388 Geology of 



distance beyond the front ranges, where a few portions of the frontal 

 moraines are still preserved about two miles from the eastern foot of 

 the limestone hills near Mount Somers ; total length about sixty- 

 miles. In the second period of its existence, w T hen the large lake 

 above the gorge of the Eakaia was formed, this branch after its 

 retreat produced in its turn Lake Heron. The frontal moraines on 

 the southern side of that lake are still well preserved, and the bed of 

 its former outlet towards the Ashburton is clearly denned. The present 

 outlet of the lake, however, uniting with the River Cameron, has now a 

 reverse flow to the upper Eakaia. 



In the river bed of all the Eakaia branches, remnants of morainic 



accumulations mostly of a frontal character are met with, showing 



that the glaciers of which the trunk glacier was formed when 



retreating remained either stationary for some time, or what is 



still more probable, may be taken as the boundary of the new 



advance of the glaciers, after a temporary retreat to higher regions. 



Although the space at my command will scarcely allow me to go into 



details, I think that I should give here one striking example, proving 



that in some cases the latter theory is supported by most remarkable 



facts. The Eakaia, opposite Fighting Hill, makes a sharp bend 



towards the south before it enters the gorge proper. Here the banks 



consist first of 70 to SO feet of lacustrine deposits (silt), above which 



about 400 feet of river shingle repose. The whole section shows most 



instructively how the river slowly advancing with its delta, has gradually 



tilled up the large lake once existing here after the retreat of the 



glacier. At this bend begins a remarkable channel running with an 



average breadth of 200 feet for about three miles in a straight line. 



After ascending four well marked river terraces in its course, it abuts 



against a small rocJie moutonnee of quartziferous porphyry standing in 



the centre of the valley, not far from the ferry. It was doubtless 



formed after the river channel A (section No. 7 on plate No. 7) had 



been excavated by the Eahaia. but before any lower ones had been 



hollowed out ; because if we continue its course in a N/W. direction, 



it is parallel with the course of the river now flowing here, 500 to 600 



feet below it. It is evident that when this small glacier advanced in 



such a striking manner, the great Eakaia lake had not only entirely 



been tilled up by river deposits, but the Eakaia had already begun 



to excavate its bei into these deposits, by which four well defined 



terraces had been produced. 



This remarkable channel is so striking a feature in the country that 



