tHE NATUfeAt HiSTdRV Op CtotfiS* 47 



tnbist atmosphere, the character of the upper part ofteh iapa 

 preaches more nearly to the cirro-stratus than the Cttrllsj 

 The more perfectly distiiut and local tiie shower, and the 

 clearer the rest'of the air from other clouds, the more pera 

 feet the crown of cirrus, which, indeed, sometimes assumes 

 aa almost geometrical precision in its form and internal 

 structure; the threads of the cirrus tending from all sides 

 directly towards the top of the column. 



The pure nimbus Commonly moves with the wind, and Increased %f 

 from the rapidity of its passage affords but littlt to th^ l-ain- 'c"^*^^^* 

 gauge. But it often happens, that it is formed in the mid^ 

 of cumuli, which have already arrived at a great size* Irt 

 this case the latter may be seen to enter successively ihtb 

 the focus at the top of the column, whence they never 

 Emerge; being visibly converted to the purpose of supply- 

 ing materials for the irrigation, which thus becomes more 

 abundant; and the shower is also occasionally thus propa* 

 gated in a direction opposite to the wind. 



The nimbus, moreover, does not always originate in a Chisig^ftt 

 fcirrus. The cumulus, and more often the cumulo-stratUs, 

 may be seen to expand at their summit into a cirrose sheet» ' 



tvhile the lower part is resolved into rain. On the contrarVj 

 the rain suddenly ceasing^ and the nimbus remaining entire^ 

 the sharp extremities of the crown often retire into it ; the 

 sides assume the swelling folds, and the character is ex* 

 changed for that of d|:imulo-stratus. When the shower has 

 expanded itself, and the sheets break, the superior portions 

 tisually turn to the cirro-cumulus or cirro-stratus, and the 

 ioweir to the cumulus. When a total evaporation of the rfe- Iridicaite>4§, 

 maining cloud follows a shower, it is a very favourable prog* 

 hostic. A nimbus is frequently accompanied by a cirro^ 

 stratus or two lying near it, and on a level with the densest 

 part of the cloud. The nimbus of thunder-storms has many 

 *f these, as before observed of the cumulo-stratus, arranged 

 at different heights ; which, with the grotesque form of eath 

 6loud, and the hazy state of the niedium> are sufficiently 

 tiharacteristic of the high electric state of the air at such 

 timesji and want Only an attentive perusal (in nature) to en* 

 *bTe the observer to ascertain it on future occasions. It ap* 

 pears, that the cumulo-stratus passes to the nimbus by a 



suddea 



