Eepokt on thk Mines and Mining Exhibit. 817 



annual report of the State Geologist, wlucli gives approximately the 

 boundaries between the norite and tlie gneisses. In 1892 Prof. J. F. 

 Kemp, of Oolumbia College, undertook the study of Essex county under 

 the auspices of the State Museum, and tlie 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 phitonie mass, 

 they go sufficiently far to show that it occupies but a small part of 

 the Adirondack wilderness .and can be,. inclj.ided in, a circle, of- about 

 fifty miles diamiter with its center in ,the vicinity of Keene Valley. 

 Within this plutonic area are the principal peaks of the Adirondack 

 mountain group. Tlie 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 Pluronian 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 

 Vanuxem with additions by C. E. Hall, J. F. Kemp and T. G. White 

 in Essex county, and by F. J. H. Merrill in Warren and Hamilton 

 counties. In St. Lawrence, JefEerson and Lewis counties Prof. Smyth 

 has given information concerning 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 the 

 Potsdam in Clinton county. 



An examination of the shores of Lake George was made for the 

 Museum in 1891 by Mr. E. M. Blake. 



From the base of the palaeozoic upward the geological formations of 

 New York were quite accurately studied in the original survey, but 

 the work of mapping the boundaries was not very carefully done, and 

 though at the present time there is much new information in the 

 possession of those who have made special studies of these formations, 

 but little new material has been published, and it has not been possible 

 within the time at the author's disposal to consult those in possession of 

 unpublished material. The author's personal observations on the palseo- 

 zoic groups have been chiefly confined to the upper and lower Helderberg 

 limestones and the strata immediately adjacent to them, in Greene, 

 Albany and Schoharie counties and at various points to the westward 

 along the principal lines of railway. The principal guide used in the 

 preparation of the geological base was the Agricultural and Geological 

 map of New York, published by authority of the Legislature in ISli. 

 In revising the boundaries given on this map the four geological dis- 

 trict reports of New York have been carefully studied, and from them 

 many corrections have been introduced, although the old map was based 

 on the material contained in those reports. This was particularly notice- 

 able in mapping the outcrop of the upper Helderberg limestones, which 

 on the old map is shown far to the northward of Otsego and Schuyler 

 lakes, although Vanuxem reported the occurrence of the corniferous 



