Dr. C. Davison on Earthquake- Sounds. 63 



Thus, as a general rule, the beginning of the sound precedes 

 that of the shock, but occasionally coincides with it, especially 

 when the earthquake is weak. For weak shocks the epochs 

 of maximum intensity of both always coincide ; while, for 

 stronger shocks, the epoch of maximum intensity of the sound 

 generally coincides with, but sometimes precedes, that of the 

 shock. The end of the sound hardly ever precedes, but often 

 coincides with, that of the shock in weak earthquakes, and in 

 both strong and weak earthquakes more frequently follows it 

 than otherwise. 



Time-Relations with regard to Distance from the Epicentre. — 

 The great majority of the records are from places not far from 

 the epicentre. The effect of distance on the time -relations is 

 shown more clearly in the next Table (p. 64), in which the 

 number of observations is given for each epoch and district ; 

 but for convenience of comparison the figures in the other 

 columns are percentages of the numbers of observations. This 

 Table of necessity refers only to the stronger earthquakes. 



It appears, then, that the beginning of the sound generally 

 precedes that of the shock in all parts of the sound-areas, even 

 close to the epicentre. 



The epochs of maximum intensity of the sound and shock 

 coincide, as a rule, especially in the central counties and 

 outer ring ; but in the inner ring of counties observations of 

 precedence increase in frequency. In the case of the Hereford 

 earthquake, an analysis of the observations according to di- 

 rection, though it rests on a small number of records, indicates 

 that the percentage of observations of coincidence undergoes 

 a marked decrease in the inner ring in the counties traversed 

 by the longer axis of the isoseismal lines, while in those which 

 lie along the shorter axis it is nearly constant. The much 

 weaker Leicester earthquake of 1893 leads to a somewhat 

 similar conclusion. The epoch of maximum intensity of the 

 sound preceded that of the shock at 19 places, which are, as a 

 rule, near the ends of the longer axis of the disturbed area ; 

 and coincided with it at 18 places, which are not far distant 

 from the epicentre or shorter axis, and in two cases close to 

 the ends of that axis. 



In the Pembroke earthquake of 1892, the end of the sound 

 generally followed that of the shock all over the disturbed 

 area ; in that of 1893, observations of coincidence increase 

 with the distance from the origin. On the whole, the per- 

 centages for this epoch in the Hereford earthquake do not vary 

 much with the distance. In the Leicester earthquake of 1893 

 the end of the sound preceded that of the shock at 16 places 

 generally near the longer axis of the disturbed area, and 



