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326 ' Sketch of the Geology of 



two feet in diameter^ of coarse red conglomerate; embrac- 

 ing nodules of quartz^ talcose slate^ and perhaps sand- 

 stone. It Is difScult to say whether they originated from 

 a secondary or transition formation. That they were 

 brought from a northerly direction, by a diluvial current, 

 admits of no doubt. But whether any fragmentary rocks 



^ 



occur in that direction, nearer than the valley of the St. 

 Lawrence, may be doubted. I have'^been shown speci- 

 mens, however, from the eastern part of Maine, contain- 

 ing petrifactions of testacea. The rock is a fine, very 

 hard, gray, or reddish sandstone. In a similar rock, 

 which is extremely hard, recently sent me from Frank- 

 fort, not far from the mouth of Penobscot river, numerous 

 moulds and casts of shells occur. I should infer from 

 hand specimens, that this rock is graywacke; if it be not 

 rather a variety of trap; or rather a sandstone almost 

 changed into trap ! I noticed in it three or four genera 

 of shells; but do not feel prepared to name them. 



A single tertiary formation exists around Portland, 

 composed chiefly of horizontal layers of clay. The 

 upper part of the bed, to the depth of several feet, seems 

 to have been disturbed by aqueous agency; but lower 

 down, the layers are distinct. * It is the blue plastic clay, 

 so common throughout New Endand: and which I have 

 denominated the newest tertiary , in my Report on the 

 Geology, Sec. of Massachusetts. After descending several 

 feet, however, in the clay beds of Maine, we reach a 

 stratum of a lighter blue color ; and in this, shells are 

 found, partially or wholly converted into stone. 1 have 

 found them only at a remarkable slide on the north side 

 of Presumpscut river, near Pride's Bridge, in Westbrook; 



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occur 



that 



