210 'r>rttisactions. 



The results of the investigation in the case of the other 

 rivers will be best seen by examining the generalised section 

 of eioch river shown on Plate X, figs. 1-6. These s<^ctions 

 have been prepared in the following manner : The heights 

 of all the esooxpraents on the left bank were added, and divided 

 by the number of .sections across the river : this gives the 

 height of the left bank. The same thing was done with those 

 on the right. Then the width of all the terraces from the first 

 escarpment on the left bank to the river-bed were added, and 

 divided })y the number of sections taken, and this gives the 

 breadth of the 'eft bank, and a similar calculatioix that of the 

 right bank. The average Avidth of the bed was also taken, 

 and the black spot in the bed shows the average position of the 

 main body of water in the stream. It wall be seeji that the 

 general result shows to a very marked degree that the left bank 

 is much more abrupt than the right — that is. that the rivers 

 have corroded that bank to which the influence of the earth's 

 rotation tends to deflect the.m. 



It may be pointed out that if the Waimakariri had been used 

 in the investigation, it would have given very exaggerated 

 results of the same nature as those shown by the other rivers, 

 as in its lower course its first terrace on the right bank is about 

 nine miles from the present bed of the stream. 



The Rakaia is the only river observed that has higher banks 

 on its right bank than on its left. Von Haast concludes — 

 and is, I beheve, generally supported by other geologists — that 

 the Ashburton was at one time much the biggest of the three 

 rivers now known as the Rangitata, Ashburton, and Rakaia — 

 or, indeed, that these rivers were one, and emptied themselves 

 in the positio]\ now occupied by the present Ashburton. This 

 joint river deposited upoji the plains a huge fan, whfse froiit 

 edge stretched southwards past the present Rangitata ajid 

 northwards past the present Rakaia. This fan is still fairly evi- 

 dent, especially in the cliffs along the Ninety-mile Beach, wh'ch 

 cliffs rise from 10 ft. at the mouth of the Rakaia to 60 ft. at the 

 Ashburton, and fall away to 20 ft. or less at the Rai-gitata. 



Standing on the right bank of the Rakaia with my level, 

 it was only by looking backwards up the plain that I could find 

 a point on the left bank as high as that on which I stood, for 

 I was standing on the fan of the old Ashburton ; and the same 

 was true while standing on the left bank of the Rangitata. 

 On the opposite side of the river, and in a direction at right angles 

 to its flow, there was no land as high as that on which I stood, 

 for here, too, I was on the old Ashburton fan, but on its southern 

 edge. Now, the presence of the fan will easily account for the 

 height of the right b^nk of the Rakaia, if we can find any reason 



