126 British Association, 



that a small mass of matter were acted on and modified by fire, it 

 might present veins within it ; but still no theory is assigned why 

 these veins are so produced : here there is the action of fire, and con- 

 sequently, after being acted on, the phaenomenon may be regarded as 

 eflPected by igneous agency;— yet how can this explanation be ap- 

 plied to sedimentary rocks r — to say, therefore, contemporaneous 

 formation, is to use an unmeaning term. Suppose it may be ascri- 

 bed to molecular attraction, still the cause is wanting; and although 

 it might be of some avail in explaining the formation of globular 

 masses, yet it is of no use in the present case, as we have to do with 

 masses occurring in planes. In order to solve Mr. Henwood's ques- 

 tion, we must know the angles which the veins make with each other, 

 and also with the horizon, and the relative height of the strata on each 

 side of the lines of dislocation. Mr. Hopkins considered that Corn- 

 wall was an unfavourable countyfor explaining these phsenomena, as its 

 rocks were generally unstratified ; and he would ))refer a county like 

 Derbyshire, where the regularity of the stratification offered much fa- 

 cility in finding the necessary data. — Mr. De la Beche considered 

 Cornwall as perfectly suited for explaining these phaenomena on Mr. 

 Hopkins's theory. In this county there exists a fossiliferous system, 

 which has manifestly been upheaved by the granite, and is penetrated 

 by the same granite veins which traverse the primary rocks. — Mr. 

 Phillips said that we should not restrict the term contemporaneous, 

 the real point urged by the Cornish miners being, that there was 

 no displacement. Still we must seek for explanation in other di- 

 stricts. In these, the mechanical theory must be at once acknowledged 

 to be true, when we see the disturbance in fossiliferous rocks, in some 

 cases even in an intersection of their organic remains. But this 

 theory ought not only to explain the direct phaenomena, but must ac- 

 count for the exceptions ; and in such cases, as in Cornwall, we must 

 regard the structure of the rocks — their regular divisions and joints, 

 which are independent of stratification, — veins may even occur in 

 these divisions. In the north of England, the contents of veins are 

 found to vary according to the containing rocks ; and he considers 

 the circumstance of spar stuff occurring in the Cornish veins as not 

 opposed to the idea of mechanical force, but as dependent upon elec- 

 tric agency. — Mr. J. Taylor, jun. stated, that, in the course of his expe- 

 rience in practical mining, he had observed certain conditions neces- 

 sary for the profitable working of metals. In the oldest, or scar lime- 

 stone, he had observed that the miner was not remunerated ; but in 

 newer lead measures he had a better chance of success, as in grits 

 and shales. The best chance was in altered rocks. In Cardiganshire 

 he had observed a remarkable case in a slaty rock : where very schis- 

 tose, the workings were poor ; but where the rock was diced, as the 

 workmen call it, they were certain to be rich ; the strike of the altered 

 rock being N. and S.,and that of the veins E. and W. He had seen 

 remarkable proofs of the mechanical theory in North Carolina, espe- 

 cially in the rich veins of iron ore of that country. — Mr. Sedgwick 

 instanced the discussion now before the Section, as a proof of how 

 much one branch of science was assisted by another: we here saw 

 the application of Physics to Geology j he could record also the as- 



