RAIN 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 clond 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- 
Warm 
winds and 
cold moun- 
tains. 
The rain- 
drop. 
