PORTION OF THE COSMOS. THE SUN. 289 



certain rapidity of vibrations which produces very high 

 temperatures, in either case the Sun, as the chief source of 

 light and heat, may elicit and animate magnetic forces on 

 our planet, and especially in its gaseous envelope, the 

 atmosphere. The early knowledge of thermo-electric pheno- 

 mena in crystallised bodies (tourmaline, boracite, and topaz), 

 and Oersted's great discovery in 1820, according to which 

 every conductor of electricity exerts, during the time that the 

 electric current is passing through it, a determinate action 

 upon a magnetic needle, gave practical manifestation of 

 the intimate relations subsisting between heat, electricity, 

 and mgnetism. The ingenious Ampere, who ascribed all 

 magnetism to electric currents situated in a plane perpen- 

 dicular to the axes of the magnets, based on the idea of this 

 relationship between heat, electricity, and magnetism the 

 hypothesis, that terrestrial magnetism, (i. e. the magnetic 

 charge of the Earth), is produced by electric currents passing 

 round the planets from east to west, and that the solar heat 

 being the exciter of these currents, the diurnal variation 

 of the magnetic declination is the result of the change 

 of temperature produced by the diurnal change in the Sun's 

 altitude. The thermo-electric experiments of Seebeck, in 

 which differences of temperature in the points of connection 

 of a circle, made of bismuth and copper, or ether dissimilar 

 metals, cause a deflection of the magnetic needle, supported 

 Ampere's views. 



A new and brilliant discovery of Faraday's, the following 

 out of which by the author is taking place almost simulta- 

 neously with the printing of these pages, throws an unexpected 

 light on this important subject. "Whereas earlier investigations 



