o NEW YORK STATE MUSEUM 



fered deformation only to the extent of being jointed and faulted. 

 Except for recent mere surface decay they are practically as when 

 they cooled and solidified. They have therefore never been deeply 

 buried, as have the rocks which they cut, but, on the contrary, 

 seem to have formed not far from the surface, since some of them 

 contain numerous gas cavities. Hence the larger part of the early 

 erosion of the region must have been effected before their appear- 

 ance and yet after the intrusion of the earlier eruptives. 



The region was yet a land area at the time and so continued for 

 a space. The result of the long protracted erosion of the surface 

 was to wear down the old mountains to mere stumps, producing 

 a region of comparatively low altitude and quite insignificant 

 relief. There were stream valleys with low divides between and 

 numerous low, rounded hills, whose tops were apparently no more 

 than a few hundred feet above the valley bottoms as a maximum. 



This old land area was of much greater extent than the present 

 Adirondack region, though that was apparently a more elevated 

 part of the surface then, as now, of less relief however and lower 

 altitude. While the last, finishing erosion touches were being 

 given to the present Adirondack region, the sea had already begun 

 to encroach on its borders, either because of a sinking of the land 

 area or a rising of the sea level. This movement persisted also for 

 a long time, and the region seems to have become an island in the 

 midst of the sea, of constantly shrinking area as the waters rose 

 around it, till finally they seem to have overtopped it, completely 

 submerging the whole. It is possible that a small area may have 

 persisted above sea level throughout, though, it is not likely, and 

 in any case it was very small. 



As each successive zone of the district passed beneath the sea, 

 it ceased to suffer wear on its surface and began to receive deposit 

 instead. The last portion of the present Adirondack region to 

 pass beneath the sea would seem to have been the southern part. 

 Since subsidence and deposition were x)roceeding at the same 

 time, each new layer of deposit would encroach a little farther 

 on the old land surface than the preceding one. In other words, 

 they overlapped on its slopes. The subsidence of tliis old laud area 



