THE FORCES THAT PRODUCE STORMS. 



6^ 



32°, as long as vapour remained to be condensed and frozen. 

 And thus we find that the difference in the temperature of 

 the two adjoining parts indicated in the table, would be 

 established for some time, however short it might be. 



It has been often observed that, when the temperature near 

 the surface of the earth has been greatly below the freezing 

 point, upon a fall of snow occurring, the temperature has 

 suddenly risen to 32° ; and it commonly remains there as 

 long as the snow continues falling. Now it is known that 

 this snow often descends from a considerable height in the 

 atmosphere, and it is to be presumed that it brings the air, 

 which is found to have a temperature of 32°, down with it. 

 The same fact is frequently observable in high latitudes, where 

 the cold is intense. However low the surface temperature 

 may have previously been, on a considerable quantity of snow 

 falling it shews a tendency to rise to 32°. Such changes near 

 the surface indicate, that in the part of the atmosphere in 

 which the snow was formed from floating particles of water, 

 whatever might be the height, the temperature in that part 

 could not be below SS'^*. 



It is not necessary to suppose that in cold latitudes, under 

 the circumstances described, vapour shall be actually carried 

 up to so great a height as ten thousand yards, or to any other 

 particular height approaching it ; but what has been observed 

 in those latitudes gives reason to believe, that snow and 

 spiculae of ice are there formed from vapour at greater eleva- 

 tions than has been hitherto imagined. Our object at present 

 however is, not to shew precisely what occurs in such lofty 

 regions, but to explain the kind of laws that govern the 

 atmospheric changes that take place in them, and to point 

 out that to whatever extent these changes do occur, they 

 must be under the control of the laws that have been 

 exhibited. 



In high latitudes, where the cold is intense, but little vapour 



