126 REPORT—1858. 
first set is 31m., of the second 29m., being thus respectively 4m. and 2m. shorter 
than at San Francisco. The average height of the first set of waves was 0°17 foot 
lower than at San Francisco, and the second as much higher. This fact, taken with 
the difference in the times of oscillation, induces Prof. Bache to suppose that the 
difference in the two series was due to interference, which is also suggested by the 
position of San Diego in reference to the islands separating the Santa Barbara Sound 
from the ocean. 
The difference in the periods of tide on the arrival of the waves at each place 
would tend to produce discrepancies. The first series at San Diego arrived ona 
rising tide of 4 feet, while at San Francisco it was upon a falling tide of 2 feet. The 
second at San Diego arrived at near high water, and was chiefly upon a falling tide 
of 7 feet, while at San Francisco it was upon a rising tide of 4 feet. 
The forms of the waves accord remarkably at both stations. 
The tide-gauge at Astoria gives less instructive results, the bar at the entrance of 
the Columbia River having no doubt broken up and greatly reduced the waves, even 
if they arrived at the entrance unbroken. The gauge showed a disturbance, but 
irregular and confused, which was also apparently preceded by (other) unusual’ 
oscillations of the water; and Prof, Bache sees reason to think that the San Diego 
gauge indicates disturbances of the water of an abnormal character previous to the 
great earthquake shock, as well as following it at intervals for several days. The 
normal time for high and low water does not seem to have been disturbed by the 
superposition upon the tide-wave of the abnormal or earthquake waves. 
From these results Prof. Bache draws the following conclusions as to the rate of 
translation of the great sea-waves of the earthquake, 
The latitudes and longitudes of the stations are :— 
Lat. N, Long. W. Time. 
5 1 o 1 hs 
San Diego ...... tera Oo Ae 117 13 7 49 
San Francisc0...c.e,.000) 34 48 122 26 8 10 
SiImMOdA. ccssccenssaucteeotod, 20 121 62 14 44 
The distance from San Diego to Simoda is therefore 4917 nautical miles, and from 
San Francisco to Simoda 4527 nautical miles. Assuming the first account of the 
disturbance at Simoda at 9 a.m. or at 22d. 23h. 44m. Greenwich mean time, and the 
first great wave 30 minutes afterwards, Prof. Bache proceeds to calculate the rate. 
There appears to be some typographical errors in the figures, which slightly affect the 
result which he arrives at, viz. 363 miles per hour, or 6:0 miles per minute. Cor- 
recting the erroneous figures, the result would appear to be,—the first disturbance at 
San Francisco was at 23d, 12h. 22m., or 12h. 38m. after that at Simoda, and the 
first great wave at 23d. 4h.42m., giving the same interval (of 30m.). The distance 
and time therefore give a rate of 368 miles per hour, or 5°966 miles per minute. 
Assuming the second account (9h. 15m.), the time of transmission when reduced 
would be 12h. 13m,, and the rate of translation 370 miles per hour, or 6°20 miles 
per minute. 
The San Diego observations, assuming 9h. Om. as the time of transmission at 
Simoda, give 13h. 50m., which, when reduced, gives a rate of translation of 355 
miles per hour, which is almost identical with the corrected reduction of the San 
Francisco observations. 
Although not directly connected with our subject, it is interesting to state that 
Prof. Bache deduces from these results a probable mean depth for the Pacific Ocean 
on the paths traversed by these great sea-waves of from 2100 to 2500 fathoms, 
(See also Amer. Journ. of Science, vol. xxi. 2 ser. January 1856.) 
I deem no apology needed for this lengthened abstract of Prof. Bache’s communi- 
cation, not only because it is, up to the present time, almost the only record of 
scientific pretensions, of the phenomena of earthquake great sea-wayes, but as a 
model for those who may be engaged in tidal observations upon British or 
European coasts, of what is needed to make their results connect usefully with the 
requirements of those occupied in seismica! inquiry. The extreme value of self- 
registering tide-gauges, and the great importance of multiplying these round our 
own coasts, and upon those of our Mediterranean and antipodal stations, are forcibly 
shown by the remark of Bache, that but for these instruments, the very 
