SUBCUTANEOUS EROSION 29 



no indications of the rock material which must have been deposited 

 had water erosion been responsible for their formation. As regards 

 these chasms, this is, I think, a fair statement of what water has not 

 done. 



The task of water has been to remove by infinitesimal quantities 

 the material deposited between the rock walls ; to flush, if indeed 

 such a verb can be applied to an enormously tardy process, and 

 scour out material already deposited in the valleys ; to render visible 

 what a mightier force had already accomplished. Erosion, in fact, has 

 brought to light, not created, the rock-bound valleys of Tutira. When 

 the plateaux which I have supposed to have been the original shape of 

 the run canted to the east, making the station a series of tilted terraces, 

 these deep interstices had been already moulded. 



About the nature of the force that has severed the sea-floors 

 upon which Tutira sheep now run, yet incompletely severed them, 

 that has severed them, yet not severed them in parallel lines, 

 any suggestions I can offer are little likely to be of value. There 

 seems, however, to have been a twofold motion the one cracking 

 them in lines running north and south, the other incompletely parting 

 these strips or oblongs of country into numerous short unparallel 

 asymmetrical gaps east and west. The fissurings extending north and 

 south are attributable probably to the effects of subsidence as segment 

 after segment canted towards the east. The gaps east and west, 

 with their broad horse-shoe beginnings, are less easy to account for. 

 They may be due to shrinkage by evaporation whilst their rocky 

 material was still plastic ; their shape forbids the idea of cracking or 

 fissuring. 



Although no satisfactory solution can be offered as to their origin, 

 much can be said as to the manner in which they have been brought 

 to view. Each range shows its own slight modification of the general 

 geological plan. In order, therefore, not to confuse the reader and 

 darken counsel with a multiplicity of detail, I propose to work stage 

 by stage from past to present conditions. The reader is invited to 

 contemplate an ideal section of a hill range in the conglomerates of 

 central Tutira before erosion had begun its work. 



In the beginning, then, when the main rivers of Tutira ran hun- 

 dreds of feet above their present levels, the surface of our imaginary 

 section seemed whole, unwrinkled, ungapped, and inclining gently 



