Magnetism and the Trade Winds. 289 



to the southward and westward of them in the SE. trade- 

 wind region of the earth should have a scanty supply of rain, 

 and mce versa. 



Now, the extra-tropical part of New Holland comprises a 

 portion of land thus situated in the southern hemisphere. 

 Tropical India is in its NE. trade-wind region, and should 

 give it a slender supply of rain. But what modifications the 

 monsoons of the Indian ocean may make to this rule, or what 

 effect they may have upon the rains in New Holland, my in- 

 vestigations in that part of the ocean have not been carried 

 far enough for a decision. 



Taking up the theory of Ampere with regard to the mag- 

 netic polarity induced by an electrical current, according as 

 it passes through wire coiled yvitli or coiled against the sun, 

 and expanding it in conformity with the discoveries of Fara- 

 day, we perceive a series of facts and principles which, being 

 applied to the circulation of the atmosphere, make the con- 

 clusions to which the charts have led me, touching the con- 

 tinual " whirl" of the wind in the Arctic regions against^ 

 and in the Antarctio with the hands of a watch^ very signifi- 

 cant — much more so than I had supposed them to be. 



In this view of the subject we see light springing up from 

 various sources, by which the shadows of approaching con- 

 firmation are clearly perceived. One such source of light 

 have we from the university of Greifswald, in Prussia. 



Likening the atmosphere with its magnetic spirals of oxy- 

 gen to the coils of a wire, and the poles of the earth as the 

 ends of the helix used by Professor Von Feilitzsch, we might 

 almost fancy that he was experimenting expressly with the 

 view of throwing light upon the general course of atmosphe- 

 rical circulation. 



'' If," says he in his letter to Dr Faraday, " we observe 

 two such neighbouring particles near the external south pole, 

 then will the more near repel a south pole with the intensity 

 s ; the more distant will turn to a north pole with the inten- 

 sity w', but in such a manner that n \s. But outwardly these 

 two excited magnetisms act with the difference of the power 

 s — n' ; but this is in one case south polar, consequently of 

 the same kind as the exciting south pole. The contrary will 



