XX NOTES. 



tions accompanying auroras extend to regions of the Earth where the auroral 

 light is not seen, he, in 1823, arranged with our common friend Kupffer for 

 simultaneous hourly observations being made at Paris and at Kasan, almost 47 

 east of Paris. Similar simultaneous observations of the declination were set on 

 foot by me in 1828, by Arago, Reich, and myself, in Paris, Freiberg and Berlin. 

 See Poggend. Ann. Bd. xix. S. 337. 



( ra ) p. 81. The memoir of Rudolph Wolf, referred to in the text, contains his 

 own daily observations of solar spots, from the 1st of January to the 30th of 

 June, 1852, and a comparison of Lament's periodical declination-variations with 

 Schwabe's results on the frequency of the solar spots in the interval from 1835 

 to 1850. This memoir WHS presented on the 31st of July, 1852, at a meeting 

 of the Society of Natural Sciences at Berne, while the more detailed memoir of 

 Colonel Sabine (printed in the Phil. Trans, for 1852, Pt. I. p. 116121) had 

 been presented to the Royal Society of London at the beginning of March, and 

 read at the beginning of May in the same year, i.e. 1852. According to the 

 most recent examination of all the observations which have been made on the 

 solar spots, Wolf finds the mean period, between 1600 and 1852, to be ITU 

 years. 



( 74 ) p. 83. Kosmos, Bd. iii. S. 400 and 419, Anm. 30 (English edition, p. 

 290 and civ. ; Note 489). Bismuth, antimony, silver, phosphorus, rock-salt, ivory, 

 wood, slices of apple, and leather, when placed in the vicinity of a powerful mag- 

 net, all show diamagnetic repulsion, and equatorial, L e. east and west, axiality. 

 Oxygen (pure, or mixed with other gases, or condensed in the interstices of char- 

 coal) is paramagnetic. In reference to crystallised bodies, see what has been 

 discovered, in relation to the position of certain axes, by the sagacious Pliicker. 

 (Poggend. Ann. Bd. 73, S. 178 ; and Phil. Trans, for 1851, Art. I. 2836 

 2842.) The repulsion by bismuth was first recognised, in 1778, by Brugmans, 

 and, at a later period, more thoroughly examined by Le Baillif in 1827, and by 

 Seebeck in 1828. Faraday himself ( 2429^2431), Reich, and Wilhelm 

 Weber, who, since 1836, has been so uninterruptedly active in the advancement 

 of the knowledge of the Earth's magnetism, have brought forward the connection 

 of diamagnetic phenomena with those of induction. (Poggend. Ann. Bd. 73, 

 S. 241 and 253.) Weber tried to satisfy himself that diamagnetism has its 

 source in Ampere's molecular currents. (Wilh. Weber, Abhandlungen tiber 

 electro-dynamische Maasbestimmungen, 1852, S. 545 570.) 



( ra ) p. 84. For producing this " polarity," the magnetic fluids in every par- 

 ticle of oxygen are separated by the Earth's "actio in distans," a certain amount, 

 in a determinate direction, and with a determinate force. Every particle of 

 oxygen thus represents a small magnet, and all these small magnets react upon 



