Appendix G. HUMIDITY OF DIFFERENT ELEVATIONS. 423 



the evolution of heat during the condensation of these vapours. It 

 will be seen by the pages of my journal, that continued sunshine, 

 and the consequent heating of the soil, is almost unknown during 

 the summer, at any elevation on the outer or southward ranges of 

 Dorjiling: but the sunk thermometer proves that in advancing 

 northward into the heart of the mountains and ascending, the sun's 

 effect is increased, the temperature of the earth becoming in summer 

 considerably higher than that of the air. With regard to the 

 observations themselves, they may be depended upon as comparable 

 with those of Calcutta, the instruments having been carefully com- 

 pared, and the cases of interpolation being few. The number of 

 observations taken at each station is recorded in a separate column ; 

 where only one is thus recorded, it is not to be regarded as a single 

 reading, but the mean] of several taken during an hour or longer 

 period. I have rejected all solitary observations, even when accom- 

 panied by others at Calcutta; and sundry that were, for obvious 

 reasons, likely to mislead. Where many observations were taken at 

 one place, I have divided them into sets, corresponding to the hours 

 at which alone the Calcutta temperature and wet-bulb thermometer 

 are recorded,* in order that meteorologists may apply them to the 

 solution of other questions relating to the distribution of heat and 

 moisture. The Dorjiling observations, and those in the immediate 

 neighbourhood of that station, appeared to me sufficiently numerous 

 to render it worth while classing them in months, and keeping them 

 in a series by themselves. The tensions of vapour are worked from 

 the wet-bulb readings by Apjohn's formula and tables, corrected 

 for the height of the barometer at the time. The observations, 

 except where otherwise noted, are taken by myself. 



* Sunrise; 9*50 a.m.; noon; 2 - 40 p.m. ; 4 p.m., and sunset. 



