20 



Article II. 



Rest/Its of the Observations made by the Magnetic Association in 

 the year 1836. Gottingen. Edited by Carl Friedrich 

 Gauss, chc? Wilhelm Weber*. 



[Being the First Annual Report of the Magnetic Association.] 

 INTRODUCTION. 



Among the numerous phfenomena of terrestrial magnetism, 

 with which we can only become acquainted by continued ob- 

 servations, accurately performed at various points of the earth's 

 surface, none are in need of a more rigorously systematized co- 

 operation of obsen^ers, than the irregular variations to Avhich 

 we find this force to be subject. It is sufficiently well known 

 that the Variation, the Dip, and without doubt the Intensity also, 

 (although with respect to the latter, which has but recently been 

 admitted into the circle of inquiries, sufficient observations are 

 still wanting) continually undergo changes — secular changes, 

 which attract our attention only after long intervals of time, but 

 which eventually become very considerable, — and periodical 

 changes, varying according to the yearly and daily period. But 

 for these regular changes, a rigorously systematized cooperation 

 of observers, at various stations, is not essentially necessary, al- 

 though highly desirable for the purpose of hastening the exten- 

 sion of our knowledge ; in these points, every obsei-ver, even in- 

 dependently of others, may contribute useful additions. 



Such, however, is not the case with respect to the in-egular vari- 

 ations to which only of late years a larger share of attention has 

 been devoted. Hiorter and Celsius observed, nearly a century 

 ago, that during the appearance of an aurora borealis, the mag- 

 netic needle undergoes irregular and, frequently, very great os- 

 cillations ; and this was subsequently confirmed by numerous ob- 

 senations made by others. Hence it might have been concluded, 

 that the same forces which produce the phasnomenon of an aurora 

 borealis act also at the same time upon the magnetic needle ; 

 and further, that this action must extend to veiy considerable di- 

 stances, since the northern lights are generally visible over a wide 

 circuit. We obtain a still greater notion of the wide extension 



* Translated hy Mr. ^V. Francis. The translation has been revised by Professor 

 Lloyd and Major Sabine. 



