We see that the maxima and minima years of the two phenomena very nearly coincide. The accord is so evident that we may calculate the diurnal variation as proportional to the increase in the number of sun-spots. This is shown by the two last lines of the table. The yearly variation is again exactly the same as that of polar lights, as the following table indicates, in which the disturbances of magnetic declination, horizontal intensity, and vertical intensity are compiled for Toronto, Canada; for comparison the means of these three magnitudes are added for Greenwich. The unit of this table is the average annual variation: TORONTO Jan. Feb. Mar. April May June July Declination =0.57= 0.84 1.11 =1.42= 0.98 =0.53= 0.94 Horizontal =0.56= 0.94 0.94 =1.50= 0.90 =0.36= 0.61 Vertical =0.57= 0.74 1.08 =1.49= 1.12 =0.50= 0.71 Aug. Sept. Oct. Nov. Dec. Declination 1.16 =1.62= 1.31 0.78 0.76 Horizontal 0.75 =1.71= 1.48 0.98 0.58 Vertical 1.08 =1.61= 1.29 0.75 0.61 GREENWICH Jan. Feb. Mar. April May June July Means 0.93 =1.23= 1.22 1.09 0.81 =0.71= 0.81 Aug. Sept. Oct. Nov. Dec. Means 0.90 1.15 =1.18= 1.02 =0.83= The daily variation of the disturbances has been analyzed by Van Bemmelen for the period 1882-1893 and for the observatory of Batavia, on Java. The maximum occurs there about 1 P.M., and is about 1.86 times as great as the average value for the day. The minimum of 0.48 occurs at 11 P.M. Between 8 P.M. and 3 A.M. the disturbances are almost as rare as about 11 o’clock at night. The variation is greatest with that declination which has its maximum of 3.26 at 12 M., and its minimum of 0.14 at 11 P.M. The period of almost 26 days first investigated by Hornstein has also been refound in the magnetic variations and disturbances by Broun, Liznár, and C. A. Müller. It must be added, however, that Schuster does not consider these data as in any way conclusive. The moon has also a slight influence upon the magnetic needle, as Kreil proved as early as 1841. The effect is in a different sign in the northern and southern hemispheres, and may be likened to a tidal phenomenon.