C: Davison — On Earthquake- Sounds. 211 



' is always perceived. When the blow occurs it is generally in the 

 midst of the tremors, and at the moment that they are the most 

 intense, and accompanied with the loudest noise." ^ 



In studying the more recent British earthquakes, I have received 

 many observations on this point, of which the following examples 

 may be given : (1) The epicentrum of the Kintyre earthquake of 

 July 24, 1890, was a few miles from Clachan : 'at which place the 

 shock began with a series of slight tremors lasting for twenty 

 seconds. These tremors gradually " increased in intensity until a 

 vibration was felt like what would be caused by a heavy stone 

 falling from a very great height," and this vibration, again, was 

 followed by tremors lasting for five seconds. During the whole 

 time of the tremulous motion a sound was heard like the crashing 

 of falling stones, and, coincidently with the principal vibration, a 

 dull "thud" as of a suppressed explosion.^ (2) In nine different 

 accounts of the Inverness earthquake of November 15, 1890, a 

 similar phenomenon was described. At Boleskine, for instance, an 

 observer " heard a sound as if a heavy train was approaching, .... 

 it gradually got louder and louder until it seemed to go right 

 through the house, shaking the pictures and china ornaments on 

 the walls." (3) Still more to the point, perhaps, is a remark made 

 hj an observer at Boscastle (Cornwall) of the earthquake felt there 

 on March 26, 1891. This earthquake consisted of two distinct 

 shocks separated by an interval of a few seconds. The sound was 

 loudest just at the times when the shocks were felt, and continued, 

 though more faintly, during the whole of the interval between them. 



A. Eelations of the Sound to the Disturbed Akea. 



1. Variations in the Nature of the Sound and in its Relation to the 

 Shock throughout the Disturbed Area. — In every earthquake, of which 

 sufficiently numerous observations have been made, the sounds vary 

 greatly throughout the disturbed area, not only in intensity, but 

 also in character, duration and relation to the shock. 



In the great Neapolitan earthquake of 1857, so ably studied by 

 the late Mr. Mallet, the sounds were heard over an area roughly 

 elliptical in form, its longer axis being directed about N.W. and S.E. 

 All the observers towards the northern and southern extremities of 

 this area described the sound as "a low, grating, heavy, sighing 

 rush, of twenty to sixty seconds in duration, some thinking that it 

 was also a sort of rumbling sound, but with none, a distinct, well- 

 defined explosion, or several in succession." Those " who were 

 situated towards the middle of the sound-area, and towards its east 

 and west boundaries, on the contrary, very generally described the 

 sound, as something of the same character as to tone, but with more 

 rumbling .... and as shorter and more abrupt both in commence- 

 ment and ending, and in duration." ^ 



The Inverness earthquake of November 15, 1890, was, I believe, 



1 Edinburgh New Phil. Journ. (1841), vol. xxxi. p. 261. 



2 Geol. Mag. (1891). Vol. VIII. pp. 453-4. 



3 ' The Neapolitan Earthquake of 1857,' vol. ii. p. 288. 



