1820.] Philosophical Transactions for IS19, Part II. 445 



Anderson's paper is to combat this opinion, and to give what he 

 considers as the true account of the tides in the straits of Dover, 

 and an explanation of the phenomena. He cruized for two 

 years in these straits, or their neighbourhood, and had in conse- 

 quence an ample opportunity of making himself acquainted with, 

 the tides. The following were what he observed to take place r 

 Between the easternmost point of Fairleigh and the North. 

 Foreland, the tides rise from seven to eight feet higher than on 

 either side of these points. After the tide has run east for two 

 hours and three quarters, it is high water by the shore, and the 

 water continues to fall during the last three hours and a quarter 

 that the tide runs east. When the tide begins to run west, it 

 is half ebb ; and the water continues to fall for two hours and 

 three quarters after the tide has begun to flow west, at which 

 time it is low water. The course of the tide continues to flow 

 westward for two hours and three quarters longer, during which 

 time the water gradually rises by the shore, making nearly half 

 flood by the land at the time the current of the tide ceases to rua 

 to the westward. The tide then turns to the eastward, and after 

 it has moved in that direction for three hours and a quarter, it is 

 high water by the ground. 



Such are the phenomena. They are obviously incompatible 

 with the old explanation ; namely, that they are occasioned by 

 the meeting of the two tides moving in opposite directions. 

 Capt. Anderson ascribes them to the sudden narrowing of the 

 Enghsh channel at Dungeness to a space not amounting to half 

 its former breadth. This occasions the waters to rise in that 

 narrow channel, and to continue to rise till they find a vent, 

 which happens after the tide has flowed for three hours and a 

 quarter from the west. By this time, all the sands without the 

 North Foreland are covered, and afford a greater vent for the 

 discharge of the accumulated water. The extensive flats also 

 on both sides the channel, on which the sea now flows in hke a 

 torrent, demand a greater supply than is received through the 

 Dungeness passage. Hence, from this period, the water is 

 drawn off from the places where it had accumulated, and begins 

 to fall gradually by the shore during the remaining three hours 

 and a quarter, in which the current of the tide runs to the east- 

 ward, making half tide of ebb by the ground within the Straits 

 of Dover and the two reservoirs, or basins, when the current of 

 the tide ceases to run to the eastward ; at which time it is high 

 water every where without these limits, allowing for the equalities 

 of the coast, the water having now generally acquired a level. 



When it is high water without the North Foreland, as at 

 Margate, the Kentish Knock, &c. and the tide, which is the true 

 or regular ebb tide, returns to the westward through the Downs^ 

 the water still continues to fall within the Foreland, and on to 

 the easternmost point of Fairleigh, for two hours and three 

 quarters of the first of the true or regular ebb tide ; because the 



