184 Me. J. Betce on the Recent Progress of the 



stations of Toronto, St. Helena, and Hobart town, the former having 

 summer while the latter has winter ; and St. Helena scarcely any dis- 

 tinction at all. The epoch of change at all the stations, from one class 

 of phenomena to the other, is the sun's passage across the equinoctial. 

 This cleai'ly points to an effect of the sun upon the magnetism of the 

 earth as a mass. It has been found, too, that the changes of vai-iation 

 in the two half-yearly periods almost coincide with the day of the 

 equinox ; but it requires some time to complete the change, and bring 

 round a marked difference in the variations. Gen. Sabine states that 

 this may be compared to the change in the induced magnetism of a 

 ship, by a change in geographical position ; it is not accomplished at 

 once. The greater proximity of the sun in December than in June, has 

 also been shown to produce an effect on the intensity of the force ; but 

 by no more than '002 of the whole. This also is the same at all the 

 stations — clearly pointing to solar influence on the whole earth. Now, 

 it is remarkable, as showing how erroneous were om* former ideas, in 

 regarding these variations as due to terrestrial temperature, that M. 

 Dove has proved that, at this very period, namely, in the months between 

 October and February, when the indination and total force are greatest, 

 and the sun nearest us, the aggregate temperature of the whole earth 

 is less than at the opposite season — a diminished temperature clearly 

 due to the smaller quantity of land in the southern hemisphere. This 

 most emphatically points to great cosmical influences, quite beyond the 

 earth and its atmosphere, and indicates the sun as a vast magnet. 

 But conclusions still more interesting and remarkable, regarding a con- 

 nection with, and dependence upon the sun have been established. I 

 have already referred to the solar spots, and their periods of abundance 

 and paucity — in these, also, we now detect a relation to magnetic dis- 

 turbance. When the spots are at a minimum state of exhibition, only 

 30 or 40 appear in a year ; but when at a maximum state, 300 or 

 400. The period from minimum to minimum is ten or eleven yeai's. 

 Now, it has been found that unusual magnetic disturbances or storms, as 

 they are called, coincide with the period of abundant spots, and that 

 these storms run thi'ough a decennial period, or recur, after ten years, 

 of similar character and intensity. The year 1843 was a year of mini- 

 mum in the spots ; 1848, a year of maximum. From the former to the 

 latter, the magnetic disturbances increased in frequency and aggregate 

 values ; the aggregate in 1848 being three times greater than in 1843. 

 The relation being thus suspected, calculations for previous dates of 

 maximum and minimum among the spots, and of magnetic disturbances, 

 were entered into, and the results have shown that, so far back as the 

 accurate system of observations has gone (about twenty-six years), 



