Ch. IX.] VEINS IN PRIMARY ROCKS. 189 



John's gossan- lode b is thrown downwards by c 18 fathoms. 



The tin lode a 18 



a upwards by b 8 



a *i*wj-:- d 9 feet. 



Mr. Hawkins has mentioned a circumstance attending the 

 heaves in this mine, which must not be omitted. " The 

 middle segment of Huel Peever tin lode," he says, "was 

 found to be much wider than the two others, and in a state 

 of great disorder ; and some fragments of the upper segment 

 were carried off with the slide, or, more correctly speaking, 

 strewed along the line of removal, to the distance of several 

 feet. Traces of this disorder were likewise observed at the 

 top of the lowest segment, occasioned by the gossan-lode." * 



5. Veins and elvan-courses often come into contact with each 

 other ; and the same phenomena result from this interference as 

 from that of veins with each other. Indeed, as already ob- 

 served, elvan-courses^ when metalliferous, are called by the 

 miners lodes, as stated by Mr. Carne in the instances of Huel 

 Unity and Rosewall-hill mines*; and they are justified in 

 their view, since they exhibit the same appearances as veins : 

 even Mr. Carne, although he has placed them in his con- 

 venient class of doubtful veins, says, that the evidence appears 

 strongly in favour of their being true veins, f 



In general, elvan-courses are traversed by all veins, which 

 commonly pass through without producing any alteration in 

 the original position of the separated parts of the elvans ; but 

 many instances occur in which the phenomena of heaves are 

 exhibited. In the fourth chapter, examples of heaves by 

 quartz-veins and a flucan have been already described ; and 

 Mr. Hawkins, in his account of the lodes of Polgooth mine, 

 states, that the elvan is at one place heaved by a slide, and in 

 another it heaves the metalliferous veins. The vein B, he 

 says, has been mistaken for a continuation of St. Martin's lode 



* Geol, Trans, of Cornwall, vol. ii. p. 791. f Ibid. p. 83. 



