Refreshing Rain 115 



drops are squeezed out of the humid air by a cold 

 current. The water-bearing air rises because it is 

 warm. The icy air from the high altitudes descends 

 to take its place; the two meet and interpenetrate, 

 and there is a rain — a gentle, even rain, or a down- 

 pour, depending on the coldness of the descending, 

 and the humidity of the ascending currents. When 

 the humid air rises very high, its moisture is con- 

 verted into snow, and if it be dense, the snow- 

 flakes, as they fall, gather others, and when they 

 reach the lower stratum of rain-pouring mist, they 

 become filled with it, congeal it, and come swiftly 

 to the earth as hail. But in the summer-time, 

 especially, the cold and warm currents often meet 

 on a level, and then there is a slender cataract along 

 the line of contact, which moves forward against 

 the current of cold air, or goes the other way 

 against the current of humid air — depending upon 

 which blows the stronger. This is our passing 

 summer shower, and when the line of contact is 

 directly overhead we are in the heaviest part of the 

 rain. But sometimes, though rarely, an ascending 

 column of fully ladened air is caught between two 

 or more currents of cold wind coming from various 

 directions to fill the vacuum. They crowd in upon 

 it, drive it upward till it extends like a huge pillar 

 black and high, and, in their conflict, set it to whirl- 

 ing like a spindle. If this conflict take place near 

 the surface, we have a whirlwind, and if it be very 

 strong we call it a cyclone. But if it occur above 



