1858.] Meteorological Observations on Parisnath Hill. 



23 



Taking therefore the observations at Calcutta as correct, the 

 readings on the hill had to be altered to suit the corrected tempera- 

 tures. It will be seen from the following table that these altera- 

 tions, reaching at the most 0.005 inches, keep within the limits of 

 admissible errors. This is in so far satisfactory, as it confirms the 

 adjustment of temperatures, showing that the common incidental 

 irregularities of the barometrical readings might have produced the 

 deviations. 



VI. — Table of corrected Barometrical Headings on the Hill. 



Date. 



Time. 



Original Read- 

 ing. 



Corrected Head- 

 ing. 



Error. 



1st April. 



Noon. 



26.021 



26.026 



+ 005 





1 



26.0U6 



26.002 



— O.004 



3rd April. 



8 



25.944 



25.940 



— 0.004 





10* 



25.971 



25.974 



-h 0.003 





11 



25 968 



25.969 



+ 0.001 





Noon. 



25.960 



25,959 



— 0.001 





3 



25.872 



25.873 



-f 0.001 





4 



25.856 



25.858 



+ 0.002 





5 



25.849 



25.847 



— 0.002 





7 



25.860 



25.856 



— 0.004 



Barometrical Difference. — There is another way of controlling the 

 curve of real hourly mean temperatures. It consists in comparing 

 the curve with the course of the hourly variation of the difference 

 between the barometrical pressures (b — b'), obtained by deducting 

 the pressure of the upper station from that of the lower one. If the 

 barometrical pressures at each station, as is generally assumed, repre- 

 sent the Mass of the atmospheric column which presses upon the 

 Mercury of the barometer, their difference must give the weight of 

 the column of air between the stations, measured by a column of 

 Mercury of an equal basis. 



The weight of a fixed volume of air, being dependent on the 

 barometrical pressure and the temperature, changes in a direct pro- 

 portion as the former and, to a certain extent, inversely with the 

 latter. The variation in the weight of such a volume of air, when 



* 10 h. 10 m. 



