1864.] 



General Sabine on Magnetic Disturbances, 



247 



V. " A Comparison of the most notable Disturbances of the Magnetic 

 Declination in 1858 and 1859 at Kew and Nertschinsk, preceded 

 by a brief Retrospective View of the Progress of the Investiga- 

 tion into the Laws and Causes of the Magnetic Disturbances/' 

 By Major-General Edward Sabine_, R.A., President of the 

 Royal Society. Received April 28^ 1864. 



(Abstract.) 



The author commences this paper by taking a retrospective view of the 

 principal facts which have been established regarding the magnetic disturb- 

 ances, considered as a distinct branch of the magnetic phenomena of the 

 globe, from the time when they were first made the objects of systematic 

 investigation by associations formed for that express purpose, at Berlin in 

 1828 and at Gottingen in 1834, and dwelHng more particularly on the 

 results subsequently obtained by the more complete and extended researches 

 instituted in 1840 by the British Government on the joint recommendation 

 of the Royal Society and of the British Association for the Advancement 

 of Science. 



The Berlin Association, formed under the auspices of Baron Alexander 

 von Humboldt, consisted of observers in very distant parts of the European 

 continent, by whom the precise direction of the declination-magnet was 

 recorded simultaneous^ at hourly intervals of absolute time, at forty-four 

 successive hours at eight concerted periods of the year, which thence ob- 

 tained the name of Magnetic Terms. By the comparison of these hourly 

 observations it became known that the declination was subject to very con- 

 siderable fluctuations, happening on days which seemed to be casual and 

 irregular, but were the same at all the stations, consequently over the con- 

 tinent of Europe generally. This conclusion was confirmed by the Got- 

 tingen x\ssociation, established at the instance and under the superintendence 

 of MM. Gauss and Weber, by whom the **Term-observations " were extended 

 to six periods in the year, each of twenty-four hours' duration, the records 

 being made at intervals of five minutes. The number of the stations at 

 which these observations were made was about twenty, distributed generally 

 over the continent of Europe, but not extending beyond it. They were 

 continued from 1834 to 1841. The observations themselves, as well as the 

 conclusions drawn from them by MM. Gauss and Weber, were published in 

 the well-known periodical entitled ' Resultate aus der Beobachtungen des 

 magnetisclien Vereins.' The synchronous character of the disturbances, 

 over the whole area comprehended by the Association, was thoroughly con- 

 firmed : the disturbing action was found to be so considerable as to occa- 

 sion frequently a partial, and sometimes even a total obliteration of the 

 regular diurnal movements, and to be of such general prevalence over the 

 greater part of Europe, not only in the larger, but in most of the smaller 

 oscillations, as to make it in a very high degree improbable that they could 



