consists of loose materials _, part of this material is being eroded. 

 At other places, however, no materials are being carried away but 

 material is deposited. From these observations MTo Cornaglia 

 developed a theory according to which the coasts where material drift 

 occurs can be divided into "flat coasts" and "steep coasts" o The 

 steep coasts are retreating unless they consist of a material of 

 strong resistance 5 because no material is deposited » Flat coasts on 

 the other hand are advancing o Mro Cornaglia states that the limit 

 between steep coasts and flat coasts is where the bottom of the ocean 

 slopes at about 1 to 4.0 o 



If a particle lies on a sloping ocean bottom^ gi'avity will try to 

 pull the particle out into the deepo The outward pull will bs stronger 

 the steeper the bottom is o This tendency to seaward movement can be- 

 combined mth the influence of the waves as shown in Figure 2o When 

 the bottom is sloping it is, harder for the Tv-aves to move the particle 

 lan(iward and easier to move it to sbHo Only minimum speeds are now 

 needed „ On flat coasts the particles move landward, but on coasts 

 with a certain steepness the space f'-b-g' is greater than the space 

 h'-d-i'_, T/hich means that the naterial moves seavrardo 



Finally, it may happen that tte two spaces are equal in sisco 

 In this case the particles will be moved equally toth ways over a 

 middle position, and the resultant transport will be nil» As the 

 influence of the waves on the bottom decreases with the depth of the 

 water, while the inlTuence of gravity is unchanged j, this position of 

 no resultant movement for a certain steepness of tte bottom, etco will 

 occur only at a certain depthj, or depth curare ^ which MTo Cornaglia 

 calls the "neutral line" » Inside this line the particles mjove land- 

 ¥rard and outside it they move seaward „ 



It will be understood that on each coast there are to be found 

 numerous neutral lines, as there is a neutral line for each size of 

 wave, each size of material^ etoo It is^, of course,, especially 

 interesting to know the position of the neutral line which is so far 

 seaward that beyond it even the finest piece of sand will be Koved 

 seaward, even when the strongest hurricane is blowing toward the 

 shores o On very steep coasts, ac:;ording to MTo Cornaglia^ this 

 neutral line will be so close to the coast line that the whole front 

 of the shore is eroded, provided th^.t the material of the shore is 

 not very hard. This is often the case around headlands as tte slope 

 of the bottom is most often steepest hsreo At these places one can 

 vdry seldom find despoited materials o 



This is Mro Cornaglia ^s theory in brief j it seems sour.d, bat e:<- 

 amination shoT/s it is not valid „ It seems to be unimportant in the 

 movement of a particle deposited on the bottom, whether the latter 

 slopes at 1 bo 10, 1 to /^O, or 1 to 70o A simple calculation shows 

 that- the influence of gravity is minimal compared to the pressure 

 created by the waves « iurthermore, experience shows- that deposits 

 ar3 to be found on very steep coasts (Stevns, Mpen and other places). 

 The fact that deposits are seldom to be found near headlands can be 



