Geological Society. 457 



The experienced miner by no means implicitly relies on 

 even the must promising symptoms, for all of them at 

 times are found . to mislead ; the following, however, arc 

 those in fa-.-onr of which he is more especially prepossessed : 

 all gosssny lodes in general, the early discovery of pyrites 

 with portions of yellow copper ore, also of blende and of" 

 galena, aid t'.ie cnttinguf a good course of water, especially 

 if it he warm. 



The discovery of veins is effected in various ways : the 

 ancient mode of shoding or tracing up water courses, when 

 pieces of ore are found to occur among the rolled stones 

 in their channtio, is now rarely resorted to. The common 

 method is to work drifts across the country from north to. 

 souih, by which all veins in the district thus examined are 

 sure to be cut through. \'eins are often found in driving 

 adiis and levels for the working of known lodes : and not 

 nnfreqiiently are stumbled on by mere accident in digging 

 ditches and foundations of walls. 



December 18 — The President in the chair — the continu- 

 ation of Mr. Philips's paper on the veins of Cornwall was 

 read. 



The contents of a vein may be divided into those which 

 are valuable and those which are not so ; the latter, forming 

 generally by far the iaroest portion, are technically called 

 deads, and are left in the vein both to avoid the unnecessary 

 expense of raising them to the surface, and for the very 

 important purpose of preventing the two wails of the vein 

 from collapsing, and thus destroying the works : in addition 

 to the deads, sirong pieces of timber are frequently made 

 use of. Sometimes large wedge-shaped fragments of rock, 

 called by the miners horses, occur in the vein, partially 

 cutting off the regular contents of the lode, though seldom, 

 if ever, entirely obstructing it. Veins of copper ore are 

 however particularly liable to capricious and total obstruc- 

 tions without any obvious cause. In proportion as the rock 

 becomes harder, the vein always becomes more narrow. 



. One of the lirst objects in opening a new mine is to drive 

 an adit or Iwrizontal gallery from the lowest convenient 

 level, for the purpose of carrying off all the top water. One 

 adit often serves two or three mines : and there is one 

 (called the deep adit) which opens on one of the creeks of 

 Falmouth harbour, the entire subterranean length of which 

 is about 24 miles. 



Copper veins, which fifty years ago were considerc<l by 

 the Cornish miners to he peculiar to schist, liavc ol late 

 beed found in the parishes of Gwctmah nnd Kcdruih, to 



