FOURTH REPORT OF THE DIRECTOR I907 1 3 



Both the Potsdam and the Theresa formations have large repre- 

 sentation on the Alexandria quadrangle, but the chief interest 

 attaches to the Precambric rocks; The main rock of the Thousand 

 Island region is a granite gneiss, a bathylith of probable Laurentian 

 age. Near its edges it holds abundant inclusions of schists, and 

 passes by increase of these into a belt of schists cut by granite, 

 these dikes diminishing as one recedes from the main granite mass. 

 There is much in these schists to suggest that they are impure lime- 

 stones transformed by the contact action of the granite gneiss. 

 This Alexandria bathylith seems to have been much richer in miner- 

 alizing agents than was the similar Antwerp bathylith of the Theresa 

 quadrangle. A coarse granite is also present which seems of later 

 date. 



Eastern Adirondacks. For a number of years, Prof. James F. 

 Kemp, who has excellently served the State work in geology, has 

 continued his investigations in the eastern Adirondacks. Under the 

 auspices of the United States Geological Survey Professor Kemp 

 has long devoted close attention to the intricate problems presented 

 by the crystalline rock region of the Elizabeth town, Ausable, ]\It 

 Marcy and Lake Placid quadrangles. By an arrangement entered 

 into with Professor Kemp, the Director of the United States 

 Geological Survey and the Director of the Xew York State Survey, 

 this work is now transferred to the supervision of this office with 

 full assent to the eventual publication here of all the results acquired 

 whenever the work shall have been completed. Under this under- 

 standing, Professor Kemp has reviewed and continued his work 

 on these quadrangles. Some problems which seemed determined in 

 the past have been of necessity reopened, for it was inevitable that 

 there should be some gaps in the record and some former deter- 

 minations requiring corroboration. During the past season Pro- 

 fessor Kemp's work has been concentrated upon the Elizabethtown 

 quadrangle, which is not only the most thickly settled of the four 

 mentioned but economically the most important. Since the earlier 

 fieldwork in this area was done, in 1896-97, we have come to 

 recognize the great syenitic series of eruptive rocks which was im- 

 perfectly noted under other terms in earlier reports and thus made 

 to accord with a scheme of classification at that time apparently 

 satisfactory. This area, moreover, is on the border between the 

 central j;northosite mass and the outer Grcnville sedimentary and 

 other gneisses. There are puzzling intermediate types and on the 

 tvhole a complicated assemblage of rocks whose relations await 

 determination. In the 10 years past there has also been extensive 



