THE NEW ZEALAND SOUND BASINS 



37 



(Fig.13) (in New England, New South Wales), may suffice. Here a 

 valley some 3,000 feet deep is seen, many overlapping spurs being 

 noticeable. 



We will suppose that convergence of plateau remnants to heads 

 of canyons, as also of these deep valleys into each other, is a common 

 feature. 



With the increase in ice-volume, the valley becomes gradually 



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Fig. 12. — Sketch section across Milford Sound. (From a photo.) To the left 

 are seen the effects of the heavy ice-thrusts just below the convergence of Arthur, 

 Cleddau, and Harrison Cove streams. Fifty yards from its cliff, the Sound is 1,500 

 feet deep. 



filled with a glacier. With increased volume or convergence (the 

 confluent ice-surfaces will generally keep at same level) comes added 

 velocity. The directions of flow have been determined for it and its 

 tributaries by the preglacial streams, and the lines of maximum 

 depth and motion will be along the portions vertically above the old 

 stream channels. Even should the glaciers fill the valleys, the higher 



