94 HOBBS— CHARACTERISTICS OF THE [April 22, 



continent. The material of these moraines consisted mainly of 

 rounded and polished rock fragments, and is obviously englacial 

 material.^** Along the land margin of the Cornell ice tongue Tarr 

 found a nearly continuous morainic ridge parallel to the ice front. 

 This ridge usually rests at the base of the ice foot, and is sometimes 

 a part of this foot, wherever debris has accumulated and protected 

 the ice beneath from the warmth of the sun. Such an accumula- 

 tion causes this part of the glacier to rise as a ridge. In other 

 cases the ridge is, however, separated from the ice margin, and 

 sometimes there are several parallel ridges from which the ice front 

 has successively withdrawn"^ (see Plate XXVIII, B). 



According to von Drygalski the marginal moraines of the 

 Greenland ice sheet as regards their occurrence, form, and com- 

 position, are in every way like those remaining in northern Europe 

 from the time of the Pleistocene glaciation, and this is true of those 

 which run along the present border of the inland-ice as well as of 

 those still mightier ancient moraines which follow at certain dis- 

 tances."- These moraines are generally closely packed blocks with 

 relatively slight admixture of finer material. They are the largest 

 where the ice border enters the plains, or pushes out upon a gentle 

 slope, and they are smallest where the ice passes steep rocky angles. 



It is worthy of note that the marginal moraines of Greenland 

 become locally so compact and resistant that they oppose a firm 

 obstruction to the ice movement. Then the ice pushes out laterally 

 into the marginal lakes which develop there or pushes up upon the 

 moraines. It thus comes to arrange its layers parallel to the slope 

 of the morainic surface or, in other words, so that they dip toward 

 the ice.^^ 



Another type of marginal moraine which was mentioned by 

 Mohn and Nansen from south Greenland, and later fully described 

 by Chamberlin from north Greenland, is explained by the upturn- 



^ Mohn u. Nansen, " Wissenschaftlichen Ergebnisse von Dr. F. Nansen's 

 Durchquerung von Gronland, 1888," Pet. Mitt. Ergiinziingsb., 105, 1892, p. 

 91. 



" R. S. Tarr, "The Margin of the Cornell Glacier," Am. GcoL. Vol. 20, 

 1897, p. 148. 



^' Gronland-Expedition, /. c. 



^S'on Drygalski, /. c, p. 529. 



