614 THE JOURNAL OF GEOLOGY. 



ably something over 650,000 tons, and of zinc ore only about 

 250,000 tons. 



With such facts in mind it is of interest to note that the 

 deposits to which they relate are the subjects of renewed study 

 at the present time, and the prospect of increased demands upon 

 them, above referred to, makes the revival of the discussions of 

 their origin and mode of deposition most timely. 



At the recent meeting of the American Institute of Mining 

 Engineers, held as part of the International Engineering Con- 

 gress, three papers were presented bearing, in whole or in 

 part, upon the ores of the Mississippi Valley, and another, on 

 the Bertha zinc mine of Virginia, described an ore body belong- 

 ing essentially to the same class. These papers were by Messrs. 

 F. Posepny 1 , W. P. Jenney 2 , S. F. Emmons 3 , W. P. Blake 4 , and 

 W. H. Case 5 , respectively. 



The first of these papers, by Professor Posepny, is a descrip- 

 tion and discussion of ore deposits in general, in which he advo- 

 cates their deep-seated origin through the medium of hot solu- 

 tions derived from great depths. The second paper, by Dr. 

 Jenney, is an exposition of his views concerning the origin of 

 the Mississippi Valley ores, derived from his recent studies in 

 the region. He repudiates the explanation of lateral concentra- 

 tion advocated by Whitney and Chamberlin, and reverts to the 

 old ideas of Owen and Percival, that the ores have come from 

 below, thus harmonizing with Posepny. The other three papers 

 are principally descriptive, though Mr. Emmons quotes Dr. 

 Jenney's conclusions as applied to the Mississippi Valley ores. 



Posepny's direct reference to the ores here discussed is brief. 

 He marshals few facts from the region itself in support of his 

 theory, but rather argues, in a negative way, that no great 

 obstacles exist there which would prevent its accceptance. Thus, 



1 The Genesis of Ore Deposits. 



2 The Lead and Zinc Deposits of the Mississippi Valley. 



5 Geological Distribution of the Useful Metals in the United States. 



4 The Mineral Deposits of Southwest Wisconsin. 



5 The Bertha Zinc Mine. 



