40 NEW YORK STATE MUSEUM 



season, was in charge of Mr Martin. The quadrangles mentioned 

 may be considered now to have been completely covered and the 

 reports thereupon practically ready for publication. 



In the central Adirondack region the Blue Mountain quadrangle 

 was surveyed by Prof. W. J. Miller in continuation of work begun 

 the preceding season. There are certain important details registered 

 for this region which may be indicated as follows : 



Grenville series. Two extensive belts of Grenville limestone 

 with associated hornblende and pyroxene gneisses have been mapped 

 in the southern half of the quadrangle. One of these occupies the 

 broad valley around Indian Lake village and extends westward up 

 the Cedar River valley for fully 1 1 miles, and the other reaches from 

 Blue Mountain lake eastward across the quadrangle by way of the 

 Rock River valley, the two belts being joined through the valley 

 south of Rock lake. Smaller areas of similar Grenville rocks occur 

 in the vicinity of Unknown pond and in the vicinity of the Chain 

 lakes. Also a little Grenville gneiss was found in the extreme 

 northeast. 



Syenite-granite series. Rocks of this series comprise by far the 

 most of the region. They range from a basic, gabbroic facies to a 

 truly granitic facies. Granite porphyry was found in one small area 

 only. Certain of these rocks show interesting relations, but they 

 still await microscopic examination. 



Gabbro. A number of gabbro stocks or dikes of the typical 

 Adirondack sort were discovered in addition to those reported for 

 191 3. At two localities northeast of Long Lake village there are 

 considerable masses of peculiar, light-gray, coarse-grained, basic, 

 igneous-looking rocks which, at the present writing, are still of 

 rather uncertain age and origin. 



Diabase. No diabase dikes were located in addition to the two 

 already reported from the shores of Long lake. 



Structural features. Though quite variable, the strike of the 

 foliation is in a general way nearly east-west over the quadrangle, 

 the dip in the north usually being southward, and in the south 

 usually being northward. 



Three faults only could be definitely located, two across the 

 southeastern portion of the quadrangle and the third already re- 

 ported as passing through Long Lake. 



Glacial and postglacial features. In all, 18 sets of glacial striae 

 have been located. These range from south 20° to 50° west, and 

 are so situated as to prove that the great ice current across the 

 region was southwestward. Well-rounded glacial pebbles of 



