1. For vertical motion. (_a_) For the first 200 feet. The velocity depends upon the initial force—the greater the charge of dynamite the greater the velocity. (_b_) For the second 200 feet. The above law only appears in experiments IV. and V., but it must be remembered that the origins of I. and III. were farther removed from A than IV. and V. The speed of the wave during the second 200 feet is always less than during the first 200 feet. 2. For normal vibrations. Here the speed between A and C is all that was measured, but we again see that the greater the initial force, or the nearer we are to the origin of the disturbance, the greater is the velocity. This velocity is greater than the velocity of the vertical or transverse vibrations. 3. For transverse vibrations. If we assume that the vertical vibrations are a component of the transverse motions we see the same law as before—namely, that the nearer we are to the origin of the disturbance the greater is the speed with which that disturbance is propagated. It will be observed that the chief law here enunciated respecting the decrease in speed of earth vibrations is the same as that pointed out by General Abbot, from which it only differs by its being in all cases proved without the introduction of personal errors, for the same explosion, along the same line of ground and for different kinds of vibrations. CHAPTER V. EARTHQUAKE MOTION AS DEDUCED FROM OBSERVATION ON EARTHQUAKES. Result of feelings—The direction of motion—Instruments as indicators 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—Radiation of an earthquake—Velocity of propagation. _Result of Feelings._—As the result of our experiences, and by observations upon the movements produced in various bodies, we can say that an ordinary earthquake consists of a number of backward and forward motions of the ground following each other in quick succession. Sometimes these commence and die out so gently that those who have endeavoured to time the duration of an earthquake have found it difficult to say when the shock commenced and when it ended. This was a difficulty which Mr. James Bissett in Yokohama, and the author in Tokio, had to contend against when, in 1878, they commenced to time shocks between these two places. Sometimes these motions gradually increase to a maximum and then die out as gradually as they commenced. Sometimes the maximum comes suddenly, and at other times during an earthquake our feelings distinctly tell us that there are several maxima.