GE()LO(ilCAL EXPLORATIONS AND LITERATURE— 1884. 99 



Whitney, J. D., aud Wadsworth, M. E. The Azoic system and its projwsed 

 subdivisions. Bull. Mus. Ooiiip. Zool. Harvard Coll., Geol. Ser., Vol. I, 1884, pages 

 xvi and 331-5G5. 



Ill tliis artirle Whitney and Wadsworth review all the literatim^ relat- 

 ing to Foster and Whitney's Azoic system, and eonchide that no basis 

 exists for its subdivision. The "diorites" of the 31ar([uette district are 

 again asserted to be eruptive, as are also the iron ores and jaspilites of the 

 area. "The only evidence that the Wisconsin geologists have that the 

 Laurentian and Huronian ai-e what they ])urport to be is lithological, and 

 thev liave advanced no sound argument showing that tliev form distinct 

 ages in the Azoic system" (p. 4!I7). 



JULIEN, A. A. Genesis of the crystalline iron ores. Eng. and Min. .Tour., 

 Vol. XXVII, February 2, 1884, pages 81-83. 



The author maintains the sedimentary origin of the jasper ores of the 

 Marquette region. lie ad^■ances the view that they were originallv frao-- 

 mental rather than chemical sediments. The ores are supposed to liave 

 been washed as fragments from preexisting- rocks, and to have l)ecome 

 mixed with other similarly 'derived detritus. Their present condition is 

 thouglit to be due to metamorphism. 



Smock, .John C. Geological distribution of the iron ores of the eastern 

 United States. Eng. and Min. Jour., Vol. XXXVII, January-June, 1884, pages 

 217-218 and 230-232. 



Smock, ill his geological classitication of the important iron-ore deposits 

 of the country, places the magnetite and hematite of the Marquette district 

 iu the "Huronian period." 



Wadsworth, M. E. Litliological studies. Memoirs Mus. Comp. Zool. Harvard 

 Coll., Vol. XI, Part I, Cambridge, 1884, pages 13(5-139, 7 plates. 



Ill his chissitication of the basic terrestrial and meteori(r rocks the 

 author describes thin sections of the Presque Isle and Ishpeming serpentines. 



