcnts does 

 not alarm them — and many veins, which in the upper part 

 yielded only barren gossan, have been productive in zones of 

 from 200 to 400 metres. It was at first supposed that the 

 richness diminished a little bej'ond 400 metres, but now 

 many mines have been successfully extended to 500 and 600 

 metres. 



In this country, as in all metalliferous districts, many 

 mines now in great activity have been re-opened after the 

 first works had proved unproductive. The last example of 

 the mines of Wheal Maria in Devonshire deserves to be men- 

 tioned. They consist of a vein near Tavistock, which had 

 been anciently mined, and which was again opened without 

 success in 1843, after being abandoned for thirty-five years. 

 Researches recommenced under the direction of Mr Hitchens, 

 an experienced miner, and were attended with the most 

 brilliant success of which the annals of Cornwall can furnish 

 any account. 



Such instances of veins pronounced exhausted in regard 

 to depth, abandoned, and afterwards successfully resumed, 

 when the works received an energetic and judicious impulse, 

 are to be met with in all metalliferous districts. The follow- 

 ing is one of the most recent : — • 



The vein of cupriferous quartz at Rheinbreitenbach is of a 

 classical character in the country of the Rhine, and celebrated 

 among us for its beautiful specimens of phosphate of copper 

 and lamellated malachite. In its deepest parts, the normal 

 mineral of this vein consisted of variously-coloured copper ore, 

 which forms ribbons or chaplet-shaped agglomerations, and 

 the mining had been carried on by means of a gallery 1000 

 metres in length. After a long period of productiveness, the 

 works descended below the level of this gallery, and were 

 abandoned for the ordinary reasons, which affirm that a repo- 

 sitory becomes impoverished and limited in depth. The pro- 

 duce had become moderate, the waters caused interruption, and 

 accidents had limited the field of operations. It was com- 



