84 TERRESTRIAL MAGNETISM. 



magnetism to a polarised ray of light, and the rotation of 

 the polarised ray under the intervention of an altered mole- 

 cola r condition of the substance which is made the conduct- 

 ing medium both of the ray and of the magnetic current 

 (Phil. Trans, for 1846, 2195 and 22152221); 

 3. On the remarkable property possessed by oxygen gas 

 (the only one of the gases which is paramagnetic) similar to 

 that possessed by soft iron only in a much weaker degree, 

 of assuming polarity under the inducing influence of the 

 earth, as soft iron does in the presence of a permanent 

 magnet(75). (phfl. Trans. 1851, 22972967.) 



1849. Professor William Thompson, of Glasgow : A 

 mathematical theory of magnetism, Phil. Trans, for 1851, 

 Part i. p. 243285. (On the problem of the distribution 

 of the magnetic force, compare 42 and 56, with Poisson, 

 in the Mem. de 1'Institut, 1811, Part i. p. 1; Part ii. 

 p. 163.) 



1850. Airy on the present state and prospects of the 

 Science of terrestrial magnetism, a fragment of a very 

 promising essay. 



1852. Kreil, Influence of the Moon on the magnetic 

 declination at Prague in the years 1839 1849. On the 

 earlier labours of this exact observer, and on his first con- 

 jectures regarding the lunar influence, see Osservazioni sull j 

 intensita e sulla direzione della forza magnetica istituite negli 

 anni 1836 1838, all' I. E. Osservatorio diMilano, p. 171 ; 

 and his Mag. und Met. Beobachtungen zu Prag, Bd.' i. 

 S. 59. 



1853. Faraday on lines of magnetic force, and their 

 definite character. 



1853. Sabine: on the lunar diurnal variation of the 



