82 Transactions. — Miscellaneous. 



lateral streams contain considerable quantities of boulders and gravels 

 which floods of ordinary magnitude are incapable of moving, the larger 

 rocks and boulders serving as dams or buttresses for supporting smaller 

 matter above them. But, whatever the relative size and force of these 

 lateral streams may have been, there was one character which they all had 

 in common before the occurrence of the great floods of 1868, namely, that 

 they had evidently never changed their courses, at aU events for some 

 distance upwards from their debouchures onto the main terrace, since this 

 had been left permanently above water by the cutting down of the present 

 main river-channel. This is a point of great importance, and to be care- 

 fully borne in mind in connection with the observations referred to in the 

 sequel. The hills and mountains on each side of the gorge are steep and 

 hummocky, generally bare of forest, but covered with tussock grass and 

 fern, and with the other vegetation characteristic of such localities in the 

 South Island. 



The valley of the main river rises from about 800 feet at the mouth 

 of the gorge to about 1200 at its upper end in the Hanmer Plain, Mount 

 Tekoa, on its western side, attaining an elevation of upwards of 5000 feet on 

 a base of less than ten miles from the bank of the river. I am bound to be 

 thus particular in describing the physical features of this gorge, and, indeed, 

 of all the country in which I noticed extraordinary marks of the flood in 

 question, because the changes effected by it in those physical features afford 

 the chief proofs in support of my proposition. To these changes I wiU refer 

 after completing my general sketch of the country affected, so far as this is 

 necessary for the purposes of this paper. The gorge I have been describing 

 terminates at the Hanmer Plain, which, like that of the Hurunui, lies 

 nearly east and west, and is also surrounded by mountains. The main 

 river flows into the plain from a gorge at its western end, and after flowing 

 along its southern side to about the middle of the plain, turns abruptly 

 into the one which I have lately described. At the point where this occurs 

 it is met by two smaU rivers, one called the Percival, flowing directly across 

 the plain from the northward, and the other called the Hanmer, flowing 

 from the westward in a course directly opposite to that of the main river. 



These rivers are very insignificant in size compared to the Waiau-ua, but 

 in times of flood each of them brings down to the latter a large quantity of silt 

 and gravel, partly derived from the shingle of the plain and partly carried 

 into it by the innumerable rivulets which drain the surrounding mountain 

 . slopes. When, however, the whole of the rivers are in flood, the waters of 

 the Percival and Hanmer are banked up at the confluence, and form a large 

 expanse of practically still water, the effect being that, as in the case of the 

 Pahau and the Hurunui hereafter referred to, a considerable quantity of silt 



