Mr. T. Hopkins on the Meteorology of Bombay. 469 



That mere alterations of thermometric temperature and of 

 vapour pressure, either jointly or separately, do not produce 

 the fall of the barometer from ten in the morning to four in 

 the afternoon, may be proved by facts when the registration 

 of the wet-bulb thermometer is given ; but unfortunately this 

 is seldom done. In the Plymouth report by Mr. S. Harris 

 that registration is to be found ; and there it may be seen that 

 the temperature theory does not harmonize with the facts. 

 But in the account of the meteorology of Bombay, as given 

 by Colonel Sabine, there is no notice of that instrument. Va- 

 pour pressure, as ascertained by the dew-point, is there ex- 

 hibited as one of the two causes which determine barometric 

 fluctuation, — thermometric temperature being considered the 

 other; and these two causes are by him represented as suffi- 

 cient to account for the facts and form the basis of his theory, 

 which for convenient reference I have called " the temperature 

 theory." 



In remarking at present on the Bombay report, I propose 

 to confine myself principally to objections to the theory ad- 

 vanced to account for the phasnomena, and do not intend to 

 show in a detailed form what were the real causes in operation, 

 seeing that all the facts required are not furnished. Had an 

 account of the evaporation that took place been given, I would 

 have attempted to trace the vapour that was produced after 

 ten o'clock, until it was condensed in the higher part of the 

 atmosphere and converted into cloud, with the effects of that 

 conversion on the barometer ; but without the registration of 

 the wet-bulb thermometer this cannot be satisfactorily done. 



In the report the facts contained in the following table are 

 given for Bombay in 1843, — of mean temperature, mean ba- 

 rometric pressure, mean tension of vapour, and mean gaseous 

 pressure at every second hour. 



