THE WATURAL HISTORY OP CLOUDS. 4jg 



^Hces a cloud, which, in regard to both its form s^d ita 

 rapid growth, may be compared to a mushroom. 



The cumulo-stratus usually prevails iu the completely 

 overcast sky. In this it presents appearances not easy to be 

 described, but which may be classed by a due attention to 

 the theory of this cloud. At present it is Intended to com- 

 prehend under it every mode of union between different 

 ftrata, which is not productive of rain. Future investiga- 

 tion may point out distinctions, which at present we are not 

 prepared to make. 



This modification is most frequent during a tnean elevation Indicaiionst 

 af the barometer, or that which is denominated changeable^ 

 when the wind blows from the west, with occasional devia* . 

 tions towards the north and sotth. In respect to tempera- 

 ture, it has a wide range, and may usher in a fall of snow, 

 as well as a thunder-storm. Of the latter, indeed, it i'* 

 among the regular harbingers, but with peculiar appearances. 

 During the suffocating calm which prevails before the first 

 discharge of the atmospheric electricity, it may be seen in 

 different points of the horizon, rapidly swelling to a stupen- 

 dous magnitude, most curiously wreathed and curled, 

 ♦* fretted and embossed" in its substance, and flanked at dif- 

 ferent heights by the delicate opake streaks of the cirro-stra- 

 tus. The whole presents a spectacle of peculiar magnifi- 

 cence, in contemplating which one may imagine an invisible 

 agent coUet'trng in this immense laboratory the energies of 

 the storm, and arranging innumerable batteries for the sub- 

 se«[uent explosions. 



It will appear by what we have already stated, that the 

 cumulo-tstratus affords in general a doubtful prognostic. 

 When it is formed in the morning, the day often proves 

 (fair, though overcast ; and if the cirro-stratus has contri- 

 buted to its formation, there will probably ensue heavy 

 shewers on the second or third daj. When it subsists a long 

 time, the character of its superior spreading part may be 

 consulted, which, if it be decidedly either that of the cirro- 

 stratus, or clrro-cumuliis, the usual result of their appear- 

 ance may be expected. 



Of the Nimbus, 

 To have a correct notion of this cloudy the reader has'only Nimbus 4«' 



to 



