i06 0» the MGdlficaiions of Clouds, and 



But we see the nature of this process more perfectly lit 



viewing a distant shower in. profile. 



If the cumulus be the only cloud present at such a tiinej 

 we may observe its superior part to become tufted with nas- 

 ' cent cirri. Several adjacent clouds also approach and unite 

 laterally by subsidence. 



The cirri increase, extending themselves upward and la- 

 terally, after which the showei" is seen to commence. At 

 other times the converse takes place of what has been de- 

 scribed relative to the cessation of rain. The cirro-stratus 

 is prcvioujly formed above the cumulus, and their sudden 

 miion it? attended with the prodiiction of cirri and rain. 



In either case the cirri vegetate, as it were, in proportion 

 to the quantity of rain falling, and give the cloud a cha- 

 racter by \\ hich it is easily known at great distances, and 

 lo which, in the langiiage of meteorology, we may appro- 

 priate the nimbus of the Latins *. 



When one of these arrives hastily with the wind it brings 

 but little rain, and frequently some hail or driven snow. 



In heavy showers, the. central sheet once formed, is, as it 

 were, warped to windward, the cirri being propagated above 

 and against the lower current, while the cunmli arriving 

 ■with the latter are sueccbsively brought to and contribute to 

 reinforce it. 



Such are the phcenomena of showers. In continued 

 gfentle rains it does not appear necessary for the resolution 

 of the clouds that the different modifications should come 

 into actual contact. 



It is sufficient that there exist two strata of clouds, one 

 passing beneath the other, and each continually tending to 

 horizontal uniform diffusion. It will rain during this state 

 of the two strata, although they should be separated by an 

 interval of many hundred feet in elevation. Sec an instance 

 in De Luc, Idees siir la Meteorologie, tom. ii. p. 52, Sec. 



As the masses of cloud are always blended and their ar- 

 Tan<rement destroyed before rain comes on, so the reappear- 

 jince of these is the signal for its cessation. The thin sheets 

 of cloud which pass over during a wet day, certainly receive 

 from the humid atmosphere a supply proportionate to their 

 consumption, while the latter prevents their increase in 

 bulk. Hence a seeming paradox, which yet accords strictly 

 with observation, that for any given hour of a wet day, or 

 any given day of a wet season, the more cloud the less raini 



* Qnalis vrbi ad terras abrupto svdere nimiiis 

 It mare p^i intdium, miseris \\c\i J>iCiLiu Ivnge 

 Uorre;>cunt coi'da agricolis. 



