Dr. J. R. Mayer on Celestial Dynamics* t-OS- 



pnrtant of the above. According to Pouillet's measurements, a 

 square metre of the earth's surface receives on the average 

 4*408 units of heat from the sun per minute. Since one unit 

 of heat is equivalent to 367 Km, it follows that one square 

 metre of the surface of our globe receives per minute an addition 

 of vis viva equal to 1620 Km, or the whole of the earth's, 

 surface in the same time 825,000 billions of Km. A power 

 of 75 Km per second is called a horse-power. According to 

 this, the effect of the solar radiation in mechanical work on one 

 square metre of the earth's surface would be equal to 0*36, and 

 the total effect for the whole globe 180 billions of horse-powers. 

 A not inconsiderable portion of this enormous quantity of vis viva 

 is consumed in the production of atmospheric actions, in con- 

 sequence of which numerous motions are set up in the earth's 

 atmosphere. 



In spite of their great variety, the atmospheric currents may 

 be reduced 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 

 towards the equator; whereas the heated air of the tropics' 

 ascends to the higher parts of the atmosphere, and flows from 

 thence towards the poles. In this manner the air of each he-i 

 misphere performs a circuitous motion. 



It is known that these currents are essentially modified by 

 the motion of the earth on its axis. The polar currents, with 

 their smaller rotatory velocity, receive a motion from east to* 

 west contrary to the earth's rotation, and the equatorial cur- 

 rents one from 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 important conclusion was proved by La- 

 place. 



The 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 

 motion in an opposite direction; so that the resultant of all 

 these motions is, as far as the axial rotation of the globe is con-, 

 cerned, =0. 



Phil. Mag. S. 4. Vol. 25. No. 169. May 1863. 2 E 



