280 THE PHYSICAL GEOGUxVPHY OF THE SEA. 



518. Having traveled with the calm belt to the north or south, 

 Its motions, the cloud-ring leaves a clear sky about the equator ; 



the rays of the torrid sun then pour down upon the solid crust of 

 the earth there, and raise its temperature to,a scorching heat. The 

 atmosphere dances (§ 356), and the air is seen trembling in ascend- 

 ing and descending columns, with busy eagerness to conduct the 

 heat off and deliver it to the regions aloft, where it is required to 

 give dynamical force to the air in its general channels of circula- 

 tion. The dry season continues ; the sun is vertical ; and finally 

 the earth becomes parched and dry ; the heat accumulates faster 

 than the air can carry it away ; the plants begin to wither, and the 

 animals to perish. Then comes the mitigating cloud-ring. The 

 burning rays of the sun are intercepted by it : the place for the 

 absorption and reflection, and the delivery to the atmosphere of 

 the solar heat, is changed ; it is transferred from the upper surface 

 of the earth to the upper surface of the clouds. 



519. Eadiation from land and sea below the cloud-belt is thus 

 Meteorological proc- interrupted, and the excess of heat in the earth is 

 ®^^" delivered to the air, and by absorption carried up 

 to the clouds, and there transferred to their vapors to prevent ex- 

 cess of precipitation. In the mean time, the trade- winds north 

 and south are pouring into this cloud-covered receiver, as the 

 calm and rain belt of the equator may be called, fresh supplies in 

 the shape of ceaseless volumes of heated air, which, loaded to 

 saturation with vapor, has to rise above and get clear of the clouds 

 before it can commence the process of cooling by radiation. In 

 the mean time, also, the vapors which the trade-winds bring from 

 the north and the south, expanding and growing cooler as they 

 ascend, are being condensed on the lower side of the cloud stra- 

 tum, and their latent heat is set free, to check precipitation and 

 prevent a flood. While this process and these operations are go- 

 ing on upon the nether side of the cloud-ring, one not less im- 

 portant is, we may imagine, going on upon the upper side. There, 

 from sunrise to sunset, the rays of the sun are pouring down with- 

 out intermission. Every day, and all day long, they play with 

 ceaseless activity upon the upper surface of the cloud stratum. 

 When they become too powerful, and convey more heat to the 

 cloud vapors than the cloud vapors can reflect and give off to the 

 air above them, then, with a beautiful elasticity of character, the 



