Mr. William Phillips on the Veins of Cornwall. 131 



which it joins the vein to the extremity in the valley. This may 

 perhaps be the case with some, but the practice is not uniform. 

 By making them on an inclined plane, a freer current would be 

 given to the water, yet much of their benefit would be lost, even 

 although their declination were not to exceed one inch in a fathom. 

 For, in supposing this plan to have been pursued in the driving of 

 the deep adit above mentioned, which, from its extremity to North 

 Downs mine, is about four miles or 3520 fathoms long, it will be 

 obvious that if a declination of one inch in a fathom be allowed, 

 the elevation of the adit at North Downs mine would be about 

 300 feet above its extremity ; an elevation nearly if not quite 

 equal to that of the surface of the mine. If therefore in the 

 driving of an adit any allowance be made for the current of water 

 it may be presumed that the interest of the miner will induce him 

 to make it as small as possible. 



Country, 



Veins containing copper, as well as those containing tin are found 

 both in granite and in schist, though until within the last 50 years, 

 it was esteemed in Cornwall a hopeless expectation to find a vein 

 containing copper in the former of these rocks. Experience has 

 however in many instances, in the parishes of Redruth and Gwen- 

 nap, as well as in some others, proved that veins of copper ore are 

 found in granite. In both of those parishes granite and schist have 

 in some mines been found to alternate ; this alternation has not, as 

 I conceive arisen from their stratification, but from the casual uneven- 

 ness of the first being supplied by a deposition of the second. It has, 

 I believe, been but rarely noticed that the course of a vein has been 

 along their junction; but some instances of this have certainly 



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