ox THE AFTER-SHOCKS OF EARTHQUAKES. i;',p, 



recorded ;it Tokyo during eighteen years, from 1876 to 1893. (see 

 Table X\'II) is sliewn in Fig. 21. (4). The curve presents three 

 mnxinia which occur respectively in ]\rarch, May. and December; and 

 three minima wliirh oceur resper^tivelv in Januarv. April, and August 

 or September.^ 



(])) Sn.wioinffricnl OJiAcrvatiouH over All JaprDi. 



The hourly distribution of 3S42 earthquakes in Japan (hiring six 

 years, from 1.SS5 to ISDO, (see Table XIX). is sliewn in Fig. li). (?,). 

 The diurnal fluctuation presents again f/nvv iJUi.rinHi, wdiich occur 

 respectively between 2 and 3 a.m., between 2 and 3 j).m., and iDetweeii 

 10 and 11 p.m.. the successive intervals being 12, 8, and 4 hours; and 

 tlircc minima, whieh occur respectively between midnight and 1 a.m.. 

 between 8 and 9 a.m., and between 5 and (! p.m.. the successive 

 intervals being 8, 9, and 7 hours. The mean curve, drawn in red. 

 seems to indicate a slight vtu'iation, having a maximum in the early 

 morning and a minimum in the evening. 



Fig. 19, (5) shews the liourly distribution of 5333 earthquakes 

 in Japan, including the after-shocks of the Mino-Owari and the 

 Krigoshima earthquakes,, (see Table XX). The character of the curve 

 is very similar to that in Fig. 19, (3) above described. 



Tlie monthly distrilnition of earth»pi:dves during the same six 

 years'- is shewn in Fig. 21, (5). The annual fluctuation indicates 

 tlirfr nui.ri !)}((, occurring respectively in February, May, and Xovember; 

 and tliire minima, occurring respectively in April, August, and 

 December. 



§ 28. ConcIu4ons. 



Titrée distinct maxima and minima occur in the diurnal fluctua- 

 tion of the frecpiencv of after-shocks as well as in that of ordinarv 



1 The maximum in March and the minimum in April, wbicrli are liere very sli^^'ht, are 

 markedly shewn in the Kumamoto curve, Fi^. 21, (I). 



2 See Table XIX. 



