14 BIRDS OF THE WATER 



wear and tear, have themselves moved. 

 There is, however, growing on the stream's 

 edge, immediately above the fall, a certain 

 kowhai tree, whose bole is, I believe, a foot 

 or two nearer the chasm's rim than twenty- 

 five years ago. At all events, there can ])e 

 no doubt that the action of the water is 

 slowly tending lakewards, and although this 

 is at present almost imperceptible, yet there 

 are reasons to suppose that under certain 

 possible circmnstances it might l^ecome rapid, 

 and that thus the alluvial deposits of the 

 lake basin, accumulated during centuries, 

 might be washed away in weeks. At any 

 rate, because there has been almost no 

 movement for years, it does not necessarily 

 follow that such conditions will continue, 

 and many instances of sudden erosion have 

 occurred on Tutira even in my tune. One 

 will suffice. After years of quiescence the 

 ditch, three feet deep and two feet wide, 

 draining Kaihekanui flat, became in a single 

 flood and in a few hours, a chasm one 

 hundred and forty feet wide, fifteen feet 

 deep, and three hundred feet long. The 

 water had at last, after thirty years, got 



