422 Procei'.diiiijs. 



advancing beyond the eastei'n boundaries of the ranges now bordering the 

 Canterbury plains proper. Of these gigantic ice streams, the glacier advancing 

 through the then iinited valleys of the Southern Ashburton and Northern 

 Hinds was, if not the largest, at least equal in size to the Eakaia glacier, 

 owing to the fact that it received enormous additions from the valley of the 

 Rakaia (by the lake Heron) and from that of tlie Rangitata (by the lakes 

 Tripp and Acland depressions).* It will thus at once become manifest that 

 Captain Hutton's argument (p. 387) concerning the small size of the pi-esent 

 Ashburton and Hinds rivers falls to the ground, and that he was not sufficiently 

 acquainted with all the facts given in that report of mine. 



We thus have north of Tiraaru four distinct fans, namely, those of the 

 Waimakariii, Rakaia, Ashburton, and Rangitata, with smaller rivers having 

 their sources in the front ranges running between them ; the Selwyn between 

 the Waimakariri and Rakaia fans, the Northern Ashburton between those of 

 the Rakaia and of the Ashburton — jSTorthern Hinds ; and the Southern Hinds 

 between the latter and the Rangitata fans. The gravel formation of these 

 fans, where they remained undisturbed, does not warp, as Captain Hutton 

 assumes, round the spurs of the hills at the same level that it has at the river 

 gorges, but has a steady fall towards the small streams flowing between the 

 fans of the two large glacier torrents ; however, in some instances, this has 

 been concealed by detritus from the mountains, or by re-arrangement of the 

 original river beds on the surface of the upper portion of the plains when the 

 glaciers retreated. But, I may add, the general outlines are nevertheless clear 

 and distinct. 



In my geological notes on the Malvern Hillst I have given an illustration 

 of this. I have shown how the great Rakaia glacier, having also an outlet by 

 the upper course of the river Selwyn, covered with its gravel deposits the 

 lower eminences forming the Malvern Hills, west of the dolerite range, and had 

 its outlet in a N.E. direction in the neighbourhood of Little Racecourse HUl, 

 thus throwing, doubtless, the bed of the Waimakariri more to the north. 

 When this glacier outlet ceased to flow and to deposit any more boulders and 

 gravel in the district alluded to, the Waimakariri soon began to remove the 

 alluvial beds thus formed by the Rakaia branch, until harder rocks upon which 

 they were reposing were reached. This fact alone, I trust, will prove that a 

 detailed examination of all physical features in that portion of the country is 

 requisite to enable us to understand the sometimes complicated nature of the 

 fluviatile beds, and that my explanation of the formation of the Canterbury 

 plains is not a mere hypothesis, but based upon a great number of observations 

 made during a number of years. 



* See "Heport on the Formation of tlie Canterbury Plains," by Dr. Haast, p. 9, ttucq. 

 ■\ Kep. Geol. Expl., 1871-72, pp. 33 — 30. 



