August 23, 1900] 



NA TURE 



401 



frequently the amenities of the beaches of seaside resorts, and 

 their use and enjoyment by visitors, are impaired by structures 

 as ugly as they are useless to attain the object in view, and in 

 other cases the construction of costly works is rapidly followed 

 by their destruction by the sea. 



It is proposed as shortly as possible in this article to state the 

 coriditions that have led to the present state of the cliffs and 

 coast, and the conditions under which the material is drifted 

 along the shore. For the purpose of illustration, the coast-line 

 of the south-west of England between Start Point and the Solent 

 has been selected, as this presents features of unusual interest for 

 the study of coast destruction and the drift and accumulation of 

 beach material. The cliffs between these two points consist of a 

 series of rocks of varying degrees of hardness, showing in many 

 places almost vertical faces to the sea, and ranging in height up 

 to 500 or 600 feet. The destruction of these cliffs leads to the 

 deposit, on the beach at their base, of fragments of rock, or 

 inland gravels derived from their summits, which are converted 

 by wave action into shingle, consisting of pebbles of varying 

 character and size, but generally shaped into the form of flattened 

 ovoids, readily distinguishing them from the angular gravels due 

 to glacial drift, or the rounded pebbles rolled down inland rivers. 



Originally, no doubt, these cliffs descended to the bed of the 

 English Channel with the same slopes as characterise their land 

 faces, and were washed by the deep water of the sea without 

 the intervention of the sand beaches which now stretch from 

 them, and which, where they exist, have an almost uniform 

 inclination along all parts of the coast. 



The present form of these cliffs is due to the destructive 

 action of the waves, or to landslips and weathering from rain 

 and frost. The wearing away has not been regular. Head- 

 lands composed of hard rocks project out boldly to low-water 

 mark and beyond, while the softer rocks which formerly ad- 

 joined them have been gradually worn away, leaving indents of 

 various shapes and depths. 



Some indication of the original position of the coast, and the 

 distance to which it extended beyond the present line, is afforded 

 by the remains of a raised beach, portions of which, consisting 

 of pebbles which have been subjected to marine action, are to 

 be found at Portland Bill on the east of Lyme Bay, at Hopes 

 Nose, near Torquay, at Brixham and in Start Bay on the west. 



These beaches are at a much higher level than the present 

 water-line. The direction of this old beach was located by the 

 late Sir J. Prestwich as running in an unbroken line at ten miles 

 outside the present shore between the thirteen- and twenty- 

 fathom contour. There are also patches of gravel near the 

 nine-fathom contour extending all round the bay at about a mile 

 from the shore. 



The coast-line has been broken up into three principal indents 

 between the two headlands, namely, Lyme Bay, Weymouth 

 Bay and Bournemouth Bay ; the contour of which again is split 

 up into numerous minor bays and coves, the greater number of 

 which have their own peculiar characteristics and contain their 

 own peculiar accumulations of shingle. Two of these shingle 

 banks, namely, the Chesil Bank in Lyme Bay, and that at 

 Hurstcastle at the entrance to the Solent, are, perhaps, the most 

 remarkable accumulations to be found anywhere round the coast 

 of Great Britain ; while at Axmouth is one of the most extensive 

 landslips of which there is any record. The fight between sea 

 and land is continuous and unceasing, with the result that the 

 area of this country is gradually being reduced. 



The rivers which discharge into the sea along the south 

 coast are few and insignificant in character, and are utterly in- 

 capable of transporting from the land the large amount of stones 

 or sand now found on the coast. In some cases they have been 

 blocked up by the littoral drift. A careful consideration of all 

 the circumstances can therefore only lead to the conclusion that 

 some of the results which have been attained must be due to 

 other and mightier forces than those now in existence. These 

 forces may probably be ascribed to the .same agencies that gave 

 to this country the shape which it now assumes, and by which 

 the valleys and rivers were scooped out. 



At the close of the last great Ice Age the melting of the vast 

 bed of snow which then covered this country must have led to 

 large torrents of water escaping seaward, which would carry with 

 them the debris from the rocks broken up by frost and ice, in 

 the shape of boulders, gravel and sand ; and besides leaving de- 

 posits in the valleys and those which are to be found on the 

 summit of the cliffs, would carry the degraded material to the 

 sea and form a talus at the level of the water. This deposit, 



KO. 1608, VOL. 62] 



after the wear and tear caused by the waves during long ages, 

 resulted in the present sand beaches. 



It is certain that the enormous mass of sand which now covers 

 the littoral of the sea cannot have been deposited by existing 

 agencies. The degradation of the cliffs that takes place is quite 

 inadequate to account for its existence ; more especially as only 

 the harder rocks have afToided the material of which the sand is 

 composed, the softer detritus having been carried away in sus- 

 pension to the depths of the ocean. The sand of the seashore 

 consists almost entirely of grains of quartz of a nearly uniform size, 

 and even where flints abound in the sea cliffs and in the shingle 

 on the beach, this material is conspicuous by its absence in the 

 sand of the shore. 



As pointed out in my letter in Nature of November 30 last, 

 only about one-third of the flints lying on the beaches along the 

 south coast, not only in the part dealt with but also on those 

 bordering on the chalk cliff's extending from Brighton to the 

 North Foreland, and in the large accumulations at the Chesil 

 Bank and Dungeness, are derived from the chalk, the colour of 

 the majority of the flints being different shades of brown, &rey, 

 white and red, the former being most prevalent, whereas nints 

 from the chalk are invariably black with a white exterior coating- 

 If the above assumption as to the deposit of land detritus on 

 the coast be correct, it affords a reasonable explanation of this 

 phenomenon. 



Another proof that the large accumulations of shingle along 

 the coast are not due to agencies at present operating, is afforded 

 by the fact that the Chesil Bank and Hurst Bank, where the 

 supply of new material drifting along the coast is limited, have 

 not varied materially in shape or increased in size during the 

 time to which the most ancient records relating to them extend, 

 the fresh supply coming from the cliffs being only sufficient in 

 these cases to make up the wear and tear caused by the waves. 



The supply afforded by the degradation of the cliff's is after 

 all limited in quantity, and only about equal to making good 

 the waste due to ihe constant wave action on the shingle. If 

 from any cause an abnormal accumulation takes place on any 

 particular part of the coast, denudation immediately sets in on 

 the coast beyond. Instances of this are afforded by the ex- 

 tension of the Point at Dungeness and the banking up of the 

 shingle on the west side, which has led to a diminished supply 

 all along the Dymchurch and Hythe coasts. The construction 

 of the Admiralty Pier at Dover has led to the denudation of the 

 coast to the northward along St. Margaret's Bay. The pier at 

 Shoreham Harbour for a time denuded the supply at Hove and 

 Brighton ; and it is found universally to be the case that where 

 the drift has been stopped by the debris from the fall of the 

 cliffs acting as a groyne extending out to low water, or where 

 artificial works have arrested the progress of the drift, the coast 

 beyond has suffered from denudation. 



There is no continuous drift of shingle throughout the whole 

 length of this coast, but the material is confined to the various 

 bays and the banks where it has been accumulated. It has 

 been stated that the land gravel found along the foot of the 

 chalk cliffs at the east end of the English Channel may have 

 been derived from the waste of the gravel beds of the cliffs of 

 Dorset and Hampshire, and that pebbles found on the Chesil 

 Bank have been derived from the coast of Devon ; but an 

 examination of the coast shows that under present conditions, at 

 any rate, this is neither the case nor physically possible. For 

 this to have occurred the shingle must not only have passed the 

 numerous headlands which project into the water, but also the 

 approaches to Southampton and Portsmouth, in which the depth 

 of the channels is from five to ten fathoms. 



Nearly every bay and cove along the coast here dealt with has 

 its own peculiar accumulation of shingle, which does not travel 

 beyond the projecting headland, and in many cases there are 

 long intervals along the shore where the rock is bare. Thus 

 the shingle in Slapton Bay is of a different character from that 

 found in any other part of the same coast. It consists almost 

 entirely of round white quartz pebbles, resembling peas in 

 shape, and averaging from an eighth to a quarter of an inch in 

 diameter. This shingle not only covers the beach, but has been 

 thrown up into a bank, the top of which is above the level of 

 high tides, and has drifted across a deep indent in the bay, into 

 which two fresh-water streams discharge, entirely closing this 

 from the sea and forming it into a fresh-water lake about two 

 miles long. The quartz pebbles of the Slapton beach do not 

 drift beyond the eastern horn of the bay, and are not to be 

 found in the next recess. All along the Devonshire coast 



