I9I0.] INLAND-ICE OF THE ARCTIC REGIONS. 93 



the position of the obstruction. The experiments of Hess*' give 

 results which are consistent with those of Case. Hess employed in 

 his experiments parallel wax disks of alternating red and white 

 colors, and these were forced under hydraulic pressure through a 

 small opening. It was found that the layers turn up to the surface 

 in this " model glacier " apparently as a result of the friction upon 

 the bottom and at only moderate distances from the opening where 

 the energy of the active moving substance pressing from the rear 

 has to some extent been dissipated. 



In Chamberlin's studies of certain Greenland glaciers, he was 

 permitted to observe the effect upon the motion of the glacier of 

 low prominences in its bed. These observations are confirmatory 

 of the experiments described.*^ 



The swirl colks or eddies which Suess has suggested as occur- 

 ring below nunataks, in order to account for certain lakes in Nor- 

 way, seemed to be much less clear, and it is a little difficult to 

 assume an eddy in the ice which is in any way comparable to the 

 eddies of water. 



Marginal Moraines. — Inasmuch as the rock appears above the 

 surface of the ice of the Greenland continental glacier only in the 

 vicinity of its margins, and here only as small islands or nunataks, 

 the rock debris carried by the Greenland ice must be derived almost 

 solely from its basement. As described in detail by Chamberlin, 

 it is the lower lOO feet of ice to which englacial debris is largely 

 restricted.*^ Medial moraines, if the term may be properly applied 

 to those ridges of rock debris which upon the surface of the ice 

 go out from the lower angles of nunataks, have been frequently 

 described by Nansen and others. They seem to differ but little 

 from certain of the medial moraines which have been described 

 in connection with the larger mountain glaciers. 



Nansen has mentioned heavy terminal moraines in the Austmann 

 Valley where he came down from the inland-ice after crossing the 



*' " Die Gletscher," 1904, p. 171, fig. 28. 



** " Recent Glacial Studies in Greenland." Annual address of the Presi- 

 dent of the Geological Society of America, Bull. Geol. Soc. Am., Vol. 6, 

 1895, PP- 199-220, pis. 3-10. 



*^ Chamberlin, /. c, p. 205. 



