BY B. C. ANDREWS. 507 



(3) The glacial floods of New Zealand, 



To establish the fact that the lake and sound basin contours 

 of South- Western New Zealand are practically the expression of 

 ice-flood attack along preglacial channels and not the result of 

 recent subsidence, will be to justify the introduction of a brief 

 account of their origin into this discussion, for it will then be 

 seen that they represent the early attack of streams on lofty 

 plateaus, such attack — even in the enormously elevated land 

 blocks of New Zealand —having given rise at the outset to deep 

 canons, with floors at times developed thousands of feet below sea- 

 level, and that also before such time as lateral corrasion had found 

 opportunity to appreciably widen the canons themselves. This 

 would materially help us in our efforts to understand the origin 

 of the peneplain, since it would demonstrate the futility of 

 expecting peneplains to be formed, in homogeneous masses, at 

 heights differing at all materially from the main base-level. In 

 the following brief explanatory notes the details of movement as 

 exhibited by glaciers need not concern us. Professor T. C. 

 Chamberlin* appears to have satisfactorily shown that glacial 

 motion " involves only the momentary liquefaction of minute 

 portions of the mass, while the ice, as a whole, remains rigid, as 

 its crystalline nature requires. Instead of assigning a slow 

 viscous fluidity, like that of asphalt, to the whole mass, which 

 seems inconsistent with its crystalline character, it assigns a free 

 fluidity to a succession of particles that form only a minute 

 fraction of the whole at any instant." It will, however, be 

 sufficient for our purpose to note that the general aspect of glacial 

 motion is analogous to that of a viscous mass. 



The difficulties apparently attending the conception of a stream 

 origin for the lake and sound basins of New Zealand appear to 

 be: — 



(1) The apparent impossibility of excavating rock basins, thou- 

 sands of feet in depth below main base-level, by stream-action. 



* T. C. Chamberlin p. 11. 



