188 Physical Geography of 



tinuous talus of debris. This large range is separated from Mount 

 Torlesse and the Thirteen Mile Bush range (Big Ben) by the valley of 

 the Acheron, Lake Lyndon, and the valley of the Porter. These two fine 

 ranges, separated by Porter's Pass, forming such a conspicuous object 

 from the streets of Christchurch on a fine winter's day when they 

 appear entirely covered with snow, may be considered the southern 

 continuation of the Puketeraki range. The highest peak of Mount 

 Torlesse is 6136 feet high, whilst Big Ben, the summit of the Thirteen 

 Mile Bush range, reaches only an altitude of 5224 feet. Both ranges 

 are covered on the eastern slopes with large beech forests, of which 

 the upper limit is about 4500 feet. 



I have already pointed out that the divergent chain, between the 

 Upper Eakaia and Eangitata rivers, rises in Mount Arrowsmith, still 

 high above the line of perpetual snow. This is the more conspicuous, 

 as its eastern continuation has been cut off entirely by the remarkable 

 broad plains, former glacier channels, which here unite the valleys of 

 the Eangitata, Ashburton, and Cameron with that of the Eakaia. 

 However, the cluster of mountains, which lies here to the east of this 

 broad old glacier course, rises still to a considerable altitude, of which 

 the highest summits of the Mount Somers range reach about 7200 feet, 

 whilst Mount Hutt, forming such a conspicuous object, as viewed 

 from the Canterbury plains, is 6800 feet high. This is the highest 

 mountain rising directly from the Canterbury plains. From Mount 

 Forbes, at the head of the Macaulay, a magnificent chain runs south, 

 forming mostly pyramidical peaks, but not high enough for the forma- 

 tion of snow-fields to any extent. This range, which forms the western 

 boundary of the upper Eangitata plains, is called the Two Thumb 

 range from the peculiar form of its twin summits, appearing as if two 

 thumbs had been put against each other. Its southern continuation, 

 Mount Sinclair, is considerably lower, although still 7022 feet high; 

 further south, on the eastern shores of Lake Takapo, it is called the 

 Dobson range, where its highest summit has now an altitude of 6271 

 feet, falling abruptly to Burke's Pass, 2464 feet. On the southern 

 side of this pass, the continuity of the range is much broken by several 

 passes, such as the Mackenzie and Hakataramea Passes, all former 

 glacier channels for the enormous ice masses of the great Waitaki 

 glacier during the great New Zealand Glacier Period, here passing 

 over and between the ranges, which have lost much of their altitude 

 and are worn down and rounded off, as observed in all glacialized 

 countries. More to the south, longitudinal ranges, still 5000 to 6000 



