EARTHQUAKES ON THE PACIFIC COAST 121 



a little after 8 a. m. (VI)? "severest for 18 years; no damage to 

 buildings," no very heavy articles overturned (VI). [Note: on 

 1883, Sept. 5th, a shock (VI) Avas felt at Los Angeles. — E. S. H.] 

 — San Diego: scarcely felt (II). (Pasadena Daily Star; also /S. F. 

 Alta, Chronicle, Mar. 7, 8.) 



18S8. March 28; 1:41 a. m. 



S. F.: slight shock, but sufficient to awaken a sleeper (V). Direc- 

 tion of shock nearly N. and S., on duplex seismometer, 917 Pine 

 Street. Professor Davidson says duration % second, and shock 

 from W. to 'E.—S. F. Bulletin, Mar. 29. 



1888. April 9; 7.50 a. m. 



Kiverside: slight shock (IV) N. E. and S. W. {8. F. Bulletin, April 

 9, Chronicle, April 10.) 



1888. April 12; about 5:15 a. m. 



Eiverside: the shock sufficient to waken sleepers (VI), with loud 

 noises accompanying. Colton, 5.30 a. m. (S. F. Chronicle, April 

 13.) 



1888. April 13; 7:33 p. m. 



Carson (Nev.), S. W. to N. E. Light.— C. W. F. 



1888. April 28 [8:45 p. m.]. 



On the Lick Observatory seismograph an earthquake record was 

 found April 29. From the trace of this shock the following data 

 are taken. The dimensions given below are to be divided by 3.3 

 for the horizontal and by 1.6 for the vertical components, to 

 get the actual earth movements. The times are given in seconds 

 after a zero epoch arbitrarily assumed. The pen which marks 

 the W. and E. components registered a line j\ of a millimeter 

 wide throughout. There appear to be wideniugs of this line as 

 early as fifteen seconds before the zero adopted, but the ampli- 

 tude of E. and W. tremors is never more than j% of a millimeter 

 during the whole shock and the time of their beginning cannot 

 be fixed. I presume we have here a case where the normal 

 vibrations were strictly in an E. and W. plane. The transverse 

 vibrations which arrived later are therefore N. and S. and of their 

 full size in the diagram. We may then dismiss all further consid- 

 eration of the E. and W. wave. It had scarcely a measurable 

 amplitude. At seconds the N. and S. tremors begin to show; 

 the whole record of the vertical component is lost till 17 seconds. 

 At 3 sec. the earth moved S. of the neutral line 1 mm. 



5 " N. " 1 " 



6 " S. " 1 " 

 9 " S. " 1 " 



10 " N. " 1 " 



