Geology. 



115 



a very sudden change of temperature to unpleasant coldness. At Point 

 San Juan there was observed considerable commotion in the water, at- 

 tended with a strong rushing sound, and two unusually heavy surf swells 

 immediately following the last shock. 



This shock was felt distinctly at the saw-mill some eight miles east of 

 San Bernardino, about seventy miles east of Los Angeles, and at Santa 

 Barbara, about one hundred miles in a westerly direction. At Los Angeles 

 the shock occurred at fifteen minutes after eight in the evening. 



Aug. 12, 9-J- a. m. — A light shock of an earthquake was felt at George- 

 town, which lasted about three seconds. The vibration apparently came 

 from the north. Between this date and the 10th of July there were four 

 other light shocks, the dates of which are not recorded. 



Oct. 21, 7f p. Ms — A smart shock of an earthquake was felt in San 

 Francisco. The buildings situated over the water were violently shaken. 

 There was much commotion in the water of the harbor a few minutes 

 preceding the shock, which caused several vessels to heave heavily at their 

 hawsers and cables. 



Oct. 27, 3 p. m. — A light shock was felt in the valley of Clear Lake. 

 On the same day a shock was felt at Downieville, which lasted about five 

 seconds. At Goodyear's Bar it was more severe than at the preceding 

 locality. 



Dec. 5, 11.20 a. m. — The shock of an earthquake was felt at Humboldt 

 Bay, which lasted about three seconds. There were two vibrations, the 

 last being the most severe. 



Dec. 11, 4 a. m. — A shock was felt in San Francisco and at the Mission 

 Dolores ; at the latter place it is represented as having been quite severe. 



Jan. 2, 1856, 10 a. m. — A light shock in San Francisco, which lasted 

 about three seconds. The shock came from the north and was undulatory. 



The whole number of which I have a record for 1855, amounts to 

 twelve only ; but there may be others which have escaped my notice on 

 account of absence from the city. 



The following table will show the number of shocks for each year, and 

 for each month of the year, for six years from 1850 to 1855 inclusive: 





1850 



1851 



1852 



1853 



1854 



1855 



No. for each 

 month iu six 

 year. 











2 



1 



2 



5 











1 





1 



2 











1 



2 





4 











2 



1 



1 



4 







3 







2 





6 







1 





1 



1 



1 



5 



July, 









1 



2 



1 



4 















1 



2 











1 



1 





3 



October, 









2 



2 



2 



6 



November, 







11 



2 







13 







2 



1 



2 





2 



7 





5 



6 



12 



15 



12 



11 



61 



From the above it will be seen that of the total number of shocks in 

 six years in this State, forty-seven have occurred during the spring, sum- 

 mer and autumn months, and fourteen during the winter months. 



