140 Transactions. 



On the other side of the divide between this valley and that of the 

 Rakaia, in the neighbourhood of Browning Pass, the strike of the beds 

 lies right across the main valley leading up to the pass ; but when the 

 valley of the Wilberforce is traced up to the blufi which closes its upper 

 end almost completely it turns to the north and follows the line of the 

 strike exactly. The beds here dip north-west, and the scarp slope has 

 formed a line of clifi, composed of loose unstable rock extending for some 

 miles, and quite imscalable from the east except at the pass itself, where 

 the western wall has been broken down to some extent. This line is con- 

 tinued down the valley of the Taipo on the western slope of the range in 

 almost perfect alignment as far as the junction of that river with the Seven- 

 mile Creek, when the river makes a right-angled bend across the strike before 

 it flows through its gorge to join the Taramakau. The parallelism of the 

 upper waters of the Arahura, which are in close proximity to those of the 

 Taipo, is noteworthy in this connection. 



In the Whitcombe Pass, between the head of the Rakaia and the Whit- 

 combe River, a tributary of the Hokitika, the direction of the strike of the 

 beds corresponds fairly accurately with the long narrow trench which rims 

 N. 10° E. for a distance of twenty miles through the range, and is occupied 

 in Westland by the Whitcombe River and in Canterbury by the Louper 

 Stream (Bulletin No. 6 (n.s.), N.Z. Geological Survey, 1908; maps). When 

 the direction of the pass is followed south across the Rakaia there is no sign 

 whatsoever of the persistence of the trench. This valley is as marked in the 

 alignment of its valley-walls as that of the Upper Bealey and the Otira, 

 and the agreement in both cases with the folding of the beds seems to 

 indicate that the former of Dobson's causes is the dominating one in deter- 

 mining the directions of the valleys in the neighbourhood of the passes, 

 though Morgan {loc. cit., p. 73) inclines to a fault origin for the Whitcombe 

 Valley. 



If we now consider the passes at the head of the Godley, Tasman, 

 Hunter, and Makarora Rivers, they appear to conform more generally 

 to the average strike of the beds in those regions, and this, and not the 

 presence of a series of major earth-fractures, may be the explanation of their 

 orientation. 



The actual passes where they cross the main di\'ide seem, therefore, to 

 be controlled in direction by the strike of the folded greywackes. In some 

 cases, however, other general causes must be present which have had a 

 determining effect on the course of the upper streams— e.,*;., there is such 

 a marked resemblance in the headwaters of the Waimakariri and Rakaia 

 that it can hardly be the result of chance. The chief source of the Wai- 

 makariri is the WTiite River, which rises in a glacier on Mount Davie, to the 

 west of Mount Greenlaw, a mass which apparently blocks the valley when 

 looking up-stream from the Bealey Township. The course of the White 

 River Valley is for about three miles in a north-easterly direction, parallel 

 to the strike of the beds, with its south-eastern side a wall of precipitous 

 rocks standing almost vertical in agreement with the high dip ; but the 

 river breaks through this barrier in a course cut at right angles past the 

 north-eastern end of Mount Greenlaw, receives a tributary from the north- 

 east, and then flows about south-west, almost parallel to its original direc- 

 tion, past the front of Mount Greenlaw, and then finally turns again almost 

 at right angles to the south-east and follows that general direction past 

 Bealey and the Cass towards the sea. 



The case of the Rakaia is analogous. The Lyell Glacier discharges by 

 a river which runs north-east along the strike of the beds behind the- 



