150 PROCEEDINGS OF THE CALIFORNIA 



The oscillations were watched carefully by Mr. J. Roach and myself for half 

 an hour, at which time they ceased. The maximum of the mercury column was 

 a fraction over an inch, which was attained through vibrations of one-fourth to 

 one-eighth of an inch rapidly repeated and continuous, and as gradually, through 

 a series of lighter vibrations, the displacement would diminish and the column 

 subside to its former level ; this was three times repeated, the column at no time 

 being at rest. The period of time occupied by the column in reaching its max- 

 imum of disturbance each time was from eight to twelve minutes. There was 

 no apparent cause for this disturbance, unless it be attributable to a series of 

 light vibrations of the earth occurring in a vertical direction, and to that cause 

 I am disposed to assign it. 



The passing of carriages on the street did not affect these vibrations of the 

 column, for they continued in the same manner when those vehicles were not 

 passing. While the oscillations were going on, I took a sledge and struck some 

 half a dozen blows on an anvil block in the workshop, which did not make any 

 perceptible difference in the movements of the column ; after it had come to 

 rest, the same experiment was repeated, but the column did not in any manner 

 react to the concussion thus produced. 



1861. 



During 1861 there has been but one earthquake recorded in the State. 

 July 4th, 16h. 11m. — A severe shock of earthquake occurred at San Francisco. 

 It consisted of three distinct waves following each other in very rapid succes- 

 sion. Its effects to the east of the city in the San Ramon Valley were more 

 severe. Near the house of Mr. Larabie it opeued a large fissure in the earth. 

 In the vicinity of Mr. Porter's it opened a new spring of water, and a small 

 running stream was also caused near Mr. Hunt's. For several days after, 

 light shocks were repeated at intervals. 



1862. 



September 29th, 15h. 5m. — A very smart shock of earthquake at San Fran- 

 cisco. This was felt at Petaluma. 

 December 23d, 20h. 19m. — A smart shock at San Francisco. 



1863. 



During the year 1863 we have had five earthquakes, and unmarked by any 



serious event. 



January 25th, 2h. 20m. — A severe shock was experienced at San Diego, con- 

 tinuing from five to eight seconds. There was no undulation in this instance, 

 the shock consisting of a series of sharp jars. It was preceded by a pro- 

 found rumbling sound. 



February 1st, 16h. lm. — A very smart shock at the Mission San Juan, Mon- 

 terey County. At Gilroys the shock was felt (or another) fifteen minutes 

 later. The latter town is near twelve miles east of the Mission. At both 



