1858.] Meteorological Observations on Parisnath Hill. 



35 



nainely, that an addition of watery vapour to the air would not 

 affect the equilibrium, or density of the latter, solely increasing the 

 local pressure upon the mercurial column of the barometer. 



Prom the above considerations it would appear, that this view, if 

 allowed to approach the truth practically in the mean of a larger 

 number of days, is hardly admissible if applied to single cases. 



I will subject it to a further test by deducing with its assistance 

 the weight of the dry air, at different hours, between Calcutta and 

 Parisnath hill, and comparing the values which will be thus obtained 

 with those derived by calculation. 



The results obtained for S in the foregoing discussion, taking the 

 watery vapour into account, agreed well enough with the observed 

 barometrical differences, to justify a belief, that the quantities 

 employed in their calculation, although subject to a certain amount 

 of error, would not differ essentially from their true values. 



Determining with the same quantities the individual weight of 

 each, the dry air and the watery vapour in the composition of the 

 barometrical difference, the sum of both will always be equal to the 

 value of S as obtained by calculation. 



These weights are contained in the following Table. 



Table XI. — Weights of dry air and Watery Vapour. 



3rd April. 



Weight of 



Weight of 



S. 



S. 



Deviation or 



Dry Air. 



Vapour. 



Calculated. 



Observed. 



Error. 



9 A. M. 



3.823 -f 



■ 0.050 = 



= 3.873 



3.876 



— 0.003 



10* 



3.816 -r 



■ 0.053 = 3.869 



3.873 



— 0.004 



2 P. M. 



3. 784 -f 



. 0.052 = 3.836 



3.837 



— 0.001 



3 



3 789 -f 



• 0.049 = 3.838 



3.839 



— 0.001 



4 



3.783 -f 



• 0.055 = 3.838 



3.843 



— 0.005 



5 



3.785 ■+ 



■ 0.055 = 3.840 



3.844 



— 0.004 



6 



3.787 4- 



- 0.055 = 



= 3.842 



3.846 



— 0.004 



According to this table the weight of the dry air between the 

 stations, or the specific gravity of the air on the 3rd decreased 

 towards the time of the greatest heat and oscillated between the 

 hours 2 and 6 p. m. round a mean value, without having shown at 

 that time a decided inclination to rise. The weight of the watery 



* 10 h. 10 m. 



F 2 



