206 Physical Geography of 



The Rakaia. 



The hydrographical system of the Rakaia, 1547 miles in extent, has 

 its western boundary along the central chain from Mount Tyndall to 

 Mount Harman, a distance of forty-eight miles in a straight line. 

 The main branch, to which the native name has been preserved, has 

 for about twenty-one miles a straight west and east course, and a 

 shingle bed from one to two miles broad, beginning at the very head 

 of the valley, where, as described in the first part, the Ramsay glacier 

 would abut against Mein's Knob, a high roche moutonnee advancing 

 considerably into the valley from the main range, did not the outlet 

 of the Lyell glacier undermine and wash the terminal face of the 

 former away. The two glaciers at the head of the main Rakaia are of 

 considerable size, although not reaching in magnitude the principal 

 glaciers forming the sources of the "Waitaki. The most westerly, the 

 Lyell glacier, is eight miles long, and nearly a mile broad at its 

 terminal face ; it is formed by the neves of the north-eastern slopes of 

 the Mount Tyndall range, and the eastern slopes of Mount Lyell. 

 The Ramsay glacier, having a southern course, is seven miles long, 

 and has about the same breadth at its terminal face as the other ; both 

 being much more expanded in their middle portion. The first 

 important tributary is Whitcombe's stream, which, issuing from the 

 Martius glacier on Whitcombe's Pass, after a course of four miles, 

 joins the Rakaia two miles below the Ramsay glacier. Thirteen miles 

 below the same point, the Cameron joins the main river, bringing the 

 united waters of the Cameron glacier which descends from the eastern 

 slopes of Mount Arrowsmith, and of Lake Heron which lies about ten 

 miles to the south.* Six miles below this latter junction, theMathias, 

 an important affluent, enters the main valley from the north-north- 

 east. Issuing from the Xeave glacier (378S feet), it has a course of 

 eighteen miles, the upper portion for about eight miles having a gorge- 

 like character, whilst the last ten miles possess the usual features of 

 broad shingle reaches, but the boulders in its bed are generally very 

 large, and several ancient moraines cross the valley from side to side 

 where the river is confined in a narrower channel. Several large 

 affluents join the Mathias on both banks in its upper course, the most 

 important tributary, however, being received ten miles below its 

 glacier source, which comes from the north-west and drains the 



* Lake Heron is four miles long, and two miles broad, being narrowed considerably in ih& 

 centre by two large deltas. 



