78 cosmos. 



tion assumed by freely-oscillating bodies under external mag- 

 netic influences {Phil Transact for 1846, § 2420, and Phil. 

 Transact, for 1851, pt. i., § 2718-2796); (2) Regarding the 

 relation of electro-magnetism to a ray of polarized light, and 

 the rotation of the latter by means of the altered molecular 

 condition of the bodies through which the ray of polarized 

 light and the magnetic current have both been transmitted 

 {Phil Transact, for 1846, pt. i., § 2195 and § 2215-2221); 

 (3) Regarding the remarkable property which oxygen (the 

 only gas which is paramagnetic) exerts on the elements of 

 terrestrial magnetism, namely, that like soft iron, although 

 in a much weaker degree, it assumes conditions of polarity 

 through the diffused action of the body of the earth, which 

 represents a permanently present magnet* {Phil Transact, 

 for 1851, pt. i., § 2297-2967). 



ful magnet, are exhibited by bismuth, antimony, silver, phosphorus, 

 rock-salt, ivory, wood, apple-shavings, and leather. Oxygen gas, either 

 pure or when mixed with other gases, or when condensed in the inter- 

 stices of charcoal, is paramagnetic. See, in reference to crystallized 

 bodies, the ingenious observations made by Plucker concerning the 

 position of certain axes (Poggend., Annal, bd. lxxiii., s. 178; and 

 Phil Transact, for 1851, § 2836-2842). The repulsion by bismuth 

 was first recognized by Brugmans in 1788, next by Le Bailiff in 1827, 

 and, finally, more thoroughly tested by Seebeck in 1828. Faraday 

 himself (§ 2429-2431), Keich, and Wilhelm Weber, who, from the 

 year 1836, has shown himself so incessantly active in his endeavors to 

 promote the progress of terrestrial magnetism, have all endeavored to 

 exhibit the connection of diamagnetic phenomena with those of induc- 

 tion (Poggend., Annalen, bd. lxxiii., s. 241-253). Weber has, more- 

 over, tried to prove that diamagnetism derives its source from Am- 

 pere's molecular currents. (Wilh. Weber, Abhandlungen iiber electro- 

 dynamische Maassbestimmungen, 1852, s. 545-570.) 



* In order to excite this polarity, the magnetic fluids in every par- 

 ticle of oxygen must be separated, to a certain extent, by the actio in 

 distans of the earth in a definite direction, and with a definite force. 

 Eveiy particle of oxygen thus represents a small magnet, and all these 

 small magnets react upon one another as well as upon the earth, and, 

 finally, in connection with the latter, they further act upon a magnet- 

 ic needle, which may be assumed to be in or beyond the atmosphere. 

 The envelope of oxygen that encircles our terrestrial sphere may be 

 compared to an armature of soft iron upon a natural magnet or a 

 piece of magnetized steel ; the magnet may further be assumed to be 

 spherical, like the earth, while the armature is assumed to be a hollow 

 shell, similar to the investment of atmospheric oxygen. The magnet- 

 ic power which each particle of oxygen may acquire by the constant 

 force of the earth diminishes with the temperature and the rarefaction 

 of the oxygen gas. When a constant alteration of temperature and 

 an expansion follows the sun around the earth from east to west, it 

 must proportionally alter the results of the magnetic force of the earth, 

 and of the oxygen investment ; and this, according to Faraday's opin- 



