574 Proceedings of the British Association. 



shock by which the instruments were affected occurred on the 30th 

 July. 1841. The inverted pendulum in Mr. Macfarlane's house at 

 Comrie, vibrated to the extent of half an inch, in a direction south and 

 north ; whilst at Tomperran (about 1| mile east of Comrie), an instru- 

 ment on the principle of the common pendulum vibrated east and west. 

 The instruments for shewing vertical movements were but slightly af- 

 fected. Mr. Macfarlane describes this shock as very severe, though not 

 so violent as that of October, 1839 : estimating the former at 10, the in- 

 tensity of this shock may be represented by 8. The shock was dis- 

 tinctly double, and the noise and vibrations accompanying it are des- 

 cribed as very loud and violent, both as observed within houses and 

 in the open air. Twelve shocks are said to have been felt in the course 

 of the day ; the weather was cold and inclined to stormy, at the time 

 of this occurrence, and for a day or two before and after. The trees 

 in the neighbourhood of Comrie are described as much agitated. The 

 shock was felt eastward, at least as far as Newburgh, about 38 miles 

 from Garrichrow ; westward to Dalmally, about the same distance ; 

 as far north as Glenlion 30 miles ; and southward to Alloa and Stirling, 

 20 or 30 miles. All the shattered chimneys noticed near Duniva, were 

 on walls, &c. running N. and S. ; those on E. and W. walls being un- 

 touched. The injured buildings stood on a gravelly soil ; but the dis- 

 tance from rocks below was unknown. There was nothing in this 

 weather previous to the earthquake, to give any notice of its approach ; 

 indeed, after a course of some years' observation, no exact rule in this 

 respect has been obtained; even a period of wet weather, which was 

 formerly thought the constant forerunner of frequent and violent 

 shocks, is not always succeeded by them; and, on the other hand 

 earthquakes have occurred when the sky was clear and open. The 

 spot from which the earthquake shocks in Perthshire appear to origi- 

 nate, being situated about a mile to the north of Duniva, it is not 

 difficult to understand why walls running N. and S. were affected ; and 

 those from E. to W. untouched.— 3. On the 9th Sept. 1841, another 

 pretty severe shock was felt at Comrie, about 10' before midnight. 

 The following morning the Association's instrument in the steeple 

 was inclined | of an inch to the south: that in the Comrie House § 

 an inch to the north. This disagreement in the indication may perhaps 

 be accounted for by the occurrence of two other shocks in the course 

 of the night, and previously to the examination of the instruments : 

 the weather during the two preceding days was remarkably wet and 

 close. — 4. On the 8th June, of the present year, two shocks were felt at 

 Comrie, between 1 and 2 a.m. The horizontal pendulum recently sent 



