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CHAPTER V. 



SUBCUTANEOUS EROSION. 



THE original appearance of Tutira has been described. We have yet 

 to trace the agencies by which its contours have been modified. It 

 will be remembered that the station was pictured in the beginning as 

 a serious of plateaux afterwards tilted towards the east, these tilted 

 terraces or canted plateaux smooth and unbroken by fissures. The 

 evolution of the comb system, the development of these fissures, has 

 yet to be described. It has, I think, been brought to light by a very 

 remarkable process of subcutaneous erosion, a process akin to the dis- 

 solution of a dead beast when first the flesh decays, then the skin 

 shrinks and shrivels, whilst only at the last do the bones protrude. 

 In this transformation water has been the chief agent, but before 

 proceeding to state what water has done it will simplify our task to 

 state what water has not done. 



Water has not created the dry cliff system. Water has not 

 scoured out the solid rock of these strange valleys walled in by preci- 

 pice. Both sense and sight forbid the supposition. There is no lateral 

 soakage whatever into them. In hundreds of instances, except the drops 

 that actually fall on to their surfaces from the sky, no extraneous water 

 has ever reached them. Rock erosion by scour has not occurred, because 

 water has been able to pass away from the contiguous lands on either 

 side through beds of grit and sand. The junction of their double walls 

 of cliff is not lanceolate but horse-shoe shaped. It bears no resemblance 

 to the typical commencement of a water-worn ravine. The difference 

 between the width of the valleys as measured from cliff to cliff at two, 

 twenty, and two hundred yards from their beginnings is out of all 

 proportion to the necessities of scour, supposing such a process had 

 ever been at work. Finally, at the mouths of these valleys there exist 



