1910] 



on Mannetic Storms. 



777 



the four equinoctial months being 16, or nearly double. But in the 

 Antarctic 81 out of every 100 days at midsummer had a range ex- 

 ceeding 120', while the corresponding figure for the equinoctial 

 months was only 31. 



§ 9. The phenomena of magnetic storms appear, at least at some 

 stations, to be largely influenced by the hour of the day. Table VI. 

 gives some figures for Greenwich derived from the hours of beginning 

 and ending in Mr, Maunder's lists for the years 1848 to 1903, as 

 well as some figures which Dr. Van Bemmelen has given for Batavia. 



Table VI.— Diurnal Vaeiation in Magnetic Storms at Greenwich 

 (Mr. E. W. Maunder) and Batavia (Dr. W. van Bemmelen). 



At Greenwich, no less than 60 per cent, of the storms commenced 

 during the eight hours 1 to 8 p.m., while only 9 per cent, then ended. 



§ 10. There is yet another influence on magnetic changes, which 

 requires to be considered. Eeferring some little time ago to Prof. 

 Hale's discovery of the Zeeman effect in light from sun-spot areas, an 

 eminent physicist is reported to have said : " Until we understand 

 better than we do these solar processes . . . we may do well to cultivate 

 a humbler frame of mind than that indulged in by some of our col- 

 leagues." If the scientific man associates a partiality for sun-spots 

 with some exaltation of mind, the unscientific man for his part is apt 

 to regard it as qualifying for admission to a lunatic asylum. As one 

 who has devoted considerable time and attention to the subject, it is 

 thus incumbent on me to walk Avarily. With this end in view, I 

 think I cannot do better than call attention to the figures in Tal)le 

 VII., in the preparation of which bias is quite impossible. Maxima 

 are in heavy type. 



Prof. Wolfer, of Zurich, and his predecessor, Prof. Wolf, have 

 made a special study of sun-spots, and their tables of sun-spot fre- 

 quencies, going back to 1749, command world-wide respect. While 

 Wolfer's figures are given in Table A^II. as a measure of average 

 sun-spot activity for each year from 1890 to 1900, it may be added 

 that closely parallel results would be derived from the Astronomer 



