304 Dr. C. Davison — British Earthquakes. 



The area disturbed by the earthquake is for the most part sparsely 

 inhabited, and I have not been able to obtain sufficient records for 

 drawing any isoseismal lines. So far as I can ascertain, the boundary 

 of the disturbed area is an ellipse, passing to the north of Fort 

 "William and luverlochy, some miles to the west of Aros in Mull, and 

 to the south of Ardrishaig, Lochgilphead, Glendaruel, and Carrick 

 Castle in Argyllshire. This curve, which I have not reproduced on 

 account of its approximate nature, is about 69 miles long, 58 miles 

 wide, and contains about 3,100 square miles. Its centre is about 

 5 miles east of Oban, and its longer axis is roughly pai-allel to the north- 

 western boundary fault of the Highlands. The intensity of the shock 

 was probably 6, but it was strong enough to cause some slight damage 

 to buildings at Kilninver and Cuilfail Hotel (Kilmelford). 



The shock consisted of two distinct parts, of which the first was 

 regarded as the stronger at Aros and Kilmore (near Oban), and the 

 second at Delavich and Inverinan (near Kilchrenan) and Port Appin. 

 The mean duration of the shock was 5^ seconds, and that of the 

 interval between the two parts 2-3 seconds. 



The sound was heard by 98 per cent, of the observers, and was 

 compared to passing waggons, etc., in 44 per cent, of the records, to 

 thunder in 23 per cent., to wind in 2, to loads of stones falling in 10, 

 to the fall of a heavy body in 4, and to explosions in 17 per cent. The 

 beginning of the sound preceded that of the shock in 67 per cent, of 

 the records, coincided with it in 29, and followed it in 4 per cent. ; 

 while the end of the sound j)receded that of the shock in 8 per cent, 

 of the records, coincided with it in 38, and followed it in 54 per cent. 

 The duration of the sound was greater than that of the shock in 81 per 

 cent, of the records and equal to it in 19 per cent. 



The earthquake may have been caused by a slip along the great 

 northern boundary fault of the Highland district, but the evidence is 

 so scanty that nothing more than the possibility of such a connection 

 can be suggested. 



8. Oohil Earthqualce : J'unelith, 1907. — Time of occurrence, 1.59 a.m. 

 A slight shock felt at Menstrie, consisting of two vibrations, and 



accompanied by two banging noises. 



9. Ochil Earthquake : June 20th, 1907. — Time of occurrence, 3.36p.m.; 

 intensity, 4 ; number of records 2, from 2 places. 



A rather strong shock, felt at Alva and Menstrie, and preceded and 

 accompanied by a loud rumbling noise. 



10. Swansea Earthquake : Juiy ord, 1907. — Time of occurrence, 

 3.40 a.m. ; intensity, 4; centre of isoseismal 4, in lat. 51° 38"1' N., 

 long. 4° 2'8' W. ; number of records 21, from 14 places, and 13 

 negative records from 1 2 places. 



The boundary of the disturbed area is an isoseismal of intensity 4, 

 and is 23 miles long, 14 miles wide, and about 250 square miles in area. 

 Except towards the east, it coincides with the isoseismal 8 of the 

 earthquake of June 27th, 1906. Its centre is 5 miles west of Swansea, 

 and 2 miles west of that of the isoseismal 8 of the earthquake of 1906. 

 The direction of the longer axis is approximately E. 4° N. 



The shock consisted of a single series of vibrations, with an average 

 duration of 3| seconds. The sound was heard by all the observers, 



