32 



GLACIAL GEAVELS OP MAINE. 



On the northern and northwestern slopes of rather high hills deep 

 sheets of fine, clayey till abonnd. The till is in general thinner on the 

 hilltops and in the valleys than on the intermediate slopes. This fact, 

 combined with the rounded, flowing outlines of the mass, gives to these 

 hillside accumulations of till a shape somewhat lenticiilar in cross section, 

 but they often extend for miles along the sides of a ridge. 



In the southwestern part of the State, hills of mammillary or lenticular 

 shape abound, but they are not so large or numerous as the lenticular hills 



Fig. 2.— Section across deep lenticular sheet of till; Keuts Hill, Eeailfleld. 



of till so abundant in certain parts of New Hampshire and Massachusetts. 

 Sometimes, as at the eastern end of Portland, there is a rock nucleus, above 

 and around which the till collected ; but more often no such nucleus appears 

 anywhere on the sxirface, and if it exists it must be of small size as com- 

 pared with the Avhole hill. 



Professor Hitchcoclv and j\Ir. Warren Upham named them "lenticular 

 hills" in the reports of the New Hampshire survey. Similar masses 

 appear to have previously received the name of "drumlins" in Great 



Britain and Ireland, and this 

 name is now generally adopted. 

 In Maine the di'umlius of the 

 southwestern coast region are 

 mostly roundish or slightly elon- 

 gated. Back farther from the 

 coast, and especially in the eastern part of the State, there are many which 

 take the form of ridges, sometimes a mile or more long, with arched cross 

 section, like the osars. They contain no water-washed material like the 

 osars, and are substantially parallel with the glacial scratches of the region. 

 Often I have traveled a long distance in the wilderness in search of a 

 "horseback" which had been described to me, and which I anticipated find- 

 ing to be an osar, only to find it a mass of till. Such a ridge has been cut 

 by the Penobscot River at the mouth of South Twin Lake. The local 



-Section iicross Muujoy Hill, Portland. Kock overlain by 

 lenticular mass of till, and tliat by glacial gravel. 



