58 THE PENOKEE IRON BEARING SERIES. 



but wlien cxiiiiiinert in detail, and in places where the relations can be seen, they 

 prove to be ernptive (pp. Gfi-6S). 



(2) As to iin unconformity between the so-called Laurentian and 

 Hnronian, referring to my statement as to this relation in Geology of Wis- 

 consin — 



He- states that a perfect case of nonconformability exists at "Penoka gap," 

 Wisconsin, to which we have before referred; but, if we remember correctly Mr. 

 Wright's personal statement to us, neither was the junction seen nor the kind of 

 junction known that the two made with each other. It is too fast to assume, as has 

 been done by Messrs. Brooks, Irving, and Wright, that the strike and dip of a foliated 

 rock is the strike and dip of its stratification. This is especially the case when the 

 view that they were ever stratified is still a disputed point (p. 25). 



We have heretofore seen that the view that the " Huronian " unconformably over- 

 lies the "Laurentian" has been only supported by the fact that the foliation of the 

 latter did not conform in its dip to the lamination of the former. This proof is of no 

 value unless it can be shown that both rocks are stratified and in situ. That the 

 latter is not so, we have seen in numerous localities. Heretofore the two systems 

 have not been observed in contact, but recently statements have been published that 

 their junctions have been seen in other regions.' The statement is made that Itoth 

 rocks are stratified, but no proof is adduced to show on what the conclusion is founded, 

 and although the contacts were said to show beautifully, nothing was published indi- 

 cating that the kind aud manner of the junction was observed. It would seem that 

 even here the decision coucerning the unconformability was based on the tbliatiou 

 only (p. 70). 



Irving. (R. D.). The Mineral Resources of Wisconsin, Trans. Am. Inst. Min. 

 Eng., vol. VIII, 1880, pp. 487-508, accompanied by a geological map of Wisconsin, and 

 adjoining portions of Michigan, Minnesota, Iowa, and Illinois. 



As the title indicates, the object of this paper is to give an account of 

 the mineral resources of Wisconsin, as developed to date. Prefacing this, 

 however, is given an outline account of the geological structure of the 

 state. In this are included a number of references to the Penokee district, 

 but nothing is given of interest in the present connection that is not included 

 in vol. Ill of the Geology of Wisconsin, already referred to at length. 



Wright (C. E.). Annual Report of the Commissioner of Mineral Statistics of 

 the State of Michigan for 1880. Lansing, 1881. 



'Geol. of Wis., vol. iii, 1880, pp. 98, 108, 117. 



