327 



ON THE ORIGIN AND DEVELOPMENT OF ORE DEPOSITS IN 

 THE WEST OF ENGLAND. 



Bt J. H. COLLINS, F.G.S. 



Chap. III. — Eock Change as concerned in the Formation 

 OF Ore Deposits.* 

 Sec. 9. — Surface tension and electricity. 



The effects of surface tension in assisting the underground 

 circulation, and, aided by outwardly impelled currents, in making 

 it universal, have already been considered. Its influence as a 

 depositing agent has also been touched upon — we have now to 

 consider it a little more in detail. 



That the actual circulation through fissures will be greatly 

 affected by the size of such fissures is obvious, for very narrow 

 openings will be liable to speedy closure from the deposition of 

 suspended matters, and very wide ones will favour deposition 

 owing to the check of the current, while those of intermediate 

 size wiU often be kept open by its fiow. But in very narrow 

 openings the chemical precipitation will often be very different, 

 owing to the existence of what is known as capillarity, due to 

 surface tension. Mr. E. Hunt, while not doubting the existence 

 and potency of electric currents in veins, yet considered that 

 surface tension was often the immediately effective agent in the 

 formation of ore deposits ; and M. Becquerel was of the same 

 opinion.! 



The mechanical effects of surface tension under ordinary 

 circumstances are marked when considerable masses of matter 

 are concerned. But as the masses are reduced, the acting 

 surfaces are not reduced in equal proportion, so that finally 

 phenomena which are apparently inconsistent with the action 

 of gravity, and which are really independent of it, become 

 evident. Thus a very small quantity of water when poured out 

 on a fiat surface forms itself into a sphere under the infiuence of 



* Continued from the Journal B.I.C., No. 38, p. 184, 



t See " a contribution to the history of Mineral Veins," Trans. Bo]/. Geol. 

 Soc. Corn., ix, 23. 



