Comparison of Earthquake Diagrams simultaneously obtained 

 at the Same Station by two Instruments involving the 

 Same Principle, and thereby proving the Trust- 

 worthiness of these Instruments. 

 By 



Seikei Sekiya. 



Professor of Seismology, Science College, Imperial University. 



With Plates VIII.— XI. 



In 1883, Prof. J. A. Evving contributed a valuable, and now 

 well-known, work on Earthquake Measurernent to the memoirs pub- 

 lished by this University, in which he described the theory and 

 construction of seismographs of his own invention together with 

 earthquake diagrams that were obtained by the use of these instru- 

 ments. These diagrams have given many new and important results, 

 and in several cases settled, in a decisive manner, questions relating 

 to the character of earthquake motions. 



This short paper is intended to treat of the further examination of 

 similar diagrams recently obtained, and to prove the trust-wortliiness 

 of Horizontal Pendulum Seismographs. This is done by comparing 

 the two diagrams of the same earthquake simultaneously registered by 

 two instruments placed side by side in the Observatory. With this 

 object in view two pairs of earthquake diagrams are given, which were 

 originally photographed from the smoked glass plates on which they 

 were recorded. 



