36 Dr. C. Davison on Earthquake- Sounds. 



place at the time when the shock is strongest. It then 

 assumes a rougher, more grinding or grating character, 

 occasionally, but not often, being heard as a loud report or 

 crash. As this is a feature which does not seem to have 

 attracted much attention, the following examples from 

 different British earthquakes are given in illustration. 



At Penryn, the Cornwall earthquake of 1892 consisted of 

 two distinct vibrations, each followed by tremulous motion ; 

 each was also accompanied by a sound like the crash of a 

 heavy weight on the floor above and followed by a rumbling- 

 sound like that of a waggon roaring along the street, con- 

 tinuing after the shock and dying away in the distance. At 

 Lamphey, during the Pembroke earthquake of 1802, a sound 

 was heard for three seconds resembling that of sea-waves at 

 a distance, followed for two seconds by a deep heavy boom 

 of thunder, during which the shock was felt, and this by a 

 sound like sea-waves dying away in about three seconds. 



Many observations of this kind were made during the 

 Hereford earthquake of 1896. For instance, at Dilwyn in 

 Herefordshire, there was a rumbling as of a train going 

 over a bridge, with a terrific crash, such as is heard in a 

 thunderstorm, at the instant when the shock was strongest, 

 the rumbling dying away afterwards for some seconds. 

 Again, at Horsley in Gloucestershire, the sound was first 

 like a violent wind among trees ; then, while the shock 

 lasted, like a very heavy traction-engine close to the house, 

 and, at the instant when the sound was loudest and the 

 shock strongest, the rumbling was accompanied by a sort of 

 grinding noise, which appeared to be under the observer's 

 house, and sounded as if a landslip was in progress. 



When the sound is compared to wind, a change is fre- 

 quently observed. Thus, Prof. Papavasiliou records, on the 

 authority of M. de Biasi, that a strong shock felt in Zante 

 on June 31 {sic), 1896, ' fut precedee d'un bruit pareil 

 d'abord a celui du vent, puis a celui d'une voiture " ; and a 

 similar change was observed in the same island on. Sept. 23, 

 1896*. During the Hereford earthquake of 1896, the change 

 generally took place at or about the instant when the shock 

 began or ceased to be felt ; as at Batley, in Yorkshire, where 

 the shock was preceded by a sound as of a rushing w T ind, 

 and was accompanied by a low rumbling noise like distant 

 thunder. 



Though some exceptions to the conclusion will be noticed 

 later, it thus appears that, as an earthquake-shock increases 

 * Observatoire National d'Athenes, Bull, Mens. Seismol. 1 annee, 

 1896. 



