98 T. C. Mendenhall — Seismoscopes and 



portanee in regard to an earthquake is the knowledge of the 

 nature and location of its origin and it is generally admitted 

 that this can be obtained only through the study of individual 

 instances. The natural method is to proceed from the known 

 effect to the unknown cause, and for a time progress in seis- 

 mology consisted largely in painstaking and laborious investi- 

 gations of the destructive effects of earthquakes from which it 

 was believed a knowledge of their ultimate origin might be 

 deduced. Little in the way of experiment had been attempted 

 and nothing was known of the really complex motion of the 

 earth -particle when subjected to the influence of an earthquake 

 wave. False assumptions were made with regard to this motion 

 and erroneous and perplexing conclusions resulted. The great 

 work of Mallet on the Neapolitan Earthquake, although of 

 much importance in its day, and always a monument to his in- 

 dustry and devotion to the science, can not now be considered 

 as of any great value as a solution of the problems involved. 



The importance of earthquake measurements by means of 

 specially constructed instruments was recognized by Mallet, 

 however, and he undertook the design and construction of such 

 instruments at an early date. The problem seemed at first easy, 

 but investigation proved it to be of considerable difficulty. In 

 a general review of the state of the science in his report to the 

 British Association in 1858 Mallet says,* "twelve years ago the 

 construction of seismometric instruments appeared a compara- 

 tively easy matter. It is only at a very recent period that 

 experiments and observations as to the actual phenomena, the 

 velocity and direction of the shock, etc., have begun to show the 

 real difficulties of the subject." But even at this time Mallet 

 failed to recognize the true nature of the disturbance produced 

 by an earthquake, and the several seismometers which he de- 

 vised, and which will be found described in the report already 

 referred to, are practically of no value. One of them, which 

 was extremely elaborate in its construction, he considered com- 

 petent to furnish, from a single station, all of the elements 

 necessary for the determination of the seismic focus. Another, 

 the arrangement of two rows of cylinders of varying diame- 

 ters in lines at right angles to each other, is probably the most 

 widely known of all earthquake machines as it is described in 

 many encyclopaedic articles and treatises on Geology in which 

 the subject is discussed. It may be said, however, that a more 

 useless device has never been proposed. 



A notable advance in our knowledge of the subject and par- 

 ticularly of instrumental Seismology has been made during the 

 last- half dozen years and it must be largely attributed to the 



* On the Facts and Theory of Earthquake Phenomena — Report of the British 

 Association, 1853. 



