Periodicity of Earthquakes. 



465 



analysis. As the absolute frequency of earthquakes in 

 different districts is extremely variable, the average number 

 of shocks per hour in each case is represented by unity, so 

 that the results may be directly comparable. The epochs are 

 given in the mean local time of the place of observation, with 

 two exceptions, namely, Japan and Italy, in which the standard 

 times are those of 135° E. and 15° E. respectively. In the 

 Table, however, the figures for Japan refer to mean Tokio 

 time,, for Japanese after-shocks to mean time of 135° E., and 

 for the Italian stations to mean Rome time. 



pp. 

 pp. 

 pp. 

 pp. 

 pp. 

 pp. 



Tokio.— Japan 

 4-14, 39 ; vol. vi 



100-108 : 

 127-134: 

 212-213 ; 

 160-162 ; 

 214-215. 



Japan. 

 Seismol. Soc. Trans, vol 

 ., 1883, pp. 32-35 ; vol. 



viii., 

 vol. x., 1887, pp. 97-99 ; vol. xv., 

 Brit. Assoc. Rep. 1886, pp. 414-415 ; 

 1888, pp. 435-437 ; 1889, pp. 295-296 ; 

 1891, pp. 123-124 ; 1892, pp. 93-95 ; 



1880, 

 1885, 

 1890, 

 1887, 

 1890, 

 1893, 



Duration of record, 1876-1881 and 1883-1892. Number 

 of earthquakes, 1204 ; in winter, 661 ; in summer, 543. 



This valuable record begins in the latter half of 1872, and, 

 up to the end of 1892, contains 1304 entries. From the end 

 of 1875, the earthquakes were registered by means of seismo- 

 graphs, Palmieri's being in use until April 1885, and the 

 Gray- Milne seismograph after that date. Towards the close 

 of 1882 the list is incomplete, owing to the removal of 

 the instrument to a new station. For general purposes this 

 would be of little account ; but as I wished to compare the 

 results obtained from the six winter months (October to 

 March) with those obtained from the six summer months 

 (April to September), this year has been omitted. 



Harmonic 

 Component. 



Whole year, 



Winter. 



Summer. 



Am pi. 



Epoch, 

 h m 



Am pi. 



Epoch. 

 h m 



Ampl. 



Epoch, 

 h m 



1st (24 hours) ... 

 2nd (12 hours)... 

 3rd (8 hours) ... 

 4th (6 hours) ... 



5th (4| hours) ... 



i 



1 6th (4 hours) 



•130 

 •082 

 •098 

 •118 

 •030 

 •024 



A.M. 



10 14 



10 22 

 6 28 

 3 7 

 1 8 

 3 27 



•093 

 •123 

 •086 

 •143 

 •059 

 •097 



A.M. 



10 39 

 9 26 

 6 31 



2 56 

 1 49 



3 11 



•176 

 •085 

 •111 

 •096 

 •060 

 •058 



A.M. 



9 58 

 12 

 6 2:> 



3 26 



4 2 

 58 



