400 J. R. Mayer on Celestial Dynamics. 
consumed in the production of atmospheric actions, in conse- 
quence of which numerous motions are set up in the earth’s at- 
mosphere. 
In spite of their great variety, the atmospheric currents may 
be reiuced to a single type. In consequence of the unequal 
heating of the earth in different degrees of latitude, the colder 
and heavier air of the polar regions passes in an under current 
toward the equator; whereas the heated air of the tropics as- 
cends to the higher parts of the atmosphere, and flows from 
thence toward the poles. In this manner the air of each hemi- 
sphere performs a circuitous motion. 
It is known that these currents are essentially modified by the 
motion of the earth on its axis. "1 olar currents, with their 
smaller rotatory velocity, receive a motion from east to west con- 
trary to the earth’s rotation, and the equatorial currents one 
west to east in advance of the axial rotation of the earth. 
The former of these currents, the easterly winds, must diminish 
the rotatory effect of the globe, the latter, the westerly winds, 
must increase the same power. The final result of the action of 
these opposed influences is, as regards the rotation of the earth, 
according to well-known mechanical principles, =.0; for these 
currents counteract each other, and therefore cannot exert the 
least influence on the axial rotation of the earth. This import- 
ant conclusion was proved by Laplace. ; 
e same law holds good for every imaginable action which 
is caused either by the radiant heat of the sun, or by the heat 
which reaches the surface from the earth’s interior, whether the 
action be in the air, in the water, or on the land. The effect of 
every single motion produced by these means on the rotation of 
the globe, is exactly compensated by the effect of another mo- 
tion in an opposite direction; so that the resultant of all these 
motions is, as far as the axial rotation of the globe is concerned, 
= 0. 
In those actions known as the tides, such noe Het oe 
by which the} 
-four hours; it is clear that much more powerful effect 
d by the sun’s heat would hide this action from observa- 
‘influence of these air-currents, however, on the rota- 
the earth, is, according to the laws of mechanics, 
: ae é 
