MICHIGAN ACADEMY OF SCIENCE. 43 



EARTHQUAKES VIEWED IX A NEW LIGHT.* 



William Herbert Hobbs. 



Mr. President, Members of the Michigan Academy of Science, Toadies and 

 • Gentlemen : 



It is safe to say that the last twelve years have registered an advance of 

 our knowledge of earthquakes not paralleled by that of any earlier period of 

 the same length, if it is, indeed, by that of all earlier time. The collection of 

 data essential to so grand an achievement has necessarily extended over a 

 somewhat longer i)eriod and has been made in earthquake countries, more 

 especially, however, in Italy, Austria and Ja]:)an. Nowhere else has earth- 

 quake study attained to such Avell-planned refinement as in Japan. It may 

 seem, therefore, somewhat remarkable that the two men to whom more than 

 to any others we owe the recent advance of seismology, are residents 

 of countries within which earthquakes belong to the rare and curious, 

 rather than to the most common of natural phenomena. The Count de 

 Montessus de Ballore, who has given us the new science of seismic geography 

 and who has discovered a law to connect earthquakes with the relief of the 

 country, is a major of artillery in the French Army. Professor John Milne, 

 to whom more than to any one else we owe the so-called "new seismology," 

 or the study of "unfelt earthquakes," now resides near the little station of 

 Shide, upon the Isle of Wight. Both these distinguished seismologists have 

 made earthquakes the study of a lifetime, and each was formerly a resident 

 in provinces which, to use the picturesque continental expression, have been 

 tormented by eartluiuakes. 



The grander results of recent earthcjuake study may ])e summed up in a 

 few words. Perhaps most important of all, the long supposed genetic con- 

 nection of earthquakes and volcanoes has been shown to be without a basis of 

 fact. Speaking ))roadly, the earth provinces where volcanoes are "found 

 are generally those of important earthquakes, and light earth shocks are an 

 accompaniment of all grander volcanic eruptions, as they are likewise of 

 explosions in mines or of the passage of a railway train; but as regards the 

 great earthquakes, it is found that they show no quick sympathetic relation 

 to volcanic outbursts within the same province. Further, it has been found 

 In' the Count de Montessus as the result of the analysis of no less than 170,000 

 separate earthquake shocks, that a law connects the seismicity (which we 

 may translate the " earthquakeness ") of a province with its topographic 

 relief. Other things being equal, the steeper the slope, the greater the dan- 

 ger from earthquake shocks. 



The most sensational of the newer revelations in siesmology has resulted 

 from the "distant" study of earthquakes at properly equipped earthquake 

 stations. In the year 1883 Professor Milne wrote, "it is not unlikely that 

 every large earth([uake might, with proper appliances be recorded at any 

 point on the land surface of the globe." The fulfillment of this cautious 



* Address delivered by invitation at the annual meeting of the Michigan^Academy of 

 Science. 



