Hurton.—On the Lower Gorge of the Waimakariri. 451 
That a river running in a shingle plain should make straight for a rocky 
hill and, instead of flowing round it, should cut it in two, is a remarkable 
phenomenon; and it is an account of this phenomenon and an attempt to 
explain it that forms the subject of the present paper. 
First as to the facts which have to be explained. Both Gorge Hill and 
Little Gorge Hill are formed of thin bedded slates and sandstones dipping 
75° to W.S.W. at the bridge, but getting flatter higher up the river. On 
the right bank is Gorge Hill, 863 feet above the level of the river-bed at the 
bridge.* From the summit a spur runs towards the river in an E.N.E. 
direction. Its altitude at the river gorge is about 270 feet. Then, follow- 
ing the same line, comes a depression occupied partly by the river, partly by 
gravel beds, and then, still eontinuing the same direction, is Little Gorge 
Hill, 216 feet high. "The depression in the slate rocks between these two 
hills forms a steep-sided, flat-bottomed eol, in which the river has cut a 
narrow perpendieular gorge about 90 feet in depth; the remainder of the 
eol being eovered with beds of river shingle, capped by a deposit of silt 
which, in colour and in structure, resembles the silt deposit at Lyttelton. 
No fossils have been detected anywhere in the neighbourhood, except the 
so-called annelid tubes in the slates. 
` The plains at the north-west foot of Gorge Hill are 192 feet above the 
river-bed at the bridge, and they extend from thence to the Malvern Hills 
without any terraces. The plains at the north-east foot of Little Gorge 
Hill are also 192 feet above the river-bed, and from here also they stretch 
over to Oxford without any terraces, except some small ones formed by the 
River Eyre which have nothing to do with the subject of the present paper. 
The river-bed, both above and below the gorge, is very wide and deeply 
terraced ; but all the terraces, when they approach the gorge from above, 
contract suddenly and then, below the gorge, expand again as suddenly as 
they contracted, thus appearing like an hour-glass, the narrow neck of 
which is at the gorge. It is evident, therefore, that the river has never 
left the gorge since it first began to cut into the plains and form terraces. 
However much it may have swayed from side to side, either above or below, 
the hard rocks of the gorge have always held it like a vice ever since it 
began to cut below the present level of the plains. But how is it that the 
plains are at exactly the same level on both sides of the gorge hills? And 
how is it that the river has cut through the hill instead of running round it? 
* The heights of the two Gorge Hills are taken from the trigonometrical survey of 
Canterbury as given by Dr. von Haast in his ** Geology of Canterbury and Westland,” 
P. 476; the levels of the terraces are from the survey for the Oxford and Sheffield rail- 
way, kindly supplied me by Mr. G. P. Williams. All the levels here given are calculated 
from the bed of the river at the bridge, taken as the datum. This datum is 808 feet above 
high-water mark at Sumner. The figures on the plan show the height in feet above the 
river-bed at the bridge, 
