THE IXVERNKSS EARTHQUAKES OF NOV. 15 TO DEC. 14, 1890. 621 



2. Nature of iJte Shocl\ — The nature of the shock varied consi- 

 derably throughout the disturbed urea, this variation being of course 

 a necessary consequence of the position and magnitude of the seismic 

 focus. I will first give a few descriptions in detail out of a large 

 number received. 



Beauly : A heavy rumbling sound was heard before and during 

 the shock. Throe distinct vibrations were first felt, more intense 

 to begin with, and were followed by a tremulous motion; the whole 

 lasting about 8 or 10 seconds. The vertical motion was very per- 

 ceptible, first upward and then downward. 



Dingwall : A heavy rumbling sound was first heard, followed by 

 a violent quivering of the ground, consisting of about 10 or 12 

 vibrations, first increasing in intensity and then gradually dying 

 away. The duration of the shock, excluding that of the sound, 

 was 5 seconds. 



Drumnadrochit : "First a tremulous shake, then four strong 

 vibrations, and again a tremulous shake. I would say four weak, 

 four strong, and again four weak vibrations. AVith the last shake 

 of the strong vibrations there was a distinct heave. A very loud 

 jsound accompanied the shock, becoming louder the greater the 

 vibration, but ending more abruptly than the quiver." The dura- 

 tion of the shock alone was 6 seconds. 



Glen Urquhart (at the schoolhouse) : " It began with a noise 

 like the distant sound of cannon, which grew louder and louder, and 

 a tremor of the' ground, at first slight, but which rapidly increased 

 in violence, and culminated in a quick lurching motion of the floor. 

 Both sound and motion then died away as they grew." 



These accounts will show sufiiciently the nature of the shock ; 

 and I will now give a brief summary of the others. 



The intensity of the vibrations was greatest near the beginning 

 at Beauly and Invermoriston, about the middle at Dingwall, Dores, 

 Drumnadrochit, Glen Urquhart (the schoolhouse), and Inverness, 

 and towards the end at Fowlis station and Invergorden. 



In most cases the observations are not sufficiently detailed to 

 determine any law in the distribution of places according to the 

 duration of the shock or the number of vibrations felt. For the 

 most part, however, prominent and well-marked vibrations were 

 felt only in the neighbourhood of the epicentrum, these being often 

 preceded and followed by tremors ; and towards the boundary of 

 the disturbed area the shock was only perceptible as a faint tremu- 

 lous motion. 



At the following places the motion was distinctly felt to be partly 

 vertical : — Aldourie, Beauly, Bunclirew, Bunchrubin, Cawdor, 

 Clunes station, Conon, Dolrachnie, Dingwall, Dores, Dyke, Fort- 

 rose, Invermoriston, Inverness, Moy, Ilafibrd, lledcastle, and Tor- 

 breck. It will be noticed that none of these places is at a greater 

 distance than twenty-five miles from the epicentrum. At places 

 more distant than this the direction of the motion, when referred 

 to, is always described as horizontal. 



The vertical motion was first upward and then downward at 



