94 GAUSS AND WEBER ON TERRESTRIAL MAGNETISM. 



after noon, and descending in the following hours of the fore- 

 noon ; thei'c is, on the other hand, scarcely a trace of this in the 

 three winter terms, Plates IV. V. and IX. All our experience 

 shows that partial or even total obUteration of the regulai* move- 

 ments by the iri*egular is a very common occurrence. In the years 

 1834 and 1835 some terms occurred in which the regular course 

 was not at all obscured by any considerable anomalies, although 

 there was no Avant of smaller ones. But what renders the ano- 

 malous oscillations so remarkable, is their extraordinaiy coinci- 

 dence, generally even in the smaller instances, at different sta- 

 tions ; nay, commonly at all the stations, only in dissimilar pro- 

 portions of magnitude. It is quite unnecessary to demonstrate 

 this agreement in individual instances : a view of the representa- 

 tions of the six terms will speak sufficiently for itself. 



We cannot at present decipher these enigmatical hierogly- 

 phics of nature : Ave must first endeavom* to procure from the 

 most diversified sources, authentic, numerous, and minutely faith- 

 ful copies, in the confident hope, that Avhen these rich materials 

 are accumulated, the key to their hidden meaning will not be 

 long wanting. In the mean time I may be allowed to add a few 

 remarks, which may assist in the formation of a more correct 

 judgement concerning them. 



Fu'st, it must not be forgotten that these anomalies are but 

 comparatively small modifications of some of the eflfects of 

 the great terrestrial magnetic force ; that we must distinguish 

 between the force itself and these supervening alterations ; 

 and that nothing in the present state of our knowledge obliges 

 us to ascribe both to the same or to similar causes. There- 

 fore those who think it probable that these anomahes are 

 the effects of electric currents, or of action, perhaps far beyond 

 our atmosphere, (which view we leave entirely to its own merits) 

 may continue to do so, without having to relinquish on that 

 account the old view, of a force, resicUng in the soUd portions 

 of the earth, or rather being the collective action of all its mag- 

 netized particles. If, according to the opinions of some phi- 

 losophers, the interior of the earth be supposed still in a fluid 

 state, the constantly advancing solidification, and the conse- 

 quent thickening of the sohd crust of the earth, would offer the 

 most natiu-al explanation of the secular variations of the mag- 

 netic force. 



But we willingly leave the uncertain ground of hypothesis. 



