Appendix H. EFFECTS OF TEMPEEATUHE OF SOIL, &c. 



413 



however, vary extremely according to exposure and amount of 

 sunshine ; and I should expect that the greatest' differences would 

 be found in the sunny climate of Tibet, where the sun's heat is most 

 powerful. Were nocturnal or terrestrial radiation as constant and 

 powerful as solar, the effects of the latter would be neutralised ; but 

 such is not the case at any elevation in Sikkim. 



This accumulated heat in the upper strata of soil must have a very 

 powerful effect upon vegetation, preventing the delicate rootlets of 

 shrubs from becoming frozen, and preserving vitality in the- more 

 fleshy roots, such as those of the large rhubarbs and small orchids, 

 whose spongy cellular tissues would no doubt be ruptured by severe 

 frosts. To the burrowing rodents, the hares, marmots, and rats, 

 which abound at 15,000 to 17,000 feet in Tibet, this phenomenon is 

 even more conspicuously important ; for were the soil in winter to 

 acquire the mean temperature of the air, it would take very long to 

 heat after the melting of the snow, and indeed the latter phenomenon 

 woiild be greatly retarded. The rapid development of vegetation 

 after the disappearance of the snow, is no doubt also proximately 

 due to the heat of the soil, quite as much as to the increased strength 

 of the sun's direct rays in lofty regions. 



I have given in the column following that containing the tempera- 

 ture of the sunk thermometer, first the extreme temperatures of 

 the air recorded during the time the instrument was sunk ; and in 

 the next following, the mean temperature of the air during the 

 same period, so far as I could ascertain it from my own obser- 

 vations. 



Series I. — Soane Valley. 









o 







m T3 

 <D j3 > 



mate 

 mp. of 

 uced. 



& a 



Locality. 



Date. 



Elevat 



Depth. 



Temp, of 

 sunk Therm. 



Extrc 



Temper 



of Air obs 



Approx 



Mean Te 



Air ded 



SC73 



s % 









ft. 



ft. in. 











Mudduupore 



Feb. 



lltol2 



440 



3 4 



71-5 



62-0 to 77-5 



67-0 



+ 4-5 



Nourunga . . 



Feb. 



12 „ 13 



340 



3 8 



71-7 



57-0 „ 71-0 



67-3 



3-4 



Baroon 



Feb. 



13 „ 14 



. 345 



2 4 



68-5 



53-5 ,, 76-0 



67-6 



1-9 



Tilotho . . . 



Feb. 



15 „ 16 



395 



4 6 



76-5 



58-5 „ 80-0 



67-8 



8-7 



Akbarpore . 



Feb. 



17 „ 19 



400 | 



2ther.4 6 



„ 5 6j 



76-0 



56-9 „ 79-5 



68-0 



8-0 



