55 



are on the south side ; the branches seen on the opposite side 

 have, generally speaking, allowed the mineral to escape from the 

 veins. An oblique fissure on the south side, called a caunter, 

 formed contemporaneously with an east and west vein, produces 

 the same effect as the small oblique branches, viz. enriching 

 one part of the east and west fracture at the expense of another : 

 the lode north of the oblique vein would be found comparatively 

 poor. These facts may be observed in Cornwall in various parts, 

 and particularly in the mines of Dolcoath, Tin Croft, and North 

 Roskear. 



The feeders or roots of the split veins may be seen in the 

 mines of St. Just, the bunches of mineral depending entirely 

 upon them ; the principal being those coming in from the granite 

 in a S.S.E. direction, and forming diagonal shoots of ore from 

 their junction northward, as represented in Plate XV. The 

 tin ore formation in the St. Ives consols may be described as 

 a number of large roots coming in from the south-east, con- 

 verging into one grand trunk, and growing northward at an 

 angle of about eight degrees from the horizon, surrounded by 

 the granite. A similar split vein may be also seen on the banks of 

 the Tamar, having the principal feeding veins or roots on the 

 south-east side, in tender ground under the bed of the river. 

 Split veins, cross courses, &c. are not productive without the 

 feeders, the latter being the only means by which the contents 

 of the bordering rocks can be brought into them. 



The split veins of all mining districts are of the same nature ; 

 therefore as these effects are matters of fact, and easily referred 

 to, we shall not enter into further details. All split veins, be 

 they quartz, carbonate of lime, hornblende, or any other, have 

 been formed in the same manner, and consequently the contents 

 are arranged in longitudinal plates. 



The influence of the impermeable Splits on the accumulation 

 of the Minerals in the Transverse Fractures. 



Independent of the " bunches " of mineral being found cor- 

 responding to certain channels, the amount of the deposits in 

 the fissures is considerably influenced according to the position 

 of the intersecting splits. (Plate XVII.) 



