212 Physical Geography of 



bounding the gorge to the south, and where an ancient glacier channel 

 can easily be traced. "Where the river leaves the front ranges, it flows 

 in a narrow gorge, about 600 feet deep with terraced banks on 

 both sides, in which for the lower 300 feet, the alternating 

 sandstones and slates, standing at a high angle, form perpendicular 

 walls ; but soon the rocks disappear and fluviatile and morainic accumu- 

 lations take their place. These high banks, although gradually getting 

 lower as we ascend the Canterbury plains, continue to accompany the 

 northern banks of the river, for thirty-two miles, to the sea coast, 

 where they are still about twenty feet high. The southern banks 

 however, disappear nine miles before reaching the coast, the channel 

 of the river, on the so-called Island, being liable to shift with every 

 freshet. The Eangitata, like all the principal rivers forming the 

 Canterbury plains, does not receive any tributaries in its lower course, 

 their gigantic fan-like alluvial deposits being highest near their present 

 river channels. 



The Waimaeaeiei. 

 The Waimakariri, another of the important rivers crossing the Can- 

 terbury plains, next claims our attention. If we draw a straight line 

 from Mount Greenlaw to the Hurunui saddle, the watershed along the 

 central chain belonging to its hydrographical system is thirty miles 

 long, thus being of greater extent than that of the Eangitata ; how- 

 ever, the mountains at the head of the northern river are not so high, 

 nor the snow -fields so extensive, and consequently the amount of 

 water coming from the Southern Alp's proper is not so consider- 

 able in the Waimakariri, although the Poulter and Esk nearly make 

 up for the difference. In fact, although the hydrographical basin of 

 the river is nearly twice as large as that of the Eangitata, and within a 

 few miles of the same extent as the Eakaia, it nevertheless ranks third 

 as to the amount of water it brings to the sea. The main source of 

 the "Waimakariri is a glacier at the head of the White river, having its 

 origin in the snow-fields on the northern slopes of Mount Greenlaw, 

 4162 feet above the sea-level. After receiving several tributaries of 

 glacier origin, the White river, as it has been named from the peculiar 

 colour of its water, generally thick from finely triturated matter, 

 originating from the action of the glaciers on their rocky bed, unites 

 five miles from its origin with the northern Waimakariri, which having 

 a south-south-east course, meets the former at a right angle. That 

 course is continued after this union of the two confluents, the valley 



