SERIES C. VELOCITY TABLES. fi41 



two classes of annual resultants is therefore about nine degrees (8° 48 by one mode 

 of reckoning and 9" 38 by another), the divergence being greatest in winter. In 

 passing into the adjacent geographical zones, it is significant that, within the limits 

 of the Polar and Equatorial systems of winds, the places represented on the chart 

 with like uniformity exhibit divergence, but in the contrary direction, i. e., the 

 dotted arrow for velocity^ is at the left hand of the continuous arrow for time. 



The average velocity of all winds in the United States differs little from 7 miles 

 an hour,^ being slightly in excess in the northeastern part of the Union, and less 

 in the States nearer the centre of the continent. The anemometer gives greater 

 figures than those obtained by estimation. The velocity in the mean direction on 

 the hypothesis that the winds from every point of the compass move with an 

 average velocity (given in column IV) is 1.7 miles per hour. But the true velocity 

 in the mean direction, when each wind is allowed its own separate velocity, is nearly 

 2.0 miles per hour, 



' In the " Winds of the Northern Hemisphere" the average liuurly velocity of all winds was given 

 as 5.8 miles ; and the mean resultant obtained from the actual distances was stated to be S. 81° 44' W 

 1,74 miles per hour ; and that obtained by disregarding velocity S. 85° 59' W. 1.53 miles per hour. 



81 July. 1875. 



