ORIGIN AND DEVELOPMENT OF ORE DEPOSITS. 147 



from the West of England mining region. That a very large 

 number of valleys in the "West of England coincide in direction 

 with faults which are not ore-bearing in any notable degree, 

 is of course well-known, but there are also many which 

 correspond to mineral veins. Thus, the Valley of the Teign 

 coincides with and appears to have been occasioned by the 

 lead lode which has been so extensively worked at Erank 

 Mills, and the Lower Luxulyan Valley coincides with the course 

 of the Treffry Iron Lode. 



The Valley of the Exe coincides with a north and south fault 

 for a considerable distance, as beds which ought to be continued 

 across it in the line of strike are found to have been heaved out 

 of their places. The boundary line between the carbonaceous 

 series and the " grauwacke " of North Devon and Brushford, is 

 heaved more than half-a-mile to the southward on the left bank 

 of the Exe near Exe bridge, and the junction line of the red 

 sandstone and carbonaceous series near Washfield, on the North 

 of Tiverton, and also near the latter place, is thrown nearly half- 

 a-mile to the southward on the east side of the river.* 



In Ligger Bay several cross-courses may be seen in the 

 cliffs. The largest of these which, is 3 or 4 fathoms wide, dips 

 eastward some 60° or 70° ; the country on both sides consists of 

 killas, but on the east it is of a pale greyish colour, while that 

 on the west is deep blue. Among other valleys which appear to 

 coincide with faults, may be mentioned the picturesque valley of 

 the Fal, from Tregoss Moor to Terras Bridge, and the small valley 

 which runs between Dolcoath and Cook's Kitchen, which latter 

 coincides with what is known as the " great cross-course " of the 

 Camborne and Illogan district. This is nearly perpendicular, 

 nevertheless it heaves the lodes from 50 to 70 fathoms to the 

 right. The coincidence in direction of the valleys, joint-systems, 

 and lodes of the St. Just district has been adverted to by Mr. N. 

 Whitley and Miss Elizabeth Carne, and the similarity of direction 

 observed between ordinary joints and lodes has been remarked 

 by Mr. Henwoodjf the connexion has also been dwelt upon 

 in the foregoing pages. 



*Delabeche. Eep. on the Geol. of Cornwall, &c, p. 294. 

 f Trans. Roy. Geol. Soc. Corn., v. 168, 173, 279, &c. 



