122 



SCIENCE 



[N. S. Vol. XXIX. No. 734 



a layman, and present impressions ac- 

 quired chiefly during somewhat amateurish 

 work on the physical history of the San 

 Francisco earthquake. That event was so 

 far unforeseen that no seismologists 

 were at hand, and the duty of investiga- 

 tion fell, in the emergency, on a volunteer 

 corps of geologists and astronomers. For 

 me it proved a fascinating subject, and 

 interest did not cease with the completion 

 of the special task. 



But while this much is offered by way of 

 explanation, and to prevent misunder- 

 standing, you are not to infer that an 

 apology is made because I tresspass on 

 fields to which I have no title, for I am an 

 advocate of the principle of scientific tres- 

 pass. The specialist who forever stays at 

 home and digs and delves within his pri- 

 vate enclosure has all the advantages of 

 intensive cultivation— except one; and the 

 thing he misses is cross-fertilization. 

 Trespass is one of the ways of securing 

 cross-fertilization for his own crops, and 

 of carrying cross-fertilization to the pad- 

 dock he invades. Hypotheses, the trial 

 theories which compete for development 

 into final theories, spring by the principle 

 of analogy from earlier and successful 

 theories, and the broader the investigator's 

 knowledge of explanatory science the 

 greater his opportunity to discover hy- 

 potheses that may be applied to his own 

 problems. Progress is ever through the 

 interaction of the sciences one on another; 

 and scientific trespass is one of the profit- 

 able modes of interaction. The trespasser 

 brings with him a mental attitude and a 

 mental equipment which are new to the 

 subject, and whether or no the idea he 

 contributes eventually "makes good," its 

 contribution creates a new category for 

 observation and opens a new avenue of 

 inquiry. And he carries back with him 

 the pollen of new ideas. 



Next to verity, the factors which give 



value to an earthquake prediction are 

 definiteness as to time and place. If the 

 geologist Whitney, in warning San Fran- 

 ciscans forty years ago that their city 

 would suffer by earthquake, had been able 

 to specify the year 1906, and to convince 

 them that he had warrant for his proph- 

 ecy, the shock, when it came, would have 

 been a phenomenon only and not a catas- 

 trophe. If any of those mysterious 

 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 differ- 

 ent. 



PLACE 



Let us consider first the possibility of 

 scientific forecast as to place, and in so 

 doing let us assume the point of view of 

 the resident. The factor in which he is 

 personally interested is the factor of 

 danger — danger to life, danger to prop- 

 erty, danger to the present generation. 

 Except as a matter of curiosity, he is not 

 concerned with faint tremors and minor 

 shocks, nor with violent shocks likely to 

 come after centuries of immunity. It will 

 be convenient, at least for this day and 

 hour, to embody our point of view in a 

 concise term, and the adjective mallo- 

 seismic will be used to designate localities 

 likely to be visited several times in a cen- 

 tury by earthquakes of destructive vio- 

 lence. 



Experience. — The most important of all 

 bases for the indication of earthquake 

 localities is experience. Where tremors 

 have been frequent in the past, there they 

 are to be expected in the future. This 

 premise hardly requires discussion, for it 

 is founded on our confidence in the con- 

 tinuity of the great processes concerned 

 in the evolution of the earth. We recog- 

 nize indeed that continuity may f £iil in any 

 particular case, but we always assmne it 

 as far more probable than discontinuity. 



