SUNSPOTS AND VOLCANIC AND SEISMIC PHENOMENA. 41 



Since that time I have succeeded in collecting numerous 

 facts which throw further light on the question and 

 strengthen my former conclusions. 



Since 1902 the frequency and violence of earthquakes 

 and eruptions have declined almost to a minimum ; at the 

 same time there has been a marked rise in solar activity. 

 The last sunspot minimum occurred approximately at 

 1901*8, but the total spotted area was in 1902 lower than 

 in 1900. The previous cycle was a long one, lasting from 

 1889*3 to 1901*8, or 12*5 years. The maximum occurred in 

 1893, after a period of increase in sunspot activity lasting 

 only 4*3 years. The period of decrease was long, lasting 

 8*2 years. 



The mean spotted area as given in the Monthly Notices 

 Roy. Astr. Soc. was in the minimum year 1901 only 29 

 millionths of the sun's disc (corrected for foreshortening) 

 as compared with 



111 millionths in 1899 

 75 „ „ 1900 



62 „ „ 1902 



Prom September 18th, 1902, spots began to appear regu- 

 larly on tbe sun's disc, while violent earthquakes and 

 volcanic eruptions became of much less frequent occurrence. 

 The chief outbursts of volcanic and seismic disturbances 

 since that time were at the September Equinoxes of 1902 

 and 1903, the Santa Maria eruptions in November 1902, 

 and the Andijan earthquake in December 1902. The com- 

 pilation (Appendix II.) shows that 1903 was, as compared 

 with 1902, a very quiet year. This was only to be expected 

 if the theory advanced in my previous paper holds true. 



II. Causes of Earthquakes. — Milne in his "Earthquakes" 1 

 states that the primary causes of earthquakes are telluric 



1 Vol. lvi., International Scientific Series. 



