MICHIGAN AND WISCONSIN. 495 



careful examination of the literature showed that there was no published 

 evidence of more than a superficial study of the relations of the ore to 

 the associated schists ; but all was based on theoretical views. Now 

 the examination described previously was made for the express purpose 

 of determining the relations of the ores and schists, without regard to 

 any one's views. It showed that — wherever their relations could be 

 determined — they were those of an eruptive rock in contact with a 

 sedimentary one. These things were described and figured, and no one 

 has yet attempted to meet the evidence, either to deny it or explain it 

 away. 



Two other attempts to discredit this view, besides that of Dana, were 

 made. One was by Prof. J. S. Newberry, who, being evidently unable to 

 meet the evidence given, contented himself by remarking that "to be 

 asked to believe that the ore sheets are intrusive is a greater strain 

 upon my credulity than it can endure." In other words, he takes espe- 

 cial pains to show that scientific questions are with him merely a matter 

 of theoretic belief, and not one of evidence and facts. ("The Genesis 

 of our Iron Ores," School of Mines Quarterly, Nov., 1880, p. 8.) 



The second attempt was made by Dr. A. A. Julien, who likewise 

 ignored the evidence, and confined himself to saying, " The mineralogical 

 constitution and infusibility of these ores, their distinctly sedimentary 

 lamination, etc., clearly testify to the unsoundness of these hypotheses." 

 (Proc. Phila. Acad. Nat. Sci., 1883, pp. 335-346 ; Trans. N. Y. Acad. 

 Sci., 1882, II., pp. 6-8, 13-17.) If these ores are regarded as an extru- 

 sion from the molten interior of the earth, their mineralogical constitu- 

 tion and infusibility have no bearing upon the question ; but, on the 

 other hand, if they are of sedimentary origin Dr. Julien must explain 

 how it was that later they became plastic, so as to become intrusive, as 

 they plainly are. That they are distinctly sedimentary in their lamina- 

 tion, or that the jaspilite is a fine silicious sand, we deny. Messrs. Ju- 

 lien and Newberry both show in their writings that they have not made 

 themselves acquainted with the mode of occurrence of the Marquette 

 iron ore, either by observations in the field, or by study of the published 

 descriptions. Dr. Julien's paper is especially replete with errors. 



Passing now to the Azoic rocks of Wisconsin we find that in 1876 

 Mr. E. T. Sweet pointed out a supposed unconformability between the 

 Laurentian and Huronian at Penokee Gap, stating (Trans. "Wise. Acad., 

 1875-76, III., pp. 43-44) : — 



"When, the railroad cut is completed at this locality, the absolute junction 

 of Laurentian and overlying Huronian will doubtless be exposed. There can 



