CHAPTEK XLIV 



RAIN 



HE explanations of this morning account for the 

 formation of clouds. A continual evaporation 

 takes place on the surface of the damp earth as well 

 as on the surface of the different sheets of water, 

 lakes, ponds, marshes, streams, and above all the 

 sea. The vapors formed rise into the air and remain 

 invisible as long as the heat is sufficient. But since 

 heat diminishes as the height increases, there comes 

 a time when the vapors can no longer be kept in com- 

 plete solution, and they condense into a mass of 

 visible vapor, into a fog or cloud. 



"When, after a chill encountered in the upper 

 strata of the atmosphere, the cloud-mist reaches a 

 certain degree of condensation, little drops of water 

 form and fall in rain. At first very small, tlu\\ in- 

 crease in volume on the way by the union of other 

 similar little drops. Their size on reaching us is 

 proportioned to the height from which they fell, but 

 iH-vor exceeds the limits suitable to the part rain is 

 intended to play. If too large, the rain-drops would 

 t';ill heavily on the plants they are to water, and 

 would lay tlx-m flat on tin- -round, drad. And what 

 would happen if tin- condensation of vapor, in-tr;id 

 of takin .dually, should he sudden .' There 



would no longer descend from In -av. -n rain drops, 



L97 



