EAST NEPAL AND THE SIKKIM HIMALAYA MOUNTAINS. HI 



Temperature of the earth. — This, at 2^ to 3 feet depth, varies 

 %vith the temperature of the month, but is hardly affected by 

 the diurnal variation, except in extreme cases. In summer, 

 throughout the rains, May to October, the temperature is that 

 of the month, which is imparted by the rain to the depth of 

 11 feet during severe continued falls (of 6 to 12 inches a day), 

 on which occasions I have seen the buried thermometer indicat- 

 ing a temperature above the mean of the month. Again, in 

 the winter montlis, December and January, it stands 5° above 

 the monthly mean ; in November and February 4° to 5° ; in 

 March it is a little below the mean temperature of the month, 

 and in October above it ; April and May being sunny, it stands 

 above their mean temperature ; June to September a little be- 

 low the mean temperature of each respectively. 



In the middle and upper zones the sunk thermometer always 

 stands considerably above the mean of the month, the sun's rays 

 being more powerful and frequently felt, the rain less ; and the 

 earth, being cooled less by nocturnal radiation than it is warmed 

 by solar, accumulates heat to a certain depth. Thus in January, 

 at 13,000 feet, I have found it 17° above the mean temperature, 

 though the soil was frozen hard for 16 inches; and in July, at 

 the same elevation, 7'5° above the mean temperature. In August 

 I have seen it + 8° at 12,000 feet, in September + 74° at 

 15,400 feet, and in October + 12° at 16,800 feet; in July 

 -|-7'6° at 12,800 feet, and in October -f 10*5° at the same spot ; 

 in December + 9^ at 13,500 feet with several inches of frozen 

 soil. It is probable that the intense winter cold of the upper 

 zone does not materially affect the soil at 3 feet deptli, for there 

 is always a sufficiently deep covering of snow^ after the second 

 week of January to protect the soil from excessive cold. 



Solar radiation. — From a multitude of desultory observations 

 with the black bulb thermometer, I conclude that at 7000 feet, 

 67° above the temperature of the air is the average maximum 

 effect of the sun's rays on a black bulb thermometer* through- 

 out the year, amounting rarely to + 70° and + 80° in the 

 summer months, and more frequently in the winter. These re- 

 sults, though greatly above what are obtained at Calcutta, are 

 not much, if at all, above what prevail at the foot of the hills 

 and up the Gangetic valley. This effect is greatly increased 

 with the elevation. At 10,000 feet, in December, at 9 a.m., 

 I saw it mount to 132° with a diff. of -1-94°, whilst the tempera- 

 ture of sliaded snow hard by was 22°; at 13,100 feet, in 



* From the mean of very many observations I find that 10° is the 



iiveriige (UfFerence between two otherwise equal and similar white and 

 black bulb thermometers at the level of the sea. 



