1867.] the Western Himalaya and Afghan Mountains. 113 



must have been very gradual, if we keep in mind what brought on 

 that decrease ; and as the glaciers retreated, animals advanced and 

 soon populated the high plateau of the Himalaya. These animals 

 have left their remains interred in the clayey grits of these elevated 

 lands. It may appear strange that elephants once lived at such a great 

 height, and in a climate so cold, but the osseous remains found in the 

 elevated plateau of Mexico belong to true elephants of extinct 

 species,* and the Siberian mammoth which was covered by a warm fur, 

 lived on the leaves of conifers and roamed over the ice-drift. There is 

 therefore no doubt that these animals had a great plasticity of organism, 

 and could adapt themselves to very extreme climates. 



The mammals discovered in the plateau of Thibet and Ladak, all 

 belong to extinct species. On the other hand, all the shells which I 

 have been able to collect in the old alluvium found near the foot of 

 the Sub-Himalaya belong to living species, and it is therefore most 

 probable that the older alluvium of the plains of India, and the high 

 plateau of the Himalayas belong to the post-pliocene epoch. 



From the above considerations, and the present state of our know- 

 ledge, it appears that the Afghan and Himalayan mountains suffered 

 their last upheaval during the pliocene period. 



99. — The description of the deposition of beds subsequently to the 

 great upheaval has been given incidentally in the preceding paragraph ; 

 the glaciers began to melt, great lakes were formed in several localities. 

 The Kashmir valley is a good example, Rukshu is another, and so is 

 Abbottabad valley. These lakes at first fed large rivers, and both lakes 

 and rivers had a considerable power in carrying mud, sand and boulders, 

 and thus raising their beds by several hundred feet ; but as the water- 

 fall diminished, the lakes and rivers diminished also, and the rivers 

 soon began to cut for themselves deep ravine-like beds in the middle 

 of their ancient bottoms, leaving on each side a great river-terrace. 



Before the rivers had lost their great volume, however, and while 

 they filled the whole of their original beds, they floated icebergs of 

 sufficient dimensions to carry blocks of stone of great size. The Salt- 

 Range for a time intercepted the free passage of the waters towards the 

 south and a shallow lake filled the whole country between it and the 



* Cosmos, Otte's translation, Vol. I. page 280. 



15 



