146 PHYSICAL GEOGRAPHY OF THE SEA, AKD ITS METEOROLOGY. 



dew, causing it to descend in tlie black fogs of London. Any 

 circumstances, therefore, which may cause the dust that ascends as 

 a straw-coloured cloud from the Orinoco, to radiate its caloric and 

 collect moisture in the sky, may cause it to descend as a red fog 

 in the Atlantic or Mediterranean. 



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

 What is the agent ^rg ouglit to rcst Satisfied, provided other proof can 

 acTosfthe^caim belts? be obtained; I rather offer them in the true philo- 

 so]}hical spirit of the distinguished microscopist himself, simply as 

 affording, as far as they are entitled to be called an explanation, 

 that explanation which is most in conformity wdth the facts 

 before us, and which is suggested by the results of a novel and 

 beautiful system of philosophical research. It is not, however, my 

 pro^dnce, or that of any other philosopher, to dictate behef. Any 

 one may found hypotheses if he will state his facts and the rea- 

 soning by which he derives the conclusions which constitute the 

 hyi^othesis. Having done this, he should patiently wait for time, 

 farther research, and the judgment of his peers, to expand, confirm, 

 or reject the doctrine which he may have conceived it his duty 

 to proclaim. Thus, though we have tallied the air, and put 

 labels on the wind, to "tell whence it cometh and whither it 

 goeth," yet there evidently is an agent concerned in the circulation 

 of the atmosphere whose functions are manifest, but whose j^resence 

 has never yet been clearly recognized. When the ?jr vrliich the 

 north-east trade-winds bring down, meets in the equatorial calms 

 that which the south-east trade-winds convey, and the two streams 

 rise up together, what is it that makes them cross ? where is the 

 power that guides that from the north over to the south, and that 

 from the south up to the north ? The conjectures in the next chapter 

 iis 10 " the relation between magnetism and the circulation of the 

 atmosphere " may perhaps throw some light upon the answer to 

 this question. 



