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BULLETIN or THE MUSEUM OF COMPARATIVE ZOOLOGY. 



knowledge in that region, and, before the extrnsion of the more recent 

 eruptive rocks, they probably had a much wider distribution upon the 



surface than they now have. 



The granites are not derived by metamorphism from any part of the 

 series of rocks (stratified group) which they envelop, but are truly 

 eruptive rocks, whose extrusion has occurred since the formation of the 

 stratified group. Tiierefore the granites, as we know them in their 

 present position, are younger than the stratified group. 



The felsites are eruptive rocks, more recent than the granites. There 

 were at least two eruptions of felsite in each ai'ea, and in the southern 

 area there were probably three eruptions. 



The fragmcntal material associated with the felsite upon Break-heart 

 Hill is a volcanic ash ; elsewhere the fragmental rocks have generally 

 been formed of material eroded and deposited by water. 



The very porphyritic felsite between Long Pond and Prospect Hill, 

 part of the felsite of Wakefield and at Cliftondale, and jjrobably the 

 dark-colored felsite of the Maiden Highlands, are younger than the 

 tufas and conglomerates with which they are associated. 



The diorites are eruptive, and younger than the felsites. 



The diabases and melaphyres are the youngest eruptive rocks of this 

 region, and there has been, in the order of eruption beginning with the 

 granites, a general progress from silicious to basic rocks. 



^1 





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