RED FOGS AND SEA DUST. 123 



pose that it is not always in the atmosphere, for the storms that 

 take it up occur only occasionally, and that when up, and in pass- 

 ing the same parallels, it does not, any more than the vapor from a 

 given part of the sea, always meet with the conditions — electrical 

 and others — favorable to its descent, and that these conditions, as 

 with the vapor, may occur now in this place, now in that. But 

 that the fall does occur always in the same atmospherical vein or 

 general direction, my investigations would suggest, and Ehren- 

 berg's researches prove. 



294. Judging by the fall of sea or rain dust, we may suppose 

 that the currents in the upper regions of the atmosphere are re- 

 markable for their general regularity, as well as for their general 

 direction and sharpness of limits, so to speak. 



295. We may imagine that certain electrical conditions are nec- 

 essary to a shower of " sea dust" as well as to a thunder-storm ; 

 and that the interval between the time of the equinoctial disturb- 

 ances in the atmosphere and the occurrence of these showers, 

 though it does not enable us to determine the true rate of motion 

 in the general system of atmospherical circulation, yet assures us 

 that it is not less on the average than a certain rate. 



296. I do not offer these remarks as an explanation with which 

 we ought to rest satisfied, provided other proof can be obtained ; 

 I rather offer them in the true philosophical spirit of the distin- 

 guished microscopist himself, simply as affording, as far as they 

 are entitled to be called an explanation, that explanation which is 

 most in conformity with the facts before us, and whifch is suggest- 

 ed by the results of a novel and beautiful system of philosophical 

 research. It is not, however, my province, or that of any other 

 philosopher, to dictate belief. Any one may found hypotheses if 

 he will state his facts and the reasoning by which he derives the 

 conclusions which constitute the hypothesis. Having done this, 

 he should patiently wait for time, farther research, and the judg- 

 ment of his peers, to expand, confirm, or reject the doctrine which 

 he. may have conceived it his duty to proclaim. 



2^7. Thus, though we have tallied the air, and put labels on 

 llie wind, to " tell whence it com.eth and whither it goeth," yet 

 lliere evidently is an agent concerned in the circulation of the at- 



