X CONTENTS. 



CHAPTEPv III. 



EARTHQUAKE MOTION DISCUSSED THEORETICALLY. 



PAGE 



Ideas of the ancients (the \iews of Travagini, Hooke, "Woodward, 

 Stuckeley, Mitchell, Young, Mallet) —Nature of elastic waves 

 and vibrations — Possible causes of disturbance in the earth's 

 crust — The time of vibration of an earth particle — Velocity and 

 acceleration of a particle — Propagation of a disturbance as de- 

 termined by experiments upon the elastic moduli of rocks — The 

 intensity of an earthquake — Area of greatest overturning mo- 

 ment— Earthquake waves — Reflexion, refraction, and interference 

 of waves— Eadiation of a disturbance 41 



CHAPTER ly. 



EARTHQUAKE MOTION AS DEDUCED FROM EXPERIMENT. 



Experiments with falling weights — Experiments with explosives 

 — Eesults obtained from experiments — Relative motion of two 

 adjacent points — The effect of hills and excavations upon the 

 propagation of vibrations— The intensity of artificial disturb- 

 ances—Velocity with which earth vibrations are propagated — 

 Experiments of Mallet — Experiments of Abbot — Experiments 

 in Japan — Mallet's results — Abbot's results —Eesults obtained 

 in Japan 57 



CHAPTEPv Y. 



EARTHQUAKE MOTION AS DEDUCED FROM OBSERVATION 

 ON EARTHQUAKES. 



Result of feelings — The direction of motion — Instruments as in- 

 dicators of direction — Duration of an earthquake — Period of 

 vibration— The amplitude of earth movements — Side of greatest 

 motion — Intensity of earthquakes — Velocity and acceleration of 

 an earth particle — Absolute intensity of an earthquake — Eadi- 

 ation of an earthquake — Velocity of propagation . , .67 



