INTRODUCTION. 



The vast region extending from Long Island Sound, north- 

 easterly, and nearly insulated by the St. Lawrence, Richelieu, 

 and Hudson Rivers, and Lake Champlain, is well marked 

 off, geographically, from the rest of the continent. Dr. 

 Ezekiel Holmes, 1 recognizing the geographic distinctness of 

 this most eastern member of the continent, and its almost com- 

 plete isolation by water, an isolation that appears to have been 

 perfect during the first part of the Paleozoic era, has correctly 

 termed it a peninsula. Newfoundland is a detached portion 

 of this geographic unit. In its geologic relations, also, the 

 region indicated is readily separable from the adjoining terri- 

 tory. The rocks are mainly crystallines, and, except in the 

 lower part of the valley of the Hudson, cannot be connected, 

 along their strikes, with the rocks of other regions. 2 The 



1 Ann. Report on the Agriculture and Geology of Maine, 1861, p. 100. 



2 The Paleozoic sediments of this region, it is true, are continuous through the broad 

 interval between the Adirondaoks and the Highlands of the Hudson, and were probably 

 connected, at one time, through the valley of the St. Lawrence, with the more exten- 

 sive deposits of the same age to the westward. Yet the crystallines are to so great an 

 extent the predominant rocks of this large territory, and, as the writer conceives, have 

 had, as a whole, an origin so vastly more remote than the most ancient of the uncrys- 

 talline sediments (these newer formations being regarded as merely superficial deposits, 

 often obscuring, but not essentially altering, the main structural features of the region), 

 as to warrant leaving the latter out of view in these general remarks. 



OCCAS. PAPERS B. S. N. H. — III. 1 



