CHAPTER III. 



PRELIMINARY DESCRIPTION OF THE SUPERFICIAL 

 DEPOSITS OF MAINE. 



A brief general description of the drift of Maine will be given in 

 language which for the g-reater part is consistent with any theory as to the 

 origin of the drift. 



Erosion is the general name given to the process whereby a portion 

 of the parent rock is removed from its place by any geological agency. It 

 is a complex process, consisting of the preparatory work of detaching 

 fragments from their original position by solution, chemical decay, weath- 

 eiing, water-logging- of porous beds, abrasion, concussion, and all other 

 forms of fracture, and of their subsequent removal by some drift agency. 

 The word is sometimes used for the preparatory work only, exclusive of 

 the subsequent removal. 



PREGLACIAL DEPOSITS. 



So far as yet determined, all the rocks of Maine are Paleozoic or still 

 more ancient. The fact that no marine beds of Mesozoic or Tertiary age 

 are found proves that the area within the State has been above the sea 

 since Paleozoic time — unless, indeed, deposits of later age have been eroded 

 or remain to be discovered. At Brandon, Vermont, are sediments deposited 

 in a Tertiary lake of fresh water. Although they were not so firmly cemented 

 and consolidated as the ancient rocks, the great glacier was not able wholly 

 to erode them. Similar beds might have been laid down in Maine, and, if 

 extensive, might have escaped erosion by the ice-sheet. I have, therefore, 

 carefully examined the till, especially in the vicinity of the deeper lake 

 basins, but thus far have found no fragments of such Tertiary lieds. It 

 has long been known that marine beds of Tertiary age are found on the 

 coast of southeastern ^lassachusetts, and fragments have been dredged off 



