36 TUTIRA 



upright walls ; the third, erosion by percolation of rain - water plus 

 erosion by springs, and supplemented further by a certain slight slow 

 widening as well as by a deepening of the valley no longer within 

 exactly perpendicular walls. 



These conclusions have been reached by working from considerable 

 heights above sea-level downwards. They can, I think, be proved, to 

 use an arithmetical term, by ascent. The reader has but to trace the, 

 course of the main streams, to follow up their tributaries, lastly, to 

 mark the sources from which the tributaries themselves are fed. Our 

 conclusions too have been reached by deduction. Corroboration by 

 the dry light of the inductive method is easy. We can drop ideal 

 sections and consider actual conditions. 



Shrinkage shows itself in every stage ; there are endless modi- 

 fications, but although details differ, the general principle is unmis- 

 takable, the pattern clear. Beginning with instances where the sagging 

 is still in its preliminary stage, a fold can be instanced on the Heru-o- 

 Tureia block parallel with and to the south of the steep horse-trail 

 known as the " Zigzag." Although close to the enormous gorges of 

 the highest range on Tutira, this particular narrow fold remains but 

 a fold ; on the other hand, in the " Waterfall " paddock the cliffs are so 

 hummocky as to have remained innominate. The " comb " pattern is 

 hardly recognisable ; teeth and interstices alike are so little in evidence 

 that the plough has passed over both. Again, the laps of the " Second 

 Kange " have sagged so little that only the outlines of the cliffs show 

 beneath the humus covering ; the teeth have not yet broken through 

 the gums. 



On the " Sand Hills " the interstices are extraordinarily wide, whilst 

 the back of the "comb" is less emphasised than usual. On the "Tutu 

 Faces," where the " teeth " are set particularly near to one another, folds 

 are to be found varying from those hardly noticeable to others enclosed 

 by cliffs from ten to fifteen feet high. The " Nobbies " range, a duplicate 

 in miniature of the Heru-o-Tureia, is gapped in lines more nearly parallel 

 to one another than elsewhere. Everywhere, however, erosion has taken 

 place subterraneously, subcutaneously ; be the sags deep or shallow, 

 wide or narrow, salient or unseen, the ancient original humus still 

 blankets the surface. 



Where the " comb " system is distinctly marked on Tutira, there 

 is little more to say of its peculiar system of underground drainage, 



