TERRESTRIAL MAGNETISM. 89 



1848-J-, and this in a very regular manner. Without his 

 being aware of these results, the comparison of the monthly 

 means of the same years, 1843 1848, derived from obser- 

 vations taken at places separated from each other by almost 

 an entire diameter of the globe (Toronto in Canada, and 

 Hobarton in Yan Diemen Island), had led Colonel Sabine 

 to infer the existence of a similar variation-period in the 

 frequency and amount of the magnetic disturbances or 

 storms. He suggested that a purely cosmical cause might 

 be found in the perturbations observed to take place in the 

 sun's atmosphere with a frequency varying according to the 

 same approximately decennial period, f 3 ) Schwabe, the 

 most diligent observer of the solar spots among astronomers 

 now living, had found (as I have related in a preceding 

 volume), ( 84 ) in a long series of years, from 1826 to 1850, 

 a periodical variation in the frequency of the spots, the 

 maxima falling in the years 1828, 1837, and 1848; and 

 the minima in the years 1833 and 1843. "I have not/' 

 he adds, " had the opportunity of examining a continuous 

 series of older observations, but I willingly subscribe to the 

 opinion that this period may itself be a variable one." An 

 analogy to such " periods within periods" as are here 

 supposed, is presented to us in the luminous processes of 

 other self-luminous celestial bodies or suns, as in the very 

 complicated periodicity of the variations in the light of 

 /3 Lyra3 and Mira Ceti, investigated by Goodricke and 

 Argelander.( 85 ) 



If we consider with Sabine, that the magnetism of the 

 Sun manifests itself in the increased magnetic force of the 

 Earth at the time of her perihelion (i. e. when she is nearest 

 to the Sun), we may be the more surprised that, according 



