MAGNETISM. 191 



lar or irfegular manifestation of the terrestrial force is detected 

 by uninterrupted and simultaneous observations. A variation 



cially at the times of the solstices and equinoxes, from hour to hour, 

 and often from half hour to half hour, for five or six days and nights 

 uninterruptedly. I had persuaded myself that continuous and uninter- 

 rupted observations of several days and nights (obsers'atio perpetua) 

 were preferable to the single observations of many months. The ap- 

 paratus, a Prony's magnetic telescope, suspended in a glass case by a 

 thread devoid of torsion, allov^ed angles of seven or eight seconds to be 

 read off on a finely-divided scale, placed at a proper distance, and 

 lighted at night by lamps. Magnetic perturbations (storms), which oc- 

 casionally recurred at the same hour on several successive nights, led 

 me even then to desire extremely that similar apparatus should be used 

 to the east and west of Berlin, in order to distinguish general terres- 

 trial phenomena from those which are mere Iqcal disturbances, depend- 

 ing on the inequality of heat in different parts of the Earth, or on the 

 cloudiness of the atmosphere. My departure to Paris, and the long 

 period of political disturbance that involved the whole of the west of 

 Europe, prevented my wish from being then accomplished. CErsted's 

 great discovery (1820) of the intimate connection between electricity 

 and magnetism again excited a general interest (which had long flag- 

 ged) in the periodical variations of the electro-magnetic tension of the 

 Earth. Arago, who many years previously had commenced in the Ob- 

 servatory at Paris, with a new and excellent declination instrument by 

 Gambey, the longest uninterrupted series of horary observations which 

 we possess in Europe, showed, by a comparison with simultaneous ob- 

 servations of perturbation made at Kasan, what advantages might be 

 obtained from corresponding measurements of declination. When I 

 returned to Berlin, after an eighteen years' residence in France, I had 

 a small magnetic house erected in the autumn of 1828, not only with 

 the view of carrying on the work commenced in 1806, but more with 

 the object that simultaneous observations at hours previously determ- 

 ined might be made at Berlin, Paris, and Freiburg, at a depth of 35 

 fathoms below the surface. The simultaneous occurrence of the per- 

 turbations, and the parallelism of the movements for October and De- 

 cember, 1829, were then graphically represented. (Pogg., Annalen, 

 bd. xix., 8. 357, taf. i.-iii.) An expedition into Northern Asia, under- 

 taken in 1829, by command of the Emperor of Russia, soon gave me an 

 opportunity of working out my plan on a larger scale. This plan was 

 laid before a select committee of one of the Imperial Academies of 

 Science, and, under the protection of the Director of the Mining Depart- 

 ment, Count von Cancrin, and the excellent superintendence of Pro- 

 fessor KupfFer, magnetic stations were appointed over the whole of 

 Northern Asia, from Nicolajefi', in the line through Catharinenburg, Bar- 

 naul, and Nertschinsk, to Pekin. 



The year 1832 {Gdttinger gelehrte Anzeigen, st. 206) is distinguished 

 as the great epoch in which the profound author of a general theory of 

 terrestrial magnetism, Friedrich Gauss, erected apparatus, constructed 

 on a new principle, in the Gottingen Observatory. The magnetic ob- 

 servatory was finished in 1834, and in the same year Gauss distributed 

 new instruments, with instructions for their use, in which the celebrated 

 physicist, Wilhelm Weber, took extreme interest, over a Ijfrge portion 

 of Germany and Sweden, and the whole of Italy. {ResuUate der Beob. 

 des Magnetischen Vereins im Jahr 1338, s. 135, and ^oggend., Annalen, 



