ON SEISMOLOGICAL INVESTIGATION. 



107 



V. Earthquakes and Small Changes in Latitude. 



In vol. xvii. of the ' Seismological Journal of Japan,' 1893, p. 17, 

 I drew attention to the observation that the period of maxima increase 

 in latitude in Berlin apparently coincided with maxima of earthquakes 

 recorded in Japan. 



If we compare the wanderings of the pole from its mean position for 

 the years 1895-1898 ^ with registers of earthquakes which have disturbed 

 continental areas or the whole world, we find a somewhat similar relation- 

 ship. This is shown in the accompanying table, the pole displacements 

 being measured from Albrecht's figure. 



A conclusion suggested by this table is that, during intervals when the 

 pole displacement has been comparatively great, large earthquakes have 

 been fairly frequent, and vice versd. In the yearly totals this is marked. 



If we turn to a figure given by F. R. Helmert, showing variations in 

 latitude as determined from 353 sets of photographic records made on 

 forty-two days in the months of April, May, and June, 1897 (see 'Bericht 

 iiber eine neue Reihe von Polhohen-Bestimmungen, &c., im Jahre 1897,' 

 F. R. Helmert, Potsdam), we see that successive daily means frequently 

 differ from 0"-l to 0""2 amongst themselves. Equally large differences 

 exist between the separate observations from which these means are 

 deduced. 



That is to say, successive observations may show differences as great 

 as the annual maximum displacement of the pole, which is about 0''''25 

 from a mean position. 



If on Helmert's figure we plot the large earthquakes for these months,, 

 it is seen that in the time of their occurrence they closely coincide with 



' See Bericht iiber den Stand der Hr^orscAung der Breiten- Variation am Schlussr 

 des Jahres 1898, von Th. Albrecht. 



