396- PHYSICAL GEOGRAPHY OF SIKKIM. Appendix E. 



single mountains alone, on the meridional ridges, have at one time 

 supported and at another denied the assertion, that the snow lies 

 longer and deeper on the north than on the south slope of the 

 Himalayan ridge. 



The great accumulation of snow at 15,000 feet, in the parallel 

 of P, exercises a decided influence on the vegetation. The alpine 

 rhododendrons hardly reach 14,000 feet in the broad valleys and 

 round-headed spurs of the mountains of the Tunkra and Chola 

 passes ; whilst the same species ascend to 16,000, and one to 17,000 

 feet, at T. Beyond the latter point, again, the great aridity of the 

 climate prevents their growth, and in Tibet there are generally none 

 even as low as 12,000 and 14,000 feet. Glaciers, again, descend to 

 15,000 feet in the tortuous gorges which immediately debouch from 

 the snows of Kinchinjunga, but no plants grow on the debris they 

 carry down, nor is there any sward of grass or herbage at their base, 

 the atmosphere immediately around being chilled by enormous 

 accumulations of snow, and the summer sun rarely warming the soil. 

 At T, again, the glaciers do not descend below 16,000 feet, but a 

 greensward of vegetation creeps up to their bases, dwarf rhododen- 

 drons cover the moraines, and herbs grow on the patches of earth 

 carried down by the latter, which are thawed by the more frequent 

 sunshine, and by the radiation of heat from the unsnowed flanks of 

 the valleys down which these ice-streams pour. 



Looking eastward or westward on the map of India, we perceive 

 that the phenomenon of perpetual snow is regulated by the same 

 laws. From the longitude of Upper Assam in 95° E to that of 

 Kashmir in 75° E, the lowest limit of perpetual snow is 15,500 to 

 16,000 feet, and a shrubby vegetation affects the most humid localities 

 near it, at 12,000 to 14,000 feet. Receding from the plains of India 

 and penetrating the mountains, the climate becomes drier, the snow- 

 line rises, and vegetation diminishes, whether the elevation of the land 

 increases or decreases ; plants reaching 17,000 and 18,000 feet, and 

 the snow-line, 20,000 feet. To mention extreme cases ; the snow- 

 level of Sikkim in 27° 30 is at 16,000 feet, whereas in latitude 35° 30 

 Dr. Thomson found the snow line 20,000 feet on the mountains near 

 the Karakoram Pass, and vegetation up to 18,500 feet — features 

 I found to be common also to Sikkim in latitude 28°. 



