MAGNETIC DISTURBANCES. 141 



February ; that is to say, precisely at the time when the 

 earth is nearest to the sun, and moves in its orbit with the 

 greatest velocity. 82 



I have already treated in the Picture of Nature 83 of the 

 simultaneity of many magnetic storms, which are transmitted 

 for thousands of miles and indeed almost round the entire 

 circumference of the earth, as on the 25th of September, 

 1841, when they were simultaneously manifested in Canada, 

 Bohemia, the Cape of Good Hope, Van Diemen's Land, and 

 Macao ; and I have also given examples of those cases, in 

 which the perturbations were of a more local kind, passing 

 from Sicily to Upsala, but not from Upsala farther north in 

 the direction of Alten and Lapland. In the simultaneous 

 observations of declination which were instituted by Arago 

 and myself in 1829 at Berlin, Paris, Freiberg, St. Peters- 

 burg, Casan, and Nikolajew, with the same Gambey's instru- 

 ments, individual perturbations of a marked character were 

 not transmitted from Berlin as far as Paris, and not on any 

 one occasion to the mine at Freiberg, where Eeich was mak- 

 ing a series of subterranean observations on the magnet. 

 Great variations and disturbances of the needle simultan- 

 eously with the occurrence of the Aurora borealis at Toronto 

 certainly occasioned magnetic storms in Kerguelen's Land, 

 but not at Hobarton. When we consider the capacity for 

 penetrating through all intervening bodies, which distin- 

 guishes the magnetic force, as well as the force of gravity 

 inherent in all matter, it is certainly very difficult to form a 

 clear conception of the obstacles which may prevent its trans- 

 mission through the interior of the earth. These obstacles 

 are analogous to those which we observe in sound-waves, or 

 in the waves of commotion in earthquakes, in which certain 



82 Sabine, in the Phil. Transact, for 1850, pt. i, p. 216. Faraday, 

 Exper. Researches on Electricity, 1851, pp. 56, 73, 76, 2891, 2949, 

 2958. 



83 Cosmos, vol. i, p. 185 ; Poggend. Annalen, Bd. xv, s. 334, 335 ; 

 Sabine, Unusual Disturb, vol. i, pt. i, pp. xiv xviii; where tables are 

 given of the simultaneous storms at Toronto, Prague, and Van Diemen's 

 Land. On those days in which the magnetic storms were the most 

 marked in Canada (as, for instance, on the 22nd of March, the 10th of 

 May, the 6th of August, and the 25th of September, 1841), the same 

 phenomena were observed hi the southern hemisphere in Australia. 

 See also Edward Belcher, in the Phil. Transact, for 1843, p. 133. 



