SCIENTIFIC SURVEY. 335 



The island of Mt. Desert exhibits the boulder phenomena in a 

 more wonderful degree than those places I have mentioned. I 

 presume you have thoroughly explored the locality. You see the 

 southern brows of those lofty granitic hills everywhere crushed and 

 broken into fearful precipices ; whereas their sides turned to the 

 north, present plains of greater breadth, and dip at vastly less an- 

 gles down towards the level country beyond. The great granitic 

 boulders lie at their southern feet, and those specifically the same 

 but of less magnitude, and transported the ftirthest off, and arc more 

 worn and rounded. Wc have here as elsewhere in the Penobscot 

 bay, the evidence that it was the special business of the great 

 denuding agent to cover the barren surface with soils, and that 

 those soils are the result of local detritus — gravels, clays and sands 

 crushed and ground out of the detached rocks. 



On the Taconic slates beyond these mountains towards Ellsworth, 

 we have the debris of the Taconic formation. Still beyond through 

 Dedham, we have a granitic formation, and see the granitic boulders 

 in the most wonderful profusion and of great magnitude. They were 

 derived from the hills a little way towards the north. The same 

 peculiarity may be said of North Haven above Vinalhaven. On 

 that island, principally' a trap region, you see trap boulders and 

 rubbish. In the northern part of Vinalhaven where the Taconic 

 slates are highly altered, you see boulders of the same character ; 

 on the granite below, granitic rocks ; and still further beyond, 

 where the syenite has apparently been altered — or the cooling crust 

 originally took the form of hornblende — the ruins of hornblendic 

 rocks are found. 



Around one of the quarries to the west of Carver's harbor, the 

 ground is literally covered with boulders, some of which are enor- 

 mous. After repeated attempts, I could not make out more than 

 five per cent, of foreign rocks among them. Many of these turned 

 out of their beds, exhibit the polishing and scratching of the com- 

 mon floor rock of the island. Furthermore, if carefully turned 

 over, we find some of them left just where they had last been em- 

 ployed in scratching the ledges, the parallel scratches of the boul- 

 der being placed parallel to those of the rock beneath. Of these 

 foreign boulders we often have little or no grounds to imagine the 

 origin. We have specimens of red and blue granite, trap, gneiss, 

 mica schists, clay slates, and fossiliferous sandstones from the 

 Katahdin region. We can well suppose them to have been dis- 



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