364 BR. CHARLES DAVISON ON THE [Aug. I907, 



followed it in 14 per cent. The duration of the sound was greater 

 than that of the shock according to 40 per cent., and equal to it 

 according to 60 per cent., of the observers. 



(4) 1900, September 22nd, 4.30 p.m. 



Intensity, 4 ; centre of isoseismal 4, in lat. 56° 10'5' N., long. 3° 50*4' W. 

 Number of records, 20, from 13 places, and 17 negative records from 15 places 

 (fig. 1, p. 363). 



The boundary of the disturbed area corresponds to an intensity 

 slightly less than 4. It is 11 miles long, 7 miles wide, and contains 

 an area of 60 square miles. The longer axis is parallel to that of 

 the preceding shock, and the centre is If miles N. 17° E. of 

 Menstrie. 



The shock again consisted of a single prominent vibration, 

 followed by a tremor, as if some extremely-heavy body had fallen 

 outside the house. 



The sound was heard by 87 per cent, of the observers, 9 per cent, 

 of whom compared it with passing waggons, etc. ; 27 per cent., with 

 thunder : 9, with wind ; 36, with the fall of a load of bricks or coal ; 

 9, with the fall of a heavy body ; and 9 per cent., with the distant 

 firing of cannon. As a rule, both the beginning and the end of the 

 sound coincided with those of the shock. 1 



In addition to these four shocks, two others were also felt by 

 single observers, namely : — 



September 18th, 2 a.m., at Alva. 



September 18th, about 2,55 a.m., at Bridge of Allan. 



(5) 1903, May 15th, 6.15 p.m. 

 A distinct shock was felt generally at Menstrie. 



(6) 1905, April 23rd, 12.15 a.m. 

 A distinct movement was felt at Red Carr (near Blairlogie). 



(7) 1905, July 23rd, 12.15 a m. 



Intensity, 5 ; centre of isoseismal 4, in lat. 56° 11-3' N., long. 3° 47*6' W. 

 Number of records, 33, from 16 places, and 4 negative records from 4 places 

 (fig. 2, p. 365). 



Of 19 records of the time of occurrence, 5 are regarded by their 

 observers as accurate to within a minute. The average of these 

 estimates is 12.15 a.m. 



The boundary of the disturbed area (fig. 2, p. 365) is an isoseismal 

 line of intensity 4. It is 16| miles long, 10| miles wide, and 136 

 square miles in area ; its centre is 3| miles north-east of Menstrie, 

 and the direction of its longer axis is E. 27° N. and W. 27° S. On 

 the same map is shown a portion of the isoseismal 5 traversing the 

 district lying to the south of the Ochil Hills. Its distance from 

 the isoseismal 4 is 1| miles. 



1 These four shocks are described in a paper ' On the British Earthquakes of 

 1900 ' Geol. Mag. dec. 4, vol. viii (1901) pp. 358-61. 



