510 NEW ZEALAND SOUND (AND LAKE) BASINS, 



bufc to nothing the amount demanded by the Sound depths. It 

 is hardly conceivable that the Sounds area should have been the 

 one spot to have sunk so deeply after the release, of so great a load 

 as it was burdened with, the surrounding and but slightly sunken 

 areas being practically, at the same time, devoid of ice-load ! 



In the second place it has been claimed that mighty present- 

 day glaciers, such as those of Greenland, are not actively 

 corrading their beds, but lie, instead, inactive in fiords and 

 valleys; and that therefore even larger glaciers cannot be expected 

 to have seriously modified their channel forms. But this present 

 inactivity must occur of necessity, as has been already shown in 

 part by the author,* since the fiord bases, in common with other 

 stream-channel grades, represent the action of the mightiest flooda 

 only, and as such their slopes are altogether too slight to admit 

 of corrasion by the present drought-stricken ice-streams. Here 

 again is evident the necessity for a clear conception of the idea 

 that floods accomplish the rock corrasion and determine the 

 channel grades. Very heavy floods in ordinary rivers are not 

 infrequent, and therefore their efficiency is easily appreciated. 

 Were they, however, as in the case of the Great Ice Deluges, to be 

 of rare occurrence only, then controversy would, in turn, rage round 

 the origin of fishing holes in the river, the huge boulders in the 

 channel, the comparative freedom from debris in a channel narrow, 

 as also other peculiarities of contour along the flood-channel. 

 The drought-stream itself would be studied and its utter incom- 

 petency observed to do aught than babble around or override the 

 flood debris, and hence the conclusion might be arrived at that 

 the theory of rock erosion by water action was a delusion. The 

 great masses of flood debris would be examined and referred to a 

 period of former " intense water action " when huge floods had 

 acted so as to suspend and even transport large fragments over 

 each other, yet smoothly without much friction. Some observers 

 would, from an observed absence of much debris in certain steep 

 narrows, actually deny even the presence of a flood at those spots. 



* E. C. Andrews (h). 



