290 



CROSS COURSES. 



a vein of silver at Uspalata, in the Andes, which is nine feet in thick- 

 ness throughout its whole extent, and has been traced ninety miles. 

 Smaller veins branch off from each side of it, and penetrate the 

 neighbouring mountains to the distance of thirty miles. It is believed 

 that this vein stretches to the distance of three hundred miles. A 

 vein called the Tidswell Rake, in Derbyshire, extends some miles 

 east and west ; it is worked from the surface, and may be seen near 

 the roadside, between Great Hucklow and Tidswell. I was inform- 

 ed in Cornwall, that no vein in that county had been traced in length 

 more than two miles ; nor had any vein been worked out in depth. 

 The common width of the veins is from one foot to two feet, but 

 sometimes it exceeds thirty feet. 



In Cornwall and Devonshire, and in the mines of Northumberland 

 and Durham, the principal metallic veins range nearly east and west. 

 In the former counties they are called lodes, in the latter right-run- 

 ning veins. The north and south veins which intersect them are 

 called cross courses : these are seldom productive of ore. In plate 

 VII. fig. 3., the veins hh c c are represented as cut through by a 

 cross course. It must be borne in mind that this is a ground plan. 

 The thin cross courses filled with clay are called Jluan, I was in- 

 formed by an intelligent proprietor of mines in Cornwall, that these 

 thin cross courses invariably displace the veins, and hold up the wa- 

 ter on one side of the vein ; but it is most worthy of notice, that a 

 vein which is rich in ore on one side of the fluan, will be poor on the 

 other. Query, Is this connected with the jluan holding up the wa- 

 ter'^ In Cornwall, the cross courses displacef the east and west ;/; 

 veins ; the displacement is only a few inches in some veins, in others 

 it is several fathoms. On Alston Moor, in Cumberland, a large cross 

 course, called Old Carr's Cross Vein, cuts through two veins, called 

 Goodham Gill Vein, and Grass Field Hill Vein, and has thrown 

 them aside about fifteen or twenty fathoms. When the cross course 

 intersects the east and west veins at right angles, the displacement is 

 generally less, than when it strikes it in an oblique direction. This 

 effect will be more clearly understood by referring to Plate VII. fig. 3. 



In Northumberland and Durham, cross course's contain ore, near 

 their junction with powerful veins. In Cornwall, ores of silver and , 

 cobalt have been found in some of the cross courses ; and at the Bo- 

 tallack mine, north of the Land's End, a powerful cross course, run- 

 ning north and south, is made rich by ihe junction of east veins, 

 which resemble small rivulets, opening into a river. Their position 

 will be belter understood by referring to Plate VII. fig. 6. The di- 

 rection of the cross course or great vein running north and south, is 

 represented by the letters n, s, the direction of the small veins, rich 

 in ore, which open into it, are represented by e e e. The cross 

 course is rich in ore, to the distance of twenty or thirty fathoms, on 

 each side of its junction with a vein ; but no veins are found branch- 

 ing from the west side of the cross course. The cross course is 



