Vol. 54.] ON TEE GLACIAL GEOLOGY OF SPITSBERGEN. 221 



..of the glacier move more rapidly than the lower ; the glacier then 

 progresses by an overrolling movement, banks of ice-talus being 

 formed in front, which are subsequently overridden and again 

 incorporated in the glacier. 



(6) The Transport of Material. 



All the material carried by the glacier was either supraglacial or 

 ~ intraglacial. At least, we saw no sign of the dragging forward of 

 subglacial moraine matter. 



The supraglacial material is mostly angular, and agrees in general 

 ■characters with that of Swiss supraglacial moraines. The main 

 differences are that the erratics are usually smaller and the matrix 

 more argillaceous, both of which are due to the nature of the rocks 

 of the country and not to the glacial agencies. 



The material carried intraglacially is very abundant, and forms 

 the principal constituent of the Spitsbergen moraines. As is known 

 to be the case in Greenland, and as is assumed to have been the case 

 in the North American ice-sheet,^ the material is mainly scattered 

 ^through the lower layers of the ice ; but there are cases in which it 

 occurs throughout the whole thickness of the glacier. The material 

 may be uniformly scattered through the ice, but it is generally 

 collected along lines or into lenticular masses. It varies in amount 

 from a thin dust, which slightly discolours the ice, to moraine-stuff 

 which is simply held together by a small proportion of ice. We 

 have referred to this material as intraglacial, instead of as ' englacial,' 

 owing to the varying meaning given to the latter term. It was first 

 proposed in 1883 by Chamberlin^, who then used it in contra- 

 . distinction to ' supraglacial ' to include all ' the material embraced 

 within the glacial ice.' Later on, however. Prof. Chamberlin limits 

 ;the term to the material in the upper layers of the glacier. Thus 

 he ^ remarks : — ' The term englacial, as here used, does not include 

 such materials as may be lodged in the basal stratum of the ice 

 and brought down to the actual bottom by basal melting.' Hence, 

 Prof. Chamberlin would exclude from the category of englacial drift 

 by far the larger proportion of the material which we include in 

 ' intraglacial ' drift ; for we include therein all materials included 

 in the ice between the surface and sole of the glacier. 



Other authors, such as Mr. Warren Upham ^ — the most energetic 

 recent champion of the importance of ' englacial ' drift, — use the 

 term in a wider sense than either of the definitions just quoted. 

 The difference in terminology no doubt increases the apparent 

 difference of opinion as to the importance of intraglacially-carried 



1 W. Upham, ' Englacial Drift,' Amer. aeol. vol. xii (1893) pp. 38-39. 



^ T. C. Chamberlin, 'Preliminary Paper on the Terminal Moraine of the 

 ..Second Glacial Epoch,' Ann. Eep. U.S. Geol. Surv. no. iii (1883) p. 297. 



^ T. C. Chambei'lin, ' The Nature of the Englacial Drift of the Mississippi 

 :Basin,' Journ. Geol. vol. i (1893) p. 60. 



* W, Upham, ' Irregularity of Distribution of the Englacial Drift,' Bull. Gaol, 

 > Soc. Amer. vol. iii (1892) pp. 134-148. 



