NATURE FOR ITS OWN SAKE 
Its elastic 
skin. 
The size of 
the drop. 
cleus, so to speak, and that by augmented con- 
densation the spherule gradually grows to a 
rain-drop. Once formed, the drop has about 
it an elastic skin or envelope that prevents it 
from breaking unless pressed or struck by some 
body. Oftentimes it preserves its form against 
sharp shocks, as we may test by shaking the 
dewdrops on flowers, or observing the drops 
from a fountain that run across the surface of 
the water like pearls for some distance before 
coalescing with the main body. In the air the 
rain-drop is always perfectly round, as the 
camera shows us, even if it were not a necessity 
of that phenomenon, the rainbow. 
The size of the drop is doubtless dependent 
upon the amount of surplus moisture in the 
cloud. This in turn is dependent upon the 
temperature of the air and the extent to which 
this temperature has been reduced. Doubtless, 
too, the suddenness of condensation has some- 
thing to do with the size; and besides that the 
drop in falling probably unites with other 
drops, somewhat as globules of mercury co- 
alesce, or arain-drop running down a window- 
pane gathers other drops in its downward 
course. That the temperature has much to do 
with the quantity of vapor in the cloud, and 
