.. 















Ch.XV.1 



IN Dll'l'KRENT LATITUDES 



66 1 



cause the aerial current is made to flow upwards, and to 

 ascend to a height of several thousand feet above the sea. 

 Both the air and the vapour contained in it, being thus re- 

 lieved of much atmospheric pressure, expand suddenly, and are 

 cooled by rarefaction. The vapour is condensed, and about 

 500 inches of rain are thrown down annually, nearly twenty 

 times as much as falls in Great Britain in a year, and almost 

 all of it poured down in six months. The channel of every 

 torrent and river is swollen at this season, and much sand- 

 stone horizontally stratified, and other rocks are reduced to 

 sand and gravel by the flooded streams. So great is the 

 superficial waste (or denudation) , that what would otherwise 

 be a rich and luxuriantly wooded region, is converted into a 

 wild and barren moorland. 



After the current of warm air has been thus drained of a 

 large portion of its moisture, it still continues it northerly 

 course to the opposite flanl " ' n ™ 7 ~ ™ 



miles farther north, and here the fall of rain is reduced to 70 

 inches in the year. The same wind then blows northwards 

 across the valley of the Brahmapootra, and at length arrives 



of the Khasia 



Hiinalaj 



that those mountains, up to the height of 5,000 feet, are 

 naked and sterile, and all their outer valleys arid and dusty. 

 The aerial current still continuing its northerly course and 

 ascending to a higher region, becomes further cooled, con- 

 densation again ensues, and Bhootan, above 5,000 feet, is 

 densely clothed with vegetation.* 



In another part of India, immediately to the westward, 

 similar phenomena are repeated. The same warm and humid 

 winds, copiously charged with aqueous vapour from the Bay 

 of Bengal, hold their course due north for 300 miles, across 

 the flat and hot plains of the Ganges, till they encounter the 



Sikkim Mountains 



XIX 



On the 



ram 



southern flank of these they discharge such a deluge of 

 that the rivers in the rainy season rise twelve feet in as many 



houi 



Numerous 



four thousand feet along the face of the mountains, composed 

 of granite, gneiss and slate, descend into the beds of streams, 



* Hooker s Himalayan Journal, ined. 



