25 



tenths of the mercury occur in a hot period, it is at- 

 tended with rain and thunder, and succeeded by a cool 

 atmosphere. Sometimes heavy thunder-storms take 

 place overhead without any fall of the mercury; in 

 this case a reduction of temperature does not usually 

 follow. 



If after a storm of wind and rain, the mercury remain 

 steady at the point to which it had fallen, serene weather 

 may follow without a change of wind ; but on the rising 

 of the mercury, rain and a change of wind may be ex- 

 pected. 



During a series of stormy weather the mercury is in 

 constant agitation, falling and rising twice or thrice in 

 the space of twenty-four hours, the wind changing alter- 

 nately from south to west, and backing again to the 

 south : this alternation of winds continues until the mer- 

 cury rises to a bold elevation, when it ceases, and the 

 weather becomes settled. 



Storms of wind, especially when accompanied with 

 much rain, produce the greatest depressions of the mer- 

 cury. No storm of wind on record has blown without 

 some rain falling, although the time of its falling and 

 its amount have been variable : sometimes the rain has 

 increased with the increasing storm and sinking mer- 

 cury ; at other times the rain has fallen suddenly at the 

 close of the storm, or at the time of the minimum pressure. 



No great storm ever sets in with a steady rising baro- 

 meter. 



As far as regards the locality of Greenwich, the most 

 violent gusts of wind come from due south, and those 



c 



