630 STRATIGRAPHICAL GEOLOGY. 



schists, dipping 75° N. W. Near the crossing of Parker river are com- 

 pact green schists, somewhat serpentinous, dipping 70° and 60° northerly. 

 The slates dip 52° N. W. On the south side are the coarser conglomer- 

 ates, with porphyry pebbles, not distorted. The last outcrops on the 

 south side, before coming to the sienite area, consist of compact feld- 

 spars and siliceous slates, and a few diorites with dips like the others 

 named. The first sienitic or gneissic rocks are traversed by seams, 

 possible strata, dipping 35° N. E. 



Until further exploration, I think the porphyries may be ranked as 

 Huronian, corresponding to the similar rocks of Lynn, Saugus, and else- 

 where in the Boston basin, while the slates and conglomerates agree 

 with the related rocks of Braintree containing the characteristic trilo- 

 bite Paradoxides. 



Eruptive Rocks. 



The most conspicuous of the eruptive rocks of the Coast district is the 

 sienite of Exeter ; the quartz is often absent, and it would then be styled 

 diorite. As both types of rock are common in this district, neither name 

 is appropriate for the whole series ; but for convenience I will follow the 

 Massachusetts report, and use the name of sienite for the rock generally. 

 My father points out the distinction clearly between these rocks in his 

 report, in the eastern part of the state, in the areas which are the perfect 

 analogues of our New Hampshire ones. The best known of them in 

 Massachusetts is that of Quincy, popularly called granite. 



There are six areas of the Exeter sienite upon the south-east sheet. 

 The first extends from Alfred to Berwick, Me. This has been crossed 

 at Alfred, where a compact feldspar occupies the western border. Be- 

 tween Sanford and Lebanon are several exposures ; and Bonny Bigg hill 

 in North Berwick is of the same character. The second area, exclusively 

 in Maine, lies in York, South Berwick, and Eliot. Mt. Agamenticus 

 forms a part of it, and it is crossed on the road from York to South 

 Berwick. It extends down to Cape Neddock, also. The shape of this 

 area is like a crescent. The third and most important New Hampshire 

 area is on the line of the continuation of the first one mentioned, and we 

 cannot say with certainty they are not connected together. We have it 

 first in Rollinsford, whence it proceeds directly to Exeter and Brentwood, 

 where it passes beneath the lenticular drift hills that are so numerous 



