ON THE GENERAL CIRCULATION OF THE ATMOSPHERE. 183 
by solar radiation, and in their unequal cooling by the radia- 
tion of heat into space. The solar radiation especially heats the 
earth’s surface, and by means of this, the lower air layers contiguous 
thereto. The excess of temperature thereby produced above the 
adiabatic ground temperature (which latter corresponds to the average 
heating of the whole overlying air column), constitutes an accumulation 
of free energy, like that of a stretched spring, which can be brought 
into equilibrium again only by such a diffusion of the existing excess 
of temperature of the lowest strata upward through the entire overly- 
ing air column as shall restore the disturbed equilibrium. 
Practically this can only be done by means of air currents. In the 
vase of a locally restricted overheating there will originate at any favor- 
able place a bulging upward of the overheated air, which then in- 
creases rapidly in height, since the upward thrust increases at a rate 
proportional to the height of the natural chimney thus formed. But 
apart from its height, this chimney is to be essentially distinguished 
from an ordinary one by the fact that it has elastic walls, and that the 
pressure and density of the air strata inside, as well as outside of it, 
diminish with height. Thus the air velocity during the up-rush in- 
creases in an inverse ratio to the density, since in every minute of time, 
an equally great mass of air must pass through every section of the 
chimney. Since, in consideration of the small height of the atmosphere 
as compared with the earth’s radius, no increase of volume with the 
height need be taken into consideration, therefore, in general, the ve- 
locity of the air currents in ascending and descending must increase 
and decrease with the locally prevailing air pressure. 
Hence, also, in the case of an up-rush of air, more of the solar energy 
accumulated in it is transformed into the vis viva of moving masses of 
air than would be the case without such an acceleration. 
In the case of an up-rush of a limited mass of air overheated at the 
ground, the final result is a local uprush with accelerated velocity up 
to the higher, and even the highest, air regions, and simultaneously a 
descent of the air strata surrounding the upward currents, with a veloc- 
ity diminishing during the descent, and finally a diffusion of the accu- 
mulated heat at the earth’s surface to all the overlying air strata, with 
arestoration of the disturbed neutral equilibrium of this part of the 
atmosphere. 
In essentially the same manner, but in its outward manifestation very 
differently, this restoration of the neutral equilibrium disturbed by 
solar radiation takes place when the overheating of the air strata 
adjacent to the ground extends over an entire zone of the earth. In 
this case the up-rush can no longer be locally restricted, but must sys- 
tematically surround the whole torrid zone. Neither can it be limited 
as to time, but the process of adjustment must continue just as long as 
the causes of disturbance. There must therefore originate a circulatory 
system embracing the whole atmosphere, which finally performs the 
