76 EARTHQUAKES. 



earthquake which had been measured the displacement 

 of the ground had been half an inch, and in another it had 

 been less than half an inch. The instruments used to 

 make these observations depended upon the inertia of 

 pendulums which at the time of the disturbance were 

 supposed to remain at rest. Observations similar to these 

 have been made in Japan. One long series were made 

 by Mr. E. Knipping for Dr. Gr. Wagener. They ex- 

 tended from November 1878 to April 1880, and were as 

 follows : — 



Number of Maximum horizontal 



Earthquakes motion of the ground 



10 . . . • . -0 to 0-15 mm. 



7 -15 „ 0-5 „ 



8 -5 „ 2-5 „ 



2 2-5 „ more „ 



With his apparatus for vertical motion Dr. Wagener 

 also made observations on the absolute vertical motion. 

 This seldom reached -02 mm. The greatest value was that 

 observed for the destructive shock of Feb. 22, 1880, 

 which was '56 mm. 



By means of a number of instruments distributed at 

 various localities round Tokio, the chief of which were 

 pendulums with friction pointers to render them ' dead 

 beat,'' and with magnifying apparatus to show the actual 

 motion of the ground, the author arrived at results 

 similar to those obtained by Dr. Wagener — namely, that 

 the earth's maximum horizontal motion at the time of a 

 small earthquake was usually only the fraction of a milli- 

 metre, and it seldom exceeded three or four millimetres. 

 When we get a motion of five or six millimetres, we 

 usually find that brick and stone chimneys have been 

 shattered. 



The results obtained for vertical motion were also very 

 small. In Tokio it is seldom that vertical motion can be 



