C. Davison — On Earth quahe- Sounds. 213 



quick claps of thunder. The noise abated as gradually as it had 

 begun. It was limited to a small space, and was not heard in a 

 basaltic district at the distance of a few miles." " Neither on the 

 surface of the earth," he adds, " nor in mines 1600 feet in depth was 

 the slightest shock to be perceived." ^ 



The following accounts throw additional light on the subject : 

 (1) At East Haddam, Conn., U.S.A., on May 16, 1791, at 8 p.m., 

 two shocks were felt in quick succession, of which the first wag 

 the more violent. Soon after, these were followed by a third and 

 slighter shock, and this, again, by nearly one hundred feebler shocks 

 throughout the night. " Subterranean noises are constantly heard at 

 East Haddam, whence its Indian name, Morehemodus, or the place 

 of noises. After this shock, both noises and shocks became less 

 frequent." In several cases noises were heard about this time 

 unaccompanied by any shock. (2) In Piedmont, on April 2, 1808, 

 at 5.43 p.m., an earthquake of intensity VIII., according to the 

 Eo.ssi-Forel scale, was felt, its centre of disturbance having 

 apparently been at Pignerol. This was followed by a large number 

 of slighter shocks (Mallet records about 300) until July, 1809, 

 after which they became less frequent. At Barga, La Tour and 

 other places in the district, subterranean noises were often heard 

 without any accompanying shock. (3) In the island of Meleda, in 

 the Adriatic, noises were heard during a still longer period, from 

 March, 1822, to February, 1825. Mallet remarks that they " do not 

 seem to have been accompanied by any true earthquake shocks, or, 

 at least, any such felt were extremely slight ; " but, according 

 to Humboldt, they were " occasionally accompanied by shocks." 

 (4) At St. Jean-de-Maurienne (in Savoy) and the surrounding 

 district, 49 principal shocks were felt between October 4 and 

 December 28, 1839, " and many more indistinct ones which were 



not recorded They were generally preceded or accompanied by 



subterranean noise, and sometimes this noise was heard without any 

 sensible shock." (5) On October 3, 1839, a remarkable series of 

 shocks commenced at Comrie, in Perthshire. " The shocks were in 

 general very slight, but sometimes rather severe, and were generally 

 accompanied by subterranean noises, variously described as like 

 distant thunder, the reports of artillery, the sound of a rushing 

 wind, etc. The noise .... was often heard without any sensible 

 shock at the time." It would appear from these examples that 

 subterranean sounds without any accompanying earthquake especially 

 characterise those districts where slight shocks are very frequently 

 felt, as if the sounds and shocks were manifestations, differing only 

 in degree and the method in which we perceive them, of one and 

 the same class of phenomena.* 



1 Vol. i. p. 205-6. 



^ Mallets Catalogue of Recorded Earthquakes, Brit. Assoc. Rep. 1854, pp. 28, 

 31, 68-84, 138, 152, 162, 166, 288, 290 ; Humboldt's Cosmos, vol. i. p. 205, foot- 

 note. Possibly also of seismic origin are the phenomena known as the Barisfil Guns, 

 "sounds resembling the fire of heavy cannon at a distance, which are heard at 

 various points in the Delta of the Ganges and Brahmaputra, and in the hills to the 

 north of it" (Brit. Assoc. Eep. 1891). 



