32 GRIESBACH : GEOLOGY OF THE CENTRAL HIMALAYAS. 



proved to be the valleys north of the Gangotri and Mana glaciers, 



the Girthi valley in Joheir, and the Lissar valley in Dharma. Parts 



of the first are altogether inaccessible, whilst the remainder of it 



even was most difficult to travel over. The Girthi valley (plate 10) 



is a deep trough, with an almost vertical trias-carbon cliff forming its 



right side, and with enormous glaciers descending from the Nanda 



Devi peaks on its left side. The Lissar valley is similar; the eastern 



or left side of it is formed by more or less precipitous cliffs of 



palaeozoic and trias beds, whereas on the right side of the river is a 



succession of huge moraines and cones of debris, shot out by the 



large glaciers of the Takachull and Bambadhura peaks (fig. 4 and 



pis. 14, 15 andi6). 



In a mountainous country, subject to extensive erosion by rivers, 



weathering and sub-aerial changes, it may be 

 Glacial deposits. . , . 



expected that distinct traces of former glaciation 



have entirely disappeared, or are at least very difficult to recognize 

 amongst the more recent results of glacial or river erosion. Never- 

 theless, here and there one may detect isolated traces of glacial de- 

 posits of by-gone periods. Amongst them may be reckoned the high- 

 level terraces which are now found far above the present base of the 

 valleys, forming occasionally mere patches which are preserved from 

 complete denudation in sheltered parts of the great river-gorges which 

 are cut through the Central Himalayas. It is highly probable that 

 glaciers did once extend to far below their present level ; for instance, 

 the Milam glacier must once have reached far down the Gori valley, 

 to a point somewhere half-way between Milam and Munshiari, where 

 I found moraine matter, through which the Milam river has eroded 

 its present bed. 



I met with much clearer instances of the former extension of 

 glaciers in the tracts north of Niti. There, the heights below the Dalda- 

 kharak group of peaks, on the right side of the Dhauli Ganga, are 

 profusely strewn with boulders of metamorphic rocks, chiefly of 

 granitic gneiss, such as composes the greater part of the range 

 between Niti and the Kamet. 



( 32 ) 



