390 PHYSICAL GEOGRAPHY OF SIKKIM. Appendix E. 



west wind, which blows during the afternoons of the winter months 

 over the plains, and along the flanks of the outer range, and is a 

 dry surface current, due to the diurnal heating of the soil. "When 

 it is considered that this wind, after passing lofty mountains on the 

 outer range, has to traverse eighty or one hundred miles of alps 

 before it has watered all the forest region, it will be evident that 

 its moisture, must be expended before it reaches Tibet. 



Let the figures in the accompanying woodcut, the one on the 

 true scale, the other with the heights exaggerated, 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 Himalaya at 

 300. The lower rugged outline represents one meridional ridge, 

 with all its most prominent peaks (whether exactly or not on the 

 line of section) ; the upper represents the parallel ridge of Singa- 

 lelah (D.E.P.), of greater mean elevation, further west, introduced 

 to show the maximum elevation of the Sikkim mountains, Kin chin - 

 junga (28,178 feet), being represented on it. A deep valley is 

 interposed between these two ridges, with a feeder of the Teesta in 

 it (the Great Rungeet), which runs south from Kinchin, and turning 

 west enters the Teesta at R. The position of the bed of the Teesta 

 river is indicated by a dotted line from its source at T to the plains 

 at S ; of Dorjiling, on the north flank of the outer range, by d ; of 

 the first point where perpetual snow is met with, by P ; and of the 

 first indications of a Tibetan climate, by C. 



A warm current of air, loaded with vapour, will deposit the 

 bulk of its moisture on the ridge of Sinchul, which rises above 

 Dorjiling (c?), and is 8,500 feet high. Passing on, little will be 

 precipitated on e, whose elevation is the same as that of Sinchul ; 

 but much at f (11,000 feet), where the current, being further 

 cooled, has less capacity for holding vapour, and is further exhausted. 

 When it ascends to P (15,000 feet) it is sufficiently cooled to deposit 

 snow in the winter and spring months, more of which falling than can 

 be melted during the summer, it becomes perennial. At the top of 

 Kinchin very little falls, and it is doubtful if the southerly cur- 

 rent ever reaches that prodigiously elevated isolated summit. The 

 amount of surface above 20,000 feet is, however, too limited and 



