¢ Proceedings of the Asiatic Society of Bengal. [N.S., XVII,. 
a shower of nearly 1} inches of rain. This latter process has 
in fact been 30 times as effective as the former in rainfall pro- 
duction. Obviously then, the process of dynamical cooling is 
much more important in its bearing on rainfall in nature than 
any mixing of air which may take place in the atmosphere ; and 
moreover it is a process which is constantly occurring wherever 
winds are blowing over rising ground, such for instance as in 
India from sea level to the Himalayas: we may regard it in fact 
at the only cause of effective rainfall in nature. 
. ody of air containing moisture, but still unsa- 
turated, if raised from sea level through several kilometres 
in the atmosphere will begin to fall in temperature at the adia- 
Saturation Curve : Water Vapour 
Grammes per m? 
lapse rate does not exceed these values the condition is stable. 
tr any reason, such as the heating of the ground by 
a tendency for upward convective currents to form. The result 
