Philosophy of Storms. 131 
formed cloud by the cold of diminished pressure, will be forced 
down to the surface of the earth, bringing with it the caloric of 
elasticity which it received from the condensing vapor ; if so, the 
heat experienced at the time of this descent, will be very great. 
These hot blasts of air will alternate with cold blasts, for the 
air which is forced down from great heights in the annulus will 
not only be very hot, but very dry, having condensed its vapor, 
in its previous ascent. Now when this hot dry air flows inwards 
again towards the volcano and ascends, it will not form cloud, 
because of its want of vapor ; and therefore the process of cloud 
forming will cease, and consequently rain and hail will cease too, 
until more air from a greater distance that has not been deprived 
of its vapor flows in and ascends. 'Then cloud will again begin 
to form and the violence and rapidity of the outflowing of the 
air above will be increased by the evolution of the caloric of elas- 
ticity, the barometer will rise rapidly in the annulus and fall in the 
central part of the ascending column, and these alternations may 
continue while the volcano is in activity, more particularly if the 
violence of the volcano itself should be increased periodically. 
As air cannot move upwards without coming under diminished 
pressure, and as it must thus expand and grow colder and conse- 
quently form cloud—any cause which produces an upmoving 
column of air, whether that cause be natural or artificial, will pro- 
duce rain, when the complement of the dew point is small, and the 
air calm below and above, and the upper part of the atmosphere 
of its ordinary temperature. 
Volcanoes therefore under favorable circumstances will produce 
rain; sea breezes which blow inwards every day towards the 
centre of islands, especially if these islands have in them high 
mountains, which will prevent any upper current of air from 
bending the upmoving current of air out of the perpendicular 
before it rises high enough to form cloud, such as Jamaica—vwill 
produce rain every day ; great cities where very much fuel is 
burnt, in countries where the complement of the dew point is 
small, such as Manchester and Liverpool, will frequently produce 
rain; even battles, and accidental fires, if they occur under favor- 
able circumstances, may sometimes be followed by rain. Let all 
these favorable circumstances be watched for in time of drought, 
(and they can only occur then,) and let the experiment be tried. 
If it should be successful, the result would be highly beneficial 
to mankind. 
