REVIEWS 911 



Hills ' describes the geology of the Walsenburg Folio of 

 Colorado. 



The principal mass of the Greenhorn Mountains consists of 

 coarse and fine-grained granites and gneisses, hornblende, mica, 

 and chlorite-schist,and subordinate masses of garnet-and epidote- 

 schist, and occasional vein-like bodies of coarse pegmatite. The 

 schistose rocks are more prominent at the southern extremity of 

 the mountains than elsewhere, while the granite and gneissic 

 rocks are more prominent in the main mass toward the culmi- 

 nating point. 



Their origin probably dates back to the Archean period. 

 No further correlation is attempted. 



Watson 2 describes the granitic rocks of the Piedmont 

 Plateau of Georgia and concludes that they were not all con- 

 temporaneous in origin. Some of them are pre-Cambrian, while 

 others may possibly be later in age. However, the youngest 

 acid intrusives could not have been later than, if as late as, the 

 last great Appalachian disturbance or uplift. 



Kemp, Newland and Hill 3 further discuss the geology of 

 Hamilton, Warren and Washington counties, extending the 

 observations noted in previous reports to the west and south. 4 

 The additional points of interest are the occurrence of anortho- 

 sites in Johnsburg, in Warren county, the southernmost exposure 

 yet known in the eastern mountains, and "the increasing 

 certainty of the existence of sedimentary gneisses in Fort Ann 

 and Johnsburg townships." 



1 " Walsenburg Folio, Colorado," by R. C. Hills, Geo/. Atlas of the U. S., No. 

 68, 1900. 



2 " The Granitic Rocks of Georgia and their Relationships," by Thomas Leonard 

 Watson, American Geologist, Vol. XXVII, 1901, pp. 199-225. 



3 "Preliminary Report on the Geology of Hamilton, Warren and Washington 

 Counties," by J. F. Kemp, D. H. Newland, and B. F. Hill, Eighteenth Ann. Rept. 

 State Geologist of New York, published in Fifty -second Rept. N. Y. State Museum, Vol. 

 II, 1900, pp. 141-62; with geological maps. 



4 For general discussion of classification of geology of these counties see Rept. of 

 the New York Stale Geologist for 1897, published in Fifty -first Ann. Rept. New York 

 State Museum, Vol. II, 1899, pp. 499-553- Summarized, Jour. Geol., Vol. IX, 1901, 

 p. 444. 



