104 THE VERMILION IRON-BEARING DISTRICT. 



of the same age, it is evident that great care must be taken in the use of the " Pewabic 

 quartzite" for correlation purjDoses. Several different rocks have been included 

 under this one title, hence the "Pewabic quartzite" as defined can not be relied 

 upon as marking a definite horizon in the succession of the geological formations in 

 northeastern Minnesota [pp. 208-209]. 



In an appendix Dr. Bayley states that the first two of the above 

 conchisions had been reached by W. M. Chauvenet a number of years 

 before, as the result of work done in the vicinity of Akeley Lake for the 

 Lake Superior division of the United States Geological Survey in 1883 and 

 1884. Dr. Bayley was not aware of Mr. Chauveuet's conclusions until 

 after his own had been arrived at, Mr Chauvenet's being contained in an 

 unpublished report submitted to Prof R. D. Irving (p. 209). 



WiNCHELL, N. H. The Kawishiwin agglomerate at Ely, Minn. : Am. Geologist, 

 Vol. IX, 1892, pp. 359-368. 



This article contains a description of a greenstone which is found in 

 the Keewatin of the Vermihon district of Minnesota and which possesses a 

 peculiar structure. 



On clean exposures the greenstone is seen to be not homogeneously 

 massive, but to be composed of irregularly rounded to oval bodies of mas- 

 sive greenstone ranging from 6 to 16 inches in diameter, surrounded by 

 and separated from each other by relatively narrow masses of fine-grained 

 chloritic schist, which winds about among the masses, its schistosity coin- 

 ciding with the surfaces with which it is in contact. The peripheries of these 

 massive bodies are all amygdaloidal, the long direction of the pores being 

 perpendicular to the surface of the round body. 



The author explains the rock as an agglomerate, the rounded bodies 

 being bombs that were hurled into the air by volcanic forces and fell into a 

 hot ocean, in which was being deposited a fine volcanic mud which now 

 forms the fine schist between the bombs. In other words, "The source of 

 such rocks was igneous, but their structure is aqueous" (p. 367). 



Van Hise, C. R. Correlation papers, Archean and Algonkian: Bull. U. S. 

 Geol. Survey No. 86, 1892, pp. 51-208, map, PI. Ill, op. p.. 52, and pp. -±40-529. 



This bulletin, on the pages indicated, contains a thorough digest of the 

 various articles that had appeared concerning the Lake Superior pre-Cam- 

 brian geology prior to the time of its publication. The author's interpretation 

 of the structure and stratigraphy of the various regions is based upon his 



