218 THE PHYSICAL GEOGRAPHY OF THE SEA. 



around our planet, uj) and down the eartli : it travels up and down 

 the ocean, as from north to south and back. 



604. It is broader than the belt of calms out of which it rises. 

 As the air, with its vapors, rises up in this calm belt and ascends, 

 these vapors are condensed into clouds (§ 602), and this condensa- 

 tion is followed by a turgid intumescence, which causes the clouds 

 to overflow the calm belt, as it were, both to the north and the 

 south. The air flowing off in the same direction assumes the 

 character of winds that form the upper currents that are counter 

 (Plate I.) to the trade-winds. These currents carry the clouds 

 still farther to the north and south, and thus make the cloud- 

 ring broader. At least, we infer such to be the case, for the rains 

 are found to extend out into the trade-winds, and often to a 

 considerable distance both to the north and the south of the calm 

 belt. 



605. Were this cloud-ring luminous, and could it be seen by an 

 observer from one of the planets, it would present to him an ap- 

 pearance not unlike the rings of Saturn do to us. Such an ob- 

 server would remark that this cloud-ring of the earth has a motion 

 contrary to that of the axis of our planet itself — that while the 

 earth was revolving rapidly from west to east, he would observe 

 the cloud-ring to go slowly, but only relatively, from east to west. 

 As the winds which bring this cloud-vapor to this region of calms 

 rise up with it, the earth is slipping from under them ; and thus 

 the cloud-ring, though really moving from west to east with the 

 earth, goes relatively slower than the earth, and would therefore 

 appear to require a longer time to complete a revolution. 



606. But, unlike the rings of Saturn through the telescope, the 

 outer surface, or the upper side to us, of this cloud-ring would ap- 

 pear exceedingly jagged, rough and uneven. 



607. The rays of the sun, playing upon this peak and then upon 

 that of the upper cloud-surface, melt away one set of elevations 

 and create another set of depressions. The whole stratum is, it 

 may be imagined, in the most turgid state ; it is in continued 

 throes when viewed from above ; the heat which is liberated from 

 below in the process of condensation, the currents of warm air as- 

 cending from the earth, and of cool descending from the sky, all, 



