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SCIENCE 



[N. S. Vol. XXV. No. 632 



tinctly Alpine form. As to the strength of 

 glacial erosion in excavating the valley 

 troughs, it is said that ' not a few of the 

 valleys may have been deepened 400 to 700 

 feet in their upper parts, while in some cases 

 * * * the deepening may have been consider- 

 ably more.' In view of this, explicit mention 

 of ' valley deepening ' as well of the ' round- 

 ing and widening of valley bottoms ' might 

 have been made in the list of features for 

 which glacial erosion is held responsible, as 

 quoted above. Here, as in so many other 

 glaciated valleys, the depth of the glacial 

 tarns, many of which occur in the upper 

 reaches of the valleys, is by no means a full 

 measure of the depth of glacial erosion— the 

 rock basins simply indicate an excess of ero- 

 sion at one point over that next down-valley, 

 a fact which might have been more clearly 

 presented. Hanging lateral valleys occur but 

 are not numerous; nevertheless they certainly 

 deserve a place in the list of ' the distinctive 

 features of glaciated mountains,' where for 

 some reason they are omitted. 



The morainal deposits, which occur where 

 the local glaciers ended in the descending 

 valleys on the mountain flanks, are discussed 

 in some detail; good examples of moraines 

 and morainal lakes are figured. About half 

 of the lakes of the district — all of small size — 

 are of this origin; the other half occupy 

 glacially excavated rock basins higher up the 

 valleys, as already indicated. Changes in 

 drainage due to glacial erosion are noted, 

 an example of glacial capture previously re- 

 ported by Matthes being here figured. (The 

 titles of two figures illustrating this ' capture ' 

 have been by oversight interchanged.) A case 

 is cited in which a glacier failed to remove all 

 the decayed rock at a certain point, while 

 rock surfaces not far away show severe wear. 

 Although this is a minor feature, and cer- 

 tainly to be expected as a common result of 

 glacial activity, the citation is of importance 

 in connection with other cases of larger area 

 where the failure of a glacier to remove de- 

 cayed rock has been urged as evidence of in- 

 efficiency of glacial erosion in general. The 

 facts, as here recorded, again emphasize the 

 principle that glaciers, like rivers, erode 



vigorously in one place, feebly in another, and 

 make extensive deposits in a third. 



D. W. J. 



GLACIAL EROSION IN THE HIMALAYAS 



It has been frequently remarked by those 

 who are still unconvinced of the capacity of 

 glaciers to deepen valleys and excavate lake 

 basins, that the absence of valley lakes in the 

 glaciated districts of the Himalayas is strong 

 testimony on the negative side of the problem. 

 The reply has been made that the glaciated 

 parts of the Himalayan valleys probably had 

 so strong a slope in preglacial time that the 

 overdeepening by glacial erosion did not pro- 

 duce profound lakes, and that such lakes as 

 were produced have already been filled with 

 waste by the heavily loaded rivers of those 

 lofty and often barren mountains. But a 

 specific example of glacial erosion in the inner 

 Himalayan region east of the vale of Kash- 

 mir, has recently been described by Ellsworth 

 Huntington, under the title, 'Pangong, a 

 glacial lake in the Tibetan plateau' {Journ. 

 Geol., XIV., 1906, 599-61Y), from which it 

 appears that valley glaciers have actually pro- 

 duced lakes there, as well as in other moun- 

 tain ranges. Pangong, or Pangkong, at an 

 altitude of 14,000 feet, about 40 miles long 

 and 142 feet deep (as stated by Drew), is the 

 distal member of a series of lakes of which the 

 total length is 105 miles, with a maximum 

 breadth of four miles. The enclosing moun- 

 tains rise in steep slopes for the first 1,000 

 or 2,000 feet, and then at gentler slopes 3,000 

 or 4,000 feet more to peaks 20,000 feet in alti- 

 tude. Large moraines, old enough to be much 

 eroded, are found some twenty miles down the 

 main valley from the end of the lake. 

 Glaciated knobs are found along the valley 

 floor, perched erratics occur up to 600 feet 

 over the lake surface, and at least one lateral 

 valley hangs distinctly above the main valley. 

 Pangong does not overflow at present; its sur- 

 face is thirty-five feet lower than a barrier, a 

 mile farther down the valley, which Drew 

 took to be an alluvial fan formed by a side 

 stream, but which Huntington gives good rea- 

 son for regarding as a rock sill or inequality 

 in the deepened valley floor. The glacial 



