DISTURBANCES AT BOMBAY. 141 



But from five to ten in the morning, whilst the 

 land breeze is declining^ through an increase of 

 general temperature, and a consequent reduction 

 of gaseous pressure over the land, the barometer 

 is not sinking, as might be expected, but it is, on 

 the contrary, rising. Whence, then, comes the 

 force that now raises the barometer ? It is from 

 the increased pressure of the additional vapour 

 which, during this time, is produced by evapo- 

 ration from the surface of the earth. As the 

 temperature rises in the morning, evaporation 

 becomes more active, and additional vapour is 

 thrown into the atmospheric space, which adds 

 to the vapour pressure. Thus, while one consti- 

 tuent of the atmosphere in the locality is increasing 

 in quantity, and adding to the aggregate pressure, 

 other constituent portions, through a rise of tem- 

 perature, are pressing with diminished force on 

 the surface, exhibiting to us at the same time 

 the apparent contradiction of a rising barometer, 

 and an alteration of wind that shows a diminishing 

 atmospheric pressure. These phenomena are, 

 however, the natural results of the independent 

 action of the different aeriform substances that 

 constitute the atmosphere. 



Each of these constituents exists in the atmo- 



