BAIN AND SNOW 



91 



As soon as the warm air of the sea meets the 

 cold air of the land a chilling-down process be- 

 gins and condensation into clouds is the result. 

 The coast is the line of condensation, and as 

 these clouds move into the cold interior their 

 vapor-carrying capacity grows less and less un- 

 til finally rain is precipitated. 



Another illustration of cloud and rain mak- 

 ing is often seen in the spring of the year, 

 when a warm air blowing from the south 

 meets a cold air blowing from the west. The 

 warm air is forced up and over the cold air, 

 clouds are formed all along the line of con- 

 tact, and heavy rain is not the unusual result. 

 Again, a sirocco blowing up from the south 

 across the Adriatic will make the cool stones in 

 the pavement of the Piazza San Marco at Ven- 

 ice "sweat ;" and when this sirocco meets the 

 Southern Alps and is tilted up into the cold 

 snow regions of the peaks, condensation, clouds, 

 and rain follow. 



Just how the rain-drop is formed seems not 

 better known than the constitution of the 

 spherule of moisture in the cloud. A recently 

 advanced theory would seem to argue that 

 moisture forms upon and about the tiny dust- 

 particle in the air, using the particle as a nu- 



