174- SIGNS OF RAIN. 



without any high objects in their vicinity, some 

 are inclined one way and some another, there is 

 disturbance in the lower part of the air, and the 

 probability is, that it will soon rain, even though 

 at the time there be not a single cloud to be seen. 

 Clear skies are, indeed, at some seasons, and in 

 some places, often more treacherous than cloudy 

 ones ; because, especially in places near the sea, 

 or high mountains, there are clouds of day and 

 clouds of night, which are regularly formed in the 

 atmosphere, and again dissolved there, even in the 

 finest weather. When the air is still, and the 

 smokes ascend in tall columns without blending 

 much with the air, it is a sign of rain, because it 

 shows that the air near the earth is in a state in 

 which it will absorb or dissolve no more moisture ; 

 and it is the under stratum of the air that keeps 

 up the clouds ; so that when these are formed and 

 again absorbed, the absorption takes place at their 

 under sides, and not at their upper, just as the 

 snow showers that fall upon the hot and dry fields 

 in the spring, melt below by the heat of the earth 

 sooner than above by the heat of the sun. Some- 

 times the smoke, when abundant, and when the 

 air does not evaporate the water, and allow the 

 soot to fall to the ground, forms a long flat stratum 

 like a thunder- cloud ; and that, like the thunder- 

 cloud, shows that there will be showers, or rain 

 falling from a considerable height, and therefore in 

 large drops. The reason is, that a portion of the 

 lower air resists the descent of the cloud, while 

 the upper air is parting rapidly with the moisture 

 that it contains. In these cases the evaporative, 

 or drying power of the lower air, is often wholly 

 occupied in resisting the descent of the cloud, so 



