303 Vn the Modrficathns of Clouds, anct 



Of the Stratus. 



This modification has a mean degree of density. 



It is the lowest of clouds, since its inferior surface com* 

 monly rests on the earth or water. 



Coutrar)f to the last, w hich may be considered as be- 

 longing to the day, this is properly the cloud of nighty 

 the time of its first appearance bcuig about sun-set. It 

 comprehends all those creeping mists which in calm evcn» 

 ing ascend in spreading sheets (like an inundation of water) 

 from the bottom of valleys and the surface of lakes, rivers^ 

 &c. _ _ 



Its duration is frequently through the night. 



On the return of the sun the level surface of this cloud 

 begins to put on the appearance of cumulus, the whole at 

 the same time separating from the ground. I'he continuity 

 is next destroyed, and the cloud ascends and evaporates, or 

 passes off with the appearance of the nascent cumulus. 



This has been long experienced as a prognostic of fair 

 weather*, and indeccT there is none more serene than that 

 which is ushered in by it. The relation of the stratus to 

 the state of the atniosphcre as indicated by the barometer, 

 &LC. appears notwithstanding to have passed hitherto with^ 

 out due attention. 



Of the C'trro-'cumtdusi 



The cirrus having continued for some time increasing or 

 stationary, usually passes either to the cirro-cunmlus or the 

 cirro-stratus, at the same time descending to a lower station 

 in the atmosphere. 



The cirro-cumulus is formed from a cirrus, or from a 

 number of small separate cirri, by the fibres collapsing 

 as it were, and passing into small roundish masses, in which 

 the texture of the cirrus is no longer discernible, although 

 they still retain soniewhat of the same relative arrangement. 

 This change takes place either throughout the whole mass 

 at once, or progressively from one extremity to the other.- 

 In either case, the same effect is produced on a number of 

 adjacent cirri it the same time and in the same order. It 

 a))pears in some instances to be accelerated by the approach 

 of other clouds. 



This modification forms a very beautiful sky, sometimes 

 exhibiting numerous distinct beds of these small connected 

 clouds, floating at different altitudes. 



* At nebulae iiiagis ima petunt, campoque recumbunt. 



yirgil, Gc'or^, lib. i. 

 Th« 



