222 Capt. Beaufort's Account of an Earthquake at Sea, 



dently the same as the cause of the decrease of the dip, and 

 the increase of the westerly variation in the same places, 

 viz. the motion of the magnetical North-Pole in Siberia to- 

 wards the east ; hereby the dip and intensity in the neighbour- 

 hood of this pole may decrease more than in greater distances 

 from it, and the horizontal needle may turn its northern ex- 

 tremity more towards the American North Pole. But as this 

 latter pole also has a slow motion against east, it is probable, 

 that in the north-westerly parts of the Atlantic Ocean, for in- 

 stance at Iceland and Greenland, the intensity is increasing. 

 The greatest difficulty on this inquiry, is to get a perfectly 

 invariable magnetical cylinder, or needle. I hope to surmount 

 this difficulty, and I shall, on another occasion, communicate 

 the result of my endeavours. 

 Christiania, June 3d 1826. 



Art. IV. — Account of an Earthquake at Sea, felt in the Me- 

 diterranean, on the 2§th November 1810, in his Majesty's 

 frigate Salsette. In a letter from Captain Beaufort 

 R.N. F.R.S. to Dr Brewstek. 



Sir, 

 As it appears from a passage in your last Journal, that yon 

 are desirous of putting on record notices of earthquakes that 

 have been felt at sea, the following account of one which I 

 witnessed in the Mediterranean is at your service. 



On the 29th of November 1810, at 7 a. m., his Majesty's 

 frigate Salsette being about nine leagues S.W. by W. (true) 

 from the island of Cerigo, and ten leagues south from Cape 

 Matapan, the sky suddenly assumed a remarkably black and 

 threatening appearance, which, however, spent itself before 

 eight o'clock in heavy rain. The wind had changed during 

 the shower from E.S.E. to N.W., where it continued the rest 

 of the day, and very faint, with the exception of one gust, which 

 will be again mentioned. At 11 a. m., solar time, while tran- 

 quilly standing to the southward, the ship was felt to quiver 

 violently from stem to stern, — the masts, yards, and rigging 

 partaking of the general tremor, and even the guns being 

 strongly affected. The agitation, which commenced with con- 



