104 CHARLES DAVISON 
without explosions occurred at 3-4 A.M., 8-9 A.M., I-2 P.M., and 
8-9 P.M., while the minima of the earthquakes with explosions 
occurred at 3-4 A.M., 8-9 A.M., 2-3 P.M., and g-10 P.M. The 
minima of the former occurred at 6-7 A.M., 11-12 A.M., 6-7 P.M., 
and 11-12 P.M., while the maxima of the latter occurred at 5-6 
A.M., NOON-I P.M., 4-5 P.M., and 1-2 A.M. In August, 1911, the 
earthquakes with eruptions attained their maximum frequency 
(205) for the year, and the earthquakes without eruptions their 
minimum frequency (38); in October, 1912, there was a maximum 
of earthquakes with eruptions (626) and a minimum of earthquakes 
without eruptions (10). A similar relation is shown in the varia- 
tion of frequency from one year to another, as will be seen in the 
following table:* 
EARTHQUAKES WITHOUT ERUPTIONS EARTHQUAKES WITH ERUPTIONS 
. Strong Small 
Sensible Unfelt Total Explosions Ouburee Total 
TOTES hai tse 57 321 378 ° 577 577 
ST ONEA} Bul Reel 124 563 687 ° III IIII 
IMO a eR 6 28 34 25 7IOL 7126 
TODA ects wi clecs II 37 48 I 30 ate 
LOWS seer aces 44 65 109 ° 
TOT Okeueweysieies: 64 165 229 ° 2 2 
2. ETNA 
Etna rises from a nearly circular base, measuring 428 square 
miles, to a height of 10,870 feet. Earthquakes occur on all sides 
of the mountain, and, for many years past, they have been espe- 
cially frequent beneath its southeastern flank. In the present 
section, I propose to describe a few typical earthquakes on this 
flank, and to refer very briefly to the distribution of the epicenters 
within the area covered by the volcano. 
The earthquakes belong as a rule to one of two classes, according 
as the greater axes of their meizoseismal areas are directed nearly 
along or perpendicular to the radu from the central crater. They 
may therefore be called radial and perimetric earthquakes, respec- 
tively. 
t After May 5, 1914, there was no strong outburst of the Asama-yama. 
