RAIN AND SNOW 
93 
consequently the size of the drop, we may be- 
lieve when we consider how small are the rain- 
drops in winter and how large they are in 
summer. ‘The first ones falling in a thunder- 
shower, for instance, are unusually large. Pos- 
sibly the size is caused by the outer edge of a 
heavily saturated cloud being driven by the 
wind against cold air and swift condensation 
following the meeting ; or it may be that the 
heavy drops fall from a very high cloud and 
coalesce with others in falling. It is usually 
only the first-coming clouds that cast the heavy 
drops, and after the first dash they grow finer, 
smaller, and more numerous. 
A thunder-storm comes and goes quickly, 
the moisture being in measure localized. Both 
its coming and its going present interesting, 
sometimes fantastic, forms of clouds that are 
continually torn, scattered and reunited by the 
drive forward of the wind. Usually the cloud 
isa thick one, and in its lowest part is dark, 
becoming lighter in its main body, and if it is 
a towering, cumulus cloud, its upper peaks may 
sometimes be seen before or after the storm, 
shining white in the sunlight. Beautiful by 
day, all the forms of thunder-clouds are even 
more beautiful by night, when lightning flashes 
The first 
heavy rain 
fall. 
Thunder- 
storms. 
