STUDIES FOR STUDENTS. 53 I 



accumulation in the superglacial channel, except so far as they 

 were disturbed in the process of descent. Of these there are 

 perhaps two varieties. 



(i) Superglacial osars {asar) or eskers {kames of some authors} . 

 — Under this head are to be classed such channel-deposits as 

 retained their elongated form and became ridges, and hence fall 

 under the Scandinavian type. In the earlier studies of the sub- 

 ject a considerable number of specialists would have inclined to 

 classify most osars under this head, but opinion appears to be 

 inclining toward the reference of the greater part of the osar 

 ridges to subglacial agencies. 



(2) Superglacial kames. — Sheets or pockets of assorted mate- 

 rial gathered on the surface of the ice were doubtless subjected 

 to much disturbance and re-arrangement in the process of 

 descent. The resulting deposits would constitute undulatory 

 tracts of drift or groups of hillocks for which there is perhaps no 

 specific name, but which may be thrown under the general class 

 kames for the present. 



3. Marginal deposits. 



Under this class are embraced all those deposits of glacial 

 streams that were made at the margin of the mer de glace, and 

 whose forms were dependent upon the conditions that obtained 

 at the margin. The following classes are recognized : 



o C5 o 



( I ) Kames. — To this class I refer irregular heapings of 

 assorted drift generally arranged in lines or tracts transverse to 

 glacial movement. They are often closely associated with and 

 merge into terminal moraines of till. Sometimes they largely 

 constitute the terminal moraines, the action of glacial waters being 

 so great as to assort nearly all of the material brought forward to 

 the edge of the ice. In such cases the morainic factor (in the 

 genetic sense) is found in the mechanical action of the ice in 

 restraining the action of the waters, in controlling the nature of 

 the heapings and in pushing of the accumulations, distorting and 

 modifying them. Irregular heapings of assorted drift of this 

 variety are not, however, wholly confined to border tracts, but 

 occur irregularly distributed over the area abandoned by the ice. 



