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THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL, 



195 



MOVING BEACHES. 



" I acknowledge no authority but that of observation." — Linn. 



The attention of scientific and practical men has for many years 

 been directed to the action of the sea, and tides which give motion 

 to tlie shingle, and otlier matter composing the beaches of our island, 

 and this important affair has been a subject of much specidative opi- 

 nion, but it appears not hitherto to have received that systematic in- 

 vestigation which is essential, hideed the contrariety of opinion so 

 often expressed on this subject, seems to indicate an absence of a 

 satisfactory mode of inquiry to obtain a practical and safe deduction. 



Tlie coast of Kent and Sussex seems to have attracted attention to 

 the subject of the commonly called /raedtoig 'jeacA, under an erroneous 

 presumption that such occurrences are peculiar to those shores, but 

 experience, the result of practical observation, demonstrates that where 

 nature is placed tmder similar circumstances, as to her formation, and 

 the operations of the wind, sea, and tides, there she is immutable in 

 her results, and therefore in all parts of the globe, the movement of 

 the beach is the same as is observed on the Dover, or Channel shores; 

 but in no instance throughout the world has a beach been found to travel 

 along the line from one point to another of a shore or coast. 



We proceed then to prove the egregious error so commonly adopted 

 as to the /rore/Zwg of a beach — divesting our statement of all terms 

 thati do not belong to, or which are not generally understood by 

 nautical and other persons that take an interest in this affair. 



The flood in the British channel sets in from the westward, and runs 

 with considerable velocity in many parts to the eastward; it is during 

 the time of this flood, with winds blowing from particular points of the 

 compass, that accumulation of beach occurs. 



The margin of all coasts tlu'oughout our globe having beach forming 

 the line of high and low water mark, is constantly moving, so as to alter 

 the angle considerably between the two lines. The wave falling on and 

 moving the beach (for there is no movement of the bed of the ocean 

 where the sea does not ^rea^-). talces it up, and deposits it between the 

 high and low water mark, in extraordinary tides and winds, and high 

 seas, simultaneously, and with mathematical accuracy, along a line of 

 beach to the extent of many miles, the largest pebble or shingle, and the 

 greatest quantity, forming the same into a ridge or bank, in a line pa- 

 rallel to the high water mark (Fig. 1.) ; from the commencement of 

 the shingle west, to its terminus east. A beach of sand is operated on 

 precisely in the same way, but if the beach travelled in a right line 

 with the coast, from west to east, than would the line of high water 

 beach be on an inclined plane from west to east, and in time a 

 mountain would be formed at the eastern terminus of the beach. (Fig.2.) 



FiK. 1. 



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Fig. 2. 



It is correctly stated that a groin or any natural projection beyond 

 the line of coast, intercepting tlie tide in its passage eastward, would 

 have its weather, or to speak nautically, its flood, or western side filled 

 up in the form of a right angle, but that its east, or lee side vifould be 

 without any extra accumulation, to a certain extent this is quite true ; 

 this deficiency is in proportion to the quantity left on the weather 

 side, whicli but for the projection or groin would of course obtain the 

 quantity so deposited on the west side (Fig. 3.), but at a short distance 



Fig. 3. 



east of the groin, or on its lee side, the beach assumes its natural form, 

 and the line continues till it meets with another similar interception. 

 So then the only object obtained is an additional accumulation west- 

 ward, less its amount eastward of the groin, and let it be remembered 

 that this eastern continuation goes on, although the accumulation 

 on the western side of the groin has not filled it up, to its seaward 

 end, and therefore does not pass round it. Beachy Head, Dungeness, 

 the south and north Foreland are all natural groins, but the Bays east 

 of the Head to leeward, the eastern side of Dungeness, the east Bay 

 of Dover, Deal beach, (the highest of all modern accumulation, notwith- 

 standing the projection of the south Foreland as a groin,) Margate, 

 Heme Bay; &c., all simultaneously accumulate, despite of those ex- 

 tended projections. 



The fact of the angular formation of the accumulation at the groin, 

 at once proves the direction the beach takes when thrown up by 

 the sea. As the sea, at all times during the prevalence of the accumu- 

 lating tide and wind, falls on the shore at an angle of 45°, so what it 

 lifts up, it throws on in the same direction, but if the beach moved in 

 a right line with the coast, it would fall on, and form at the groin in a 

 like line. 



The next practical fact we adduce to disprove the hypothesis of a 

 travelling beach is, that wherever a line of shingle beach is inter- 

 cepted by chalk, rock, sand, or any other material, of which such 

 part of the coast may be composed, there no pebble or shingle exists. 

 On the rocky shore west of Dover, in which there are many inter- 

 stices, receptacles for various shell fish, there is no shingle or pebble 

 found in any part of those rocks ; if the beach at Dover, &c., came 

 from the westward, it must pass over those rocks, and consequently 

 in its transit some would be deposited in the holes of the rock — 

 but it is not so. 



Captain Martin of Ramsgate, in his recently published book on that 

 harbour, states, that the beach north of Deal advances eastward at the 

 rate of one mile in GO years. A map of this part of the coast published 

 GO years ago, is before us, and Sto}ie End, (meaning the end of the 

 shingle beach, and the commencement of a sand and muddy shore,) is 

 marked thereon, and although GO years have passed away since the mark 

 was made. Beach End remains in statu quo. About 90 years have ex- 

 pired since the commencement of Ramsgate harbour, and therefore 

 according to this gentleman's statement, the beach in the vicinity of 

 Sandwich Haven, during this elapsed time, has advanced towards the 

 mouth of Ramsgate harbour, and in time would block it up, first having 

 placed itself before the entrance of Sandwich harbour. 



In a Report of the Commissioners of Ramsgate harbour, made in 

 1755, they stated " that from the east there is a drift of large shingle." 

 It would be well if recent assertions were sustained by proofs. 



Our next fact in this controversy is, that the pebbles composing 

 beaches differ much in quality, colour and size. Those at Dungeness, 

 differ from those at Dover, &c., and therefore the latter cannot be sup- 

 plied from the former. 



Having said what we think is sufficient to expose the error, in the 

 supposition that beach travels from one point to another, let us pro- 

 ceed to show the real extent of moving beach; we have already said 

 that the sea takes it up, and lodges it on the shore at an angle of 45°, 

 (the angle at which the wave falls when it does not roll in perpendi- 

 cular to the shore) ; this inclination of the wave is aided by the flood 

 tide, which gives the beach so lifted up, an easterly direction on the 

 Kentish coast, inclining with the flood as it does on all other shores. 

 On a change of wind, and with an ebb tide, the accumulating power 

 ceases, and is succeeded by the drawback, or scattering power, and the 

 beach recedes to its former lodgment, going off in the opposite angle 

 or direction — and there it remains till the accumulating power again 

 removes it. This is the extent of a moving beach. 



A shingle beach is not carried by the drawback wave so far seaward 

 as is a sand beach ; the gravity of the latter being more than that of 

 the former, it is drawn often 50 yards beyond the low water mark, and 

 there forms a bank, called by pilots, and beachmen the outer bank, over 

 which it is with much difficulty and danger passed by boats. This is 

 as we have said like the shingle brought up by the accumulating wind 

 and tide, and lodged between high and low water mark, simultaneously 

 along an entire line of coast. The shingle beach atOffordness, (formed 

 similar to Dungeness), along the coast of Norfolk, and Suffolk, round 

 the British Isle, and throughout the world is operated on in a like 

 manner, so that the opinion of travelling or moving beach being peculiar 

 to any particular coast is erroneous. Nature is, we repeat, immutable 

 in her results, acted upon by similar causes throughout the world. 



It has been asked ho >v do you account for the increase of beach ? 

 Observation has induced us to be of an opinion that there is a pro- 

 gressive principle of accretion in the pebble or shingle. Quite small 

 tine beach is sometimes in great quantities found near the low water 

 mark, and appears to be the nucleus of the larger stone or pebble. 



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