Hunt.] 48 [October 19, 



phyry adjoining the old porphyries of Passamaquoddy Bay, is inter- 

 stratified with fossiliferous sandstones which show it to be of Silurian 

 age. The same thing is observed in Cobscook Bay, near to Eastpoi t, 

 in Maine; while elsewhere similar conglomerates are met with of 

 Lower Carboniferous age. 



The fact that the primordial strata of Brain tree have suffered no 

 metamorphism is the more significant, since the beds of similar age 

 in New Brunswick and Newfoundland 1 rest uncomformably on crys- 

 talline strata supposed to' belong to the same ancient series that 

 underlies the Braintree beds, and are, like these, unaltered sand and 

 mud rocks. The alteration in the paleozoic strata along our north- 

 eastern coast is apparently confined to the proximity of intrusive 

 rocks. Thus the so-called flinty slates at Nahant, containing patches 

 and bands of epidotic matter, are, as long since pointed out by 

 Hitchcock, penetrated by great masses of eruptive greenstone, and 

 I have found that at distances of a few yards from this they appear 

 as argillites but little indurated. The Upper Silurian beds about 

 Passamaquoddy Bay are, in like manner, altered in the immediate 

 vicinity of eruptive greenstones, becoming hard, greenish and epi- 

 dotic, but the same beds a few feet distant are unchanged and earthy 

 in their aspect. 



The difficulties which have attended the study of the geology of 

 this region have arisen in part from great lithological diversities, 

 which led our early observers to separate into different classes rocks 

 of the same geological series ; while on the other hand, rocks geog- 

 nostically very unlike were brought together. These points are 

 shown in what we have cited from Hitchcock with regard to the 

 syenite and greenstone, under both of which heads he has placed 

 with true eruptive rocks others which are doubtless stratified. The 

 indigenous greenstones or diorites were at the same time separated 

 from the amygdaloids and serpentines (which were correctly looked 

 upon as stratified rocks), a misconception which could only lead to 

 confusion. I have ventured in these remarks to state briefly the 

 conclusions to which a few days of observation have led me with 

 regard to the relations of some of the rocks of this vicinity. They 

 will be found, I think, to show a greater simplicity than has hitherto 

 been supposed in the geological structure of the region, and are pre- 



1 Mr. Billings informs me that he regards the Paradoxides Bennettii (Salter) from 

 Newfoundland as identical with the Paradoxides Harlani (Greene) from Braintree. 



