458 Philosophical Society of London. 



pass freely from schist into granite, and back again to 

 schist, without any deterioration. The texture and hard- 

 ness of both rocks is liable to considerable variation, af- 

 fecting of course the profit and progress of the miner often 

 in a very remarkable degree. Tv/o shafts of Huel Alfred 

 were sunk in schist, and the cost of the one did not exceed 

 51. per fathom, while that of the other amounted to 551, 

 for the same length. 



The nietalliterous or east and west veins are crossed by 

 others, the direction of which is nearly north and south. 

 These latter are called cross courses, and rarelv produce 

 copper or tin, or any other metallic substances. The prin- 

 cipal practical advantage derived from these veins, especially 

 when consisting of clay, is, that they oppose an effectual 

 obstacle to the passage of water, and therefore the miners 

 do not willingly pierce them without some adequate object 

 in view. The disadvantage of them is, that they not only 

 interrupt the course of the metalliferous veins, heaving them 

 from a few inches to several fathoms, but not unfrequently 

 totally impoverish them, so that a long and costly search 

 after the heaved part of a vein often terminates in the mor- 

 tifying discovery that it is not worth pursuing, as was 

 strikingly exemplified in the corresponding veins of Huel 

 Jewel and Tol Cam. 



There is another species of vein called a contre or 

 caunter, the direction of which is for the most part N. E, 

 and S. W. — These are njoslly if not always metalliferous, 

 a;id often remarkably rich ; of which the mines of Huel 

 Alfred and Herland have afforded most splendid instances. 



PHILOSOPHICAL SOCIEXy OF LONDON. 



The attention of the Society during this month has been 

 directed to the subject of Hearino;, by a Lecture on the 

 Anatomy and Physiolooy of the Organ of Hearing in Man 

 and other Animals, by Mr. T. .1. Pettigrew. 



The lecture commenced by observing the difRcultv of 

 treating anatomical and physiological subjects in a suffi- 

 ciently popular manner to interest a seneral audience, and 

 bv professing an endeavour to divest it of technical phrases 

 as much as possible. 



The lecturer was aware that in many instances, in so 

 complicated an organ a> the ear, it was utterly impossible 

 lo avoid the use of the technical terms but in those he 

 endeavoured to explain, f'or the difficulty was exceedingly 

 gj-tat, when we consider that ihey are derived not only 



from 



