r84 NEW YORK STATE MUSEUM 



brought in by students, Prof. Kemp had aliso been made aware of 

 the true nature of the rock. That Hall should have called it 

 labradorite instead of gneiss is a mark of hi« acumen, since the 

 syenite type had not then been recognized in northern New York, 

 and the external resemblance to some varieties of the anorthosite 

 is very close. 



The writer's visit to the locality was a brief one, not sufficiently 

 long to permit carefully going over the whole ground. First 

 appearing in the river bed west of the village, with surface rising 

 gradually till cut off by the fault at the east edge, where their 

 altitude reaches 200 feet above the river, the extent of the pre- 

 Cambrian rocks in an east and west direction is a little over 2 

 miles. On neither side of the river the outcrops extend greatly 

 back from it, the breadth being of course greatest at the east. 



The writer's time was utilized in making a careful section 

 along the line of the Little Falls and Dolgeville railway, as that 

 seemed to' show the most continuous line of outcrops; it is 

 thought that the sections shown in the New York Central and 

 West Shore cuts must be substantially the same. Prof. Smyth 

 has studied the rocks south of the river, as exposed in the cuts of 

 the West Shore road, and our combined results indicate that the 

 exposures are of syenitic rocks throughout. 



Though this line affords a practically continuous section for 

 nearly 2 miles, the conditions for study are not wholly ideal. 

 Since the rocks are tremendously jointed, considerable weather- 

 ing has taken place along the joints, so that the rock has not 

 escaped some alteration, and the exposures consist largely of 

 vertical walls. 



The exposed syenite varies widely in appearance and composi- 

 tion, ranging from a fine grained, nearly black rock, which 

 resembles gabbro, to reddish, granitic varieties. All are pro- 

 foundly metamorphosed and rendered thoroughly gneissoid, much 

 more so than is usual with the syenites of the Adirondack region. 

 The rock is excessively crushed^ having a very finely granular 

 texture, yet nearly always uncrushed crystals, or portions of 

 crystals (augen), remain and in places are very numerous, and the 

 cataclastic structure is unmistakable. 



