LEAD AND ZINC DEPOSITS, ETC. 615 



as positive evidence in Missouri, he states that while the deposits 

 away from the granite and porphyry "islands" of southeastern 

 Missouri consist chiefly of lead and zinc ores, "other metals, 

 such as copper, cobalt and nickel occur as the Afchean founda- 

 tion rocks are approached." This circumstance, he states, is 

 "an indication that the source of the lead deposits also is to be 

 sought in depth." Whatever may be the value of this "indica- 

 tion," the facts, as stated, do not hold generally, in the opinion 

 of the writer. Professor Posepny reasons, presumably, from 

 observations made at Mine La Motte, where such conditions 

 exist. At other places, however, these changes in composition 

 are not observed as the crystalline rocks are approached. At 

 Bonne Terre copper pyrite was found in the old tipper workings 

 containing about four per cent, of nickel and cobalt. It does 

 not characterize the deeper ores. At Doe Run, a mine recently 

 opened, work is prosecuted along the old water-worn pre-Cam- 

 brian surface of the. Archean granites, amid the very conglomer- 

 ate boulders, and very little copper pyrite with cobalt and nickel 

 is found. Again, at other localities in St. Genevieve, Franklin, 

 Crawford and other counties, copper ores occur remote from any 

 granite or porphyry outcrops, and well above the basal beds of 

 the Cambrian. 



In the way of negative evidence, our author, in considering 

 the Wisconsin deposits, seems to think the absence of ores in 

 the great thicknesses of limestones and sandstones which under- 

 lie the productive horizons a by no means conclusive fact as 

 opposed to their deep-seated source, and suggests that the solu- 

 tion may have come up through a passage not yet exposed, and 

 even that fault fissures and eruptive dikes exist which have not 

 been discovered. From the fact that he refers in this connection 

 only to Whitney's report of 1862, we conclude that he has not 

 had access to the later and more exhaustive works of Strong and 

 Chamberlin. Perhaps, with the full light conveyed by these 

 reports and accompanying maps, Professor Posepny might have 

 attached more importance to the objections raised. It is difficult 

 to conceive how such a passage for the solutions as he suggests 



