PREVIOUS INVESTIGATIONS. 243 



entirely of anorthosite, but a twelve-mile radius describing a circle from 

 Marcy as a center would cut at least two limestone areas — one northeast 

 and the other southwest — while beyond them, in every direction, both 

 gneisses and limestone occur in abundance ))r()ken up into small, elon- 

 gated areas by outliers of the anorthosites. Thus while the intrusions 

 of these rocks of the gabbro family had perhaps their greatest develop- 

 ment near mount Marcy, they really form great northeast-and-southwest 

 ridges, parallel in this respect to the general trend of the Appalachians, 

 and j)erhaps coincident with one of the earliest developments of this line 

 of upheaval. 



Previous and contemporaneous Work in the Region. 



The crystalline limestones and their associated schistose rocks in the 

 eastern Adirondacks have stimulated great interest in those who have 

 studied them since 1822, in which year A. K. Jessup read before the 

 Philadelphia Academy a brief account of his own observations and those 

 made by Dr William Meade in 1810 on lake Champlain. 



The limestones are found on all sides of the mountains, as will be 

 shown later in the review of the records, but on account of the general 

 northeasterly trend of the ridges they may be spoken of in a broad way as 

 the east and the west areas. Hitherto attention has been directed chiefly 

 to the east side, because it is the more accessible; but from the west side, 

 although it is a vast tract of wilderness and fringing settlements, no less 

 interesting results will be obtained, and from it we already have most 

 important observations through the work of C. H. Smyth, Jr. The 

 limestones are less disturbed, apparently thicker, and associated with 

 underlying gneisses in areas remote from the Norian intrusions. 



Ebenezer Ennnons,-'^ in his first work for the New York survey, 1837- 

 1842, was greatly impressed by the limestones of the east side, and the 

 conclusions which he reached regarding their " igneous " character, and 

 in which he was supported by W. W. Mather,t are familiar to all students 

 of geology. 



Beginning with field-work under Emmons in 1837, the attention of 

 our honored past-president, James Hall, was likewise attracted to the 

 limestones, and culminated in 1876 in a paper read before the American 

 Association for the Advancement of Science, but never i)rinted, except 

 as a brief abstract. In this i)aper Professor Hall expressed the belief 

 that they re])resent a great formation older than the Potsdam and later 

 than the Laurentian.J 



•Report on the Second District, 1842, Primitive Liniestoiio of Ea.sex County, New York, pp 

 na, 225, 340. In the luHt two references he spenkn o( primary limestone, 

 t Report on the First Dintrict, 1843, p. 486. 

 { Btitfulo Courier, AugUHt 2.5, 1876; Am. Jour. Sci., October, 1876. 



