of the Cumulus Cloud. 139 



upwards a slight condensation takes place, that increases the 

 temperature and expansive force of the mass of air, and car- 

 ries it into higher regions. This being done successively and 

 constantly, the whole upper region is sufficiently warmed and 

 expanded to carry the small condensed particles of water, 

 the remaining steam, and the atmospheric gases to the proper 

 height, where the whole flow over north and south towards 

 the poles. The hazy atmosphere of the tropical seas is pro- 

 bably nothing more than an immense cumulus cloud, conti- 

 nually formed and carried away, north and south, the causes 

 in operation being so regular as to prevent the cloud from 

 being broken up or dispersed. At the outer edges of this 

 tropical cloud disturbances take place similar to those which 

 occur when cumuli are formed in the temperate regions. 

 When the steam is very abundant and atmospheric disturbance 

 great, the process which produces cumuli may go on and give 

 rise to heavy rains, and possibly to storms; whether that process 

 is always the sole or even principal cause in operation during 

 storms is a subject worthy of investigation, but is one into 

 which it is not proposed to enter at present. 



It has been said by some persons who object to the theory 

 here advanced, that when steam rises until it is cooled by ex- 

 pansion, sufficiently to produce condensation, upon the smallest 

 particle of the latent heat of the steam being given out the cool- 

 ing is stopped. They therefore contend that condensation could 

 not continue, as it would be terminated at the very commence- 

 ment of the process. And this would be true, if steam alone 

 existed in the atmosphere. Were nothing present but steam it 

 does not appear how there could be any considerable or con- 

 tinued rise of temperature from condensation, because any, the 

 smallest, increase of the temperature must stop the condensation, 

 and thus destroy the only source from whence is derived the in- 

 crease of that temperature. But there are gases present with 

 the steam and diffused through it, forming with it a minute me- 

 chanical intermixture. And when the condensation of steam 

 liberates caloric, the liberated caloric attaches itself to the 

 gases, as well as to the remaining portion of the steam, in- 

 creases the expansive force of these gases, causes them to 

 spring up, and to carry with them the steam that is diffused 

 through and entangled among their particles. Steam, it will 

 be remembered, forms but a small proportion of the whole at- 

 mosphere. When the temperature and dew-points are at 32° 

 of Fahrenheit, steam constitutes but a g^th P art °f tne a t- 

 mosphere ; when they are at 52° it forms a T |o tn part of it ; 

 when at 73° it is a Xth part ; and when at 80° it is only ^ n th 

 part. And as the dew-point in this part of the world is not 



