90 



Dr. J. B. Trask presented the following account of Earthquakes 

 in California in 18(30. 



During the year last passed this i)ortion of the Pacific coast has 

 been but little disturbed bj earthquakes. There have been but 

 three during this period that can be Avell authenticated, and one, 

 viz: Dec. 21st, whose character is somewhat doubtful. 



The shocks that have occurred are as follows : 



January 27th. — A severe shock was experienced at Los Angeles 

 and vicinity, which was not productive of any damage to person or 

 property. No time is given in the account. 



March loth. — A violent shock was experienced at 11 h. m. at 

 Sacramento ; the wave passed through the counties of Placer, 

 Nevada, El Dorado and Plumas. At Iowa Hill the church bells 

 were rung, also in Sacramento. At the latter place and at Forest 

 City, clocks, in many of the buildings, were stopped. This earth- 

 quake extended to the eastern base of the Sierra Nevada. At 

 Carson City it occurred at 10 h. 45m. and very violent; goods 

 Avere shaken off the shelves in many of the stores, and a general 

 panic and stampede prevailed. 



November 12th. — A smart shock was felt at Humboldt Bay and 

 its vicinity, but no damage was done. 



December 21st. — At 1(3 h. 30 m. at San Francisco a series of 

 light vibrations of the earth occurred, which continued with but 

 two remissions for the space of half an hour. These vibrations 

 were not perceptible to persons in the building otherwise than by 

 the oscillation of a mercurial column, which was equal to seven 

 inches of the barometer, and which was the mercury gau;:e of an 

 air pump that had remained stationary at 24 inches for the space 

 of four hours. At this time the column in the gauge began to 

 show much disturbance by oscillating up and down in a very rapid 

 manner without any apparent cause ; the stop screws (Farraday's) 

 were all tried at the moment and found perfectly tight, as they had 

 remained for hours previous. 



The oscillations were watched carefully by Mr. J. Roach and 

 myself for half an hour, at which time they ceased. The maximum 

 displacement of the column was a •fraction over one incli, 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 maximum 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 iliat 

 cause I am disposed to assign it. 



