Magnetism and the Trade Winds. 287 



and Dublin Philosophical Magazine and Journal of Science, 

 containing a synopsis of Dr Faraday's " Experimental Re- 

 searches in Electricity," 24th, 25th, 26th, and 27th series ; 

 and also the letter of Prof. Von Feilitzsch on the Physical 

 distinction of Magnetic and Diamagnetic Bodies. 



This acpount, though meagre, is the first account that I 

 have seen of the Doctor's discoveries relative to the mag- 

 netism of the atmosphere. 



A new era in our knowledge of the laws and the agents 

 concei*ned in the general system of atmospherical circulation 

 will probably be dated from these discoveries. 



With the accounts of them before me, I feel somewhat in 

 the condition of the tempest-tossed mariner who has been 

 buffeting with the waves in storm, clouds, and darkness, 

 until he feels himself almost bewildered and lost in the mist 

 that surrounds him ; when suddenly a light appears, and, like 

 the grateful mariner, I wished, before taking a fresh de- 

 parture, to bring up my reckoning, and to ascertain how far 

 I was out, in order to shew how great was the service ren- 

 dered by the sympathizing hand which put forth that light. 



Dr Faraday has shewn that, as the temperature of oxygen 

 is raised, its paramagnetic force diminishes, being resumed 

 as the temperature falls again. 



" These properties it carries into the atmosphere, so that 

 the latter is, in reality, a magnetic medium, ever varying, 

 from the influence of natural circumstances, in its mag- 

 netic power. If a mass of air be cooled, it becomes more 

 paramagnetic ; if heated, it becomes less paramagnetic (or 

 diamagnetic), as compared with the air in a mean, or normal 

 condition.''* 



Now, is it not more than probable that here we have in 

 the magnetism of the atmosphere that agent which guides 

 the air from the south through the calms of Capricorn, of the 

 ec(uator, and of Cancer, and conducts it into the north ; that 

 agent which causes the atmosphere with its vapours and in- 

 fusoria to flow above the clouds from one hemisphere into 

 the other, and whose foot-prints had become so palpable % 



* Phil. Mag. and Journal of Science, 4th Series, No. 1, January 1861, p. 73. 



