DISCUSSION AND ANALYSIS OF WINDS. 



695 



Yet there is a difference between the N. and the S. of the Athmtic Coast, which 

 will be best seen if we divide the Atlantic slope of the United States into three parts. 





Summer. 



Winter. 







fe 





p4 





aj 



m 



i 



^ 

 ^ 



% 

 9 

 9 



13 



H 



11 

 12 

 13 



W 

 4 

 5 

 7 



7 

 6 

 6 



m 



7 

 11 



14 

 14 

 18 



15 

 19 

 14 



33 

 28 

 17 



New England 



Middle Atlantic States — New- 

 York to N. E. Virginia. . 



S. Atlantic States, from S. E. 

 Virginia to Georgia . . . 



5 



8 

 7 



10 

 10 



12 



8 

 6 

 8 



10 

 11 



12 



12 

 14 

 17 



24 

 19 

 26 



14 

 16 



11 



16 

 15 



8 



From this table it is seen that in summer the winds are more southerly in the 

 S. Atlantic States than in the middle ones, while in New England the southerly 

 direction is more prevailing. (See Plate 8.) In the case of New England this may 

 be explained by the direction of the coast, which is nearly from W. to E. from Long 

 Island Sound to Cape Cod, so as to have the ocean to the S. Thus the already pre- 

 vailing southwesterly winds are strengthened by the relative position of land and sea. 



In winter the differences are greater between north and south, the N. W. 

 prevailing much more in New England than in the other sections, while in the 

 south the winds are more equally distributed between the different points of the 

 compass. The cause of this decrease of N. W. winds, the further we advance to 

 the S., is the following: The N. W. winds on this coast are a movement of the 

 air, tending to equalize the higher pressure in the interior of the continent with 

 the lower off the coast. They are westerly winds deflected to the N. W. by the 

 rotation of the earth. The difference of pressure in winter is much greater between 

 the coast of Nova Scotia and the interior of New England than between the ocean 

 near the Bermudas and the same latitude in the Southern States. This explains 

 why the N. W. winds are rarer in this last section, in the ordinary course of events. 

 (See Plates 8 and 14.) 



During the passing of storms there is yet another cause : the storm-centres in 

 winter pass often over New England from W. to E. In this case the winds to 

 the northward of the storm-track will be in succession E., N. E., N., and N. W., 

 these last appearing in the rear of the storm, being dry and intensely cold. In the 

 Southern States the wind will then veer from S. E. to S. and S. W., sometimes to 

 W., that is, become much more southerly. 



This distribution of the winds explains also the extremely rapid increase of 

 temperature from N. to S. on the Atlantic Coast of the United States, which is 

 greater than anywhere else in a level country. 



That the prevailing N. W. winds of New England and the middle Atlantic 

 Coast are not merely local, caused by the difference of temperature of the land 

 and sea, is proved by the strength of these winds. The relative prevalence of the 

 N. W. is much greater, if we take into account the number of miles travelled 

 instead of the number of observations only. (See Tables, Zones 9, 10, 11.) I 

 give below the mean velocity, in miles per hour, for the three prevailing winds 

 S. W., W., and N. W. in winter. 



