Dr. C. Davison—British Earthquakes. d17 
12. October 16, 1908: 9.53 p.m.—A tremor, of intensity 4 and 
duration two seconds, felt at Airthrey, Alva, Blair Ochil (Dunblane), 
Menstrie, and Red Carr. At Airthrey the shock consisted of one part, 
at Menstrie of two prominent vibrations or bumps. The sound is 
compared to an underground explosion, a clap of thunder, or the thud 
of falling rock. 
13. October 19, 1908: 9.18 a.m.—A slight tremor, with sound, 
observed at Airthrey. The shock was also felt at Blair Ochil 
(Dunblane). 
14. October 19, 1908: 9.39 a.m. 
panying tremor, heard at Menstrie. 
A noise, without any accom- 
15. Ochil Harthquake: October 20, 1908 (Principal Earthquake). 
Time of occurrence, 4.8 p.m.; intensity 7; centre of isoseismal 6 
in lat. 56° 11-4’ N., long. 3° 47°3’ W.; number of records 59, from 
34 places, and 20 negative records from 18 places. 
This is probably the strongest of all recorded earthquakes in the 
Ochil district. The intensity was not less than 7 at Alva and 
Tillicoultry, while that of the earthquake of September 21, 1905, was 
at no place higher than 6. é 
Of thirty-six records of the time, eight are regarded as being 
accurate to the nearest minute. The average of these is 4.8 p.m., 
which agrees with the majority of estimates. 
The only isoseismal which it is possible to draw is that of intensity 6, 
and this agrees so closely with the corresponding isoseismal of the 
earthquake of September 21, 1905, that it is unnecessary to reproduce 
it. Towards the north, west, and south the two curves are almost 
coincident ; towards the east the isoseismal of the later earthquake 
falls short of the other by about half a mile. Its length is 15 miles, 
width 103 miles, and area 123 square miles. Its centre is 33} miles 
EK. 48° N. of Menstrie, and the direction of its longer axis E. 25° N. 
The magnitude of the disturbed area is unknown, but it is probably 
nearly the same as that of the earthquake of September 21, 1905, 
though slightly displaced to the south, for the shock was felt at 
several places, such as Falkirk, Polmont, and Bo’ness, which are 
from one to two miles south of the isoseismal 4 of the earthquake of 
1905, while it was not felt at Comrie, Monzie, and Crieff, close to 
the northern portion of the same curve. From the district lying to 
the south of the last-mentioned places observations are altogether 
wanting. 
At several places within the isoseismal 6 (such as Alloa, Cambus, 
Greenloaning, Menstrie, and Tillicoultry) the shock consisted of two 
distinct parts, separated by an interval of about three seconds, the 
first part being much the stronger. At other places farther from 
the epicentre one part only was observed, the effect resembling that 
caused by the fall of a heavy weight or by the passage of a traction 
engine. The average of fifteen estimates of the duration of the shock 
is 23 seconds. 
The sound accompanying the shock was heard by 92 per cent. of 
1 See Quart. Journ. Geol. Soc., 1907, vol. lxiii, pl. xxvi. 
