198 NUMMULITES AND MOUNTAINS. 



it continues into A ssam and Burma, and reappears in the 

 Andaman and Nicobar Islands in the Bay of Bengal. 



It is, however, in the inner Himalaya that the occur- 

 rence of immnmlitic limestones and certain overlying 

 Tertiary rocks is of more especial interest, since it is there 

 that they attain a greater elevation than in any other part 

 of the world. It is in the upper Indus Valley, in the neigh- 

 bourhood of Leh in western Tibet, that these nummulitic 

 rocks occur; running some distance down the Indus to the 

 west of Leh, and to the eastward of that town extending 

 into Chinese territory. There is good evidence to show 

 that the arm of the sea in which these nummulitic rocks 

 were deposited communicated with the ocean to the east- 

 ward in the Bay of Bengal, instead of following the course 

 of the Indus in a westerly direction to the Arabian Sea. 

 Moreover, in some parts of this area the rocks which 

 overlie, and are, therefore, newer than the nummulitic 

 limestone, are raised to the stupendous elevation of more 

 than 21,000 feet above the sea-level. 



We have, therefore, before us decisive evidence to show 

 that those parts of the earth's surface which at the present 

 day form some of the highest peaks in the Himalaya were, 

 at the period when the London clay was deposited, below 

 the level of the sea ; and consequently that the elevation 

 of that part of the Himalaya has taken place entirely 

 since that epoch, during a period when the physical 

 features of England have altered only to a comparatively 

 slight degree. There is, moreover, equally conclusive 

 evidence to show that the elevation of the Himalaya was 

 not completed until a much later epoch of the earth's 

 history, since on the southern flanks of this mighty range 

 we find beds of sandstone containing remains of mammals 

 which lived during the Pliocene, or later Tertiary epoch, 

 raised to a height of several thousand feet above the sea- 

 level. 



The elevation of the Indus Yalley in the heart of the 

 Himalaya could not, therefore, have commenced until the 

 Miocene, or middle Tertiary epoch, while that of the outer 

 Himalayan ranges could not have been completed till far 

 into the Pliocene period, and, for all we know to the 



