400 Geology of 



towards the south diminish in height, so that near the mouth of the 

 Ashburton they only rise to 18 feet.* A few miles north of the 

 Ashburton we reach again the line, where the sea-coast meets the 

 level of the fan under consideration. 



To understand fully the combined action of the agencies at work, it 

 will be necessary to remember, that the largest fan was necessarily 

 formed by the most extensive glacier, and in consequence the fan of 

 the post-pliocene TVaimakariri could not reach so far into the sea, as 

 did the united Ashburton one, built up by the southern rivers. In 

 adopting the present data before us as the basis of reasoning, we shall 

 find that, as before observed, the united southern fan began near the 

 mouth of the Eangitata, advanced into the sea till it attained a 

 breadth greater by several miles than that which it now possesses 

 near the mouth of the present Wakanui Creek, and crossed again 

 near the mouth of the Kakaia, of which a portion has been, and 

 is now being, washed away. Continuing the same arc of this fan 

 in a north-west direction we shall reach the Selwyn several miles 

 above its junction with Lake Ellesmere, where the fan of the "Wai- 

 makariri joined it, and, in consequence, the Selwyn, like the Hinds, is 

 flowing upon the junction of both fans. During this post-pliocene 

 era a narrow arm of the sea ran along the western foot of Banks' 

 Peninsula, as shown by the drift sands and raised beaches surrounding 

 it here. The oceanic swell south of Banks' Peninsula travelling 

 towards the north, assisted by the action of the waves, very soon began 

 to disintegrate the post-pliocene accumulations. The shingle and 

 sand derived from that destruction, travelling northwards, were 

 augmented considerably by the material of the same nature brought 

 down bv the rivers, and, assisted by the two prevailing Minds, finally 

 formed a dam from the mouth of the Kakaia to that isolated volcanic 

 system, becoming every year more considerable. A peninsula was 

 soon originated, the connecting isthmus being that dam or broad 

 shingle spit behind which an arm of the sea formed a bay, moderately 

 deep and comparatively sheltered, with an entrance to the north of 

 Banks' Peninsula. Into this bay the Selwyn, "Waimakariri, and 

 probably, at one time, the Kakaia fell. Gradually the shingle and 

 sand brought down by the northern rivers, the "Waipara and Ashley, 

 travelling with a northerly swell towards the south, threw, in their 

 turn, a bar across the opening of the bay, thus forming a large 



From observations of Mr. C. W. Adams, Geodetical Surveyor, kindly furnished to me. 



