THE NEW ZEALAND SOUND BASINS 



33 



2. The channel bottoms of the incising canyons show gentle 

 grades almost to the very heads of the valleys ; huge rock basins also 

 exist, the floors of which are frequently lower than the valley bottoms, 

 and are at times far below base- or sea-level itself. 



3. Convergence of steep canyons is pronounced, and often marked 

 by the association of huge rock basins, straightened and often per- 



FiG. 8. — Crooked Arm. More advanced stage of spur truncation than in Fig. 7. 



pendicular lower canyon walls (Figs. 5, 6, and 9), surmounted by 

 steep, even slopes. 



4. An immense precipitation is shown for this area, the average 

 probably exceeding 150 inches per annum. 



5. Whatever the nature of the agency which imposed these peculiar 

 topographic features on the landscape, the recency of the same and 

 the character of the rocks acted upon have permitted of no alteration 

 in their general appearance. 



The problem under discussion is a physiographic one, inasmuch 

 as it deals with the origin of present-day surface contours. 



