Assumption of a Solar Electric Potential. 177 
same velocity the surrounding calm air must be pushed aside 
in order to make room for that which has arrived. This dis- 
placement will take place chiefly in the direction to where a 
descending current has been formed to replace the overheated 
air flowing at the surface of the earth to the place of the up- 
current. This downflowing air now becomes denser again 
correspondingly to its altitude, it is true ; but at the same time 
it retains the velocity it acquired in the upper regions. It is 
evident that the final result may be a very great velocity of 
air at the earth's surface, if the disturbance of the adiabatic 
equilibrium was qualitatively and quantitatively considerable. 
These local storms, the direction of which is modified accord- 
ing to Dove's law of rotation by the rotation of the earth, 
must become peculiarly violent if the upcurrent itself is con- 
fined within narrow limits, since then the compensating 
process, i. e. the conversion of the energy accumulated in the 
disturbance of equilibrium into air-velocity, is confined to a 
proportionately small quantity of air. Yet powerful storms, 
passing over whole continents, may also be produced by as- 
cending currents of air of wide local extent. That the descend- 
ing current produces an increase of pressure upon the ground, 
and the ascending current a decrease, follows from the laws 
of mechanical motion. The mere motion of the air, however, 
must of itself always occasion a fall of the barometer, since 
the moved air carries away with it the still air at the contact 
boundary and consequently produces a rarefaction. The final 
result of the compensation of the disturbance will therefore be 
to put greater and greater masses of air into whirling motion, 
and last of all to bring the vis viva back, by friction, into the 
form of heat. 
It follows from these considerations that the aqueous vapour 
in the air does not play the great part in the movement of the 
air that is usually attributed to it, since the phenomena of the 
motion and pressure of the air can be accounted for without 
the water contained in the air. The origin of storms, i. e. in 
this case the place of the acceleration of the masses of air, must 
only be sought, not at the surface of the earth, but essentially 
in the highest regions of the air. If the atmosphere consisted 
of aqueous vapour only, the phenomena would be altogether 
similar. Aqueous vapour is as subject to the law of adiabatic 
expansion as air ; only its density and temperature decrease 
with increasing height much less than those of the permanent 
gases of the atmosphere. According to Bitter a vapour at- 
mosphere would be about thirteen times as high as an atmo- 
sphere of air. It is true that, according to Clausius and Sir 
William Thomson, with the adiabatic expansion of vapour a 
Phil. Mag. S. 5. Vol. 16. No. 99. Sent. 1883. P 
