4 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
Prof. A. O. Leuschner, director of the Students’ Astronomical Observatory of the 
University of California, Berkeley, gives the following account of the shock as observed 
by his staff in the neighborhood of the Observatory : 
The only reliable record of the commencement of the feeble motion was secured by 
Dr. S. Albrecht and given by him as 5" 12" 06°, P.S. T. Dr. B. L. Newkirk, on the other 
hand, was the only observer who took pains to note the last sensible motion, for which he 
gives 5°13" 11°. The total duration resulting from these observations is 65 seconds. This 
is possibly not more than 5 seconds in error. | 
According to my own observations, the earthquake consisted of two main portions. 
They are based on counting seconds while carrying my small children out of the house. 
The earthquake came suddenly and gradually worked up to a maximum, which ceased more 
abruptly than it commenced. This [first part] lasted for about 40 seconds and was followed 
by a comparative lull, which was estimated at about 10 seconds. The vibrations then 
continued with renewed vigor, reaching a greater intensity than before and subsiding after 
about 25 seconds. According to these estimates the total duration of the disturbance was 
75-seconds. It is, however, safe to assume that I counted seconds too rapidly in the excite- 
ment of the moment and this duration may easily be 10 seconds too long. The total 
duration of the sensible motion at Berkeley was probably close to 65 seconds. Dr. Albrecht 
reports that while he observed several severe shocks, the strongest occurred about 30 to 
40 seconds after the beginning. 
The mean time clock of the Observatory stopt at 5" 13™ 39°, P. S. T. 
Prof. T. J. J. See, in charge of the Naval Observatory on Mare Island, San Pablo Bay, 
reports: 
I had been sleeping downstairs, lying with head to an open window, which faced the 
south, and as the house was not seriously endangered at any time I was favorably situated 
for making careful observations of the entire disturbance. I had been awake some time 
before the earthquake began and, as everything was very quiet, easily felt and immediately 
recognized the beginning of the preliminary tremors. It consisted in an excessively slight 
movement of the ground, which I compared to the gentle rustling of a leaf in a quiet forest; 
_ and then the tremors grew steadily, but somewhat slowly, becoming gradually stronger and 
stronger, until the powerful shocks began, which became so violent as to excite alarm. 
Their duration was unexpectedly long, about 40 seconds, according to estimate made at 
the time, and the subsiding tremors then began. It was just light and I could see the clock 
face, and I noticed that at the beginning the corrected reading was about 5" 11", and at the 
end about 5" 14™ 30°, so that the total duration of the disturbance including the faint 
tremors was about 3 minutes 30 seconds. The preliminary tremors occupied a little over 
a minute, the violent shocks about 40 seconds, and the final tremors about a minute and a 
half. 
The exact time of the phenomenon. — This was found by the stopping of two of the four 
astronomical clocks at the Observatory. The violent shocks were so extreme that the 
pendulums were thrown over the ledges which carry the index for registering the amplitude 
of the swing. ‘The standard mean time thus automatically recorded was: by the mean time 
transmitter, 5" 12" 37°; by the sidereal clock, 5" 12" 35°. The yard clock at the gate, which 
is simply an office clock, though electrically corrected from the Observatory daily, and 
therefore approximately correct, gave the time as 5" 12™ 33°. The agreement of all these 
clocks is very good; but I think the best time is the mean of the two astronomical clocks, 
viz.: 5" 12™ 36°. I estimate that the error of this time will not exceed about 1 second. It 
must be remembered that the preliminary tremors before the violent shocks began would 
tend to derange the motions of the pendulums, and they might separate, tho the effect 
would probably be slight, because the tremors were not violent. It is probable that both 
pendulums were hung up at the first powerful shock, but as one clock is sidereal and the 
other mean time, there is no assurance or even probability that the pendulums would be in 
the same relative position at the time of the arrival of the wave which gave the powerful 
shock. If the pendulums were not in the same relative parts of their beats, the chances are 
that one would be hung fast at least a second before the other. Now it was observed that 
the pendulum of the mean time clock was hung fast on the west side of its arc of oscillation, 
while the pendulum of the sidereal clock was hung fast on the east side. Both pendulums 
swing in the plane of the prime vertical. The difference in the time shown by the two clocks 
