XOTES ON JArAXESE EARTHQUAKES. 403 



tlie other hand, in tlie epoch of the Tokugawa Shogunato which 

 began from the commencement of the ITtli century, the records 

 of destructive earthquakes must, except for Hokkaido and 

 Liu-kiu Ishinds, be very near]}^ perfect, as it \Yas the rule of 

 the Government to let each feudal chief send in a detailed report 

 of the damage caused in his dominion by an earthquake or 

 other natural events. The earliest recorded earthquake in Hok- 

 kaido happened on the 2nd December, 1611, and that in Liu-kiu 

 Islands first in 1064. 



In the interval of 200 years from the be2;inino- of the 17th 

 century to the end of the year ISOS there were in Japan^ one 

 hundred and eight destructive earthquakes, of which eleven 

 happened in Hokkaido, and IW'O in Liu-kiu Islands. The mean 

 interval of time between two successive destructive earthquakes 

 in this epoch was, therefore, for the whole of Japan,^ 2 years and 

 9 months, or, excluding Hokkaido and Liu-kiu Islands, 3 years 

 and 2 months. 



From the above we may conclude that one part or other 

 of Japan^ is likely to be visited by a destructive earthquake 

 once in nearly every 2-j years on the average. 



III. Annual Variation of the Frequency of Destructive 



Earthquakes. 



6. The relation of destructive earthquakes to time may be 

 considered under two heads : their distribution through the year, 

 and their distribution in historic times, of which the former or 

 the annual variation of the frequency of destructive earthquakes 

 in Japan will be taken first. 



1) Foriaosa excepted. 



