A less velocity than the average belongs to the winds of the 

 equatorial calm-belt, the calm-belts at the polar limits of the 

 trade-winds, and the trade-wind belts. 



There is a 



region in the southwest of the United 



States, which has a common yearly period of winds, different 

 as are its geographical features. It includes the extreme south- 

 east of California, Arizona, New Mexico, Southern Utah, Texas, 

 Arkansas, the Indian Territory, Eastern Colorado, Eastern 

 Wyoming, Southern Dakota, Nebraska, Iowa, Kansas, and 

 Missouri. The winds are southeast, south, or southwest in 

 summer, with a great ratio of the resultant in the south, dimin- 

 ishing toward the north and east. In winter the winds are 

 mostly north and northwest. This region is equal to more 

 than a million square miles, or about one-third of the United 

 States, without Alaska. 



A comparison of the motions of clouds with the mean direc- 

 tion of the surface current, shows that they very nearly coincide 

 in nearly all regions of the United States ; the former being 

 more purely west, and having a ratio of resultant of 42 per 

 cent— nearly double that of the surface current, which is 23 

 per cent— thus showing a steadiness of motion admitting of 

 little monsoon influence ; while the lower current has a more 

 west-southwest direction between the Mississippi and the 

 Appalachian chain, and a west-northwest direction in New 

 England. 



As the northern and southern boundaries of the great west- 

 erly current are approached— at least in the United States-the 

 length of the arrows that designate the cloud current decreases 

 as much below the 42 per cent above named, as they surpass 

 that ngure m the center of the aerial stream: and thus the 

 southern limit of this system of cloud motion seems to extend 

 down to north latitude 30°, some three degrees farther south 

 than is assigned to the corresponding system of surface winds. 



lne work is rich in tabular matter, especially from Spain, 

 JNorway, Russia, Siberia and India. Twenty-six charts are 

 attached m which the general features of the wind systems are 

 aeiineated, mainly by resultants and wind-roses; the latter 

 bringing into contrast the summer and winter winds. Horary, 

 monthly and annual variation is traced ; and one chart 

 ™n C °T e f T °i the Wind with Actuations in the thermometer, 

 amount of cloudiness, and fall of rain and snow. The whole 



m SoroWv ^^ SUmmarj ° f faCtS in this de P artment ° f 



