290 THE PHYSICAL GEOGRAPHY OF THE SEA. 



shall see that in this case the currents are running in at the top 

 and out at the bottom (§ 132). 



837. The belt of equatorial calms is a belt of constant precipi- 

 tation. Captain Wilkes, of the Exploring Expedition, when he 

 crossed it in 1838, found it to extend from 4° north to 12° north. 

 He was ten days in crossing it, and during those ten days rain fell 

 to the depth of 6.15 inches, or at the rate of eighteen feet and up- 

 ward during the year. In the summer months this belt of calms 

 is found between the parallels of 8° and 14° of north latitude, and 

 in the spring between 5° south and 4° north. ( Vide Plate VIII.) 



838. This calm belt, in its motions from south to north and 

 back, carries with it the rainy seasons of the torrid zone, always 

 arriving at certain parallels at stated periods of the year ; conse- 

 quently, by attentively considering Plate VIII., one can tell what 

 places within the range of this zone have, during the year, two 

 rainy seasons, what one, and what are the rainy months for each 

 locality. 



839. Were the northeast and the southeast trades, with the belt 

 of equatorial calms, of different colors, and visible to an astron- 

 omer in one of the planets, he might, by the motion of these belts 

 or girdles alone, tell the seasons with us. He would see them at 

 one season going north, then, appearing stationary, and then com- 

 mencing their return to the south. But, though he would observe 

 (§ 188) that they follow the sun in his annual course, he would 

 remark that they do not change their latitude as much as the sun 

 does his declination ; he would, therefore, discover that their ex- 

 tremes of declination are not so far asunder as the tropics of Can- 

 cer and Capricorn, though in certain seasons the changes from day 

 to day are very great. He would observe that these zones of 

 winds and calms have their tropics or stationary nodes, about 

 which they linger near three months at a time ; and that they pass 

 from one of their tropics to the other in a little less than another 

 three months. Thus he would observe the whole system of belts 

 to go north from the latter part of May till some time in August. 

 Then they would stop and remain stationary till winter, in Decem- 

 ber ; Avhen again they would commence to move rapidly over the 

 ocean, and down toward the south, until the last of February or 



