282 THE PHYSICAL GEOGRAPHY OF THE SEA. 



4 



phere over this calm belt would, in consequence of so much heat 

 and expansion, be very much greater than it is over the trade- 

 winds or tropical calms. 



521. Returning and taking up the train of contemplation as to 

 Offices of the cloud- the officc which this belt of clouds, as it encircles 

 '■i"°- the earth, performs in the system of oceanic adapta- 

 tions, we may see how the cloud-ring and calm zone which it 

 overshadows perform the office both of ventricle and auricle in 

 the immense atmospherical heart, where the heat and the forces 

 which give vitality and power to the system are brought into play 

 — where dynamical strength is gathered, and an impulse given to 

 the air sufficient to send it thence througb its long and tortuous 

 channels of circulation. 



522. Thus this ring, or band, or belt of clouds is stretched 

 It acts as a regulator, arouud our plauct to pcgulate the quantity of pre- 

 cipitation in the rain-belt beneath it ; to preserve the due quan- 

 tum of heat on the face of the earth ; to adjust the winds ; and 

 send out for distribution to the four corners vapors in proper 

 quantities to make up to each river-basin, climate, and season its 

 quota of sunshine, cloud, and moisture. Like the balance-wheel 

 of a well-constructed chronometer, this cloud-ring affords the grand 

 atmospherical machine the most exquisitely -arranged self -compen- 

 sation. If the sun fail in his supply of heat to this region, more 

 of its vapors are condensed, and heat is discharged from its latent 

 store-houses in quantities just sufficient to keep the machine in 

 the most perfect compensation. If, on the other hand, too much 

 heat be found to accompany the rays of the sun as they impinge 

 upon the upper circumference of this belt, then again on that side 

 the means of self-compensation are ready at hand ; so much of 

 the cloud-surface as may be requisite is then resolved into invisi- 

 ble vapor — for of invisible vapor are made the vessels wherein 

 the surplus heat of the sun is stored away and held in the latent 

 state until it is called for, when it is instantly set free, and be- 

 comes a palpable and an active agent in the grand design. 



523. Ceaseless precipitation goes on imder this cloud-ring. 

 The latent heat lib- Evaporation under it is suspended almost entirely. 



trated in the proc- ■*. i i i • n • 



esses of condensa- We kuow that the tradc-wiuds encircle the earth ; 



tion from and under ^ ^ -i ^ 



the cloud-ring, true that thcv blow pcrpetuallv ; that they come from 



c"u^=e of the trade- tJ ' J 



winds. the north and the south, and meet each other near 



