42 Earthquake Waves on the Western Coast of the U. States. 
‘After allowing for the very free action of the fioat of the San 
Diego gauge, there appears to have been indications of disturb- 
ance previous to the great earthquake shocks and following them, 
occurring at intervals for several days after the 23d of December. 
h rancisco gauge presents similar indications. 
No special effect appears to have been produced upon the time 
or height of high or low water by the earthquake which merely 
caused series of oscillations upon the great tidal wave. 
roceed to draw from these results some conclusions as 
to the progress of the ocean wave accompanying the earthquake. 
The latitudes and longitude of the places referred to, are as 
follows: : 
} | Latitude N. | Longitude. pe } 
j H. M. 
San Diego, 32° 42 ETS 43/ 7 49 
San Francisco, 87 48 122 26 8 10 
Simoda, 34 40 221° 02 14 44 
The distance from San Diego to Simoda from these data is 
4917 se miles, and from San Francisco to Simoda 4527 
nautical mile 
inerdling | to one account the disturbance began at Simoda at 
9 a. m. or 224 23h 44m Greenwich mean time, and the first great 
wave half an hour after. The first disturbance at San Francisco 
was at 234 4b 12™, or 12 28™ after that at Simoda, and the first 
great wave at 234 Ah AQm giving the same interval. The dis-— 
tance and time from this account give for the —_ a“ motion of 
the wave 363 miles per hour or, 6-0 miles per min 
The second account would give for the time of wentnieinn i 
12h 13™, and for the rate of motion 370 miles per hour, or 6:2 
miles per minute. 
The San Diego observations give for the time of transmission 
of the wave from Simoda to San Diego 135 50™ by the first ac- 
count, which combined with the distance gives 355 miles per hour, 
or sensibly the same result as derived from the beginning at San 
Francisco. ‘The first great wave would give identically the same 
result. 
From the results obtained we may determine the mean depth 
of the Pacific ocean in the path of the earthquake waves. We 
have found for the rate of motion, from 6:0 to 6:2 miles per min- 
ute, and for the duration of an oscillation 35 minutes at San 
Francisco and 31 at San Diego. This would give for the length 
of the wave on the San Francisco path 210 miles to 217 miles, 
and on the San Diego path 186 to 192 miles. 
A wave of 210 miles in length would move with a velocity of 
6-0 miles per minute in a depth of 2230 fathoms. (Airy, 
and Waves, Encye. Metrop., p. 291, Table IL.) One of 217 
miles with a rans of 6-2 miles pet minute in a depth of — 
* 
