410 F. o:\rorvi : 



ween the 28tli July, 1889, niul the lOch August, 1808, there 

 were eleven destructive earthquakes, giving as average one in 

 every 10 months. 



12. If we count, instead of tlie actual number of destruc- 

 tive earthquakes, the number of years in which one or more 

 occurred, we find 78 instances in the interval of 299 years from 

 the beginning of tlie 17th century to the present lime ; the 

 maximum number of destructive earthquakes in one year, 

 namely three, having occurred in 1649 and 1662. In other words, 

 26 years in every 100 w^ere each visited, on the average, by one, 

 two, or three destructive earthquakes, the other 74 years remain- 

 ing free from such seismic disturbances. 



13. From fig. ö it will be seen that destructive earthquakes 

 happen sometimes singly or isolated, but tend to occur in 

 groups in epochs of maximum frequency. 



As a trial, I have in Table IX divided the 1Ö4 destruc- 

 tive earthquakes since the beginning of the 14th century into 

 41 groups, whose longest duration was 1~) years, the maximum 

 earthquake number included in one group being 12. 



