374 TRANSACTIONS OF THE 



intersections, may be obtained at Carclase mine nejir St 

 Austle, Cornwall, which is an immense excavation open 

 from the surface. 



The country is a decomposed granite of a greyish 

 white colour ; the lodes, which are composed of quartz 

 and schorl, being of a blackish colour and seldom more 

 than 6 inches wide : the contrast is very visible. The 

 lodes of the oldest class are nearly perpendicular ; some 

 of them have a small inclination to the south ; the more 

 recent lodes underlie rapidly southwards, and traverse 

 the others. 



The third age comprizes the oldest east and west cop- 

 per lodes, forming the great majority of all the copper 

 lodes met with in Cornwall. The oldest east and west 

 copper lodes are traversed in like manner by contra 

 lodes, cross courses, cross flukans and slides, which, by 

 parity of reasoning, are posterior to them ; as more parti- 

 cular descriptions will be given of copper lodes in another 

 portion of this work, the subject will be deferred for the 

 present. 



Contra copper lodes form the fourth relative epoch, 

 as they have never been found traversed by the other 

 older lodes. They are traversed, however, by cross 

 courses, cross flukans and slides. 



The fifth class includes cross courses ; these veins are 

 sometimes composed wholly of quartz, but they usually 

 contain, besides quartz, a large portion of flukan, and in 

 some cases the quartz appears on one side of the vein^ 

 and the flukan on the other : when this is the case, the 

 flukan is most probably the oldest. The average width of 

 cross courses is at least 6 feet ; they have been met with as 

 wide as 30 feet. Their direction is sometimes north and 

 south, sometimes west of south and east of north, seldom 

 exceeding 20° on either side. 



These veins are sometimes the cause of incalculable 



