14 



XEW YORK STATE MUSEUM 



Silurian and Lower Devonian 



The most interesting problems connected with these forma- 

 tions are those of the proper systematic position of the Lower 

 Helderberg and the mutual relations of the Medina sandstone, 

 Oneida conglomerate and Oswego sandstone. The first subject 

 has been discussed by Clarke, Williams, Stevenson and others; 

 while the second remains to be investigated. The mapping of 

 the Cambrian and Silurian formations in the Lake Champlain 

 region is based on the work of Brainerd and Seely, Cushing, 

 Kemp, van Ingen, Walcott and White, all save van Jngen's con- 

 tribution having appeared in various papers. 



The mapping of the pre-Hamilton rocks in the western and 

 northern towns of Orange county is based on the work of Ries; 

 that of the Schunemunk-Bearfort mountain area on Darton's, 

 retraced on the Schunemunk and Ramapo atlas sheets by Eckel. 

 With the exception of the small areas about Kingston and Hud- 

 son credited to Davis, Darton's work for the Hall map of 1894 

 served as the basis for the pre-Hamilton mapping of Ulster, 

 Greene and Albany counties and for the westward extension 

 of the Helderberg rocks across the state. His mapping of the 

 Niagara limestone was also used, supplemented by later work 

 by Sarle, who is to be credited with the Medina-Clinton and 

 Clinton-Niagara boundaries from Oneida lake to Lockport, and 

 with the Potsdam-Trenton, Trenton-Hudson and Hudson-Medina 

 boundaries from near Boonville and Rome to Lake Ontario. 

 Westward of Lockport a manuscript map by Gilbert and the 

 recently published map by Grabau, of the vicinity of the Niagara 

 river, were used. The mapping in Erie county south of Buffalo 

 is based on the work of Bishop, with corrections by Clarke. 

 The boundaries in Onondaga county are mainly as mapped by 

 Luther; while small areas near Skaneateles, and in Oneida 

 county near Oneida. Clinton and Utica were revised by Eckel. 



In addition to the work on the areas specified above, Clarke 

 and Luther made many manuscript corrections to the boundaries 

 shown on the map of 1894 in the central and western part of 



