^56 Modification of Clouds 



The real fact is, that the vapour which is wafted by the wind, 

 is precipitated by the cold contact of the mountain, and is 

 urged forward on its course till, borne beyond the influence 

 which caused its condensation, it is again exhaled, and disap- 

 pears. A slight inspection and consideration of the pheno- 

 mena will be sufficient to convince any one of the correctness 

 of this explanation. Reasoning from analogy, we may con- 

 clude that the process which thus proceeds, under our eyes, 

 upon the summits of the hills, likewise takes place on either 

 side of the planes of precipitation in the heights of the atmo- 

 sphere; the vapour is continually condensed, as continually re- 

 dissolved in the act of precipitation, and the cloud appears to 

 be unchanged and stationary." (Page 124'., first edition.) 



According to the electro-chemical theory of the formation of 

 clouds, however, it would be affirmed that the cloud was really 

 stationary and unchanged, in consequence of the equilibrium 

 of the electrical influence produced by the primary develope- 

 ment of the cloud, from the union ofthe constituent principles 

 of water previously existing in the gaseous state. It is barely 

 possible to apply the ingenious reasoning of Mr. Daniell to 

 this theory, and to suppose that, while the mist or vapour, 

 constituting the cloud is forming upon one side, the water is 

 simultaneously decomposed on the other side. 



We are still too much in the dark, with respect to the prin- 

 ciples that regulate atmospherical phenomena, to decide upon 

 the precise effects of electricity ; but, supposing the theory 

 alluded to has some foundation in nature, we may be tempted 

 to proceed a step farther, and connect it with the nearly 

 allied influence of magnetism. Indeed, without some such 

 power acting upon the light and movable streaks and tufts of 

 vapour which form what I call wane-clouds (Cirrus, Howard), 

 I cannot devise any satisfactory explanation of the appearances 

 which may so frequently be observed ; for, if the wind were 

 the sole agent in determining their forms and positions, they 

 ought always to stream in the direction of its current, as we 

 see is uniformly the case in the analogous instance of smoke. 

 In the case of wane-clouds, however, they as frequently appear 

 to cross, or lie obliquely to the current of the wind which blows 

 in the plane of their stratification, as the contrary ; and, some- 

 times, they may be seen in positions simultaneously so dissi- 

 milar, that it seems difficult to refer the direction of any 

 particular tuft or streak to any known agent. As an instance 

 of this, I sketched the following [Jig. 199.), a few days after the 

 occurrence of the preceding arched wane-cloud. The wind, it 

 is true, was easterly in the general direction of the streaks ; 

 but besides the shorter crossing streaks at a [Jig, 198), which 



