142 THE MICHIGAN ACADEMY OF SCIENCE. 



under the air from the polar direction, probabl}' on account of the 

 higher summer temperature of the air over the semi-tropical laud con- 

 tinents than over the oceans in the equatorial region. 



4, The common view that the eastward movement of the atmosphere 

 in the temperate zones is caused by the earth's faster rotation at the 

 equator, fails to explain and seems to be inconsistent with the fact, char- 

 acteristic of the Atlantic coast, that while in July the prevailing wind 

 is from the southwest, in January it is from the northwest. (A. Guyot, 

 page 1445 Johnson's Encyclopedia.) 



5. Even if it be true that the eastward movement of the lower atmos- 

 phere in the temperate regions is in great part due to the faster rota- 

 tion at the equator and the faster eastward movement of. the higher 

 atmosphere at latitude thirty-two degrees where it descends to near the 

 earth, if it is true, as I believe it is, that the eastward movement of the 

 upper air at the equator is faster than that of the earth, it does not 

 follow that the force which impels toward the eastward is derived from 

 and has lessened by that much the force which rotates the earth. On 

 the contrary, the expansion of the air at the equator in the forenoon is 

 the cause of the overtlow either toward the poles or eastward, and I 

 claim (further on in this paper) that that expansion and consequent 

 high pressure contribute to the earth's rotation. The force which causes 

 that expansion is the radiant energy from the sun. 



0. The question as to the source of the force of the wind which is 

 actually exerted in the temperate regions toward eastward rotation, 

 hinges, then, on the question of fact as to the eastward motion of the 

 upper atmosphere at the equator. On this point, Dr. Alexander Woeikof, 

 in his "Discussion and Analysis of Professor Collin's Tables and Charts 

 of the Winds of the Globe," says : "It has been known for a long time, 

 that above the lower current of the air of the trade winds, tiowing in 

 the lower latitudes of the northern hemisphere from N. E. or E. N. E., 

 there exists an upper one from about W. S. W. The existence of this 

 current was proved by the movement of the highest ( Cirri j clouds 

 always from some westward point, from the strong westerly winds on 

 high mountains in the trade- wind region (the Chimborazo and others in 

 equatorial South America, the peak of Teneriffe, etc.), from the trans- 

 port eastward of ashes from the eruption of the volcanoes on the island 

 of St. Vincent (West Indies), Cosiguina (Central America), and also 

 from the direction of the smoke of very high volcanoes of the tropics." 



He then mentions the "supposition" "that there was a powerful as- 

 cending current over the belt of calms and rains near the equator, and 

 that the air thus ascended flowed in the upper regions of the atmosphere, 

 in a direction contrary to the trade-winds, toward the polar limits of the 

 latter, or to about thirty degrees north latitude and descended there." 



The daily forenoon increase of atmospheric pressure constitutes good 

 evidence of a condition likely to produce a "powerful ascending current 

 over the belt of calms and rains near the equator" in the forenoon; and 

 to a less extent the same is true at that time of day both north and 

 south of the equator wherever the radiations from the sun reach the 

 earth. 



I believe that the lessened atmospheric pressure in the afternoon in 

 the same areas is good evidence that the air which in the forenoon had 

 been expanded toward the poles and somewhat into the upper regions 



