Page:The Journal of geology (IA journalofgeology11893univers).pdf/188

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 Congress, 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 belonging 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 description and discussion of ore deposits in general, in which he advocates their deep-seated origin through the medium of hot solutions 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 concentration 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 acceptance. Thus,