218 'Physical Geography of 



The Opiht. 

 Of the rivers of which the hydrographic basins lie entirely in 

 Canterbury, but which have no glacier sources, the Opihi is the most 

 important. Its principal sources are all situated in the high mountain 

 chain beginning at Pox Peak and running in a nearly north and south 

 direction to Mount lS"inirod, by which the Waitaki system is bounded 

 on the eastern side. Of the confluents of which this river is formed, 

 the Opuha is the largest, the main sources coming from the 

 eastern declivities of Pox Peak and the- Dobson range. After 

 passing through the Opuha plains, it enters amongst low palaeozoic 

 ranges till it joins the Opihi amongst the limestone hills, 20 miles 

 above its mouth . The Opihi proper has its sources in the ranges near 

 Burke's Pass, and after leaving these mountains, it flows for about 

 12 miles, diagonally, through the middle portion of the Opihi plains, 

 when, meeting the old morainic accumulations which here cross the 

 open valley, the river enters the Opihi gorge, a deep fissure, cut 

 through a hill consisting of palaeozoic rocks. This is certainly one of 

 the most remarkable phenomena in the physical geography of New 

 Zealand, where a river, instead of excavating its bed through 

 loose alluvial and morainic deposits', has actually cut a deep channel 

 through hard rocks. I have already noticed the same fact when speak- 

 ing of the lower "Waimakariri gorge. Por a distance of five miles the 

 Opihi flows through this picturesque gorge, its nearly vertical banks, 

 about 600 feet high, being clothed with luxuriant forest; it then enters 

 the limestone region where it is joined by the Opuha. After flowing 

 for six miles through a broad valley with low limestone ridges on both 

 sides, it is joined by the Tengawai, the main sources of which are 

 situated near the Mackenzie Pass. This stream receives numerous 

 affluents from the eastern slopes of the high ranges at the head of the 

 Hakataramea. Its valley is generally broad, and bounded by low hills 

 on both sides. 



The Ashley. 

 The Ashley, although not of glacier origin, is of considerable size, 

 and drains a large extent of country. Its principal sources are 

 situated on the southern flanks of xishley Head and the northern 

 portion of the Puketeraki range. Por eight miles it passes through the 

 Upper Ashley plains, during which it receives numerous tributaries, 

 mostly from the eastern slopes of the last-mentioned range ; it then 

 enters the gorge by which the old lake-bed, now forming that plain, has 



