252 General Sabine on Magnetic Disturbances, [May 26, 



limited to those two years inasmuch as the Kew record did not commence 

 until January 1858, whilst the hourly observations at Nertschinsk for 

 1860 and subsequent years have not yet reached England. The deflections 

 at Nertschinsk from the normals of the same month and hour, on forty-four 

 days in 1858 and 185P, are given in a Table similar in all respects to the 

 Table, in the Philosophical Transactions for 1863, showing the deflections on 

 the most notable days of disturbance at Kew in the same years. The com- 

 parison of the two Tables is discussed in some detail ; but it is sufficient to 

 state here that the general conclusions are quite in accordance with those 

 arrived at in the previous comparisons. 



The steps by which the author was led to a discovery of the decennial 

 variation in the magnetic disturbances, and to its identification in period and 

 epochs with the variation in the magnitude and frequency of the sun-spots 

 resulting from the observations of M. Schwabe since their commencement in 

 1826, are too well known to need repetition on this occasion. But they 

 furnish the ground on which, in this paper, he has for the first time sug- 

 gested the possibility that a cosmical connexion of a somewhat similar 

 nature may be hereafter recognized as the origin and source of one of 

 the two magnetic systems which cooperate in producing the general 

 phenomena of the variations of the magnetic direction and force in dif- 

 ferent parts of the globe. The author's suggestion is, that the one of 

 the two systems which is distinguished by its possessing a systematic 

 and continuous movement of geographical translation, thereby giving 

 rise to the phenomena of the secular change, may be referrible to 

 direct solar influence operating in a cycle of yet unknown duration. The 

 phenomena of the secular change in the earth's magnetism have hitherto 

 received no satisfactory explanation whatsoever ; and they have all the cha- 

 racters befitting what we might suppose to be the effects of a cosmical 

 cause. Some of the objections which might have impeded the reception 

 of such an hypothesis before we had learnt to recognize in the sun itself a 

 source of magnetic energy, and to identify magnetic variations observed on 

 the earth with physical changes which manifest themselves to our sight in 

 the photosphere of the sun, are no longer tenable. It is true that we do 

 not yet possess similar ocular evidence of a solar cycle of the much longer 

 duration which would correspond to the secular change in the distribution 

 of terrestrial magnetism. But careful observations of the variable aspects 

 of the solar disk can only be said to be in their commencement, and it 

 would be premature to assume that no visible phenomena will be discovered 

 in the sun which will render the evidence of connexion as complete in the 

 one case as in the other. Such evidence, however, is not a necessary con- 

 dition of an existing connexion ; the decennial period would have been 

 equally true (though not so readily perceived by us) if the sun-spots had 

 been less conspicuous. 



