I 



DESCRIPTION OF THE ECONOMIC AND GEOLOGIC MAP 367 



sthene and labradorite which may be called norite. In the work 

 of the original Natural History Survey of New York, which cul- 

 minated in the publication of the reports on the four geological 

 districts of the State in 1842 and 1843, this region was investi- 

 gated by Prof. Ebenezer Emmons. This geologist recognized 

 clearly the striking lithological difference between the 

 massive norite and the stratified gneisses which envi- 

 roned it, but gave no accurate description of their boundaries, 

 doubtless for want of an accurate map of the wilderness. In 

 1883 a map of Essex county by C. E. Hall was published in the 

 annual report of the State Geologist, which gives approximately, 

 the boundaries between the norite and the gneisses. In 1892 

 Prof. J. F. Kemp, of Columbia College, undertook the study of 

 Essex county under the auspices of the State Museum, and the 

 results of his work are embodied in the economic map.* While 

 Prof. Kemp's observations have not been carried around the 

 whole periphery of the plu tonic mass, they go sufficiently far to 

 show that it occupies but a small part of the Adirondack wilder- 

 ness and can be included in a circle of about fifty miles diameter, 

 with its center in the vicinity of Keene Yalley. Within this 

 plutonic area are the principal peaks of the Adirondack mountain 

 group. The extension of this area into Franklin county as shown 

 on the map is based on the observations of Ebenezer Emmons. 

 The northwestern part of the metamorphic area is believed by 

 Prof. James Hall to contain rocks of Huronian age. The study of 

 this region is now in the hands of Prof. C. H. Smyth, Jr., of 

 Hamilton College, and to him we look for the elucidation of this 

 question. He classifies under the name of Oswegatchie series a 

 group of crystalline limestones and gneisses. The geology of 

 the Adirondack region as given in the map is based upon the 

 original work of Ebenezer Emmons and Lardner Yanuxem with 

 additions by C. E Hall, J. F. Kemp and T. G. W hite in Essex county, 

 and by F. J. H. Merrill in Warren and Hamilton counties. In St. 

 Lawrence, Jefferson and Lewis counties Prof. Smyth has given in- 

 formation cencerning the distribution of the gneisses and other Pre- 

 cambrian rocks. On the north side of the wilderness Prof. H. 

 P. Cushing, of Adelbert College, Cleveland, Ohio, has been con- 

 ducting some field work and has revised the lower boundary of 



•See also Bull. No. 13. N. T. State Museum. 



