80 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
(5) Milne horizontal pendulum, east component, photographic registration. Seismo- 
grams, sheet No. 2. 7p, 20.5 seconds; V, 6.1; J, 700 meters; M, 255 gm.; L, 15.6 cm. 




pine me temerigincs plac coeeeeceed ae Ee ie Aurpierupe. |e Peon 
min. min. min. min. mm. sec. 
(1) North component . 24.6 34.3 oe 54.6 165 
(2) East component . 24.7 34.4 me 58.7 87.6 
(3) North component . 24.7 35.0 ae 02.7 4.0 24 
(4) East component . 24.6 34.5 witte 01.0 6.0 
(5) East component . 24.4 34.3 51.3 05.3 17 + 
m. 8. m. 8. 
AVGLALC aa mana 24 36 34 50 51.3 
Interval ee 9. ar 12 08 22 22 38.8 






Duration, (1) and (2), 6.5 hours; (3) 2.5; (4) 2.7; (5) 4.6. 
On the Zollner-Repsold records there is no clear evidence of long waves. The strong 
motion seems to have been stronger and to have lasted longer on the east component; it 
also began nearly two minutes earlier; but the north component shows a marked move- 
ment between 16" and 18" which is lacking in the east movement. 
It is interesting to compare the records from the similar instruments at Jurjew and 
Irkutsk, which are practically the same distance from the centrum. We find certain 
differences; at Jurjew the north component is apparently the stronger and holds its 
strong motion longer, but comes to rest sooner than the east component; after about 15” 
it seems to be dying down with very slight irregularities; whereas the east component 
experiences distinct disturbances up to 17" 30". We could give almost the same 
description of the movement at Irkutsk if we interchanged components. This is curious, 
as the disturbance approaches the two stations in directions making about the same angle 
with the meridian. It is unfortunate that the instruments have so little damping that 
their proper motions persist for a long time and interfere with a better interpretation of 
the seismograms. For instance, it is impossible to say whether the prolonged strong 
motion of the north component at Jurjew is due to a continued strong disturbance or to 
the proper motion of the pendulum. The east component may have felt just as strong 
and long a disturbance but its large displacement may have been checked by it. We do 
not find this difference between the components of the strongly damped pendulum at 
Gottingen, which is but slightly further from the centrum. 
The periods of the movement at Irkutsk are decidedly larger than at Jurjew; at the 
latter, during the first and second preliminary tremors the periods are about 30 seconds, 
very near the natural periods of the pendulums; at Irkutsk they are about 37 seconds 
and 50 seconds for the east and north components, respectively, in comparison with the 
natural periods of the pendulums of 25 and 35 seconds. During the large motion the 
east component did not record, and the north component is too irregular to determine a 
period, but both indicate comparatively large displacements of the ground. 
The maximum displacements of the Bosch-Omori pendulums at Irkutsk seem entirely 
due to synchronism of periods and indicate a comparatively small earth amplitude, just 
the opposite of the indications of the Repsold-Zéllner pendulums. The beginning of the 
long waves is not apparent on the Zéllner instruments unless we take it at the beginning 
of the strong motion, but appears pretty well on the Bosch-Omori records, and the period 
is about 1 minute. 
The times of arrival at Jurjew and Irkutsk are practically the same, indicating uniform 
velocities along the two paths followed. 
