322 T ransactions. 



(h.) The Fakaia Valley. 



The largest river of the district is the Rakaia, which takes its origin in 

 the Lyell and Ramsay Glaciers, on the eastern side of the main divide, and 

 runs first easterly for twenty miles and then turns south-east. It receives 

 on its north bank numerous streams which rise in small glaciers on the 

 main range and run in a southerly direction in parallel valleys till they 

 meet the Rakaia. Further down, beyond the limits of the area under con- 

 sideration, it receives two important branches — the Mathias and the Wilber- 

 force. On the south bank several fair-sized streams rise in glaciers on the 

 slopes of Mount Murray, but the main tributary is the Lake Stream. This 

 is formed from the overflow waters of Lake Heron — hence its name — but 

 its chief supply comes from the Cameron River. This rises in the Cameron 

 Glacier, on the south-east face of Mount Arrov/smith, runs in a south-easterly 

 direction for about twelve miles, and forms an extensive fan on the north- 

 west side of the lake. At this part of its course it changes its regular 

 channel frequently, running into the lake at times, but at present it joins 

 the Lake Stream about two miles below its outlet from the lake. This 

 body of water receives several streams on its eastern side, the largest being 

 the Swin. The Lake Stream runs between north and north-east and has 

 a very slight fall for several miles, but then it becomes swifter and makes a 

 descent of 200 ft. before joining the Rakaia. 



The Rakaia River and most of its tributaries are overcharged with 

 detritus, and have filled up to a fairly uniform surface the floor of the 

 glacial trough through which they run (Plate III, fig. 1). The width of the 

 flood-plane is about two miles, and on this the river forms many diverging 

 and anastomozing branches, in the way so characteristic of streams laden 

 with waste. In winter it is frequently dr}^ owing to the freezing of the water 

 at its sources ; but in spring and summer it becomes a large river, and often 

 impossible to cross on horseback, although the splitting-up into different 

 streams renders it somewhat more easy to negotiate. Near the head the 

 valley narrows somewhat, and there the river runs in a solid body of 

 water capable of rolling down stones a ton in weight. In this part of its 

 course no terraces are formed except those of temporary nature, but these 

 last long enough at times to allow of their being covered with grass and 

 scrub ; still, they are liable to rapid destruction if the river in the course 

 of its w^anderings impinges for long against their unconsolidated edges 

 (Plate III, fig. 1). 



(c.) The Lake Heron Valley: its Features and Origin. 

 (See map, p. 318.) 

 The valley through which the Lake Stream runs is a very striking 

 physical feature of the district. It is continued in a south-easterly direction 

 for nearly thirty miles, and extends across the Ashburton River as far as 

 the Rangitata. It intersects these streams nearly at right angles, and bears 

 little relation to the present principal lines of drainage. It severs the eastern 

 mountainous district of middle Canterbury from the main range of the 

 Southern Alps, and well merits some distinctive name. Haast called a 

 part of it the Upper Ashburton Plains ; but this name will hardly apply to 

 the whole extended valley. I shall refer to it in this paper as the Lake 

 Heron Valley, as that name has been used repeatedly by the recent Com- 

 mission which examined the Canterbury runs for the purpose of closer settle- 

 ment. At the upper end of the valley, about five miles from the Rakaia, 



