ON THE MAGNETIC DISTURBANCES. 489 



ties which may eventually be found to be those of the 

 sources of disturbance. The correspondence which had 

 been manifested in the fluctuations of the declination 

 in Europe was also found to prevail in much the same 

 degree when the term-day curves at different stations 

 in Canada and the United States were compared inter 

 se; but in a far less degree when the simultaneous 

 curves of the two continents were placed in comparison. 

 Indications indeed were not wanting of the participation 

 of both continents in disturbances having a common 

 origin; but additional and still stronger evidence, of 

 dissimilarity in the particular effects produced by the 

 disturbing action in different localities, gave weight to 

 the earlier inference of an admixture of forces, acting 

 simultaneously and occasioning complication, for the 

 disentanglement of which some new process of investi- 

 gation appeared to be required. Now it was obvious 

 that if more forces than one were in general action at 

 the same time, a properly directed analysis of the dis- 

 turbances at a single station might separate their effects, 

 and exhibit their respective laws more simply and 

 readily, than when additional complexity was introduced 

 by having to consider at the same time the different 

 action of the same forces at different places. In such 

 an inquiry the first questions which would present them- 

 selves for solution would be, whether any periodical 

 influence were discoverable in the mean effects of phe- 

 nomena which were themselves of occasional, and in a 

 certain sense, irregular occurrence ; and if so, whether 

 the different magnetic elements had the same or dif- 

 ferent periodic laws ; and whether, in each element taken 

 separately, the fluctuations which were observed to take 



