262 GROVE KARL GILBERT— DAVIS ItoM0,M [&£xxi; 



sions acquired chiefly during somewhat amateurish work on the physical history of the San Francisco earth- 

 quake. That event was so far unseen that no seismologists were at hand, and the duty of investigation fell, 

 in the emergency, on a corps of geologists and astronomers. . . . But while this much is offered by way of 

 explanation and to prevent misunderstanding, you are not to infer that an apology is made because I trespass 

 on fields to which I have not title, for I am an advocate of the principle of scientific trespass. 



No fenced-in scientific preserves for him ! He then points out the difficulties in the way 

 earthquake forecasting in both time and place: 



If the geologist Whitney, in warning San Franciscans forty years ago that their city would suffer by earth- 

 quake, had been able to specify the year 1906, and to convince them that he had warrant for his prophecy, 

 the shock, when it came, would have been a phenomenon only and not a catastrophe. If any of those mys- 

 terious oracles who were said to have predicted earth convulsions in 1906 had named San Francisco, and told 

 their reasons, the course of history might have been different. 



An elaborate discussion follows concerning the conditions under which the place and 

 time of earthquakes may be denned and predicted, after which comes a concise summary: As 

 to place of earthquake occurrence " malloseismic districts [districts "likely to be visited several 

 times in a century by earthquakes of destructive violence"] will eventually be subdivided 

 with confidence by means of geologic criteria." This work has been begun already, is now 

 progressing, and will probably be far advanced in the near future. But as to time of occur- 

 rence the problem is vastly more difficult, and is not likely to be solved for an indefinite period. 

 Of these two tasks, "the one lies largely within the domain of accomplishment; the other 

 still lingers in that of endeavor and hope." However, " we may congratulate ourselves that it is 

 not the place factor which lags behind, for knowledge of place has far more practical value 

 than knowledge of time." Indeed, if prediction of probable time were made, it would follow 

 that "possibly for many months, expectation would be tense, and the cost in anticipatory 

 terror would be great." If, on the other hand, the place of peril come to be known even though 

 the dates are indefinite, wise construction of buildings will provide " all necessary precautions, 

 and the earthquake-proof house will not only insure itself but will practically insure its 

 inmates." 



The moral of this is drawn in a strong condemnation of the mistaken policy of conceal- 

 ment prevalent in San Francisco after the shock, a policy based on the "fear that if the ground 

 of California has a reputation for instability, the flow of immigration will be checked, capital 

 will go elsewhere, and business activity will be impaired." It was under that policy that a 

 scientific report on the earthquake of 1868, due to a slip on another fault not far to the east of 

 San Francisco, was suppressed. But the policy is vain because it does not conceal. It merely 

 "reflects a low standard of commercial morality, which is being rapidly superseded." More- 

 over, this policy and the fear that dictates it are both based on a great exaggeration of the 

 actual danger. Risk of death by earthquakes in California is only one-tenth of the risk of 

 death from measles; and the annual premium for an insurance of $1,000 on death by earth- 

 quake should be only a cent and a half, plus the cost of its share of the insurance business and 

 its contribution to the business profits. Indeed, "if a timid Calif ornian should migrate in 

 order to escape peril by earthquake, he would incur during his journey a peril at least two 

 hundred times as great, whether he travel by steamship, sailing vessel, railway car, motor car, 

 stage, private carriage, or saddle." 



EARTHQUAKES IN ALASKA 



In reviewing Gilbert's published essays it is important not to omit the short ones, for 

 they not infrequently contain admirable passages. A case in point is the one-page preface 

 which he contributed to Tarr and Martin's report on the "Earthquakes at Yakutat Bay, 

 Alaska, in September, 1899. " 8 Here he set forth certain essential matters in a truly sagacious 

 way, as the following extracts will show. 



In its relation to man an earthquake is a cause. In its relation to the earth it is chiefly of an incidental 

 effect. It is the jar occasioned by a sudden faulting, and the faulting is a minor expression of deformation. 



« Prof. Paper 69, U. S Qeol. Surv., 1913. 



