362 GLACIAL GEAVELS OF MAINE. 



delta showing assortment of material from coarse on one side (next the 

 ridge) to very fine on the other, the stratification also becoming more and 

 more horizontal. Yet the material of the ridges often shows some horizontal 

 gradation, the finer sediment being situated at the south. The assortment 

 is not so complete when the deposit consists of ridges as where it expands 

 into a broad, flat plain. Near the coast the isolated eskers mostly take the 

 form of cones, domes, or short lenticular ridges. In the interior they are 

 almost always short ridges, which the lumbermen report as "horsebacks." 

 North of the region of the long osars they are the only form of glacial 

 gravel reported by the State geologists of Maine or others, or discovered 

 by me. Thus I have note of quite a number of short ridges in the valley 

 of the Masardis or St. Croix Eiver, which flows north into the Aroostook 

 River. It is possible that these are part of a connected series, but I can not 

 prove it. Lumbermen report great numbers of horsebacks in the region 

 di-ained by the St. John River, but many of these are elongated drumhns — 

 at least farther south I have found many of the horsebacks to be such. 



What were the conditions under which the isolated osars or eskers were 

 formed? A good type is found about a mile south of New Vineyard Post- 

 Office. The esker is situated in the jaws of a north-and-south pass through 

 the high hills. It is about 10 feet high and 150 feet long. In the pass 

 is a divide where the drainage waters part, some flowing north toward 

 New Portland, others south to Farmington. The ridge is situated on the 

 northern slope about one-fourth of a mile north of the divide. There is a 

 considerable amount of alluvium south of this divide all the way to Farm- 

 ington, and it is probable that it is some form of glacial sediments or frontal 

 matter, but this I have not proved. To the north of the esker broad open 

 valleys extend all the way to Kingfield and Mount Bigelow. In late glacial 

 time the ice would naturally linger in these valleys after the ice south of 

 the divide was all melted, since a supply could readily come from the 

 region of high hills near the Dead River. After the front of this tongue of 

 ice had retreated north of the diAade a small lake would be formed south 

 of the ice, coiafined between the ice and the hill or divide lying south of it. 

 The slopes are gentle, and this lake would not be more than 15 or perhaps 

 20 feet deep at the time when the extremity of the ice had receded as far 

 north as the position of the ridge. The lake would nowhere be more than 

 one-eighth of a mile wide. If a glacial stream poured into the sujDposed lake, 



