Hutton. — On the Lower Gorge of the Waimakariri . 453 



firstly, because there are no traces of terraces between the Gorge Hills and 

 the margins of the plains ; secondly, because having once cut the col the 

 river would be held there by the hard rocks on either side exactly as it is 

 held now ; and, thirdly, because in order to remove the shingle-beds above 

 the present level of the plains, the river must have first filled up the col 

 with gravel to at least this height before it left the col, and there is no 

 evidence of its having done so ; the highest terrace inside the col being only 

 148 feet above the river-bed. Consequently the river can never have left 

 the col since it first excavated it, and it is therefore impossible that the 

 river could have removed the missing gravel beds on each side. 



If now we take the only other possible view ; that is, we suppose — 

 although there is no evidence in favour of it — that the col was formed by 

 some other agency than the river, which merely filled it and the surround- 

 ing plains to their present level ; and then, happening to run through the 

 col when it commenced cutting down — which is very improbable — it formed 

 the present gorge. If we take this view then we shall not be able to ex- 

 plain, first, how the river could deposit flat beds of shingle, some ten miles 

 wide, between Sheffield and Oxford ; nor, second, can we explain the origin 

 of Eacecourse, and Little Eacecourse Hills, and the gravel beds round the 

 eastern base of the Malvern Hills ; which are shown by the form and 

 arrangement of the materials composing them not to be portions of old 

 moraines, although Little Eacecourse Hill contains re-arranged morainic 

 matter. Neither of these hypotheses will explain the facts. If we suppose 

 that the col was cut by the river, large masses of gravel must have been 

 removed without any apparent cause. If we assume that the river did not 

 cut the col, then we cannot account for the gravel hills rising above the 

 plains. Evidently river action alone cannot explain the whole of the 

 phenomena. 



The following is my explanation : — The shingle brought down by the 

 rivers not only formed the present plains, but accumulated to a thickness of 

 some 50 or 70 feet higher than at present. At this time Gorge Hill pro- 

 jected above the shingle, but Little Gorge Hill and a large portion of the 

 spur between the two were buried. The river, swaying about in the plains 

 between Oxford and the Gorge Hill, was arrested in its southerly swing by 

 the latter, and then, running along the north-easterly base of the hill over 

 the spur, it cut down through the gravel beds into the rocks and formed the 

 col. A period of general subsidence of the land followed, during which the 

 river partly filled up the col again with shingle, but at length, the depres- 

 sion still going on, the sea reached, and passed, this portion of the plains, 

 sweeping away the upper 50 or 70 feet and reducing all to a common level, 

 except the Eacecourse Hills. The col, remaining as the estuary of the 



