OBSERVATORIES AND THE DATA OBTAINED. 65 
the pen swung well off the plate, it does not seem to have been caught for more than 
a few seconds at a time. ‘The vertical component recorded but little even during the 
earlier phase, and when the heavy shock began, 9 seconds after the beginning, it was so 
deranged that it became permanently caught and incapable of vibrating, so that its 
record is simply a circle on the plate. The seismogram shows that there were at first 
two complete vibrations in a direction about northwest and southeast; the period of 
the first was about 1 second, that of the second about 4 seconds. ‘The first move- 
ment was towards the southeast and amounted to 7 mm.; the second movement in 
that direction was twice as far. The vertical movement was first upward and amounted 
to about 15 mm.; the period was about twice as long as that of the horizontal mo- 
tion. But this may be due to derangement by the shock. This shows quite clearly 
that the first movement of the ground was directed away from the origin of the shock. 
At the beginning of the strong motion, at 5" 12™ 548, the vibration had a period of about 
2 seconds which soon increased to 4 or 5 seconds and, at times, was even as great as 
10 seconds. The north-south component, as recorded at 5° 13™ 12%, shows an earth- 
amplitude of 4 cm. The maximum east-west amplitude recorded was about the same. 
The beginning of the strong movement was directed towards the northwest. 
CARSON CITY, NEVADA. 
Carson Observatory. Prof. C. W. Friend, director.’ 
Lat. 39° 10’ N.; long. 119° 46’ W.; altitude, 1,420 meters; distance, 2.62° or 291 km.; 
direction, N. 64° E. 
Seismograms, sheet’ No. 3. 
The instrument used was a Ewing duplex pendulum, V, 4. 
Altho the seismogram shows movements in all directions, it differs very materially from 
the seismograms of similar instruments nearer the origin. We do not find the sudden and 
irregular changes in direction, but the changes are rather gentle. At this distance from 
the origin the disturbance had become a gentle swing with a period of about 3 seconds. 
Professor Friend gave the time of arrival of the disturbance as 55 12™ 25%. This is 
3 seconds before the occurrence of the heavy shock; and we are led to the inquiry 
whether it may not refer to the earlier light disturbance, which occurred at 5° 11™ 58°. 
This, however, is negatived by two facts. If the first disturbance was felt at Carson City, 
the violent shock, which was many times stronger, should have been felt at a far greater 
distance, whereas Winnemucca and Eureka, about twice as far from the origin as Carson 
City, are the most distant points where the disturbance was noticed, and the intensity at 
these places was so much less than at Carson City, that we must suppose they all felt the 
same disturbance; it does not seem possible that Carson City could have felt the earlier and 
lighter shock and that the violent shock was not felt at far greater distances than Winne- 
mucca and Eureka. Again, if Carson City felt the earlier shock at 5° 12™ 25%, 27 seconds 
after its occurrence, the velocity of transmission would have been 291/27 or 10.8 km. /sec. 
This is greater than can be admitted, for the velocity of transmission increases with the 
distance measured along the chord, and the velocity for points ten times as far from the 
origin as Carson City is only about 8.5 km./sec. We are obliged either to suppose that 
there is an error in the time report from Carson City, or that a light local shock occurred 
in its neighborhood a few seconds before the violent shock occurred on the coast. The 
latter could not have been felt at Carson City before 5" 13™, and as there is no record 
there of two disturbances the supposition of a local shock seems improbable. It is very 
unfortunate that we can not use the Carson City observations to determine the velocity 
of propagation of the earthquake disturbance. 

1 Professor Friend died in January, 1907. 
