620 MR MILNE ON A REMARKABLE OSCILLATION OF THE SEA. 



(14.) On the 19th August 1812, at Folkestone, the sea rose and fell 3 feet per- 

 pendicular three times, in less than a quarter of an hour. l 



(15.) At Portsmouth, on the 4th March 1818, in the evening, there were the 

 highest spring tides (at about 10" 40' P.M.) ever remembered. At Hull, the fol- 

 lowing phenomena were observed : At high water, about 4 h 30' P.M., the wind 

 then blowing from the SW., with moderate weather, the tide flowed at the dock- 

 gates 18 feet 6 inches. After the tide had fallen from 1 to 2 inches, it began 

 to flow again to the height of 4 or 5 inches. A tempestuous night ensued. 

 The wind blew a heavy gale from the SW., and at high water (5 A.M.) next 

 morning, the tide flowed only 14 feet 1 inch, although, the spring tides having 

 put in, the water ought to have flowed to a higher level than on the preceding 

 evening. 



From the accounts given by Mr HOWARD of the weather on the day in ques- 

 tion, it appears that there was a very severe storm in every part of England. In 

 the Isle of Wight, it seems to have continued from 4 h 30' P.M. to II 11 30' P.M. 

 In London, it continued from 8 P.M. till past midnight. At Yarmouth, it com- 

 menced about 8 P.M. 



Mr HOWARD observes, in explanation of the tidal phenomena at Portsmouth 

 and at Hull, that, " if we suppose this gale arriving suddenly from the southward 

 (which appears to be the fact), a swell produced by the compression of the water 

 in the Channel and Straits of Dover, may have been propagated on the surface of 

 the sea northward, with greater swiftness than the storm could make its way 

 across the land to Hull. The arrival of this swell at the critical time of the tide's 

 turning, accounts for the first fact. With regard to the second, it is matter of 

 historical record, that an off-shore wind (as this was at Hull), if it blow long 

 enough, and with sufficient force, may so remove the sea from the coast as to 

 suspend a whole tide. Portsmouth and Hull were therefore placed, on this occa- 

 sion, by the operation of the same cause, in opposite circumstances. The one had 

 the highest tide ever remembered, and the other, a tide later, nearly 5 feet less 

 water than was expected." 



The only difficulty in the way of this explanation, arises from the fact, that 

 the effects produced by this supposed swell manifested themselves at Hull sooner 

 than at Portsmouth. If, however, the gale and the swell both came from the 

 southward, they should have been first felt at Portsmouth. 



(16.) In July 1832, I understand from Mr EDMONDSTONE, the sea was at the 

 Shetland Islands in a state of oscillation similar to what occurred in July last. At 

 this time, it appears, there was a furious gale of wind, which continued for several 

 days, and was fatal to many fishing boats. 



(17.) On the 12th September 1841, at Kilmore, on the south coast of Ireland, 

 the inhabitants, about noon, were attracted by a number of short, loud, but rather 

 smothered reports out at sea, which they supposed to be cannons fired by a ship 



1 Gentleman's Magazine. 



