THE 



AMERICAN JOURNAL OF SCIENCE 



[THIRD SERIES.] 



Akt. "VIII. — Seismoscopes and Seismological Investigations]; 

 by T. C. Mendenhall.* 



Seismology as a science, or at least as an observational and 

 experimental science, may be said to be the product of the past 

 three or four decades. It is true that before as well as during 

 this period some important applications of the statistical method 

 of investigation were made and the distribution of earthquakes 

 in time and space was thoroughly studied. These investigations 

 are of really high value, although they have generally resulted 

 in the overthrow of certain hypotheses which were constantly 

 appearing as to the correlation of these displays of seismic en- 

 ergy with other natural phenomena ; so that while it may be 

 said that little is yet known concerning the real nature and ori- 

 gin of earthquakes, much useful work has been done in the way 

 of elimination and possibly a reduction of the number of un- 

 known quantities involved. 



The new phase which the science has assumed may perhaps be 

 fitly described by saying that the modern seismologist studies an 

 earthquake, rather than earthquakes. In fact this is one of a 

 considerable group of problems primarily geological in their 

 nature to which, in recent years dynamical principles and phys- 

 ical methods have been applied. The knowledge of first im- 



* Read at the meeting of the National Academy of Sciences at New York 

 Nov. 8th,. 1887. 



Am. Jour. Sci.— Third Series, Vol. XXXV, No. 206.— Feb., 1888. 

 6 



