GREAT MALVERN AND LONDON. 



25 



the Worcestershire Beacon, published by Mr. Addison in a former 

 volume of The Analyst. 



If the barometer falls to a very low point, and the wind is in- 

 creasing in force, it usually blows very strong as the mercury be- 

 gins to ascend. 



When westerly winds prevail, if the current shifts only a few 

 points to the northward the barometer rises. 



We have yet to find the invariable conditions, if any such exist, 

 which determine the changes of the weather : they are not disco- 

 verable either in the pressure, temperature, or hygrometric state of 

 the atmosphere. 



It frequently happens with the barometer low, and the tempera- 

 ture of the air at the dew point, that dense, low, dark clouds roll 

 over for a day together, without rain ; whereas, with the barome- 

 ter at the same point, perhaps higher, and under the same circum- 

 stances of temperature and vapour, rain falls from every passing 

 cloud. Electrical and other changes which we cannot detect, no 

 doubt occur in the higher regions, to bring about these various 

 effects ; hence a decline of the barometer — even with a tempera- 

 ture governed by vapour, t. e., with the dew point not lower 

 than the temperature of the air — does not always portend rain. 



During winter, when the barometer rises, the thermometer 

 usually falls ; but in summer they generally rise and fall together. 

 The reason for this will be understood from what has been said 

 before; the rising of the barometer being generally accompanied 

 by clear weather. The clear days of summer are warmer than 

 the cloudy ones ; but in winter the cloudy and wet days are the 

 warmest. 



TABLE III.— Mean Dew Point at Malvern and London, 

 in 1834, 1835, and 1836. 



VOL. V. NO. XVII. 



