98 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 






SECOND 
E. ? 
nia aha Sy pees os Max. Aurion 
m. 8. ™m. 8. m,. 8. mm. 
(1) North component . 40 05 57 47? 03 40 0.47 
03 40 0.7 
(2) East component . 33 10 54 16? { 14 39.5 0.6 


Duration, 1 hour. The first preliminary tremors are not recorded, but a bell connected 
with a seismoscope rang at 13" 25". The east component began to record earlier than 
the north, and thruout gave much larger amplitudes. The maximum movement of the 
ground was at 14" 03.7" and amounted to about 0.54 mm.; at 14" 10.5™ it was 0.46 mm. ; 
its direction was nearly east-west. 
ISCHIA, ITALY, 
-R. Osservatorio Geodinamico di Casamicciola. Two installations, one at Porto d’Ischia 
and one at Grande Sentinella, about 3 km. apart. Prof. G. Grablowitz, director. 
PORTO D’ISCHIA. 
Lat. 40° 44’ N.; long. 18° 57’ E.; altitude, 31 meters; distance, 91.84° or 10,211 km.; 
chord, 9,153 km.; direction, N. 31° E. 
Foundation, trachite. 
Seismograms, sheet No. 7. 
The instruments used were: 
Grablowitz horizontal pendulums, two components: 
(1) North component: T,, 17 seconds; V, 8; J, 570 meters; e, 1.24; 7, 0.8 mm.; 
M,12kg.; L,8 cm. 
(2) East component: 7, 17 seconds; V, 8; J, 570 meters; ¢, 1.07; 7, 0.2 mm.; 
M, 12 kg:; L,8 cm. 
Vasca Sismica, two horizontal components. ‘This is a circular tank containing water; 
two floats are placed near the sides at ends of a north-south and of an east-west diameter 
respectively, and the movement of the water is magnified and recorded on a drum. The 
tank is 1.56 meters in diameter and the water is one meter deep. The movement of the 
north-south diameter is magnified 74.4 times, that of the east-west diameter 68.6 times. 
GRANDE SENTINELLA. 
Lat. 40° 45’ N.; long. 13° 54’ E.; altitude, 122 meters; distance, 91.83° or 10,210 
km.; chord, 9,151 km.; direction, N. 31° E. 
Foundation, volcanic tuff. 
Seismograms, sheet No. 7. 
The instruments used were: 
(5) Grablowitz horizontal pendulum, east component: T,, 12 seconds; V, 8; J, 290 
heieest e, 1.18; r,0.5mm.; M,12kg.; L, 10 cm. 
(6) and (7) Tieeoe Sismica, two components; it has the same dimensions as the tank 
at Porto d’Ischia. V, 90.7 for the north component and 97.3 for the east component. 
All the instruments at both stations record on smoked paper. 
