MR. PALMER ON THE MOTIONS OF SHINGLE BEACHES. 573 



and their accumulation about any particular place prevented ; and by simply reversing 

 that principle, a method of accumulating" or retaining the shingles, where they are 

 wanted, is also suggested, viz. by the reduction of the descending force of the 

 breakers. 



The effect of confining the retiring breakers to a column is also exemplified in an- 

 other manner, when the waves are driven directly upon the beach by a moderate 

 wind, or such as would produce the accumulative action. A succession of waves, 

 acting over the same lines of the beach, soon forms a slight depression, which con- 

 tinues increasing until it becomes a definite channel. The whole line of beach being 

 thus acted upon, it assumes the form of a series of banks parallel with each other. 

 The waves do not then recoil in a dispersed form, but, having broken, are again col- 

 lected and returned through the channels, and remove all loose matter from them. 

 While in this state, the beach has no progressive motion, bat continues (to use a mili- 

 tary term) " marking time," until, from the change of wind, an oblique direction is 

 given to the motion of the waves. 



Section 5. 



The progressive motion of the beach may be easily traced along the coast as far as 

 the bay called Sandwich Flats. See Plate XXVIII. The general character of the motion 

 during its progress is that which is most favourable, under every circumstance, to 

 the chances of becoming securely deposited. Every part of the coast is attempted by 

 every variety of motion in its turn, until a place of final security is discovered. 



The locality of Romney Marsh appears to have afforded the sought-for shelter, and 

 now exhibits an extraordinary example of the accumulation, which, having been com- 

 bined with sand, silt, and vegetable soil derived from other sources, has long been 

 considered an acquisition to our surface of considerable value. 



Although this tract has continued increasing to the present day, yet a great quan- 

 tity of the beach travels past it, and we do not find any other accumulation of much 

 extent between that and Sandwich Flats, beyond which there is no further trace of 

 the shingle which we have so far followed, the pebbles to the northward of these flats 

 being evidently those derived from the cliffs near about them. 



On the approach of the shingle to the Sandwich Flats, it becomes gradually dis- 

 persed, owing to the increasing inclination of the plane, until it seems to disappear. 

 A considerable extent of these flats has attained a height very little inferior to that of 

 the high-water mark of spring tides ; and it is so nearly horizontal, that the water 

 does not partake of that undulating motion upon it which has before been adverted to. 



On the Sandwich Flats there is a continual deposit of soil and silt, brought there 

 from the interior of the country by the river Stour, and which, after its exposure to 

 salt water, is particularly suitable for permanently uniting all the coarser or larger 

 fragments with which it may become intermixed. So much of the materials which 

 have composed the beach as may be conveyed to the higher parts of these flats are not 



MDCCCXXXIV. 4 E 



