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Under the first class were described the ditfereiit kinds of injury 

 done to walls, according to their direction, and the nature of the 

 ground on which they were built. Under the second were men- 

 tioned the alarm felt by the inhabitants of Strathearn during the 

 great shock of 23d October, as also the quick perception of it by 

 the lower animals, and the terror they evinced at it. 



" III. The nature of the movement of the earth's surface which 

 caused the foregoing effects was next noticed, and data were given 

 illustrating the form of the undulation which was produced. The 

 noises also that accompanied the shocks were fully described, and 

 the probable cause of them stated. 



" Various other concomitant phenomena of an unusual charac- 

 ter were noticed, such as the evolution of electricity, the diffusion 

 throughout the atmosphere of something which caused a smell, 

 variously described as ' metallic,' ' sulphureous,' and like the 

 • washings of guns ;' as also the appearance in various parts of 

 Strathearn of a fine black powder, which appeared to consist 

 chiefly of carbonaceous, and partly of siliceous and calcareous 

 matter. 



•' IV. The last part of the paper was devoted to remarks on 

 the way in which the undulation ' of the earth's' surface was 

 caused, and the circumstances which may have produced the 

 earthquakes. 



" In reference to the first point, various reasons were assigned 

 why the phenomena were more intelligible, on the supposition 

 that they were caused by vibrations transmitted through the solid 

 crust of the earth, than on the theory supported by many, that 

 they were caused by undulations in the body of molten matter on 

 which the earth's crust may be resting. These vibrations were 

 probably caused by ruptures or explosions at a considerable depth 

 beneath the earth's surface. 



" In regard to the cause of these ruptures, it was observed, that 

 the hills in the immediate neighbourhood of Strathearn are 

 chiefly primitive, and of igneous origin, and that there are nu- 

 merous greenstone and basaltic dykes, indicating renewed volca- 

 nic action at subsequent periods. There are apparently exten- 

 sive fissures in the earth's crust in this part of Perthshire. It 

 was also observed, that, during the month previous to the occur- 

 rence of the earthquake, the atmospheric pressure had been great- 

 ly less than usual ; and that the quantity of rain which fell was 

 almost unprecedented in the central parts of Scotland. There 

 appeared to be some connection between the state of the atmo- 



