216 THE PHYSICAL GEOGRAPHY OF THE SEA. 



599. Eeturning and taking up the train of contemplation as to 

 the office which this belt of clouds, as it encircles the earth, per- 

 forms in the system of oceanic adaptations, 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 w^hich give vitality and power to the 

 system are brought into play — where dynamical strength is gath- 

 ered, and an impulse given to the air sufficient to send it thence 

 through its long and tortuous channels of circulation. 



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

 around our planet to regulate the quantity of precipitation in the 

 rain-belt beneath it ; to preserve the due quantum of heat on the 

 face of the earth ; to adjust the winds ; and send out for distribu- 

 tion 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 chro- 

 nometer, this cloud-ring affords the grand atmospherical machine 

 the most exquisitely-arranged self-comjyensation. If the sun fail 

 in his supply of heat to this region, more of its vapors are con- 

 densed, and heat is discharged from its latent store-houses in quan- 

 tities just sufficient to keep the machine in the most perfect com- 

 pensation. If, on the other hand, too much heat be found to ac- 

 company the rays of the sun as they impinge upon the upper cir- 

 cumference 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 invisible vapor — for of 

 invisible vapor are made the vessels wherein the surplus heat from 

 the sun is stored away and held in the latent state until it is call- 

 ed for, w^hen instantly it is set free, and becomes a palpable and 

 active agent in the grand design. 



601. That the thermometer stands invariahly lower (§ 591) be- 

 neath this cloud-belt than it does on either side of it, has not, so 

 far as my researches are concerned, been made to appear by ac- 

 tual observation, for the observations in my possession have not 

 yet been fully discussed concerning the temperature of the air. 

 But that the temperature of the air at the surface under this cloud- 

 ring is lower, is a theoretical deduction as susceptible of demon- 



