DISTURBANCES AT BOMBAY. 145 



it was in the morning, — is represented as being 

 much above the mean. These facts present 

 strong evidence that the method of ascertaining 

 the separate gaseous pressure at present recog- 

 nized cannot be a correct one. 



We have already seen reason to believe that 

 the barometer attains its greatest height in the 

 morning through increased vapour pressure. And 

 it is to be presumed from the stillness of the air 

 at the time, that the gases were then really in a 

 state of equilibrium; it will, therefore follow, that 

 at ten in the morning, the barometer was raised 

 above its mean height, solely by the force of 

 increased vapour pressure. And at night, there 

 is another calm, when the barometric height is 

 considerable, approaching that of the morning, 

 and this pressure above the mean must in like 

 manner be presumed to result, not solely from 

 the cooling of the atmosphere, but in addition 

 from the abundant vapour that had been recently 

 furnished by cloud evaporation. The general 

 conclusion to be drawn from all these facts, being, 

 that when the atmosphere is in a state of equili- 

 brium, any rise of the barometer above the mean 

 level for the locality, climate, and season must be 

 produced by increased vapour pressure. 



