246 Sir Norman Lockyer and Dr. W. J. S. Lockyer. [Jan. 14. 



The second class of phenomena, namely, the magnetic disturbances, 

 which are more irregular in occurrence, has been classified by Mr. 

 Ellis into five groups, and tabulated by him under five separate sub- 

 heads. For the present paper, reference will only be made to one of 

 these classes, namely, that described as " great," this group represent- 

 ing the largest disturbances. The curve representing the variation in 

 number of these disturbances indicates short intermittent crests, out- 

 bursts, in fact, with rapid rises to maxima and falls to minima, and 

 comparatively long intervals of quiescence. 



Com/pafison of the Curves representing Prominence Frequency and Variation 

 of Diurnal Magnetic Range. 



Mr. Ellis, as already has been pointed out, has indicated the close 

 resemblance between the sun-spot curve and that representing the 

 variation of the magnetic elements ; and it has been shown in the 

 earlier part of this paper, that the curves representing the percentage 

 frequency of prominences near the solar equator, conform in the main 

 to the general sun-spot curve. 



There is therefore an apparent connection between phenomena oc- 

 curring in the equatorial regions of the sun (as represented by zones of 

 prominences near the equator, and sun-spots which are practically 

 restricted to these zones), and the ordinary diurnal magnetic varia- 

 tion. 



The accompanying set of curves (Plate 5) illustrates the great 

 similarity between those showing the frequency of prominences in a 

 zone about the equator (0° — 20° north and south) and the variations 

 of the mean daily range of magnetic declination ; for the sake of com- 

 parison, three other curves are added, showing the variation of the 

 mean daily area of sun-spots for the whole, and the two hemispheres of 

 the sun separately.* 



* In referring to the curve representing the variation of the mean daily areas of 

 sun-spots, it may be noted that this is obtained by combining the mean daily areas 

 of both hemispheres of the sun. A closer analysis shows, however, that this 

 variation is not the same for both hemispheres. From the year 1862, when such a 

 division of the sun's disc can be easily investigated, the northern hemisphere, 

 about the time of the two last maxima, displayed double maxima occurring in 

 the years 1881 and 1884, and in the years 1892 and 1895. About the time of 

 the maximum of 1870 this duplicity is not so marked, although when compared 

 with the curve for the southern hemisphere for this period, there is a slight indi- 

 cation of a subsidiary crest in 1872. In the case of the curve representing the 

 mean spotted area for the southern hemisphere alone, at all the three epochs of 

 maximum, the curves are single-crested and indicate sharply-defined maxima in the 

 years 1870, 1883, and 1893. 



From the above it will be seen, therefore, that the actual epochs of sun-spot 

 maxima, as determined from the northern and southern hemispheres respectively, 



