56 Dr. C. Davison on Earth quake -Sounds. 



(4) In many slight British earthquakes the sound-area 

 overlaps the disturbed area, as a rule only on one side, but 

 sometimes in every direction. The Cornwall earthquake of 

 April 1, 1898, had a disturbed area of about 175 square miles, 

 beyond which the sound-area extended for a mile or two 

 towards the south-west, north, and north-east (see fig. 3, p. 60). 

 In the Comrie earthquake of July 12, 1895, the disturbed 

 area contained only 18J square miles ; the sound-area over- 

 lapped its boundary by two or three miles towards the north 

 and west, if not in all directions. The Comrie earthquake of 

 Aug. 26, 1898, was still weaker ; the sound-area contained 

 but a few square miles, while the shock was only felt at one 

 or two places within it. 



(5) The limiting case, in which earth-sounds are heard 

 without any accompanying shock, is of considerable interest. 

 As a general rule, they appear to form part of the series of 

 after-shocks of a great earthquake, or occur as intercalated 

 members of a series of weak shocks. But it is possible that, 

 under the names of barisal guns, mist-poeffers, marinas, &c, 

 they may also be heard quite detached from an earthquake- 

 series ; though the identification of these mysterious noises 

 with earth-sounds must be regarded as uncertain for the 

 present . 



Most, if not all, great earthquakes appear to include nume- 

 rous earth-sounds among their attendant crowds of after- 

 shocks, especially in and near the epicentral regions. Even 

 in Japan, where the audibility-percentage is so low, they are 

 far from uncommon. For instance, the 3365 after-shocks of 

 the Mino-Owari earthquake recorded at Gifu between Oct. 28, 

 1891, and the end of 1893, included 10 violent shocks, 97 

 strong, 1808 weak, 1041 feeble shocks, and 409 earth- 

 sounds *. On the other hand, in Great Britain, where the 

 audibility-percentage is high, earth-sounds are occasionally 

 numerous, especially at Comrie. After the strong shock of 

 Oct. 23, 1839, one observer at Comrie noted between this 

 date and the end of 1841, 19 earthquake-shocks (10 of which 

 are described as vertical, and 7 lateral), 25 tremors, and 234 

 earth-sounds f. 



It seems unnecessary to accumulate many further examples, 

 but reference should be made to three cases in which earth- 

 sounds were especially numerous. In the island of Meleda, 

 in the Adriatic Sea, earth-sounds were heard during the 



* F. Omori, Journ. Coll. Sci. Imp. Univ. Japan, vol. vii. pt. 2, p. 113. 



t J. Drummond, Phil. Mag. vol. xx., 1842, pp. 240-247. A similar 

 series of earth-souuds followed the Comrie earthquake of March 12, 

 1795. 



