84 EAST NEPAL AND THE SIKKIM HIMALAYA MOUNTAINS. 



is resolved into isolated [)eaks, situated on the meridional ranges, 

 at distances varying from 30 to 80 miles from the observer ; their 

 snowed spurs, projecting east and west, cross one another, and 

 being uniformly white, and all brought by perspective into one 

 line, they appear to connect all the peaks into one grand un- 

 broken range of snow. The rivers, instead of having their 

 sources in the snowy mountains, all rise far beyond them ; many 

 of their sources are upwards of 100 miles in a straiglit line from 

 the plains, in a very curious country, loftier by far in mean ele- 

 vation than the meridional ridges which run south from it, and 

 though so lofty, comparatively unsnowed. This rearward moun- 

 tain region is Tibet, and into it all the Sikkim, Nepal, and 

 Bhotan rivers lead, up to a watershed whose discharge to the 

 northward is into the Yarou-Tsampu river, which becomes the 

 Burrampooter of Assam. Tibet is a very arid mountain mass, 

 the southerly wind being exhausted of vapour by these long ridges 

 long before reaching it. The maximum range in latitude and 

 elevation of the Himalayan vegetation is determined very much 

 by the length of the rivers, which, rising in Tibet as small streams, 

 increase in size as they receive the drainage from the snowed parts 

 of the ridges that bound them in their courses. Their banks, 

 between 8000 and 14,000 feet, are generally clothed witli Rhodo- 

 dendrons, sometimes to the almost total exclusion of other woody 

 vegetation, especially near the snowed mountains — a cool tem- 

 perature and great humidity being tlie most favourable conditions 

 for the luxuriant gi'owth of this genus. 



The source of this humidity is the southerly or sea wind, 

 which blows steadily from May till October in Sikkim, and pre- 

 vails throughout the rest of the year, if not as the monsoon pro- 

 perly so called, as a current from the moist atmosphere over 

 the Gangetic delta. This ruslies north to the rarefied regions of 

 Sikkim, up the great valleys, and does not appear materially 

 disturbed by the north-west wind, which blows during the after- 

 noon of the Avinter months over the plains, and along the flanks 

 of the outer range, and is a dry surface current, due to the diurnal 

 heating of tiie soil. When it is considered that this wind, after 

 passing lofty mountains on the outer range, has to traverse 80 

 or 100 miles of alps before it has watered all the Rhododendron 

 region, it will be evident that its moisture must be expended 

 before it reaches Tibet. 



Let the accompanying woodcut represent two of these long 

 meridional ridges, from the watershed to the plains of India, 

 following in this instance the course of the Teesta river, from 

 its source at 19,000 feet to where it debouches from the Hima- 

 laya at 300. The lower rugged outline represents one meri- 

 dional ridge, with all its most prominent peaks (whether exactly 



