Agitation of the Sea in Cornwall and Devon. 109 



end of a line of marbles in a long tube causes the marble or 

 marbles at the higher end instantly to fly up, while all the 

 others remain stationary. A shock of this description is 

 attended with no upheaving — no subsidence — no displace- 

 ment of any portion of the ground, but is a mere vibration 

 ti-ansmitted through the sea with as great velocity and by 

 the same laws as through a solid body. Now, if a shock or 

 rapid vibration of the deep bed of the ocean can, when trans- 

 mitted vertically, strike a ship with such violence as to make 

 all on board believe she had suddenly struck on a rock — an 

 occurrence very frequent during earthquakes ; and if, as was 

 the case in 1755 with a ship 40 leagues west of St Vincent, 

 the concussion has been so great as to throw the men " a 

 foot and a half perpendicularly up from the deck,"f surely 

 the same power, if transmitted obliquely., in the direction of a 

 shelving shore, would be sufficient to drive the marginal 

 water a considerable distance up the beach. 



2. An Account of the extraordinary Agitation of the Sea in Corn- 

 ivall and Devon, on Sunday the 2Sd of May 1847. 



The extraordinary agitation of the sea along the southern 

 coast of -Cornwall on the day above mentioned was greater, 

 and of longer continuance, than any that had previously oc- 

 curred during the last fifty years. 



It was noticed in Mount's Bay as early as 5 o'clock in the 

 morning, and continued with varying intensity throughout 

 the day. It attracted, however, most general attention about 

 5 o'clock in the afternoon, when the sea, near the time of 

 low-water, rushed into all the tidal harbours of the bay, to a 

 perpendicular height varying from about 3 to above 5 feet, and 

 then returned to its previous level, occupying about fifteen 

 or twenty minutes in this double movement. A similar influx 

 and reflux immediately succeeded, and the sea thus continued 

 to advance and retire until after midnight ; but at what hour 

 the rise and fall were greatest 1 have not been able to ascer- 

 tain. The motion resembled that of a very strong tide, or 



t Lyell's Geology, vol. ii. p. 241. 



