3G REPORTS ON THE STATE OF SCIENCE. 



III. Seismic Activity in Japan, Italy, and America during the 

 years 1700-1900. By P. M. Walker, B.A. 



With the object of finding, if possible, some well-marked synchronism 

 between the periods of maximum seismic activity in the. three widely 

 separated districts, the following plan was adopted : — 



An experimental period of eleven years was decided upon, and the 

 total activity of each area during this ' undecade ' was calculated. 

 This was done by adding together the intensities of all destructive 

 earthquakes recorded for that period. Thus, for example, 7 earth- 

 quakes of Intensity III, 13 of Intensity II, and 25 of Intensity I 

 would give a total for the eleven years of 72. This divided by 11 gives 

 the average activity for each year of that period, viz., 6.5. In this 

 manner eighteen such averages were calculated for each area and 

 plotted, see p. 37. 



With regard to synchronism, the results were not very definite. 

 The three curves show agreement at (1723-33), and again (1778-88), 

 and in a less marked degree (1823-33). The curves for Japan and 

 Italy show agreement at (1723-33), (1778-88), (1823-33), (1889-99) 

 for a high average, and synchronic periods of declining activity for 

 (1756-66), (1767-77), and (1812-22). 



IV. On the Synchronism of Seismic Activity in different Districts. 



In the British Association Beport for 1908, p. 64, I pointed out 

 that since 1902 seismic activity had fluctuated similarly on the East 

 and West sides of the North Pacific. I returned to this subject in the 

 Beport for 1909, pp. 57 and 58, and showed that during the last three 

 hundred years the times of activity in Italy, although separated from 

 each other by irregular intervals, had varied between five and twenty 

 years, and that these dates of activity in Europe closely corresponded 

 to the dates when there had been marked activity in Japan. In 

 consequence of additions which have been made during the last twelve 

 months to a catalogue of destructive earthquakes of the world, I have 

 been able to extend this inquiry and compare the times of earthquake 

 activity or quiescence of the four following important but widely 

 separated regions: the Italian Peninsula, including Sicily; Japan, 

 Formosa, and the Philippines; North, South, and Central America; 

 and China. The only earthquakes considered are those which have 

 been destructive, and for brevity I refer to the four regions A, B, C, D. 



The analyses only refer to the last two hundred years (1700-1899). 

 The reason I have confined the examination to this particular period 

 is that the records for the Philippines, and for the two Americas in 

 particular, prior to the year 1700 are but few in number. 



Because there has been an increase in the number of records kept 

 in any given country as we approach modern times, but not necessarily 

 an actual increase in the number of earthquakes which have taken 

 place, to determine whether the number of records in a district for any 



