^0 Professor De la Rive on Electrkiiy, 



from east to west. The observations so accurately made in 1829, 

 on board the Uranie by Captain Freycinet, indicated a displace- 

 jsnent in the point of intersection of the magnetic and terrestrial 

 -equators ; and it follows from those of Captain Sabine, that this 

 point is now about 13^ more to the west than it was in 1780. 

 M. Kupffer, at the close of his researches on different points of 

 terrestrial magnetism, has recognized another movement from 

 east to west in the line without declination, that is, in the line 

 which runs through all the successive points where the needle 

 points straight north. It is evident that these two motions are in- 

 timately allied, and that they give an explanation of the fact, that 

 in each place, from year to year, the declination, and the inclina- 

 tion, increase or diminish, in a regular manner. We wish we 

 could, in addition, cite those observations of M. Kupffer, which 

 relate to the variations in the mean duration of the oscillations of 

 the needle in the same place, variations which seem to depend 

 rather on those of the magnetic inclination, than on those of its 

 intensity, M. Arago, who for a great number of years has 

 been making numerous important inquiries on this subject, has 

 moreover clearly detected diurnal variations in the inclination, 

 and even in the intensity of terrestrial magnetism. 



Mr Dove has recently published, along with a preface by M. 

 de Humboldt, corresponding observations on the regular hourly 

 variations, and the irregularities of the magnetic dip, in the central 

 and eastern parts of Europe. From these labours it results, that 

 in each point the march of the magnetic oscillations, like that of 

 the oscillations of the barometer, appear to depend on the ap- 

 .parent diurnal movements of the sun ; that the extent of the 

 whole deviation is greater in summer than in winter ; and that 

 the time of the maximum of the western deviation falls, during 

 the whole year, between one and two o'clock in the afternoon. 

 Respecting the remarkable perturbations of the needle which 

 M. de Humboldt had observed, and which he has denominated 

 magnetic storms, Mr Dove has cited instances which prove that 

 they coincide, as M. Arago had also proved, with the pheno- 

 mena of the Aurora-borealis, even in countries far distant from 

 places where the Aurora-borealis is visible. This coincidence is 

 moreover supported by very many additional observations ; such, 

 for example, as Mr Fox reports, in his researches, on the varia- 



