THE 



AMERICAN JOURNAL OF SCIENCE 



[THIRD SERIES.] 



Akt. XXXYI. — Note on Earthquake-Intensity in San Fran- 

 cisco ; by Edwakd S. Holder LL.JD., Director of the 

 Lick Observatory. 



Towaed the end of 1887, the Regents of the University of 

 California published a pamphlet prepared by me bearing the 

 title " List of Recorded Earthquakes in California, etc. ;" 1 887 ; 

 8vo, pp. 78. This work contained all the information regard- 

 ing California earthquakes which I have been able to collect. 

 The information is presented in a popular rather than a scien- 

 tific form, though the Introduction contains statistics, more or 

 less valuable, relating to the distribution of the shocks by 

 years, months and seasons. 



It is the object of the present note to obtain an estimate of 

 the absolute value of the earthquake-intensity developed at 

 San Francisco during our historic period. I am obliged to 

 confine myself to San Francisco, whose records are very com- 

 plete, owing to the conscientious care of Mr. Thomas Tennant. 



With this end in view I have gone over the printed pamph- 

 let and wherever the data were sufficiently exact, I have as- 

 signed the intensity of each separate shock on the arbitrary 

 scale of Rossi and Forel, omitting every doubtful case. The 

 later papers of Professor Rockwood already contained this 

 datum. Omitting all doubtful cases, I found 948 shocks at 

 214 different stations in California which had been so well 



Am. Jour. Sci— Third Series, Vol. XXXY, No. 210.— June, 1888. 

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