1 1 8 Bulletin of Laboratones of Dcniso7i University. [Voi xii 



Canada/ by Bailey, Matthew, Ellis, and Bell In New Eng- 

 land* Wadsworth, Diller, Shaler, Bayley, G. O. Smith, H. S. 

 Williams, and Gregory have described similar areas in Massa- 

 chusetts and Maine. Other similar areas are well known in 

 Pennsylvania, Maryland, and Virginia through the investiga- 

 tions of G. H. Williams,^ Keith, ^ and Bascom.^ In the Lake 

 Superior region^ they have been long known through the con- 

 tributions principally of Irving, Van Hise, the Winchells, 

 Clements, Bayley, Wadsworth, Williams, and Grant. 



Through the studies of Clements and Brooks areas of 

 greenstone schists, similar to those of the Lake Superior region, 

 and derived from an original basic igneous rock of pre-Cam- 

 brian age, have been identified in the crystalline area of Ala- 

 bama.^ 



The rock types indicated in these areas vary from acid to 

 basic volcanics in composition, according to locality, and are 

 represented principally by such rocks as rhyolite, andesite, dia- 

 base, diorite, gabbro, and their associated tuff deposits. 



From the descriptions, the rocks of the Virgilina district 

 are closely similar in many essential features to the correspond- 

 ing altered phases of the Catoctin and South Mountain areas in 

 Virginia, Maryland, and Pennsylvania, and certain ones of the 

 famous greenstones from the Lake Superior region. When the 

 altered rocks, greenstones, of the various areas are traced by 



1 Ann. Report Canadian Geol. Survey, iS77-'S D D, 1879-S0 D, iSSg-'go F, 

 1S91. 



' Mus. Comp. Zool. Bull., Vol. V, p. 2S2 : ibid., Vol. VII, pp. 166-187, 

 1881 ; A. J. S., :886, Vol. .XXXII, p. 40 ; 8th Ann. Kept. U. S. G. S., pt. 2, 

 p. 1043; A. J. S., 1899, Vol. VIII, p. 359; Bull. No. 165, U. S. G. S., 1900, 

 212 pp. 



3 A. J. S., 1892, XLIV, 482-496; Jour. Geology, 1894, II, 1-31. 



*■ 14th Ann. Rept. U. S. G. S, 1894, pp. 285.395 ; Am. Geol., 1892, X, 365 ; 

 Bull. G. S. A., II, 156, 163. 



» Bull. No. 136, U. S. G. S., 124 pp. 



^ The literature is scattered through annual reports, monographs, and bul- 

 letins of the U. S. Geological Survey and the state reports of the surveys of 

 Minnesota, Wisconsin, and Michigan. 



' Geol. Survey of Alabama, Bulletin No. 5, 1896, pp. 84-96, 120-197. 



