KNOWLEDGE. 



January, 1913. 



question Professor Oliver, to whose article we are 

 indebted for the information which is to follow, gives 

 preliminary attention. 



Shingle banks arise when suitable materials from 

 the waste of the shore find their way into the 

 currents which run along the coast. In these shallow 

 waters the shingle is always on the move owing 

 to the action of the waves, 

 and is kept steadily moving 

 in the direction of the current. 

 Heavy seas, and on-shore 

 gales pile the shingle up above 

 high-water mark and thus 

 form the banks or beaches. 

 These are of three types : — 



(1) The Fringing Type. 

 — This is the simplest case, 

 the shingle being directed by 

 the shore current and forming 



a strip in contact with the 

 land on top of the sand beach. 

 There are many examples of 

 this kind of shingle beach in 

 Sussex. 



(2) The Shingle Spit. — Suppose now that the 

 coast line suddenly changes its direction, and turns 

 inwards, while the current running along it still goes 

 shooting past the point of deflection. The drifted 

 shingle accumulates along the line of the current 

 to form a bank or causeway, often reaching a 

 length of several miles. This type is attached to 

 the shore at the point where the current leaves 

 it, and then runs straight on or with a gentle 

 curvature towards its 

 growing distant end. 

 It generally turns 

 inward. Examples are 

 Hurst Castle Bank 

 and Blakeney Bank. 



(3) The Bar — 

 When a shingle spit of 

 this kind continually 

 stretching and grow- 

 ing touches land again 

 it forms a bar. Por- 

 fessor Oliver notes 

 that the Chesil Beach 

 which is so conspic- 

 uous a feature at the 

 Isle of Portland (its 

 eastern extremity) 

 seems at first sight to 

 belong to this 

 category; but its 



exact status is still a matter of discussion. 



(4) The Apposition Type. — Sometimes the 

 pushing current by changing its direction or force has 

 not enough strength to carry the shingle to the end 

 of the bank ; or else the end of the bank has been 

 hooked inwards so far that the current cannot reach 

 it. In these cases the spit cannot lengthen and the 

 additions of shingle are merely dropped by the 



Figure 2. Apposition type of Shingle Bank. 

 A, B, C, indicate a point of land; the arrow 

 marks the direction of coastal drift ; the suc- 

 cessive shingle banks lie to the right of the 

 figure ; modified from F. Drew. 



Scale ofhtxlzs 



Figure 3. Sketch Map of the Chesil Bank (after Bristow and 



Whitaker) to show the relations of Bank, Mainland and Fleet. 



Shingle is drawn thick black. 



current on the flank of the forming bank. These 

 additions may be lifted above the top of the bank by 

 a high tide or gale. In this way a succession of 

 more or less parallel banks may be thrown up one 

 behind another, with the result that very extensive 

 areas of shingle are produced. 



The outstanding example of this type is 

 Uungeness (see Figure 2). 



To return to the Shingle 

 Spit. As already explained, 

 the point at which the 

 spit leaves the shore is a 

 salient angle of the main- 

 land. The axis of the bank 

 runs along the line of the 

 current and generally presents 

 a gentle convex curve to 

 the sea. As a rule this 

 type runs at some distance 

 from the shore line, the 

 protected area between bank 

 and shore being occupied 

 by salt marshes subject to 

 the tides. These salt marshes 

 are practically a kind of littoral shelf on the edge 

 of which the shingle rests : and they often offer 

 facilities for reclamation. The spits which protect 

 them most often pursue their course from the point 

 where they are attracted to the mainland, without 

 any alteration in character beyond an occasional 

 narrowing or widening. The Aldeburgh bank in 

 Suffolk goes right on to its apex without alteration. 

 But usually, towards the apex, there 



appears a marked 

 landward deflection 

 in the form of a 

 hook : and frequently 

 several hooks are 

 present in close prox- 

 imity (Hurst Castle, 

 Hamstead, Dover) : 

 while, as at Blakeney, 

 there are occasionally 

 extremely complex 

 systems of hooks (see 

 Figure 1). "One of the 

 hooks at Blakeney 

 has in recent years 

 become exposed to 

 gales from the north- 

 west in consequence 

 of the wasting of 

 the top of the main 

 bank which formerly 

 masked it. At Easter, 1911, a succession of heavy 

 gales from this quarter removed the terminal portion 

 of this hook and deposited the eroded material as a 

 new bank one hundred and forty feet long, fifty feet 

 wide, and over six feet high, at right angles to the old 

 hook, on its lee side" (see Figure 5). Professor 

 Oliver concludes that a shingle spit has quite definite, 

 successive phases. There is the phase of youth in 



