364 SCIENTIFIC NEWS. 



Geological *^s '^^ost promising symptoms, for all of them at times are 

 Society. found to mislead. The following, however, are those, in favour 



of which he is more especially prepossessed. All gosany lodes 

 in general ; the early discovery of pyrites with portions of yel- 

 low copper ore, also of blende and of gelina .; and the cutting 

 a good course of water, especially if it be warm. 

 The discovery of veins is effected in various ways. 

 The ancient method of shodiiig or tracing up water-courses, 

 when pieces of ore are found to occur among the rolled stones 

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

 method is to work drifts across the country from north to 

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

 sure to be cut through. Veins are often found in driving 

 adits and levels for the working of known lodes ; and not unr 

 frequently are stumbled upon by mere accident in digging 

 ditches and foundations for walls. . 



-Decemler 18. 



The president in the chair. 



The continuation of Mr. Phillips'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 gene- 

 rally by far the largest portion, are technically called deads, and 

 are left in the vein both to avoid the unnecessary expence of 

 raising them to the surface, and for the very important purpose 

 of preventing the two walls of the vein from collaping, and 

 thus destroying the works : in addition to the deads, strong 

 pieces of timber are frequently made use of. Sometimes large 

 wedged-shaped fragments of rock, called by the miner horses, 

 occur in the vein, partially cutting off the regular contents of 

 lode, though seldom, if ever, entirely obstructing it. Veins 

 of copper ore are, however, particularly liable to capricious and 

 total obstructions, without any obvious cause. In propor- 

 tion as the rock becomes hp-der, the vein always becomes more 

 narrow. 



One of the first objects in opening a new mine, is to drive an 

 adii or horizontal gulley 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. 



