stand of sea-level, different processes must obviously have been involved 

 in their formation. This does not seem consistent with Dr. Fairbridge's 

 scheme of shore erosion, but it is so with my own. 



■ I may remark here that in New. Zealand there has been so much 

 fairly recent block-faulting that correlation of any particular bench level 

 with a particular phase of the Ice Age is peculiarly hazardous. 



I should hke to deal next with platforms of the " Old Hat " type, 

 which occur solel}'^ in impermeable rocks free from open joints, readily 

 amenable to weathering, and in very sheltered waters. Their surface lies 

 a foot or so below high- water level and they are the product, as Dr. 

 Fairbridge correctly states, of subaerial weathering. I personally regard 

 this surface as a level of permanent saturation below which subaerial 

 weathering cannot proceed. Dr. Fairbridge, on the contrary would 

 carry subaerial weathering down to the level of low water at spring tide.. 

 This manifestly would be possible for permeable rocks or those affected 

 by close-spaced open joints, but, if waves have any appreciable corrosive 

 power, the platform so produced would be eroded yielding a " normal " 

 off-shore platform. If Dr. Fairbridge's views are correct and this plat- 

 form is exposed at its present elevation merely by negative shift of sea- 

 level, then its formation should be independent of the rock in which it is 

 developed, provided that it was amenable to weathering. The nature 

 of the joint fissures and the permeability of the rock should have no 

 importance. The " Old Hat " type of bench, therefore, should not be 

 infrequent ; in actual fact it is by no means common. 



" Storm- wave " platforms are developed only in fairly resistant 

 rocks free from open joints at exposed locations such as headlands subject 

 to attack by vigorous storm-waves and \vhere reefs off-shore cause such 

 waves to sweep upon the shore as surf (or waves of translation). Their 

 surface is from a foot or two to as much as 8 ft. above high-water level, 

 dependent on the vigour of the waves by which they are attacked, and, 

 though initially rough in surface, in time may be smoothed down sub- 

 aerially to the level of shallow pools of water lying on that surface. 



Reasons which have led me to regard these benches as the product 

 of the sea at its present level are — 



tl) One can observe waves thundering on to these platforms during 

 storms. 



(2) The benches never pass far from the end of a headland- towards a 



bayhead. 



(3) When they do so, they decline in level away from the headland. 



Occasionally the change to a lower platform is abrupt. In 

 these cases observation shows that the waves responsible for 

 carving the platforms have had their vigour reduced after 

 passing the headland ; at times this reduction is because of 

 deflection. 



It is clear that the platforms are unhkely to occur in open-jointed 

 rocks, which would be disrupted freely at varied levels by pneumatic 

 and hydraulic pressures. 



In conclusion, I would claim that Dr. Fairbridge has advanced no 

 cogent reason for regarding platforms of the " Old Hat " and " Stonn- 

 wave " type as developed during a period when sea-level was higher 

 than now^ . They therefore have no value in isostatic correlation of shore 

 benches. 



359 



