Charles Davison— British Earthquakes. 295 
Achiltibuie.—(1. Observer, Mr. D. Fraser.) One series of vibra- 
tions, lasting about three or four seconds. A rumbling sound, 
beginning like a shot from a gun and dying away like a heavy chain 
dropping from a ship; the vibrations felt when the sound was 
loudest; the end of the sound followed that of the shock by about 
five seconds.—(2. Observer, Mr. R. MacRae.) A tremulous motion, 
the vibrations too rapid to be counted and all apparently of the same 
intensity. A rumbling sound like that of a conveyance passing over 
a gravel road some distance away; the beginning coincided very 
nearly with that of the shock; the end followed that of the shock by 
a very short interval. 
It will be seen that the disturbed area and the sound-area are 
approximately coincident. At Elphine, however, which is near the 
north-east end of the shorter axis of the disturbed area, the shock 
was not felt, while a rumbling sound was heard by Mr. A. Hunter 
like that of a gig passing along the road close by. Mr. Hunter was 
good enough to make several enquiries in the neighbourhood. About 
one mile nearer Ullapool, the sound, he finds, was heard and no 
shock felt, but the observer was standing, and in the open air, an 
unfavourable position for perceiving a slight vibration. At Ledmore, 
about two miles east of Elphine, neither shock nor sound were per- 
ceived. In the absence of detailed records from the south side of 
Little Loch Broom, it is impossible to say whether the disturbed 
area and sound-area were, or were not, concentric. 
Time-relations of the Shock and Sound.— The beginning of the sound 
is said to have preceded that of the shock at Inverbroom, Inverlaal, 
and (by a very short interval) at Morefield; coincided with it at 
Achiltibuie, Ardindrean and Lochinver; and followed it at Kildonnan 
and (by a very short interval) at Dundonnell Hotel, Isle Martin and 
Ullapool. 
The end of the sound is said to have preceded that of the shock 
at Dundonnell Hotel ; coincided with it at Ardindrean and Lochinver ; 
and followed it at Achiltibuie. 
Origin of the Shock.—The broken character of the country may 
be answerable to some extent for the elongated form of the disturbed 
area, and on this account it would be unwise to lay too much stress 
on the position of the epicentrum and the direction of the longer 
axis as determined above. ‘Taking them as they stand, however, we 
should infer that, if the shock were fault-formed, the direction of 
the fault-line should be N. 30° W. and 8. 380° E. The best guide as 
to the direction of hade is the greater intensity of the shock at Isle 
Martin than elsewhere; and, this place lying to the south-west of 
the longer axis, it would follow that the fault must hade towards 
the south-west; a conclusion supported by the sound being perceived 
immediately after the shock at Isle Martin, and also, perhaps, by the 
overlapping of the sound-area in the neighbourhood of Elphine. 
The fault-line must in that case lie on the north-east side of the 
axis, parallel to it and distant from it probably about one mile and 
not more than two or three miles. The length of the seismic focus 
in a horizontal direction must have been considerable, perhaps several 
