286 REPORTS OF COMMITTEES. 



course of about 100ft. per mile, it is difficult to believe that it has been 

 in existence for a long space of time. This moraine is in an ideally- 

 perfect condition, and but sparsely covered with the vegetation that 

 soon covers undisturbed rock material in the locality. 



In the valley of the Cameron Eiver, a tributary of the Upper 

 Rakaia, the signs of recent retreat are still more marked. The glacier 

 at the head of this river is larger than those in the Rangitata, and it 

 has recently occupied about a mile of the floor of the valley. The 

 valley opens out at its head into a wide amphitheatre, which has been 

 formed by the united action of two glaciers, only one of which now 

 exists, and this one is rapidly shrinking. The evidence for this is as 

 follows : — The lateral moraines are now left perched high above the 

 present level of the ice, sometimes as much as 150ft. (determinations 

 made with the aneroid) ; the terminal face has thinned out till it 

 cannot be readily distinguished under the covering of debris from the 

 frontal fluvio-glacial deposits ; the morainic heaps, which mark the 

 last great halt in the recession of the ice, are separated from the end 

 of the glacier by about 600yds. of ground covered by material which 

 has but recently been surface moraine, and is almost free from plant 

 covering. The glacier shows signs of extremely rapid collapse over 

 the whole of its lower portion. I have noted a similar phenomenon 

 in connection with the MuUer Glacier in the Mount Cook district. A 

 glacier may thus disappear over large areas at nearly the same time, 

 and not by a slow recession of the terminal face. This fact may have 

 some bearing on the rapid retreat and disappearance of an ice sheet. 



In the two localities above mentioned, observations were made 

 for use on future occasions. It is a very long time since these glaciers 

 were visited by anyone who intended to observe them carefully, so 

 that there are no reliable data by means of which their actual rate of 

 recession can be determined at present. The fact that they are retreat- 

 ing is confirmed by station managers in the neighborhood, one of 

 whom assured me that from his own observation the Ashburton Glacier 

 has retreated about three-quarters of a mile during the last 30 years. 



These notes concerning the retreat of the glaciers show that from 

 causes not adequately determined there has been a rapid recent retreat, 

 and that we are probably approaching a period of minimum glaciation. 

 No doubt the whole period of recession since Pleistocene times has 

 been marked by a series of such minima, with intervening maxima. 



The next observations that I have to record relate to the trunca- 

 tion of spurs by glaciers in the above-mentioned localities, and also at 

 the head waters of the Waimakariri. Here the valley floors are not 

 hidden under water, as is the case with the West Coast sounds, although 

 they are buried to a certain extent by the waste brought down by the 

 rivers, which in this portion of their course are not degrading their beds. 

 The details of the erosive action of the glaciers are therefore more 

 easily studied. In this area the valley systems had been thoroughly 

 developed previous to glaciation, and the following observations were 

 made on the corrosive action of glaciers on such a country, the point 

 specially noticed being the method by which spurs were truncated. 



