152 Mr. William Phillips on the Veins of Cornwall, 



It was In this mine, as has been ah'eady noticed, that silver was 

 discovered in Convocation Cross Course, as well as a very small 

 quantity in Rusty Cross Course. 



--Two channels of porphyry also occurred in this mine ; their effect 

 on the N. and S. and E. and W. veins was similar to that produced by 

 a channel of the same description in Pleasure, Fancy, and North 

 Herland mine ; their underlie and thickness are also about the same. 



The underlie of the Slide is in the same direction as that of the 

 channel of porphyry, but not so quick. Its substance was flucan of 

 three or four inches in thickness ; it passed through the cross courses 

 and flucans. It also traversed the metalliferous vein, the course of 

 which it interrupted, and heaved about fifteen inches, but whether 

 to the north or south I know not. The load of the metalliferous 

 vein was found to be richest a fathom or two along the run of the 

 slide, both above and beneath it. 



Transverse or North and South Section of Tin Croft Mine. 



PI. 7. fig. 8. 

 Tin Croft mine has been worked many years ; and has yielded 

 large profit both to the lord of the soil and to the adventurers. 

 It was first worked for tin, principally, I believe, if not wholly, on 

 the two most northerly veins. The country in which the mine is 

 situate is for the most part schistose, but some remarkable alterna- 

 tions of schist and granite were discovered while working the two 

 veins on the south, the probable cause of which appears to be this, 

 that as these veins run parallel with and at the foot of the hill called 

 Carn-brae, which is wholly of granite, the irregularities in the granite 

 were supplied by a deposition of the schist. In no other part of the 

 mine does granite appear, except that in following down two of 

 the veins, as is noted on the accompanying section, they were 



