CHAP. 1. 7- OF CLOUDS. 21 



and overhangs its base in uneven or rugged 

 folds; a preexisting cirrus, cirrocumulus, or 

 cirrostratus, or one perhaps immediately formed 

 for the occasion, alights on its summit, and in- 

 osculates. Many of these cirrostrati are some- 

 times seen attached to the cumulostratus, and 

 sometimes to intersect it. Cumulostrati fre- 

 quently remain in this state for a long time, 

 and constitute very picturesque skies. At other 

 times the processes are more rapid. The cirri 

 or cirrostrati are soon lost in the cumulostratus, 

 which increases in density, and soon becomes 

 the nimbus described in the next section. The 

 distinct appearance of the supersident cirri, or 

 cirrostrati, is not necessary to the production of 

 the cumulostratus ; on the contrary, the cumulus 

 as often passes to this cloud, and eventually to 

 the nimbus, without the visible precedence of 

 any such conjuncture and inosculation of dif- 

 ferent modifications. But it is probable that 

 the same kind of processes are going on unseen, 

 and that a similar change always takes place in 

 the electricity of the cumulus, previous to its 

 becoming the cumulostratus. The change be- 

 ing often visibly effected by the anastamosis of 

 two strata of cloud, as above described, and the 

 two strata having been found by experiment to 



