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XXXIX On a Remarkable Oscillation of the Sea, observed at various places on 

 the Coasts of Great Britain, in the first week of July 1843. By DAVID 

 MILNE, Esquire. 



(Read 19th February 1844.) 



THIS phenomenon presented a remarkable interference with those laws which 

 govern the ordinary movements of the ocean. It occurred at one place whilst 

 the tide was flowing, at another whilst it was ebbing ; in some cases, producing 

 a sudden retrocession of the waters, and in others, as sudden an impulse of them 

 on the shore. 



The period during which the sea thus continued to retreat and rise respec- 

 tively, was generally from ten to fifteen minutes. It then made a momentary 

 halt after which, it began to flow in the opposite direction, and which it continued 

 to do, for about the same period which characterised its previous movement. 



In this state of alternate flux and reflux, the sea was at most places observed 

 to continue, for three or four hours together. 



The first day on which the phenomenon was observed, was Wednesday the 

 5th July 1843. During the three following days, the oscillation was at different 

 places perceptible ; but in no case so distinctly, as on the 5th July. 



The same phenomenon appears to have frequently occurred before, and to 

 have occasionally given rise to discussions as to the cause of it. There will be 

 found a good many instances recorded in the earlier volumes of the Royal Society 

 of London, as well as in the Annual Register, and other such periodicals. In 

 several cases, the oscillation has been distinctly traced to submarine earthquakes. 

 The Lisbon earthquakes of 1755 and 1761 undoubtedly produced on the coasts of 

 Great Britain a flux and reflux of the sea, in many respects similar to that which 

 forms the subject of the present notice ; and as, on other occasions, no other ap- 

 parent cause suggested itself for these oceanic disturbances, there seems to have 

 been a general acquiescence in the opinion that they were produced by the same 

 cause. In a short notice given in the Edinburgh Philosophical Journal, of the 

 oscillations which occurred last July, I observe that earthquakes are suggested as 

 the cause. 1 



Deeming this explanation unsatisfactory, and thinking it of use to preserve 

 some record of a phenomenon, remarkable in itself, and not hitherto satisfactorily 

 explained, I have drawn up an account of the principal facts, and will venture to 

 suggest some views as to the probable cause of them. 



' Edinburgh New Philosophical Journal for January 1844, p. 188. 

 VOL. XV. PART TV. 8 15 



