THE OSAR GRAVELS OF THE COAST OF MAINE. 247 



Survey showing the sea bottom for a few miles off the coast. If 

 there were any broad gravel hills lOO to 150 feet high, such as 

 are found thirty miles north from the bays, they ought to be 

 shown, and I do not find them. The charts often report gravelly 

 bottom but it is uncertain whether this is till or glacial gravel. 

 I find no evidence that these soundings showing, gravel are con- 

 nected with ridges of any considerable size. While then it is as 

 yet impossible to know the geological significance of the gravel 

 reported on the sea floor, yet in most cases the gravels end so 

 evidently north of the shore that the interpretation is distinctly 

 favored that none of the gravel systems reach far beneath the sea. 

 No osar gravels have I been able to find on the islands situated 

 south of the apparent ends of the gravel systems. 



There are other significant peculiarities of the coastal gravels 

 than those to be named in this paper, and many collateral or 

 alternative questions and hypotheses had to be worked out. For 

 the present we confine our attention to the three following char- 

 acteristics : 



1. The decrease in the average size of the glacial gravel 

 masses as we go toward the coast till they often become cones 

 not more than twenty or thirty feet in diameter and four or five 

 feet high. In general, the marine clays are twenty feet or more 

 in depth and would easily cover out of sight masses smaller than 

 those above named. 



2. The increasing discontinuity of the osar systems, the gaps 

 between the successive ridges, massive mounds or plains, lentic- 

 ular hills, domes, cones, and mounds increasing from a few rods 

 up to two or three miles. 



3. The practical ending of the osar gravels near the north 

 ends of the fjords (fjord line). It is not meant to assert that 

 there are absolutely no osar mounds beneath the sea or on the 

 land south of the discovered gravels. But if any exist they are 

 hidden by the marine beds, and are so insignificant in size as 

 compared to the osar gravels found a few miles farther north 

 that for all practical purposes we may assume that they end. If 

 the osar mounds go on decreasing as fast southward as they do 



