Vol. 54.] ON THE GLACIAL GEOLOGY OF SPITSBERGEN. 209 



by the main stream, and when that melts they will be deposited 

 along one side of its valley. The direction of the moraines of this 

 tributary will be different from that of the deposits of the main 

 glacier ; and the moraines will be probably deposited at the foot of 

 the left bank of the valley, some distance below the tributary at 

 the mouth of which they were formed. The occurrence of small 

 terminal moraines along the sides of a valley has been recorded in 

 England and Greenland, and variously explained. 



(2) Moraines formed of Intragiacial Material 



are more important and interesting. The main characters of these 

 deposits are that the materials are subangular and rounded ; while 

 scratched and polished pebbles and boulders are abundant. The 

 coarser constituents are scattered through a line-grained matrix, 

 which is often well laminated, and may be false-bedded : this 

 matrix is frequently argillaceous. Lenticular masses of clay in 

 sand, or of sand in clay, are often present. The moraine may be 

 either well stratified, or there may not be a trace of stratification 

 in it. 



The most striking difference between moraines of this group and 

 those of the Swiss type is the much greater percentage of rounded 

 and striated boulders. Thus, in the supraglacially-formed moraines 

 of Booming Glacier, it often needed some search to find a striated 

 boulder. The following list shows the character of the intra- 

 giacial material, represented by a small heap lying in front of the 

 face of Booming Glacier : — 



Boulders. Pebbles. 



Rounded and striated 27 6 



Angular and subangular and striated ... 7 



Angular, but not striated 12 10 



E-ounded, but not striated 3 3 



The matrix was a tough clay. The proportion of pebbles was 

 smaller than usual, for in some heaps they were more numerous than 

 the boulders. 



Moraines of intragiacial material are common in Spitsbergen 

 around existing glaciers. They often form the basis of old moraines, 

 the surfaces of which are covered by a layer of supraglacial 

 morainic material. Our interest in these moraines was at once 

 roused by their remarkable resemblance iu composition to Boulder 

 Clay, On the broad plain at the foot of Booming Glacier we 

 found some square miles of a tough mud containing boulders and 

 pebbles ; it only needed to be dried and hardened in order to form 

 an ideal Boulder Clay. Clearly this deposit had been laid down by 

 land-ice, but not as a tip-heap at the end of a glacier. As the 

 glacier gradually melted away, the materials scattered through it 

 were deposited upon the valley-floor. Sections cut by streams 

 through the deposits showed them to be sometimes laminated with 

 remarkable regularity, forming clays of the type named by Good- 

 child ' gutta-percha clays.' 



