§ 204. THE ATMOSPHERE. 79 



Different belts of ttc principal belts OP baiids of wind that actual ob- 

 ''''°'^'- servation has shown to exist at sea, and which, witli 



more or less distinctness of outline, extend to the land also, and 

 thus encircle the earth. If we imagine a ship to take her depart- 

 ure from Greenland for the South Shetland Islands, she will, be- 

 tween the parallels of 60° north and south, cross these several 

 bands or belts of winds and calms nearly at right angles, and in 

 the following order : (1.) At setting out she will find herself in 



the region of southwest winds, or counter trades of the north 



called counter because they blow in the direction whence come 

 the trade-winds of their hemisphere. (2.) After crossino- 50° 

 and until reaching the parallel of 85° N., she finds herself in the 

 belt of westerly winds, a region in which winds from the south- 

 west and winds from the northwest contend for the mastery, and 

 with nearly equal persistency. (3.) Between 2>b'' and 30°, she finds 

 herself in a region of variable winds and calms; the winds blow- 

 ing all around the compass, and averaging about three months 

 from each quarter during the year. Our fancied ship is now in 

 the " horse latitudes." Hitherto w^inds with ivesting in them have 

 been most prevalent; but, crossing the calm belt of Cancer, she 

 reaches latitudes where winds with easting become more preva- 

 lent. (4.) Crossing into these, she enters the region of northeast 

 trades, which now become the prevailing winds, until she reaches 

 the parallel of 10°N., and enters the equatorial calm belt, which, 

 like all the other wind-bands, does not hold stationary limits. 

 (5.) Crossing the parallel of 5° N., she enters where the southeast 

 trades are the prevailing wdnds, and so continue until the parallel 

 of 30° S. is reached. (6.) Here is the calm belt of Capricorn, 

 where, as in that of Cancer (3), she again finds herself in a region 

 of shifting winds, light airs, and calms, and where the winds with 

 westing in them become the prevailing winds. (7.) Between the 

 parallels of 35° and 40° S., the northwest and southwest w^inds 

 contend with equal powers for the mastery. (8.) Crossing 40°, 

 the counter-trades (1) — the northwest w^inds of the southern hem- 

 isphere — become the prevailing winds, and so remain, as far to- 

 ward the south pole as our observations at sea extend. 



Such are the most striking movements of the winds at the sur- 

 face of the sea. But, in order to treat of the general system of 

 atmospherical circulation, we should consider w^here those agents 



