102 Major-General Sabine on the Cosmical Features 



than the full hourly system, sufficed to give the range of the 

 diurnal oscillation for purposes of comparison; and the series 

 thus afforded, extending from 1841 to 1851, showed that the 

 diurnal range had been greater in 1841 and 1842 than in 1843 

 and 1844, from which date (concurrently with the aggregate 

 amount of disturbance as already related) it had progressively 

 increased to 1849, whilst 1850 showed no further advance, 

 and 1851 a decided retrogression. Putting these facts together, 

 there appeared sufficient ground on which to call the attention 

 of those engaged in magnetic researches to the possibility of the 

 existence of a periodical magnetic variation, which should have 

 had its epoch of minimum about the years 1843 or 1844, and 

 its epoch of maximum about the years 1848 or 1849; and to 

 recommend the adoption of all available means of tracing its 

 continuance in future years. In this view a full discussion of 

 the particulars here adverted to was prepared for insertion in the 

 Introduction to the second volume of the ' Hobarton Observa- 

 tions ' then passing through the press, when, in the course of 

 editing the English translation of the third volume of M. de 

 Humboldt's ' Cosmos ' from the proof sheets which were sent to 

 me for that purpose by the author, my attention was arrested by 

 the Table in p. 402 of that volume, containing the results of M. 

 Schwabe's continuous and systematic observation of the solar 

 spots from 1826 to 1850, accompanied by his own general con- 

 clusion to the following effect : — " The numbers in the Table 

 leave no doubt that at least from 1826 to 1850 the solar spots 

 have shown a period of about ten years, with maxima in 1828, 

 1837, and 1848, and minima in 1833 and 1843." Any hesi- 

 tation that might have been felt in announcing the conjectured 

 existence of such a periodical magnetic variation, unsupported 

 by the coincidence of any other known cosmical or terrestrial 

 variation of similar period, was at once removed. The varia- 

 tion observed in different years in the solar spots coincided 

 perfectly with that which had just been recognized in magnetic 

 phenomena which were otherwise connected with the sun by con- 

 formity to solar hours ; and by this new and previously unsus- 

 pected relation, a very high degree of probability was given to 

 the existence of a true and direct magnetic connexion between 

 the earth and the central body of the solar system. 



The facts, of which the general import has been thus hastily 

 sketched, were made known to the Royal Society in March 1852, 

 and were fully detailed in the Introduction to the second volume 

 of the ' Hobarton Observations' published in the same month*. 

 Of course great interest and curiosity attached to the question of 



* The existence of " periodical laws discoverable in the mean effects of 

 the larger magnetic disturbances " was first announced in a communication 



