DISTURBANCES AT BOMBAY. 143 



dew, is tending to make the atmosphere lighter, 

 but the two former are the more powerful influ- 

 ences, and the barometer rises. Yet, while this 

 rise is going on, the sea breeze is declining, 

 because the cooling of the gases is making them 

 heavier over the land. But after ten at night, 

 cold ceases to be produced by cloud evaporation, 

 and no more vapour is furnished by that process, 

 whilst the reduction of vapour pressure by the 

 deposition of dew continues. The reduction of 

 vapour pressure has now superior influence on 

 the barometer, and it falls from ten in the evening 

 to four in the morning, although, during this time, 

 the gaseous atmosphere must be becoming heavier, 

 from the decline of temperature. The influence 

 of the cooler, and therefore heavier, land gases, 

 is seen in the increasing force of the land wind, 

 which, up to four or five o'clock, becomes suc- 

 cessively stronger, while the barometer is falling. 



It may be further observed, that the gaseous 

 atmosphere, is, in the temperature theory, sup- 

 posed to be at its mean pressure at Bombay, 

 about one o'clock in the day, as that is the time 

 when the barometer is at its mean elevation, and, 

 therefore, when the atmosphere in the locality 

 ought to be in a state of equilibrium, and at rest; 



