FOURTH REPORT OF THE DIRECTOR I907 1 7 



the region are comparatively common. Several occurrences in addi- 

 tion to those previously enumerated have been mapped. Associated 

 with two of these small limestone belts are graphitic schists of 

 considerable prominence. These types are believed to lend further 

 support to the sedimentary character of certain portions of the 

 series. One of the graphitic outcrops has attracted some local 

 attention looking toward development. 



It is clear, however, that the proportion of the igneous members 

 to the sediments in the basal gneiss series varies greatly in different 

 areas. In the eastern part of the Carmel quadrangle those inter- 

 preted as igneous types greatly predominate. The prevalence of 

 schists, limestones and quartzose rocks considered sedimentary, is 

 much more marked in the West Point quadrangle and especially 

 in the vicinity of the Hudson river. 



Surficial geology 



The problems relating to the impounding and drainage of surface 

 waters upon the retreat of the glacial ice, the making and breaking 

 of glacial and postglacial lakes, the molding of the present 

 topography of the country to the change in the level of the marine 

 waters and their former incursion into what are now fresh-water 

 passages, have involved investigation along lines and in areas indi- 

 cated in my report of last year, by Prof. J. B. Woodworth in the 

 northeastern region. Prof. H. L. Fairchild in the central and western 

 region and Prof. A. P. Brigham in the Mohawk valley. 



For the northeastern region Professor Woodworth has practically 

 completed the detailed mapping and report for the Schuylerville 

 quadrangle. The report will give an account of the extensive sand 

 deposits between Saratoga and Fort Edward which are not without 

 economic interest because of the occurrence of molding sands in 

 that district. The remarkable rock basins of Round lake and 

 Saratoga lake are dealt with, but a final report on these features 

 must await the detailed mapping of the topographic sheets in which 

 their southern and western portions lie. These lake depressions 

 notwithstanding their small size are of singular interest. The report 

 will contain a diagnosis of late glacial lake and river changes, adding 

 much in details to the preliminary sketch made in the report on 

 Ancient Water Levels of the Champlain and Hudson Valleys. 

 Similar work on the Rouse Point sheet lying directly east of the 

 Mooers sheet already published has progressed and the completion 

 of this map will carry the line of marine deposits from the base of 



