490 NEW YORK STATE MUSEUM 



2 Grenville belts and patches. To explain the situation of 

 some of the Grenville rock belts, inclosed on both sides as they 

 are by the later eruptives, it seems necessary to assume that they lie 

 in downfaulted troughs. They now constitute valleys with the 

 eruptives forming the adjoining ridges, as well as underlying the 

 Grenville at an unknown depth in the valleys. This makes a con- 

 siderable and quite abrupt change in the level of the upper surface 

 of the eruptive. Unless these are downfaulted troughs it seems 

 necessary to assume this curiously irregular upper surface to the 

 igneous batholite, so that the other supposition seems vastly the 

 more probable. 



The areal mapping seems to emphasize this suggestion, though 

 the evidence has not the weight it would have in a district whose 

 stratigraphy was well worked out. The boundary between the 

 Follensby-Cold River Grenville and the anorthosite and syenite 

 which adjoin it on the northeast, appears to be a fault contact, 

 though the Grenville exposures are not frequent enough to enable 

 exact mapping. The boundary between the Moose creek-Bog 

 stream Grenville, and the syenite and gneisses to the north, is also 

 suggestive of faulting. Too little is known of the relationships of 

 the Grampus gneiss to warrant any deductions from the mapped 

 contact between it and the Grampus Grenville. 



TOPOGRAPHY 



The main axis of elevation in northern New York bears south 

 through western Clinton and Essex counties to the Marcy region, 

 then swerves to a southwesterly trend which is continued through 

 Hamilton county. This line forms the major axis of the Adiron- 

 dack highland. From it the surface drops gently westward toward 

 Lake Ontario and the St Lawrence; from it the surface drops 

 more abruptly and jerkily eastward to Lake Champlain. The 

 minor axis of elevation passes westward through Essex and southern 

 Franklin counties, intersecting the other in the Mt Marcy region. 

 The general highland of the northern half of the Long Lake quad- 

 rangle constitutes the western portion of this minor axis, while 

 the entire quadrangle lies west of the major axis. 



In northern Hamilton two broad valley regions cross the major 

 axis separating the Hamilton from the Essex portion. On^ of 

 these valleys is certainly and the other probably located on a belt 

 of Grenville rocks. The lowland along the southern margin of 



