REVIEWS 443 



x\dirondack region. He concludes that the rock previously called 

 gabbro by Nason, Van Hise, Williams, and himself, south of the belt 

 of limestone in the Diana-Pitcairn area in Lewis and St. Lawrence 

 counties, is an augite syenite of igneous origin, although it passes into 

 a hornblende-gneiss which is unquestionably a result of dynamic action. 

 The origin of other gneisses has been inferred to be igneous from their 

 similarity to this gneiss which has been particularly studied, and it is 

 evidence of this kind which serves as a basis for Smyth's conclusions, 

 previously published,' that some of the gneisses on the western 

 Adirondacks are certainly, and most of them probably, of igneous 

 origin. 



With the view of exploring the central and little known portion of 

 the Adirondacks, a reconnaissance was made through the area contigu- 

 ous to the Fulton chain of lakes and Raquette Lake in the counties of 

 Hamilton and Herkimer. It was found that the heart of the Adiron- 

 dacks is made up essentially of gneiss, with minor quantities of crystal- 

 line limestone and its associated sedimentary gneisses and schists. 

 This is precisely analogous to what was found by the writer in St. 

 Lawrence, Jefferson, Northern Lewis, and southwestern Hamilton 

 counties, and by Kemp and Gushing in the eastern Adirondacks. 

 These facts lead to the conclusion that the Adirondack region, instead 

 of consisting of a great central mass of gabbro, surrounded by a nar- 

 row fringe of gneisses and limestones with quaquaversal dip, is essen- 

 tially composed of gneisses, with numerous limestone belts, having 

 northeast strike, and northward dip, and cut through on the east by 

 immense intrusions of gabbro. It is still possible, of course, that some 

 areas of gabbro may be found in the unexplored portions of the west- 

 ern half, but even should this be so, it would not materially modify the 

 above conclusion, as such masses must necessarily be isolated intru- 

 sions of no great extent, rather than parts of a large area. 



Kemp,^ in connection with the description of the magnetite 

 deposits of the Adirondacks, briefly describes the general features of 

 the geology of the gabbro and gneiss of Westport, Elizabethtown, and 

 Newcomb townships in Essex county, New York, and presents a geo- 

 logical map of the former two townships. 



'See Summary JouR. Geol., Vol. VII, p. 406. 



^ The Titaniferous Iron Ores of the Adirondacks, by J. F. Kemp : Nineteenth Ann. 

 Rept. U. S. Geo!. Surv., 1897-8, Pt. Ill, 1899, pp. 397-399. 



