428 Mr. R. C. Taylor on the Geology of East Norfolk. 



tioned these, out of many of a similar description, the com- 

 paratively insignificant height to which the sand has hitherto 

 been drifted on Yarmouth Denes (dunes or downs), will 

 scarcely be considered deserving further discussion. At all 

 events it may be stated, since the foui'teenth century the ope- 

 ration has proceeded unceasingly, and may at a future period 

 become a formidable evil to that town. It is an historical fact, 

 that part of the ground within the limits of the Burgh is arti- 

 ficially raised. The ramparts round the inside of the walls 

 were constructed in 1663, from " tliose little sand-banks which 

 the sea and easterly winds had raised on the denes." 



It is a well known fact, proved before a committee of the 

 House of Commons during the last and present session of par- 

 liament, that the chief portion of the eastern marshes is even 

 now eighteen inches to two feet below the surface of the rivers 

 which pass through them, and that the water is artificially 

 kept out by embankments and draining mills. Consequently, 

 were the operations of these to be suspended, the valleys 

 would, even under the present circumstances as to the ad- 

 mission of tides, be overflowed about the same depth as the 

 unembanked Lake of Breydon. 



All the tidal waters that proceed up the various streams and 

 tliffuse themselves over Breytlon Lake, must previously pass 

 through an opening or water-way only about 150 feet wide at 

 Yarmouth bridge ; and such are the obstructions so narrow a 

 passage and the bar present to the ingress of the tide, that an 

 eminent engineer has recently reported that the height of high- 

 water above Yarmouth bridge is from one to three feet lower 

 than at the haven's mouth. The average rise of the tide 

 throughout the year at Yarmouth bridge being only three or 

 four feet, the absolute quantity of sea water passing into the 

 interior is therefore very small. 



Let us contemplate the effect produced, when an immensely 

 increased volume of water pressed forward, unimpeded, through 

 several wide openings, as in the former state of the Saxon 

 shore. It would be contrary to all analogy to assume that 

 these inlets ever existed upon such an exposed coast, and 

 amidst such moveable materials, without bars at their mouths, 

 like the deep Forths of Scotland, to which they have been 

 improperly assimilated. Nevertheless, a large body of sea 

 water would advance, and be foi'ced, in proportion to the width 

 and depth of those openings and the absence or presence of 

 obstructions, more or less far up the valleys. The waters of 

 wide aestuaries being impelled by the force of the tides fi'om 

 behind, and being restricted in their channels as they proceed 

 by the contracting high grounds, actually attain a considerably 



hijiher 



