CHAKGE OF WEATHER. 101 



the one atmospheric current is opposed to the other, 

 the more complete must be the stagnation, the quies- 

 cence, as it were, throughout the whole mass ; and 

 when that is the case, the different temperature of a 

 wood and a lawn, or a farm-yard and a field, will be 

 quite enough to occasion a little local wind. When 

 the surface is free from snow, and the bare places, 

 such as roads, and commons, and little sand banks by 

 the sides of rivers, greatly heated, these natural ba- 

 rometers are always in action ; and when the season is 

 advancing, and the fields and trees covered with vege- 

 tation, they whisk about in all directions, cross each 

 other's paths, and mix dust and straws in whirlwinds 

 upon the land, or the water in columnar clouds, called 

 water spouts, upon the sea. That opposition or colli- 

 sion of different currents of air which lets loose those 

 little winds, is also one of the causes of rain : and, 

 in summer, they are almost certain indications of a 

 shower; though, in the early spring, that, though 

 not an unfrequent, is by no means a necessary re- 

 sult. If both currents of air are saturated, or nearly 

 saturated, with humidity, some of that is deposited 

 when they unite : but the one current is always rather 

 above the other ; and the lower one is often able to 

 dissolve the moisture as soon as it collects. Indeed, 

 the experiments that have been made with rain gauges, 

 would lead to the conclusion, that the air, near the 

 earth, always redissolves a part of the rain that falls 

 through it. 



When the sun sets, and the cold air settles down, the 

 clouds which were gathered round the setting sun are 

 carried into a stratum that dissolves them ; and the 



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