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PROCEEDINGS OF THE WASHINGTON MEETING 



nomically and structurally, but in the history of geology. It is not necessary 

 to review the literature recently summarized in United States Geological 

 Society Monograph 52 and my own report on the Keweenaw series. I may, 

 however, recall the names of Jackson and Foster and Whitney, Agassiz, 

 Pumpelly and Wadsworth, Hubbard, Van Hise and Leith among those who 

 have written on it. Very recently an important paper on Limestone Moun- 

 tain, by Case and W. I. Robinson, 1 has appeared which has a bearing on the 

 subject, as does also the work of Thwaites in Wisconsin. 2 I have also occa- 

 sion to refer to the recent work of Allen and Barrett. 3 1 have left until the 

 last honoris causa the Monographic Bulletin 23, by Irving and Ohamberlin, 

 issued just 30. years ago. 1 It would be strange if 30 years of such active 

 progress in research as the past 30 had not produced more facts and fuller 



Figuke 1. — "Ideal Sketch of the primitive Keweenaw Fault" 

 As represented in figure 24, page 113, of Bulletin 23, U. S. Geological Survey 



light on the subject in a region which has been in the meantime the seat of 

 much diamond-drilling and study. 



In this paper I briefly compare three diagrams from Bulletin 23 with three 

 others more nearly in accord with the facts as I now know them. Figures 1, 

 3, and 5 are figures 24, 25, and 26 of Bulletin 23, not pretending to be sections, 

 but diagrams to explain the view of the authors. Figures 2, 4, and 6 are 

 equally diagrams, not sections, for it would be impossible to get Limestone 

 Mountain into a section with the Keweenaw fault on a sufficiently large scale. 

 The bases are the corresponding figures of the set 1, 3, and 5 modified to 



1 Journal of Geology, vol. xxiii, 1915, p. 256. 



2 Sandstones of the Wisconsin coast of Lake Superior, Belt No. 25 of Wis. Geol. and 

 N. H. Survey. 



3 Contributions to Precambrian geology. Mich. Geol. and Biol. Survey, Pub. 18, 1915. 



4 U. S. Geol. Survey Bull. 23. "Observations on the junction between the Eastern 

 sandstone and the Keweenaw series on Keweenaw Point, Lake Superior.. 



