Chap. 13.] from the Barometer. 503 



7. When an extraordinary fall of the mercury hap- 

 pens, without any remarkable change near at hand, 

 there is fo;ne probability of a ftorrn at a diftance. 



8. The barometer will defcend fomecimes as an in- 

 dication of wind only ; nor is its rife always a certain 

 fign of fair weather, particularly if the wind is to the 

 north or the eafb. 



9. A north-cad wind generally caufes the barometer 

 in England to rife, and it is generally lowed with a 

 fouth-wcd wind. 



If the air in foggy weather becomes hotter by the 

 action of the fun alone, the fog generally diffipates, 

 and the air remains ferene ; but if the barometer falls, 

 and the change of temperature is from a fouth or fouth- 

 wed wind, the fog rifes and forms into clouds, and its 

 afcent is generally a fign of rain. 



" We have," fays Mr. Adams, " at prefent no cer- 

 tain data from obfervations, whereby certain conclu- 

 fions may be formed relative to fogs, and their con- 

 nection with rain.'* 



In winter, when the cold decreafes fuddenly, rain 

 may be expected , but in fummer, a fudden increafe of 

 heat forebodes rain. 



IV. Several prognodic figns of the weather may be 

 collected from the various appearances of the clouds ; 

 when they appear to difiblve fuddenly into air, and be- 

 come invifible, it may be confidered as a itrong indi- 

 cation of fair weather ; but, on the contrary, when 

 they feem to form themfelves^into maficsfrom the fur- 

 rounding air, and to increafe in denfity and magnitude, 

 rain may reafunably be predicted. 



Upon the approach of heavy rain every cloud rifes 



larger than the preceding one, particularly when a 



thunder-dorm is near, when f nail fragments of clouds 



collect, and in a little time cover .the whole face of the 



K.k 4 ' Iky. 



