EAST NEPAL AND THE SIKKI.M HIMALAYA MOUNTAINS. 87 



densed into a thick white mist, which hangs over the redundant 

 vegetation. A brigiit starlight night is ahnost unknown in 

 the summer months at GOOO to 10,000 feet, but is frequent 

 in December and January, and at intervals between October 

 and May, when, however, vegetation is little affected by the 

 cold of nocturnal radiation. In the regions north of K starlight 

 nights are more frequent, and the cold produced by radiation is, 

 at 14,000 feet, often severe towards the end of the rains in Sep- 

 tember. Still the amount of clear w eather during the night is 

 small ; the fog clears off for an hour or two at sunset as the 

 wind falls, but the cold north returning current chills the air again 

 soon after, and rolling masses of vapour are hence flying over- 

 head or sweeping the surface of the earth throughout the summer 

 nights. In the Tibetan regions, again, bright nights and even 

 sharp frost prevail throughout the warmest months. 



Referring again to the cut, it must be borne in mind that 

 neither of the two meridional ridges runs in a straight line, but 

 that they wand or zigzag like all mountain ranges ; and that spurs 

 from each ridge are given off" from either flank alternately, and 

 that the head of a spur on one side answers to the source of a river 

 (i.e., the head of a valley) on the other. These rivers ai-e feeders 

 of the main stream, the Teesta, and run at more or less of an 

 angle to the latter. The spurs from the east flank of one ridge 

 cross, at their ends, those from the west flank of another ; and 

 thus transverse valleys are formed, presenting many modifications 

 of climate with regard to exposure, temperature, and humidity. 



The roads from the plains of India to the watershed in Tibet 

 always cross these lateral spurs. The main ridge is too winding and 

 rugged, and too lofty for habitation throughout the greater part 

 of its length. The river channel is always very winding, un- 

 healthy for the greater part of the year below 4000 feet, and 

 often narrow, gorge-like, and rocky. Villages are always placed 

 above the unhealthy regions, on the lateral spurs, which the 

 traveller keeps crossing throughout every day's march ; for these 

 spurs give off lesser ones, and these again others of a third 

 degree, whence the country is cut up into as many spurs, ridges, 

 and ranges, as there are rills, streams, and rivers on the moun- 

 tains. 



Though the direction of the main atmospheric current is to 

 the north, it is seldom in reality felt to be so, except theobservef 

 is on the very exposed mountain tops, or watches the motions of 

 the upper strata of atmosphere. The lower currents of air rush 

 up botli the main and lateral valleys, throughout the day ; and 

 from the sinuosities in the beds of the rivers, and generally trans- 

 verse directions of their fieeders, the current often becomes an 

 east or west one. In the branch valleys draining to the north 



