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 annul us 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 — will 

 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. 



