METEOROLOGICAL, &C. 301 



air is clear, there it freezes hard. So the 

 frost takes place either on hill or in dale, 

 wherever the air happens to be clearest and 

 freest from vapour. White. 



THAW. 



Thaws are sometimes surprisingly quick, 

 considering the small quantity of rain. 

 Does not the warmth at such times come 

 from below ? The cold in still, severe sea- 

 sons seems to come down from above : for 

 the coming over of a cloud in severe nights 

 raises the thermometer abroad at once full 

 ten degrees. The first notices of thaws 

 often seem to appear in vaults, cellars, &c. 



If a frost happens, even when the ground 

 is. considerably dry, as soon as a thaw takes 

 place, the paths and fields are all in a bat- 

 ter. Country people say that the frost 

 draws moisture. But the true philosophy 

 is, that the steam and vapours continually 

 ascending from the earth, are bound in by 

 the frost, and not suffered to escape till re- 

 leased by the thaw. No wonder then that 



