INTRODUCTION. 



In the year 1887 the Regents of the University of California 

 authorized the printing and distribution of an octavo pamphlet 

 whose title was " List of Recorded Earthquakes in California, 

 Lower California, Oregon and Washington Territory, compiled 

 by . . . Edward S. Holden." This was the first systematic pub- 

 lication of the sort, and it served a useful purpose. The examina- 

 tion of past records naturally led to the consideration of the 

 best manner of making future ones. The object of such records 

 is to bring to light all the general facts as to distribution of 

 earthquake shocks, as to topographic areas, as to time, as to 

 average intensity, etc., and also to enable a study to be made 

 of particular shocks — as to velocity of transit, area of the 

 disturbed region, intensity, etc. In order to study any of these 

 questions with profit it is necessary to have some kind of a 

 measure of the intensity of each earthquake shock. The most 

 satisfactory instruments that I have seen for this purpose are 

 those invented by Professor Ewing, F. R. S. These are devised on 

 sound mechanical principles, and are well constructed by the Cam- 

 bridge Scientific Company. It was necessary at the Lick Observa- 

 tory to keep a register of the times of occurrence of all earthquake 

 shocks in order to see if the positions of the astronomical instru- 

 ments were affected. Accordingly, a set of Professor Ewing's in- 

 struments was ordered for the Observatory, and they were deliv- 

 ered in 1887. 



The Lick Observatory began its active work in 1888. A part of 

 this work consisted in the registration of earthquake shocks. 

 Reports of shocks felt elsewhere on the Pacific Coast were diligently 

 collected, and the publication of the pamphlet before mentioned 

 brought me into relations with various gentlemen who were kind 

 enough to communicate MS. notes or diaries relating to earthquake 

 phenomena in earlier years. 

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