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land, enormous glaciers descend in latitude 46 degrees 50 minutes, 
according to Darwin, to the level of the sea, their terminal face 
being ultimately washed away and carried along as huge icebergs. 
Thus the conditions for the lowering of the snow-line and of the 
excess of moisture must still be greater in that part of America 
than in New Zealand, where the neighbourhood of Australia and 
Tasmania will certainly exercise some moderating intluence, which 
in Terra del Fuego does not exist. From observations made in 
those and other regions , it is clear that the lowering of the snow- 
line does not depend on the mean temperature of the year, but on 
the low temperature of the summer. 1 
Although, as we have seen, the size of the principal glaciers 
in the Southern Alps is enormous , considering the height and nar- 
rowness of the central chain, the astonishment of the geological 
observer increases on meeting every where the signs of a still more 
considerable glaciation during former periods. There are perhaps, 
as Dr. ldaast states, nowhere in the well-known regions of the earth 
so easy of access, and in such comparatively low positions above 
the level of the sea, such clear and fresh signs of the existence of 
enormous glaciers during the pleistocene epoch, than upon the 
Southern Island of New Zealand. Far below the moraines at the 
terminal face of the present glaciers old moraines are met with, 
striking across valleys several miles broad and overgrown with a 
dense subalpine vegetation , which is nearly impenetrable to horse 
and man. Combined with them the strait courses, the great depth 
and breadth of the valleys, which are in no proportion to the rivers 
now running through them, and the rounded outlines of the lower 
mountains (roclies moutonnies ) are unmistakable indications, that the 
1 The mean summer temperature of Christchurch, from observations made in 
1864, is 61 1/ 4 °, enjoying generally a clear and cloudless sky; hut it is evident that 
at the West Coast it is much less, owing to the over-east state of the atmosphere 
and the frequent rainfalls. This will account for such a lowering of the snow-line 
on the western side of the Alps, but the mean temperature of the year will, never- 
theless, not be lower than in Christchurch, where it was 53 3 /j° during 1864, with 
an average temperature of 61° for the summer, and 44 */ 4 for the winter months; 
the warmer winter at the West Coast compensating, without doubt, for the lower 
summer temperature. 
