248 Transactions . 



to over 1,000 ft., while a few peaks reach to 1,500 ft. and more. The 

 texture of dissection is medium to tine. 



Cycles of Erosion. 



All the forms recognized appear to be due to stream-action alone. Three 

 sets of forms are recognized, corresponding to different positions of base- 

 level, and it is possible that forms are present corresponding to other pauses 

 in the movements of uplift. It is evident that such pauses did occur, for 

 remnants of coast platforms are found, in places, one above another (see 

 p. 255). Shortness of a period of standstill during which erosive pro- 

 cesses work is not in itself a reason why the period should not be dignified 

 with the name of " cycle." Huntington and Goldthwaite* have pointed 

 out the analogy between the term " cycle " applied to an erosion period 

 and the term " life " applied to the period of existence of an organism. 

 ' Life in one signification is the complete existence of a normal organism 

 during which it passes from infancy, through youth, maturity, and old 

 age to death. The life of man in this sense is seventy years. In another 

 sense life is merely the actual period of existence of any specific organism. 

 An animal whose life in the first sense of the word is fifty years may die 

 the day that it is born, but nevertheless we say that it has finished its 

 life. A cycle in the first sense is ideal and can never be realized, since 

 infinite time would be required to reduce any land-mass to the condition 

 analogous to death — that is, to a plain at absolute base-level. In the 

 second sense any region that is subjected to erosion during a definite 

 period, no matter how short, passes through a cycle and can be de- 

 scribed in terms of age and development." The term " chapter," proposed 

 by Davisf for an unfinished cycle, has not come into general use. A 

 number of such brief cycles, corresponding to pauses during the earlier 

 part of the period of uplift in the Wellington district, may have left traces 

 on the topography not yet obliterated, and the number of nearly flat- 

 topped ridges of varying height which lie spread out to the west of 

 Kaukau Peak suggests that in the future, with detailed work and accu- 

 rate mapping, some at least of them may be recognized with certainty. 

 The writer, however, feels justified at present in grouping the observed 

 features as belonging to only three cycles. 



The earliest cycle of which a record is preserved by existing topo- 

 graphic features will be called the Kaukau cycle. Base-level stood 

 perhaps 800 ft. or 900 ft. higher than at present. 



To the next, or Tongue Point, cycle belong most of the broad 

 features of the landscape as seen from a high point of view. Base-level 

 stood about 250 ft. higher than at present, and during the cycle the 

 most extensive of the elevated coastal platforms, including that at Tongue 

 Point, were cut (see p. 255). 



It was between the Kaukau base-level and the Tongue Point base- 

 level that other pauses occurred that are mentioned above. They were, 

 no doubt, brief, and the Tongue Point cycle itself was of relatively short 

 duration. It is, however, of importance on account of the very recent 

 date at which it was interrupted. 



There is, lastly, the present cycle, with present sea-level as base-level. 



* Bull. Mus. Comp. ZooL, Harv., vol. 42, No. 5, 1904. p. 239. 



t ' : Physical Geography as a University Study," Journal of Geol., 1894, p. 66. 



