618 THE JOURNAL OF GEOLOGY. 



which minute quantities of substances disseminated through vast 

 volumes of rock may be brought together. 



In evidence of the post-Carboniferous age of the deposits 

 the statement occurs several times in Dr. Jenney's paper, that the 

 ores occur in the Coal Measures. This, we think, should be 

 made with limitations. They are found in shales of that age in 

 Jasper county, and at a few other localities, but these shales are 

 in isolated patches, which occupy depressions in the older ore- 

 bearing Mississippian rocks. The metallic contents of the coal 

 may, hence, be derived, by some secondary process of transfer, 

 from adjacent ore bodies. In any case, the Coal Measures in the 

 state, as a whole, are practically destitute of these ores, and they 

 can thus hardly be stated to occur in that formation, whether 

 their absence be due to their prior formation or to limitations in 

 their distribution determined by physical causes. 



Dr. Jenney seeks further to find support for the hypothesis of 

 the deep-seated origin of the ores through analogy, in stratigraphy 

 and geologic history, with regions of the far West. This attempt 

 does not seem, in our judgment, to be successful. The last pro- 

 nounced regional disturbance of both the Ouachita and Ozark 

 uplifts was immediately after the Coal Measure, period. In 

 Arkansas this was accompanied by great flexing of the strata. 

 There is no evidence in the Ozark uplift of any intense disturb- 

 ance of post-Cretaceous date, or of the presence, even at great 

 depths, of flows of such igneous rocks as accompanied the uplift 

 and preceded the ore formation of the Rocky Mountains. As 

 already expressed, the Missouri ores cannot be properly con- 

 sidered to occur in the Coal Measures of the state. Did such a 

 profound Assuring take place in post-Cretaceous times as Dr. 

 Jenney's hypothesis requires, we should expect to find it extend- 

 ing into the body of the Coal Measures, accompanied by the ores. 

 At least faulting or other such exhibition of disturbance would 

 be found, which phenomena do not characterize these rocks. 



Over and above these considerations affecting the quality 

 of the support of this theory, there still remain the positive 

 obstacles to be disposed of. The almost entire absence of the 



