■Februaby 8, 1907] 



SCIENCE 



231 



origin of this string of lakes thus seems to 

 ■he reasonably well attested. Postglacial 

 =«limatic changes, indicated by abandoned 

 ^hore lines, are discussed in some detail. 



W. M. D. 



POSTGLACIAL AGGRADATION OP HIMALAYAN 

 VALLEYS 



The possibility that glacially overdeepened 

 'Himalayan valleys have lost their lakes in 

 -consequence of postglacial aggradation, as 

 suggested at the beginning of the preceding 

 mote, is supported by the features of the 

 Shigar valley, northeast of the vale of Kash- 

 mir, as described in an admirable essay on 

 * Die Thaler des nordwestlichen Himalaya,' by 

 'K. Oestreich, topographer of the Workman ex- 

 'pedition, 1902, and now Docent in Marburg 

 ^University (Peterm. Mitt. Ergdnz'hft, 155, 

 1906: 36 exceptionally fine plates). This val- 

 ley was invaded by huge glaciers from the 

 lofty Mustag range on the north, where gla- 

 nders of great size still remain; and Oestreich 

 -points out the strong contrast between the 

 jDroad glaciated trough of the Shigar and the 

 narrow gorge of the Indus which the Shigar 

 -joins, the village of Skardu lying near the 

 -junction. The Indus in its northwestern in- 

 ■termontane course follows for 150 miles (ex- 

 -cept near Skardu, as stated below) a young 

 -gorge, eroded some 200 meters beneath the 

 'floor of an earlier, larger and more mature 

 valley: the sides of the gorge show numerous 

 ledges between incompletely graded slopes ; the 

 iottom has no continuous flood plain, but only 

 local sandbanks at the base of the convex 

 spurs; the road can not follow the river, but 

 -4ias to rise and fall on the spurs of the valley 

 'Side. The Shigar valley, on the contrary, is 

 ■described as having been widened and deep- 

 • ened by glacial action : it has a broad, aggraded 

 ■floor, on which the river divides and wanders 

 -in a braided course : the valley sides are glaci- 

 ated and carry patches of glacial deposits. 

 The barren slopes of the desert mountains are 

 -believed to have aided in supplying waste with 

 -which to aggrade the overdeepened valley. 

 -Similar features are found also in a middle 

 .portion of the Indus valley — the Skardu basin 

 -- — for some twelve miles below the entrance of 



the Shigar; and again, to a less degree, for 

 some twenty miles farther up the Indus to the 

 entrance of the Shayok, which like the Shigar 

 brought in a great glacier from the north. 

 Before the Skardu basin was fiUed with 

 gravel, there is much probability that it con- 

 tained a lake. 



It is singular to note that, although Oes- 

 treich ascribes the deepening and widening of 

 the Shigar valley to glacial erosion, he ex- 

 plains its continuation in the Skardu basin as 

 the result of tectonic movements : the glaciers 

 did not, he says, deepen the basin by erosion, 

 but the deepening of the basin by deformation 

 attracted the glaciers to it. The text is un- 

 fortunately not detailed enough to enable the 

 reader to reach an independent judgment. 

 W. M. D. 



UPLIFTED PENEPLAINS IN THE HIMALAYAS 



In a later section of the essay referred to 

 in the foregoing note, Oestreich gives an ex- 

 cellent description of the highlands of Deusi — 

 the Deosai plains of English travelers — and 

 accounts for them as an uplifted and not yet 

 dissected peneplain. They have a somewhat 

 circular area, 24 kil. in diameter, and stand at 

 an altitude of from 3,800 to 4,000 met. ; their 

 gently undulating surface, sometimes sur- 

 mounted by subdued hills, shows no sympathy 

 with the deformed structure of their mass. 

 Mountains rise around them to 5,000 met. ex- 

 cept on the southeast, where their streama 

 escape. The whole surface has been glaciated, 

 and is now clothed in summer with grass and 

 flowers. It is pointed out that the Deusi high- 

 land is the only example of its kind on the 

 near side of the river Indus, but that similar 

 highlands exist farther inland, especially in 

 Tibet. 



It thus would seem that, as far as this part 

 of the Himalaya is concerned, it falls in with 

 a number of other mountain ranges — as re- 

 cently pointed out for the Alps by Penek, for 

 the Carpathians by Martonne, for parts of 

 China by Willis, to say nothing of various 

 ranges in the United States — in owing its alti- 

 tude not to the deformation by which its dis- 

 ordered structure was caused, but to a broad 

 uplift which took place long enough after the 



