Yol. 6^.'] OCHIL EARTHQUAKES OF 1900 TO 1907. 



363 



II. Description oe the Earthquakes. 



(1) 1900, September 17th, 3.30 p.m. 



A slight shock was felt by several persons at Menstrie. 



(2) 1900, September 17th, 10.5 p.m. 

 A slight shock was felt by several persons at Alva. 



(3) 1900, September 17th, 10.15 p.m. 



Intensity, 4; centre of isoseismal 4, in lat. 56° 11-6' IS"., long. 3° 505' W. 

 Number of records, 56, from 26 places, and 13 negative records from 11 places 

 (fig- 1). 



The boundary of the disturbed area (fig. 1, below) is an isoseismal 

 line of intensity a little less than 4 (Rossi-Eorel scale). It is 15 

 miles long, 9| miles wide, and 117 square miles in area. The 

 longer axis runs from E. 13° K. to W. 13° S., and the centre of 

 the area is 3 miles N. 8° E. of Menstrie. 



1.4° 0' I3°50'long.^". '3°4l/ 



FlG.l. EAKTHQrJtKESOI'Si:PT-.17 TH A^D Sept. 22^1900, 



Scale of Miles. 

 12 3 4 5 



S%ggJ£. 10 Qcuo3. 



56°10'K 



©Clackmannan 



All over the disturbed area, the shock consisted of a single pro- 

 minent vibration, followed by a tremor, such as would be caused 

 by a heavy weight falling on the floor and making the building 

 shake. The duration of the shock was not more than 3 seconds. 



The sound was heard by 94 per cent, of the observers, and was 

 compared in 29 per cent, of the records with traction-engines, etc. 

 passing ; in 10 per cent., with thunder ; in 5, with wind ; in 12, with 

 the fall of a load of stones, etc. ; in 17, with the fall of a heavy 

 body ; in 12, with blasting or explosions ; and in 15 per cent., with 

 miscellaneous sounds. The beginning of the sound preceded that 

 of the shock in 34 per cent., and coincided with it in 66 per cent., of 

 the records ; while the end of the sound preceded that of the shock 

 in 9 per cent, of the records, coincided with it in 77 per cent., and 



