Appendix A. METEOROLOGY OF SOANE VALLEY. 363 



deduced from the sunrise, morning and afternoon observations, 

 amounts to 4°, which, if the mean height of the hills where crossed 

 by the road, be called 1135 feet, will be equal to a fall of one 

 degree for every 288 feet. 



In the dampness of its atmosphere, Calcutta contrasts very 

 remarkably with these hills ; the dew-point on the Hoogly 

 averaging 51 0, 3, and on these hills 38°, the corresponding saturation- 

 points being 0'559 and 0*380. 



The difference between sunrise, forenoon and afternoon dew-points 

 at Calcutta and on the hills, is 13°" 6 at each observation ; but the 

 atmosphere at Calcutta is relatively drier in the afternoon than 

 that of the hills ; the difference between the Calcutta sunrise 

 and afternoon saturation-point being 0*449, and that between 

 the hill sunrise and afternoon, 0*190. The march of the dew- 

 point is thus the same in both instances, but owing to the 

 much higher temperature of Calcutta, and the greatly increased 

 tension of the vapour there, the relative humidity varies greatly 

 during the day. 



In other words, the atmosphere of Calcutta is loaded with moisture 

 in the early morning of this season, and is relatively dry in the 

 afternoon : in the hills again, it is scarcely more humid at sunrise 

 than at 3 p.m. That this dryness of the hills is partly due to 

 elevation, appears from the disproportionately moister state of the 

 atmosphere below the Dunwah pass. 



II. — Abstract of the Meteorological observations taken in the Soane 

 Valley (mean elevation 422 feet). 



The difference in mean temperature (partly owing to the sun's 

 more northerly declination) amounts to 2°*5 of increase in the Soane 

 valley, above that of the hills. The range of the thermometer from 

 day to day was considerably greater on the hills (though fewer obser- 

 vations were there recorded) : it amounted to 17°*2 on the hills, and 

 only 12°*8 in the valley. The range from the maximum to the mini- 

 mum of each day amounts to the same in both, above 20°. The 

 extreme variations in temperature too coincide within 1°4. 



The hygrometric state of the atmosphere of the valley differs most 



