LEAD AND ZINC DEPOSITS, ETC. 617 



feet wide has been mined out of such diffused ore. The crevices 

 which traverse this ore body are frequently almost blind, and can 

 only be detected by the drip of roof water. These are such as 

 occur in almost any massive rock. Further, one of the most 

 important faults in this region, which traverses the country about 

 two miles north of Mine La Motte, with an apparent throw of 

 300 feet, is entirely unaccompanied by ore, though the adjacent 

 ground has been prospected with the diamond drill. Again, not 

 a single instance can be recalled by the writer, in those mines 

 which work to the very contact with the underlying granite, 

 where faulting crevices extend down into that rock. They pos- 

 sibly do so extend in some instances, but there is no positive 

 evidence adduceable that they then continue ore bearing. Apart 

 from this, however, the association of ore and crevices, of course, 

 does not denote by any means a deep-seated source for the ore. 

 Such crevices generally act both as channels controlling their 

 distribution, and as receptacles for their accumulation whatever 

 the source of the ores. Hence, a disturbed and creviced region, 

 which is in other respects adapted to the reception of ores, will 

 be their most natural habitat. Therefore the explanation of the 

 localization of the deposits based upon such conditions is equally 

 consistent with any of the common theories of ore derivation. 

 The same, it would seem, can be said concerning the observed 

 paragenesis of the minerals and the growth of crystals, in which 

 Dr. Jenney sees additional foundation for his conclusions. If 

 we accept the broader idea of lateral secretion, which does not 

 demand that a mineral shall be derived from the very rock to 

 which it is attached, but recognizes abundant flow along crevices 

 and through porous strata and a consequent free transfer of solu- 

 tions from place to place, all the phenomena find at least an 

 equally ready explanation. It is argued further, in this paper, 

 as against the lateral secretion theory, that the metallic contents 

 of the country rocks are insufficient to have supplied the ore 

 bodies. The grounds for this statement are only suggested ; but, 

 to the best of our knowledge, the fact yet remains to be proven. 

 Due allowance is not made for the many and various ways in 



