1858.] Meteorological Observations on JParisnath Hill. 43 



which appears excessive, even for tropical climates ; Bombay being 

 situated on an Island, and Calcutta not far from the Sea, in a coun- 

 try largely intersected with canals and rivers, it is not impossible 

 that the excess of the barometric pressure during the day time may 

 partly be attributed to the difference between the quantities of eva- 

 poration during the day and during the night. Observations of the 

 hygrometer at the sea level alone would not decide the question, as 

 they are only of local importance. Here also simultaneous observa- 

 tions at some elevation above the sea level would be of great use in 

 determining the hourly mean quantities of water contained in the 

 atmosphere in a vertical direction. 



It would be premature, at present to attempt a full explanation 

 of the phenomenon which may, besides, depend on other causes, and 

 is most likely connected with the regular daily variation of the height 

 of the barometrical column. Further observations in different parts 

 of the country would be required. A direct test of the share which 

 the amount of daily precipitation by condensation and the quantity 

 of evaporation have in producing the excess of barometrical pressure 

 during the day would be found in accurate estimates of the average 

 amount of dew and fog for every day in the year, and in determina- 

 tions of the quantities of evaporation during the day and during the 

 night. 



6 2 



