PAGE Relationship of man to nature—The aspect of a country is dependent on geological phenomena—Earthquakes an important geological phenomenon—Relationship of seismology to the sciences and arts—Earth movements other than earthquakes—Seismological literature—(Writings of Perrey, Mallet, Eastern writings, the Philosophical Transactions of the Royal Society, the ‘Gentleman’s Magazine,’ the Bible, Herodotus, Pliny, Hopkins, Von Hoff, Humboldt, Schmidt, Seebach, Lasaulx, Fuchs, Palmieri, Bertelli, Seismological Society of Japan)—Seismological terminology 1 CHAPTER II. SEISMOMETRY. Nature of earthquake vibrations—Many instruments called seismometers only seismoscopes—Eastern seismoscopes, columns, projection seismometers—Vessels filled with liquid—Palmieri’s mercury tubes—The ship seismoscope—The cacciatore—Pendulum instruments of Kreil, Wagner, Ewing, and Gray—Bracket seismographs—West’s parallel motion instrument—Gray’s conical pendulums, rolling spheres, and cylinders—Verbeck’s ball and plate seismograph—The principle of Perry and Ayrton—Vertical motion instruments—Record receiver—Time-recording apparatus—The Gray and Milne seismograph 12 CHAPTER III. EARTHQUAKE MOTION DISCUSSED THEORETICALLY. Ideas of the ancients (the views of Travagini, Hooke, Woodward, Stukeley, 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 determined by experiments upon the elastic moduli of rocks—The intensity of an earthquake—Area of greatest overturning moment—Earthquake waves—Reflexion, refraction, and interference of waves—Radiation of a disturbance 41 CHAPTER IV. EARTHQUAKE MOTION AS DEDUCED FROM EXPERIMENT. Experiments with falling weights—Experiments with explosives—Results obtained from experiments—Relative motion of two adjacent points—The effect of hills and excavations upon the propagation of vibrations—The intensity of artificial disturbances—Velocity with which earth vibrations are propagated—Experiments of Mallet—Experiments of Abbot—Experiments in Japan—Mallet’s results—Abbot’s results—Results obtained in Japan 57 CHAPTER V. EARTHQUAKE MOTION AS DEDUCED FROM OBSERVATION ON EARTHQUAKES.