THEORY OF WINDS. 327 



wind has continued from a month to six weeks 

 from the northern points of the compass.* 



In addition to the above winds, opposite cur* 

 rents frequently meet in the higher atmosphere, 

 which are not observed at the earth's surface, and 

 thus cause precipitations of rain. A striking 

 proof of this was witnessed on the 4th of July, 



* According to observations made at sixteen different military 

 posts in the United States, from lat. 35 to the northern extre- 

 mity of the Republic, including those of Sir Edward Parry, in 

 the Polar regions, winds prevail from the south-west, west, and 

 north-west, nearly two-thirds of the year; or in the ratio of 

 15830 to 8785, while the northerly winds are to the southerly 

 as 1190 to 1231. In the southern portion of the Union below 

 35, eastern winds predominate over western in the ratio of 3102 

 to 1717 ; from which it would seem that they are subject to the 

 general influence that governs the regular trade winds of the 

 tropics. In the same section of country, northern winds are to 

 southern in the ratio of 508 to 721. 



As Cincinnati, lat. 39 06', affords a tolerable specimen of 

 the Ohio valley generally, it may be stated that western winds 

 prevail over eastern in the ratio of 631 to 325 ; while at New 

 York, lat. 41, they are as 580 to 279. They are also nearly in 

 the same proportions throughout the Atlantic Ocean, between 

 North America and Western Europe. (See Darby's View of the 

 United States.) 



Mr. Daniell states, that upon an average of ten years, westerly 

 winds exceed easterly in the ratio of 225 to 140 in Great Britain ; 

 while northerly winds are to southerly, as 192 to 173. (Me- 

 teorological Essays, p. 114.) During spring, the prevalent wind 

 is from the dry, cold, north-eastern regions of Russia, Sweden, 

 and Denmark. Throughout the Mediterranean, Egypt, Palestine, 

 and the south of Europe generally, the wind blows nine months 

 in the year from the northern points of the compass ; because 

 situated between the cold regions of Arctic Europe and Asia, 

 and the burning plains of Africa, where the temperature is 

 100 to 115 F. in the shade. 



