50 Mr. R. Edmonds on Earthquakes and 



reason to conclude that on these occasions, as well as on the 

 day of the great earthquake of 1755, every disturbance of the 

 sea, wherever it happened, was confined to a few furlongs from 

 that part of the bed of the sea over or near which the agitated 

 waters had previously rested ,* so that all such disturbances in 

 1755, although observed the same day on most of the European 

 coasts, were perfectly independent of one another, and proceeded 

 not from any distant disturbance in mid-ocean, but from local 

 submarine shocks beneath or close to the disturbed waters. In 

 Ealmouth harbour and Plymouth and Mountsbay, for instance, 

 where such extraordinary currents have so often simultaneously 

 occurred, no kind of disturbance has been observed in the offing*. 

 Indeed I have ascertained by personal inquiries from eye-wit- 

 nesses and other sources, whilst residing in Penzance, that such 

 agitations at the piers of St. Michael's Mount, Penzance, and 

 Newlyn (the first being two miles east, and the last one mile 

 west of Penzance pier) have always been independent of each 

 other, and none of them ever extended beyond a few furlongs 

 from the pier where it was observed. 



Assuming that the extraordinary disturbances of the sea in Ply- 

 mouth and Mountsbay on the days of the two great earthquakes 

 of 1755 and 1761 were occasioned by submarine shocks, and 

 that those in the same places in 1811, 1843, 1847, 1859, and 

 1862 were in all respects like them (neither of which facts will 

 be questioned), the only reasonable conclusion is, that all these 

 like effects must have resulted from like causes — that is, from 

 submarine shocks, whether any shocks on dry land were then 

 perceived at those places or not. This may appear more clearly 

 by considering some of the phenomena of the earthquake of 

 1755. 



If (as is universally allowed) the centre of this great earthquake 

 was deep in the interior of the earth, most of the shocks there- 

 from which reached the surface must have proceeded either verti- 

 cally, or upwards at various angles, and the times of reaching 

 the surface at different places must have been generally according 

 to their distances, or the angles of propagation, and the conduct- 

 ing- power of the intervening ground. The shocks which moved 

 through very bad conductors might have been exhausted long 

 before they could attain the surface. Some reached as far up- 

 wards as the bottom of the sea and the basins of lakes and ponds, 

 occasioning extraordinary disturbances of the waters ; and yet 

 most of them fell short of the surface of the adjoining dry lands. 

 Whilst five smart shocks were felt in Derbyshire Peak between 

 11 and 11.20 a.m., sixty fathoms under ground, only one reached 

 the surface there. Mr. Mallet mentions this and two places 

 * So also at Swansea, in 1755 (Phil. Trans, vol. xlix.p. 379). 



