CONTINUOUS AND DISCONTINUOUS OSARS. 419 



difference is due to causes arising- wholly within the ice irres2)ective of 

 the sea, we must learn what the development of osars is beyond the reach 

 of submergence, say in Nova Scotia, and show that they conform to this 

 hypothesis. 



2. If, as seems probable, the deposition of sediments in the g'lacial 

 channels was somewhat recessive, the matter of local slopes of the land 

 may have been an important factor in determining- the development of tlie 

 gravels. Near the coast we are beyond the ranges of transverse hills with 

 little obstruction to the flow of the ice, while northward the thinning ice 

 would be more obstructed by the transverse hills, except in a few of the 

 deepest valleys. It may therefore have happened that the continuous ridges 

 of the north were deposited when the ice at the place of deposition was 

 more nearly stagnant than when the more southern gravels were deposited. 



3. It is evident that the ice continued to flow after the transverse hills 

 rose above the ice sm-face, for at the low cols of the hills there are in numer- 

 ous places small rounded swells of till, a form of an incipient moraine, 

 marking where small glaciers for a time crept over the low places in the 

 hill ranges. In general these morainal ridges are small, very much smaller 

 than the Waldoboro moraine. At the time the terminal overwash aprons of 

 glacial sediments elsewhere described were formed the ice had retreated far 

 north of two transverse ranges of hills (counting from the coast region 

 backward) and the ice front was near the foot of south slopes. Here the 

 motion of the ice would naturally be more rapid. The morainal ridges 

 found near Katahdin Iron Works and East New Portland date from this 

 period, and they are rather larger than the Waldoboi'o moraine. For some 

 years I was not sure that these ridges and mounds were not a freak of the 

 subglacial till, but my observations in the Rocky Mountains have now 

 (1893) convinced me that they are moraines of englacial matter. 



We have hints here and there, then, that the rate of ice advance varied 

 from time to time during the decay of the ice-sheet, according as the gla- 

 cier terminated on an up or a down slope. Presumably the surface gradient 

 of the ice varied also. What effect these changes would have on the reces- 

 sive development of the glacial gravels remains to be determined. This 

 uncertainty embarrasses our comparison of the continuous ridges of the 

 interior of the State with the discontinuous gravels of the coast region. 



