146 ANNUAL OP SCIENTIFIC DISCOVERY. 



VIEWS ON THE ORIGIN OF TERRESTRIAL MAGNETISM. 



The following paper is comimmicated to Silliman's Journal by M. 

 Nickles, of Paris : 



The earliest view of terrestrial magnetism supposed the existence of a 

 magnet at the earth's centre. As this does not accord with the observa- 

 tions on declination, inclination and intensity, Tobias Meyer gave this 

 fictitious magnet an eccentric position, placing it one- seventh part of the 

 earth's radius from the centre. Haiisteeii imagined that there were two 

 such magnets, different in position and intensity. Ampere set aside these 

 unsatisfactory hypotheses by the view, derived from his discovery, that the 

 earth itself is an electro-magnet, magnetized by an electric current circu- 

 lating about it from east to west, perpendicularly to the plane of the mag- 

 netic meridian, and that the same currents give direction to the magnetic 

 meridian, and magnetize the ores of iron ; the currents being thermo- 

 electric currents, excited by the action of the sun's heat successively on 

 the different parts of the earth's surface as it revolves towards the east. 



A long time before the discovery of electro-magnetism, Biot was occu- 

 pied with this subject, and regarded the terrestrial magnetism as the prin- 

 cipal resultant of all the magnetic particles disseminated in the earth. M. 

 Gauss adopts this view, as an interpretation of the fact, without explain- 

 ing it. An observation made some years since has directed my attention 

 to this subject. It related to the fall of a cylindrical meteor, whose position 

 was sensibly in the plane of the magnetic meridian. Many luminous 

 meteors have been observed in this same position, or near it. 



The special position of the meteor observed by my brother and myself 

 was not fortuitous ; it was determined by the magnetic action of the earth, 

 an action which may be powerful in its influence on meteorites, consisting 

 essentially of the magnetic metals, iron and nickel. In our view, the 

 terrestrial magnet, the earth, decomposed by influence the normal fluid of 

 the meteoric mass, and so gave the meteor thus polarized the direction of 

 a compass-needle. 



In generalizing from this fact, and recalling the experiment of Arago 

 on the magnetism developed when a magnet acts upon a turning disk, we 

 ask w r hether the magnetic polarity of our planet may not be due to a like 

 cause. Considering it as proved, that the sun is polarized magnetically, 

 like the earth the sun will then be the inductor magnet, the agent which 

 decomposes the magnetic fluid of the terrestrial globe ; it will be to the 

 earth what the earth was to the meteor. This explanation does not resolve 

 the difficulty, as it does not say whence comes the magnetic polarity of 

 the sun. It implies the intervention of a magnet whose intensity is 

 superior to that of the sun, acting on this last by induction, and impressing 

 a polarity which the sun transmits to other planets of the system. It is 

 the hypothesis reversed of the central magnet, for it places in space the 



