752 WINDS OF THE GLOBE. 



PLATE 8. 



Mean Direction in the Four Seasons in toe United States. 

 [See Explauatiou of Plate 4.] 



Here, also, the mean direction of the wind in spring is nearer to that of summer, and that of 

 autumn to winter. West of the Apallachiau Chain, and north of 42° N. lat., there are more northerly- 

 winds in spring than in summer and autumn, while further .south, and west of the Mississippi, southerly 

 winds prevail already in spring. In the Southern Atlantic and Gulf States there are more northerly 

 winds in autumn than in other seasons. 



PLATE 9. 



Mean Direction in the Four Seasons in Europe. 

 [See Explauatious of Plate 4.] 



The great extension of northerly winds in the Mediterranean in summer must be noticed. On this 

 Plate are placed a few arrows, whose shafts are divided into twelve portions, corresponding to the 

 successive months, beginning with March (spring), and ending at the barb with February (winter). 

 Here, as in the preceding plate, may be observed the peculiar n_^' — ~^ " S" shape of the curves, 

 so regular a feature in the movement of the wind in the successive seasons, that it was the occasion 

 that led Prof. Coffin to his investigation of the monsoon influences delineated in the following Plate. 



PLATE 10. 



Monsoon Influences in the Four Seasons between 80° N. Lat. and 56° S. Lat. 



On this map there is a graphic representation of the forces which deflect the mean direction of the 

 wind from its annual value at each season. Taking, for illustration, the monsoon influences at 

 Easton, Pennsylvania, the manner of their representation is the following : — 



Spring being designated by I, as the first season, summer by S, autumn by A, and winter by W. 

 The opposite directions of the deflecting forces for both sides of the Atlantic Ocean is especially 

 to be noticed. It was first pointed out by Prof. Coffin in a report to the American Association for 

 the Advancement of Science, in 1848, and then embodied in his work on "the Winds of the Northern 

 Hemisphere." The direction of the deflecting forces is from the S. E. on the coast of the United 



