424 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 14, 



been thrown into perfect confusion. Hence the veins throughout 

 have a fragmentary character; and the portions remaining give 

 proof that they originally contained, besides quartz, several kinds of 

 the common spars (particularly heavy-spar), together with a con- 

 siderable admixture of galena, blende, and copper, and iron-pyrites. 

 Moreover .they either frequently contain porphyry and greenstone, 

 or these rocks have intruded as disturbers of the veins. Mining- 

 operations in such broken strata are very precarious. 



CorrebuicMU. — In a southern direction, ascending from the Tomna- 

 dasban Mines, and at a distance of about three miles, the mica-schist 

 at Correbuichill is overlain by a horizontal calcareous stratum. In 

 this rock two systems of veins have been discovered, chiefly by means 

 of surface-trenches. The one system, consisting of three veins 

 which run nearly east and west, is of small importance, on account 

 of their barrenness. But the other is the more interesting system. 

 In a straight line of about 200 yards, eighteen such veins have been 

 met with ; and it is more than probable that a far greater number 

 remain undiscovered under the shallow turf. These veins have 

 almost a mathematical parallelism, and run as nearly as possible due 

 north and south, in nearly a vertical position. Their width varies 

 from 4 inches to 3 feet. The contents are chiefly quartz, with 

 galena very rich in silver. The veins vary as to this valuable metal, 

 between 85 and 600 ounces per ton of lead-ore. The elevation of 

 the hill may be about 2000 feet above the level of the sea, and 1600 

 feet above that of Loch Tay. The veins mostly crop out in fine 

 gossan ; and in such cases the produce of ore has been favourable for 

 a certain distance downwards. As far as the field has been opened 

 by mining, experience shows that the valuable lead-ore quickly and 

 considerably diminishes in sinking, so that in about 100 feet below 

 the outcrop the veins only consist of compact white quartz. It has 

 not been ascertained what is the condition of the veins at the depth 

 where the limestone rests upon the mica-schist. In the upper parts 

 of the veins the galena not unfrequently envelopes the crystals of 

 quartz completely, thereby indicating that the galena and quartz are 

 not contemporaneous members. Copper-pyrites is rare, and still 

 more so are blende and iron-pyrites ; hence the lead-ore is of a very 

 pure and rich character. In one part of the hill a large deposit of 

 dolomite, in the form of a vein, has been met with, accompanying 

 one of the veins. Twice in the course of mining operations (which 

 some years since were suspended) the interesting and casual dis- 

 covery of native gold was made when the ore was being crushed 

 under the hammer. The veins have been repeatedly dislocated, both 

 in the horizontal and in the vertical projections. In consequence of 

 this, the veins sometimes approach quite close to each other, and it 

 becomes difficult to discover in the network of veins the identity of 

 each individual vein. The dislocations have been effected by the 

 sliding and uplifting of the strata, which, in the absence of other 

 apparent causes, and as the veins and strata have both been dislo- 

 cated together, may.be ascribed to the disturbances at Tomnadashan, 

 in the neighbourhood. Though mining- operations in such elevated 



