224 



monthly differences of temperature between the two stations, 

 with the mean temperature, rain-fall, amount of barometric 

 oscillation, and height of the barometer.' 



The final results derived from these comparisons may be 

 stated as follows : — 



1 . On the average of the year a decrement of temperature 

 below the mean is accompanied by a rain-fall and amount of 

 barometric oscillation helow the mean, and by a mean tem- 

 perature and barometric pressure ahove the mean. 



2. A decrement of temperature above the mean is accom- 

 panied by a rain-fall and amount of barometric oscillation 

 above the mean, and by a mean temperature and barometric 

 pressure helow the mean. 



3. A decrement of temperature above the mean for the 

 season is due to a cooling of the higher strata of the atmo- 

 sphere, and not to a heating of the lower strata. 



4. The production of rain is attended with a diminution of 

 the general temperature of the atmosphere, the diminution 

 being greater in the higher than in the lower strata. This 

 result, therefore, agrees with that which the Author had 

 previously derived from a discussion of the Greenwich and 

 Oxford observations ; and it indicates clearly the influence of 

 a cooling agency sufficiently powerful to neutralise completely 

 the effects of the heat supposed to be liberated during the 

 condensation of aqueous vapour into rain. 



The Author remarks that from the relations established by 

 this investigation it may be concluded that in a mass of air 

 moving from a higher to a lower latitude and acquiring an 

 increase of temperature, the change of temperature is more 

 rapid in the lower than in the higher strata ; while on the 

 contrary, in a mass moving from a low to a high latitude and 

 losing heat, the change is most rapid in the upper strata. It 

 also seems probable that one of the essential conditions in the 

 formation of a rotatory or cyclonic storm is a greater diff'er- 

 ence of temperature than usual between the successive strata 

 of the atmosphere at the point where the storm originates. 



