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The National Geographic Magazine 



less destructive than the tornadoes or the 

 floods of a single year in less favored 

 regions." While this statement may no 

 longer be strictly true, it represents a 

 feeling so general among Californians 

 that no single disaster can eradicate it. Al- 

 though there is every geological reason 

 for expecting earthquake shocks in the 



future, there is no reason why, with prop- 

 erly constructed buildings and with ade- 

 quate arrangements for extinguishing 

 fires with supplies of salt water not de- 

 pendent upon the ordinary mains, prop- 

 erty and life should not be as safe in San 

 Francisco as in any other city in the 

 country. 



THE RECORD OF THE GREAT EARTHQUAKE 



WRITTEN IN WASHINGTON BY THE 



SEISMOGRAPH OF THE U. S. 



WEATHER BUREAU 



By C. F. Marvin 

 Professor of Meteorology, U. S. Weather Bureau 



THE vast calamity wrought by the 

 recent great earthquake at San 

 Francisco amounts, it seems, to 

 little less than the complete destruction of 

 a great city. In a moment, almost, nearly 

 its whole population of over 300,000 peo- 

 ple are rendered homeless and helpless, 

 and the sympathy and concern of the 

 whole world is aroused in their welfare. 

 These great human interests command 

 the primary attention of all, but many 

 readers will doubtless be interested to fol- 

 low the simple and short account here 

 given of some things concerning earth- 

 quakes and their measurement that 

 modern science has accomplished. 



Nowadays, by the aid of seismographs 

 of almost inconceivable delicacy, a great 

 earthquake occurring at one point on the 

 globe is very certain to be recorded at 

 practically every other point at which 

 there is a suitable instrument. In the 

 present case the vast expenditure of 

 energy at San Francisco and its imme- 

 diate vicinity literally set the entire mass 

 of the earth into appreciable vibrations 

 that subsided only after the lapse of sev- 

 eral hours. Reports showing this to have 

 been the case have already been an- 

 nounced from many places, such as 

 Alaska, England, Italy, Austria, and 



islands of the Pacific. Records must cer- 

 tainly have been obtained throughout 

 Europe, Asia, and Japan. Swifter than the 

 telegraph could flash its messages of dis- 

 aster throughout civilized Christendom, 

 the trembling crust of the earth propa- 

 gated its vibrations in every direction at 

 great velocities and set the delicate regis- 

 ters of seismographs at work to write 

 automatically their mute story of what 

 was going on. 



All the principal features of one of 

 these records written at the Weather 

 Bureau in Washington, D. C, is shown on 

 page 292. The original record is inscribed 

 mechanically by a sharp needle point, 

 which traces a line upon a smooth surface 

 of paper coated with a thin layer of soot. 

 The numerous straight lines across the 

 lower portion of the present record are 

 the traces made during successive hours 

 preceding the earthquake and show no 

 motion of the ground. It is generally 

 considered that a great earthquake like 

 this at San Francisco is caused by a sud- 

 den break or fault in the strata forming 

 the crust of the earth. Exceedingly com- 

 plex vibrations, both great and small, im- 

 mediately begin to radiate in every direc- 

 tion from the origin. The very first evi- 

 dence of tremors that reached Washing- 



