134 Daniell on a new Hygrometer. 



at Dumdum, about fifty feet above the sea, it appears that on 

 the two days preceding and two days following, the one on 

 which Captain Webb observed the Nitee Ghaut, the state of the 

 barometer and thermometer at two P.M., was as under : 



Inches. Degrees. 



August 19, barometer 29.46 thermometer 88. 

 20, 29.46 84. 



21, 29.48 85. 



22, 29.48 84. 



23, 29.65 81. 



Mean 29.51 84.4 



The difference of elevation corresponding with the observa- 

 tion between the Nitee Ghaut and Dumdum is 

 16,764 feet. 

 + 50 feet. Dumdum above the sea. 



16,814 feet, height of the pass above the sea. 

 Now, if we alloAV 12^ degrees as the probable point of dry- 

 ness at the lower station, and 6 degrees at the upper, which 

 we are warranted in doing from the foregoing experiments, 

 the correction to be applied for the difference of the pressure of 

 the vapour will stand thus ; 



Inches. 



Temperature of the vapour at Dumdum 72° = 0.770 pressure. 

 Temperature of the vapour at the Nitee 



Ghaut 41° zr 0.273 pressure. 



Difference 0.497 



To be deducted from the height of the barometer at the 

 latter station : which is equal to 447 feet deducted from the 

 altitude of the pass — 



16,814 height. 

 _ 447 



16,367 corrected height. 

 This is as near as it is possible to come, without actual ob- 

 servations with the hygrometer, and the correction decreases 

 considerably the amount of the anomaly complained of in the 

 measurement of those lofty mountains. 



