ACADEMY OF NATURAL SCIENCES. 



145 



from the fact that it was felt earlier at San Francisco than at any other locality 

 east of this city within the State. We have no record as yet of its occurrence 

 along the coast of Mexico or of Oregon. 



I have been able to determine with considerable accuracy the period of time 

 at which the shock between eight and nine o'clock on the morning of the ninth 

 took place, at four localities east of the City of San Francisco, in this State ; as 

 the shock at that hour seems to have been more generally noticed than those 

 which either preceded or followed it here or elsewhere, though at this city it was 

 much less marked than the shocks at lh. 33m., 4h. 15m., and 7h., these three 

 latter occurring at those hours of the morning when most persons are sleeping. 

 The shock at 7b., produced a circular motion in the pendulum, the diameter of 

 which was about five inches. The oscillations of the pendulum in all the others 

 were in an easterly and westerly direction. 



The precise period of time at which the shock took place at San Francisco, 

 between eight and nine o'clock, is determined by the stopping of a time-piece 

 belonging to J. W. Tucker, whose rate of error was three seconds fast. The 

 time at San Diego was furnished by Mr. Cassidy, of the army, and that of the 

 Tejon Eeserve is by persons at that post. To private gentlemen at Sacramento 

 and Stockton we are indebted for the time at those places. The accompanying 

 table of latitudes and longitudes of localities named, gives the hour at which the 

 shock took place at each ; the difference or elapsed time, from which the velocity 

 was deduced, are the mean times corrected for the places named, the time as 

 given above being taken as the standard at San Francisco. 



It is proper to state that three minutes four seconds, was the greatest error in 

 time found, and the least was twenty-two seconds : 



Locality. 



San Francisco. 

 Sacramento . . . 



Stockton 



Tejon. 



San DieKO 



Lat. Lon. 



37 48 



38 32 

 37 52 

 35 00 

 32 42 



1 22 

 121 

 121 

 118 

 117 



; 



25 

 23 

 34 



16 

 13 



Velocity. 



The velocity is given in miles per minute, and by dividing the sum of the 

 same by their number, it will be found that the movement of the wave at that 

 time averages a fraction over 6.2 miles per minute. 



The results obtained from the above data approximate closely the deductions 

 of Prof. Bache on the wave which reached our shores and resulting from the 

 earthquake at Simoda on the twenty-third December, 1854, and which will be 

 found in a paper read by that gentleman at the meeting of the American Asso- 

 ciation for the Advancement of Science, during the early part of last year. 



From the facts before us, there can be but little doubt of the direction of the 

 commotion, and that it proceeded from the west, or a little south of that point. 

 The motion of the earth, as described at the different localities at which it was 

 felt, with the motion of the pendulum — which was slightly south of a west 



10 



Pkoc. Cal. Acad., vol. hi. 



July, 1864. 



