76 W. UPHAM — DERIVATION OF KAMES, ESKERS, AND MORAINES. 



from which some of them must have been derived. These are Niagara 

 limestone bowlders, which are a large proportion wherever bowlders are 

 found in this esker; but they can have been transported no more than 

 three or four miles from their parent ledges, since the northern limit of 

 the outcropping belt of the limestone lies within that distance. 



For similar reasons as in the case of the Long Island moraine, I con- 

 clude that this esker was deposited by a stream descending from the 

 dissolving ice surface, and not by any subglacial river welling upward 

 from an ice-covered tunnel traversing the lowland 200 to 250 feet beneath 

 the crest of the ridge. As a corollary linked with this conclusion, the 

 ascent of the glacial currents which had carried drift into the ice on this 

 area appears to have been sufficient to raise the bowlders within three 

 or four miles from their sources to heights exceeding 200 feet above the 

 land surface. This would be, however, perhaps no more than a gradient 

 of one degree, which gives 92 feet of rise in each mile of advance. In 

 other words, the ratio between the uplift of the bowlders into the ice- 

 sheet and their transportation forward need have been no more than 

 1 : 57, instead of the abrupt ascent which at first thought one might sup- 

 pose to be required. 



Devil's Heart Hill, North Dakota. 



Several retreatal moraines of the ice-sheet are united in a complex belt, 

 chiefly consisting of knolly and hilly till, which stretches along the south- 

 ern side of Devil's lake in North Dakota, comprising the Dovre, Fergus 

 Falls, and Leaf Hills moraines, or the seventh, eighth, and ninth in the 

 series of ele\'len which I have traced in Minnesota, North Dakota, and 

 Manitoba. At an angle in this belt, where it is joined from the south by 

 the Dovre moraine, stands the most prominent hill of all this region, 

 aloof from any high accumulations of the morainic till, and rising as a 

 cone 175 feet above its base, to a height of 290 feet, as barometrically de- 

 termined by Nicollet, above the lake, or 1,722 feet above the sea level. 

 This hill, known by the translation of its aboriginal designation as the 

 Devil's Heart, is the largest and most remarkable isolated kame that has 

 ever come under my observation. Its slopes are very steep on all sides 

 excepting the south, where the otherwise nearly round topped, conical 

 hill is somewhat drawn out into a narrow, more slowly descending ridge. 

 It consists of gravel and sand, mostly not showing pebbles on the surface 

 larger than one and a half inches in diameter. A few bowlders, however, 

 a score or more in all, are seen on the sides of the hill to its top ; and 

 one a foot long (the only one seen at the crest) is embedded in the gravel 

 one rod south of the highest point and less than one foot lower. This 



