14 NEW YORK STATE MUSEUM 



The rocks next in age are the anorthosites, which cover al- 

 most all the quadrangle. They are its characteristic rock and 

 constitute all the high peaks but one. The blue labradorite 

 rock, sometimes giving opalescent colors in the brooks, is al- 

 most universal. The syenite series enters from the north and 

 in a variety that is transitional to the anorthosites constitutes 

 Pitchoff mountain. The syenites soon fail, hov^ever, and the 

 anorthosites take their place. 



The anorthosites are cut by a number of intrusive masses of 

 basic gabbro, of w^hich the v^onderful dike at Avalanche lake is 

 a striking example. It runs from the lake to the summit of 

 the ridge, cleaving two mountains apart like a v^edge. 



There are numerous basaltic dikes which favor the north- 

 easterly fault cracks. 



The intrusive anorthosites have wrought some contact ef- 

 fects upon the old Grenville limestones which are among the 

 best illustrations of these phenomena yet noted in the Adiron- 

 dacks. The limestones have been changed in one locality to 

 masses of red garnet and green pyroxene, and in another have 

 a body of magnetite much mixed up with garnet and other 

 contact minerals. The ore body was mined to some extent in 

 the old days of the forges but is now idle. It is the only ore 

 deposit worthy of mention yet found in the quadrangle. The 

 great predominance of the anorthosites would lead us to antici- 

 pate only titaniferous ores outside of the Grenville area. 



Mineral wealth is thus lacking. The entertainment of sum- 

 mer visitors and the lumber business are the chief means of 

 support of the inhabitants. 



Southeastern New York. In my report of last year refer- 

 ence was made to -cooperative under! akin gs zvith the New York 

 City Board of Water Supply, with reference to the assembling of 

 the geological data recorded in that great engineering enter- 

 prise. During the year past, Dr Berkey has brought together 

 from these sources and from independent surveys of the contigu- 

 ous territory, begun before this form of cooperation was effected, 

 the general summary of new knowledge in the form of a bulletin 

 which has been submitted for publication. In the preparation 

 of this bulletin the immediate object has been to place in con- 

 venient form an outline of the present understanding of the 

 geology of the region and to discuss facts gathered in this ex- 

 tensive exploratory work carried on along the course of the Catskill 

 aqueduct, with special reference to the geological structures on Man- 



