Set tae 
) 
ON SEISMOLOGICAL INVESTIGATIONS. 57 
cates that in two given districts seismic activity has been constant or 
has varied similarly, z.e., there has been an agreement. The letter ‘d’ 
indicates that there has been disagreement. For example, seismic 
activity may have increased in one district while it has decreased in 
another. As to whether an entry should be ‘a’ or ‘d,’ no account has 
been taken of the greatness of increase or decrease in the number of 
earthquakes in the given period, but only whether it was a marked 
increase, decrease, or a period of quiescence. The columns in which 
the letters ‘a’ and‘ d’ occur are headed A to B, Ato ©, &c. If written 
more fully these would become A compared with B, A compared with 
GC, &c. 
Inasmuch as the Italian records are included in and form a large por- 
tion of those which refer to Europe generally, the comparison of C to D is 
of slight value. The general result indicates that in a period of 650 years 
we have had forty-four instances of agreements against twenty-eight 
instances of disagreements in the fluctuations in seismic activity im 
widely separated districts. This suggests that for the most part periods 
| i | | wan Vo aechreclyi we il. fens | 
Date | A B Cc D to to to to to | to | Totals. 
| Ba Gy Do Ge | Dr | 
1000 | TST 
to | 8 | 28 7 1 
1050 ) | | 
1100 8 Olver inva O 2 a a a@|@i\a a 6 0 
1150 BA Uh iy 8 Betas ae nies (ad che tee | me LB | 
1200 | 12 Dope 13 7 ED he Cael ata Bet Ole 
he A I diane A Gil ae ae | asst at sl) ai flies Ti o6" 40" | 
1300.4 Bibi inh tO, teal lida ce? itdyo | bd stn bh ahesk yA 
1350 8 | 64 | 12 3 a@j}a a@\;ajsda d 3 BP 
14009 37 le | ela Pao aol ge | ek 
1450 |. 13 | 16 | 18 TA iP ML Gk Ma HA li a ea 
1500 16 50'"} 14) 9 aoniaa: a d a d 3) 8 
1550 GA | AG op ao @ijod fas) aa | 88 
1600 Dies POA lsh Oe el Oue in a ad a | @ CaN ay ea | 
1660 | 10 | 60 | 2% | 18 | a) a@|/a)aj|a|a!6o 
| | 9@ | 8a | Ga | Ta | 8a | Ga | 44a | 
| | (Bd 4d | bd Bd Ad dd 
i | | ‘ { 
of seismic quiescence or of activity in various parts of the globe occur 
about the same time. This result does not, however, appear to be shown 
if we take eleven or thirty-three year periods. Of fifty-three periods of 
eleven years, A.D. 1000 to a.p. 1583, a comparison of the earthquakes 
of Europe with those of China and Japan respectively indicate that agree- 
ments and disagreements are about equally divided. A similar result is 
obtained when thirty-three year periods were taken for comparison of 
Buropean and Japanese and Chinese and Japanese earthquakes. 
Another method of determining whether there has been a time 
agreement in seismic activity in distant districts has been to plot year 
by year the large earthquakes of Japan and Italy on squared paper. The 
interval considered for each of these countries has been the last three 
hundred years. England and many other countries have been excluded 
because their records are few in number and only refer to comparatively 
feeble shocks. The two Americas have been omitted because their 
