476 NEW YORK STATE MUSEUM 



south syenite gneiss adjoins it, and on the north granitic gneiss and 

 amphiboHte, similar to the Long lake gneiss. Unfortunately no 

 contacts are exposed so that the interrelationships of the rocks are 

 most uncertain. - Since the previous outlier proved to be an in- 

 closure in later rocks it would be natural to regard this as probably 

 a similar occurrence. The rock however differs from the last, is 

 mvich mashed, the feldspar shows wide variation in composition, 

 especially considering the small size of the mass, and much scapo- 

 lite has developed. It is not impossible that it may be a small out- 

 lying intrusion, connecting beneath with the main mass, and with the 

 s^^enite cutting it out on the south. The rapid changes in char- 

 acter from place to place which it shows are more readily explicable 

 on that supposition than if it is regarded as a small fragment de- 

 tached from the main mass. But the whole question hangs upon 

 the age of the granitic gneiss, and it is therefore doubly unfortunate 

 that no contact appears. If the gneiss is older, this is a small 

 separate intrusion, or branch from the main intrusion ; if the gneiss 

 is younger it is certainly an in closure. 



The third outlier is upon the county line, 2 miles east of the sec- 

 ond. It is completely surrounded by gneisses of uncertain nature 

 and age, and no contacts are exposed. The rock is very gneissoid, 

 no feldspar cores whatever remaining in much of it. It also holds 

 from 10 per cent to 20 per cent of minerals other than feldspar. 

 The feldspar is an acid andesin instead of labradorite, being in this 

 respect like some of the feldspar of the previous outlier. Both rocks 

 are quite different from the ordinary anorthosite, while the rock 

 from the first outlier is quite normal. This is but natural if the two 

 latter represent small intrusions into earlier rocks. 



Syenite. The general syenite of the Adirondacks has a much 

 more irregular and patchy distribution than has the anorthosite, 

 and the present day surface exposures belong to a series of separate 

 masses both large and small. One of the greater of these masses, the 

 Tupper syenite, has the larger part of its present surface within the 

 quadrangle limits and, with the exception of a few outlying in- 

 trusions which are likely offshoots from it, is the only syenite mass 

 within the quadrangle. It is separated into a smaller eastern, and 

 a larger western portion' by the Follensby Grenville. But if that 

 lies in a downfaulted trough, as seems highly probable, the syenite 

 ma}^ be legitimately regarded as continuous underneath, so that the 

 separation into two masses is only apparent, and due to faulting. 



