and especially in Scotland. 77 



in a letter written next morning, — ** We felt a slight shock, 

 accompanied with a rumbling noise, last night about 9^ SO'. 

 It was much slighter than the one felt here in October 

 1839." 



23(/, 25M, a7id 26th July 1841.— Of these dates, shocks 

 were felt at Comrie. Mr M'Farlane writes; — The first 

 " occurred about 1 a.m., — say 2 on our scale of intensity. 

 The second occurred at 4*^ 45' p. m., — 3 of our scale. The 

 third was this morning about 3 o'clock, said to be also 

 pretty loud. Your instrument in my garden (to indicate a 

 vertical upheave of the ground) was moved by one of the last 

 or both (I cannot say precisely, not having looked in the in- 

 terval) nearly one degree or half an inch. The long one in 

 the steeple was also inclined, when I looked at it this morn- 

 ing, about the same distance from its centre to the west. 

 My own dip one had its index depressed about half an inch, 

 and vibrated east and west, from its point of rest, nearly the 

 same distance. The quake yesterday, I heard distinctly. A 

 few seconds after the shock, the window-sashes of the room 

 where I was, quivered audibly. The Aveather has been re- 

 markably mild and warm for some days back. Neither the 

 barometer nor thermometer seemed to be sensibly affected." 



From these data furnished by the seismometers, it is evi- 

 dent that at Comrie there was, on the 26th July, an upheave 

 of the ground from the westward, caused by a force which 

 acted from below in a direction making an angle with the 

 horizon of 40° to 60°. 



SO th Jidy 1841. — On this occasion also, the seismometers 

 were affected. Mr M 'Far lane reports, that the two inverted 

 pendulums in his house vibrated to the extent of half an inch, 

 and in a direction south and north, which is different from 

 previous indications. At Tomperran (about one and a half 

 mile east of Comrie), an instrument on the principle of the 

 common pendulum, vibrated east and west. The instruments 

 for shewing vertical movements, were but slightly affected. 



Notwithstanding the slight nature of the effects of this 

 shock on the instruments, Mr M*Farlane reports, that it was 

 very severe, though not so violent as the one which occurred 

 in October 1839. Reckoning this former one at 10, he says. 



