3*66 NEW YORK STATE MUSEUM 



wholly surrounded by, and resting on the eruptives. In the 

 writer's judgment, many more will be found when the interior 

 region is more carefully gone over than has hitherto been possi- 

 ble, and there must be others wholly concealed beneath drift and 

 ordinary forest covering ; but, as it is, they are sufficiently numer- 

 ous, and of sufficiently scattered distribution, to indicate that the 

 elastics formerly spread over the entire region, and have been 

 almost completely removed from the interior by erosion. A quite 

 possible explanation of the difference in conditions between the 

 tieart of the region and the border, between prevailing eruptives 

 holding scattered patches of the clastic gneisses and much more 

 abundant elastics with occasional eruptive knobs, is that erosion 

 has cut more deeply in the heart of the region, that it has experi- 

 -enced greater uplift and therefore greater wear than the border, 

 so that the conditions which prevail at the surface in the former 

 are yet buried at some depth below it in the latter. The occur- 

 rence of augite syenite forming the pre-Cambrian outlier at Little 

 Falls in the Mohawk valley shows that the eruptives pass under 

 the Paleozoic cover at the extreme border along with the clastic 

 gneisses, and that therefore the invasion of the elastics by the 

 eruptives from beneath was widespread and not limited simply 

 to the heart of the Adirondacks. 



If the syenite and granite be transferred from series 1 to series 

 ^, what remains of the former? It certainly is vastly diminished 

 in importance and, instead of being the most extensive of the 

 Adirondack formations, comes to be subsidiary to series 3. There 

 is however in the region a considerable body of gneiss, for the 

 most part of border distribution, which seems not to have any 

 connecition with the eruptives of series 3. Tho^ugh these gneisses 

 «eem to be in part of igneous origin, such origin for another part 

 is open to considerable doubt. Such gneisses form most of the 

 pre-Cambrian area of Clinton county and the border of Franklin 

 «.nd eastern St Lawrence counties, territory over which they are 

 singularly free from admixture with undoubted Grenville rocks, 

 small patches of which do, however, occur. Instead of having a 

 anassive character and wide distribution, with gradation from one 



