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Snoiv-Line in the Himalaya. 347 



Tola, the alteration was complete ; the flora had shrunk within 

 the most scanty limits, the bushes hardly ever deserving the 

 name of shrubs ; the few herbs that were there were stunted 

 and parched, the soil dry, and the roads quite dusty. At 

 Melam the still closer approximation of the climate to that 

 of Thibet, is clearly shewn by the occurrence of several plants 

 undoubtedly Thibetan, that are not found further to the south. 

 Such are Caragana versicolor, the (Dama) of the Bhotias, 

 which covers the plains of Thibet ; a Clematis, dwarf Hippo- 

 phae, Lonicera, and two or three Potentillas ; and no doubt 

 several others might be named. 



Now although it is to the winter and not to the summer 

 rains,* that the precipitation of snow on these mountains is 

 to be ascribed, yet the circumstances under which the vapour 

 is condensed, appeared to be the same at both seasons. 

 Southerly winds blow throughout the year over the Hima- 

 laya, in the winter with peculiar violence ;t and whatever 

 be the more remote cause of the periodical recurrence of the 

 rains, there can I think be little doubt, that the proximate 

 cause of the condensation of by far the greater portion of the 

 snow or rain that falls on the snowy mountains, is that the 

 current from the south is more damp or hot than the air in 

 contact with the mountains against which it blows ; a rela- 

 tion which holds good in the winter as well as in the sum- 

 mer. 



Thus the air that comes up from the south no sooner 

 reaches the southern boundary of the belt of perpetual snow, 

 where the mountains suddenly rise from an average of per- 

 haps 8,000 or 10,000 feet, to nearly 19,000 or 20,000, then it 

 is deprived of a very large proportion of its moisture, which is 

 converted into cloud, rain, or snow, according to circumstances. 

 And the current, in its progress to the north, will be incapa- 



• Although it does not appear to be so well known, the winter rains of North 

 Western India are as strictly periodical as those of the summer. 



t The southerly winds that prevail at considerable heights in the Hima- 

 laya, and in the countries to the north, are diurnal 2>henomena, evidently de- 

 pendent on the apparent motion of the sun ; and in their time of beginning 

 of maximum and of ending, greatly resemble the hot winds of the plains of 

 India, which have a similar origin. 



