LEAD AND ZINC DEPOSITS, ETC. 619 



precious metals in the Missouri ores is a fact which further weak- 

 ens the force of any analogy which may exist between their con- 

 ditions of deposition and those of the Rocky Mountain ores. 

 How are the objections raised by Whitney and Chamberlin, dis- 

 cussed in a previous paragraph, to be met ; such as the facts that 

 faults are practically absent from the region ; that there is little 

 ore in the underlying Lower Magnesian beds and none in the 

 Potsdam and St. Peter's sandstones ; that no deep and continuous 

 crevices like true fissures are found ; that no hydrostatic cause is 

 assigned for the ascension of the solutions from great depths. 

 How could the ores be carried across such thick pervious and 

 water-soaked strata as those of the Potsdam and St. Peter's 

 formations ? 



The generally accepted facts that the deeper-seated rocks are 

 richer in metallic constituents ; that subterranean waters are of 

 high temperature and under great pressure, and consequently 

 are powerful solvents ; that the relief of pressure and the diminu- 

 tion of temperature accompanying the ascent of such solutions 

 supply an abundant cause for the deposition of their metallic 

 burdens, are all good and enticing general reasons in favor of the 

 adoption of the theory of a deep source for all of our metalliferous 

 deposits. Yet, on the other hand, we must recognize that some of 

 our ores, notably those of iron and manganese, cannot be assigned 

 such an origin. Why is it not possible, on general grounds, that 

 other ores should be gathered as are those of these two metals ? In 

 reply, it is manifest that we cannot rely entirely upon such gen- 

 eral principles, as they are at present understood ; but must resort 

 to specific facts in connection with special cases. Few definite 

 facts relating to this Mississippian area have been adduced in these 

 recent papers which can stand as new reasons for believing in the 

 deep origin of the ores, an explanation long since offered by 

 Owen and Percival. Neither have we attempted to introduce 

 positive demonstration in opposition to it. The question seems 

 to be very much in statu quo, and, so long as it so remains, the 

 old objections hold good and must be done away with before a 

 change of opinion is warrantable. Arthur Winslow. 



