GEOLOGICAI: EXPLORATlO>»'S AXD LITEEATUEE. 83 



Thi? paper, as the title indicates, is merely preliininarv to a general 

 stady of the pre-Keweeuawan formations of the lake Superior countrv. 

 recently begun by the writer. It gives a general outline re^new of what 

 was known with regard to these formations at the time of the beginning of 

 the investigation, and also of the new material gathered to the date of the 

 paper by the author and his assistants. Although the Penokee series is 

 .several times referred to in this publication, there is nothing that needs 

 especially to be quoted here. 



Weight (Charles E. . TUe Ajrogebie Iron Range. In ilineral Re.soarces of 

 ^lichigjin, 1885. by Charles D. Lawton, Coiiimis*ioner of Mineral Stati-stics. Lan.sing. 

 1S86. pp. 131-147. 



The late Mr. Wright gives a brief accomit of the historv* of exploration 

 in the range and a detailed .statement as to the amount of development at 

 each of the mining properties at the end of the year 1885. For the most 

 part these details have little geological intere.st, but the irregular character 

 of the ore-bo<iies and their a.s,sociation with the soap r<>ck and the mider- 

 l\-ing quartzite are brought out. The onlv general jmints mentioned are 

 given bv the following quotations: 



In 1879 F. H. Brotherton. Estj.. and party Itwated. for the Canal Company, very 

 closely, the Huronian belt acnxss ranges 44, 4-5. 4»J. and 47. T. 47, and the ore vein 

 within this belt: in fact all the discoveries of iron ore made in the above towns are 

 within a hundred feet or so of the line determined by Mr. Brothertou. (P. 1-31.) 



Speaking of the A.shland mine, he savs: 



The quartzite on the foot wall -side is in places more like a hard-pressed sand 

 bank, caused appsirently from the decomjiositiou i»f the matrix or cementing material 

 of the quartzite. This is not to be wondered at. as the water forcing its way down- 

 ward naturally follows the junction of the strata, fissures, and joints, dissolving a 

 portion of the mineral ingredients of the rocks it traverses and again replacing it 

 with others. It is highly probable that the parity of .some of the soft hematites 

 is due to this very pmc-ess, as has been noted in previous nnmb&rs of this report 

 Many of the soft-ore veins were origiDally. no donbt. veiy .siliceous, but •• alkaline" 

 water filtering through them under pressure, esjiecially if by any means they had 

 liecome broken or shattered, would in time carry away the silica in .solution and leave 

 the iron oxide and other bailee: >>ehind. 



