Vol. 58.] INVERNESS EARTHQUAKE OF SEPTEMBER 1901. 383: 
The character of the sound is described by 394 observers ; 39 per 
cent. of these compared it to passing waggons, traction-engines, 
ete., 25 per cent. to thunder, 14 to wind, 8 to loads of stones falling, 
3 to the fall of heavy bodies, 4 to explosions or the firing of heavy 
guns, and 7 per cent. to miscellaneous sounds.’ 
There are the usual anomalies in the audibility and character of | 
the sound, depending on the varying powers of the observers for 
hearing low sounds. This is especially noticeable in the case of the 
heavy crashes heard by some observers at the moment when the 
shock was strongest. 
The variation in the sound throughout the sound-area was also 
normal. Its intensity gradually diminished outward from the 
epicentre, and most rapidly near the isoseismal 7, which bounds 
approximately the district in which the sound was very loud from 
that in which it was distinctly fainter. With one exception, the 
same curve includes all places at which the explosive crashes were 
heard with the strongest vibrations. Again, 34 per cent. of the 
observers within this line, and 44 per cent. of those outside it, 
compared the sound to passing vehicles, traction-engines, etc. ; for: 
thunder, the corresponding percentages are 34 and 18, for wind 8 
and 19, for loads of stones falling 11 and 6, the fall of heavy bodies 
2 and 4, explosions 7 and 3, and for miscellaneous sounds 5 and 5. 
Thus, with increasing distance from the centre, the sound became 
more uniform in character and intensity. 
Time-relations of the sound and shock.—In the follow- 
ing table, the letters p, c, and f indicate the number of records 
per cent. in which any epoch of the sound preceded, coincided with, 
or followed, the corresponding epoch of the shock. In the last line, 
I have added the average percentages for three strong earthquakes : 
namely, the Pembroke earthquakes of 1892 and 1893, and the 
Hereford earthquake of 1896. 
| Epoch of | 
Beginning. | Maximum | End. 
County. | Intensity. 
(FR || Eg 7a ate 
| eS |p isculafiieg te. Noe 
EMIVGRICS So .ozc cess seeks eet 80 | 16] 4 | 27 | 64 | 9 | 14] 50 | 56 
Be s,s 75 | 12| 12 | 25} 62/12] 9!| 41 | 50} 
Nairn & Elgin .......0....00.... 73 | 15 | 12 | 20| 70| 10 | 36 | 28 | 36 
TEA 11 en rR aD = CLD | 27s O08). 183"095 | 42 
PMiseticon: iis ces. Lae 7 147) 15,1100) |.6 |e) | 60 (40.4 
Mee vomitibss,:... oe | BO. Wid.| 5. 25175. |---| 18.) 12 | 75, 
Whole sound-area ............ eeO rl S20) Foal a lon 34 ho | 
Average for strong shocks ... 78 14] 8 | 25 | 67 | 8 | 20 | 23 | 57 
| j 
* During the night of the earthquake, there was a strong wind in many parts. 
of Scotland, which, however, generally subsided before the shock took place. 
Some of the observers may have mistaken a short gust for the earthquake-sound ; 
but more than 60 per cent. of those who refer to this type record the time- 
ta of the sound and shock in such a manner as to leave no doubt on the 
subject. 
