.85,. THE NORFOLK BROADS. 351 



the land had reached its present level the area was occupied by a great 

 estuary, the arms of which ran far up the courses of the three rivers. 

 Probably before the subsidence had reached its maximum, the 

 estuary had commenced to shoal, and in this case the silting was 

 controlled by a factor which caused it to proceed on very different 

 lines to those upon which the process has been carried out in other 

 English estuaries. The nature of this factor we will now consider. 



If one stands upon the sand dunes along the Norfolk coast as, 

 e.g., at Horsey, and looks out seawards, one notices lines of breakers 

 parallel to the shore. These are due to shoals, and if we examine 

 them, the coarsest material is found at their north-west end, indi- 

 cating that the movement of the drift and beach material is here 

 from north to south. The explanation of this movement must be 

 sought in the peculiar circulation of the tide in the southern part of 

 the North Sea : the main tide sweeps round the north of Scotland, 

 and being concentrated by the contraction of the sea, it strikes with 

 full force against the projecting coast of Norfolk, and drives along 

 it to the south. When the northern tide begins to lose power, the 

 southern tide that has been piled up in the English Channel forces 

 its way into the North Sea, and as its passage through the Straits 

 of Dover has given it a north-easterly set, it consequently follows 

 the Continental coast. The circulation in the south part of the 

 North Sea thus forms a great eddy, the tide sweeping south along 

 the East Anglian coast, and returning along the opposite shores where 

 the main projections, such as that of North Holland continued by 

 Texel and other islands, point to the north. The fact that the 

 tide practically always flows southward along this part of the English 

 coast, has the effect of piling up the sediment on the north sides of 

 the mouths of the rivers; and the gradual continuation of this action 

 results in pushing them further and further to the south. Thus the 

 Yare now opens at Gorleston, two miles to the south of Yarmouth, 

 instead of its original mouth at Caistor, three miles to the north. 

 Yarmouth itself was crossed during the passage, and the site of the 

 present watering-place was a submerged shoal so late as 1000 a.d. 

 Similarly the Aide, which opened at Aldeborough, on the north side 

 of Orfordness, has cut a new course behind the London Clay hill at 

 that point, and now opens to the south of it. The mouth of the 

 Waveney was no doubt once at Lowestoft, but as this was barred, 

 and as it was prevented travelling south by high land, it turned north 

 and joined the Yare. The Hundred Stream is reported by tradition 

 to have opened to the sea at Horsey, and such is by no means im- 

 probable ; if so, its mouth was blocked, and it had to reverse its flow 

 and become a mere tributary of the Bure.-^ 



■• Cases of the reversal of flow of rivers are rare, but well-authenticated ones 

 are known. See, e.g., the classical case of the Rhine, Sir A. C. Ramsey. Quart. 

 Journ. Geol. Soc, vol. xxx., 1874, p. 81. 



