RESUME OF LITERATURE. 117 



little or none of an original fragmental structure, while in the other the fragmental 

 texture is still distinct and the alteration has progressed to a smaller degree." He 

 then adds " that the supposed older one of the two groups of schists in the Vermilion 

 Lake belt is intricatelj' penetrated by the granites of the great areas north and south 

 of the belt."" Hence areas of Archean lie north and south of these older schists. 



It is clear that Professor Hall believes in the presence of Archean rocks 

 in the Vermilion district, although the careful reader Avill see that Professor 

 Hall's conclusion as to their occurrence there does not follow from his defini- 

 tion of Archean as reported here and from the quotation from Professor 

 Irving's report. 



WiNCHELL, N. H., Gkant, U. S., and Elftman, A. H. Twenty-fourth Annual 

 Report Geol. and Nat. Hist. Survey of Minnesota for years 1895-1898, 1899. 



In this annual report, which it is stated is the final one, there are pub- 

 lished the lists of rock specimens, with annotations, collected by N. H. 

 Winchell in 1896, 1897, 1898; a record of the field work of U. S. Grant, 

 1892-1898, and a list of specimens collected by him in 1898; also a list of 

 specimens collected by A. H. Elftman in 1895, 1896, 1897. 



In these we find statements concerning the Vermilion district, but the 

 material is not digested, and no general conclusions are stated. Conse- 

 quently it is impracticable to review the report and show its actual contents. 



Winchell, N. H., et al. The geology of Minnesota, by N. H. Winchell, U. S. 

 Grant, James E. Todd, Warren Upham, and H. V. Winchell: Final Report Geol. 

 and Nat. Hist. Survey of Minn., Vol IV, 1899, pp. 630. With 31 geologic plates. 



Structural geology of Minnesota, by N. H. Winchell: Final Report Geol. and 

 Nat. Hist. Survey of Minn., Vol. V, 1900, pp. 1-80, 972-1000. 



The first of these volumes contains an account of detailed field work 

 in northeastern Minnesota, with incidental discussion of general problems. 

 The area is treated by counties and smaller arbitrary geographic 

 divisions, in the description of which several men have taken part. This 

 manner of treatment leads to repetition in the discussion of the general 

 geologic features, and in many cases it is extremely difficult to correlate 

 the facts recorded in the diff"erent sections. 



Volume V contains an account of the general structural geology of 

 the State, by Professor Winchell, based on the detailed work described in 



« Seventh Ann. Kept. U. S. Geol. Survey, p. 437. 



