300 T'ransactions.— Geology. 
But the existence, in the localities referred to, of the ordinary evidences 
of glacier action, such as huge lateral and terminal moraines, of roches 
moutonnées, blocs perchés, ete., is not the only or even the chief circumstance 
of interest brought under our observation in connection with the former 
extension of the glaciers. On looking at a map of the Middle Island we 
cannot fail to observe a chain of lakes extending in an almost direct line from 
north to south, occurring chiefly, however, on the eastern side of the great 
range, and comprising Lakes Howick and Arthur, to the north of the Spencer 
Mountains; Lakes Tennyson and Guyon, on the eastern side of the same 
group ; Lakes Sumner and Taylor, lying between the Provinces of Nelson and 
Canterbury ; Lakes Coleridge, Lyndon, Heron, Acland, Tripp, and others, in 
ihe latter Province; and the more extensive Lakes Wanaka, Wakatipu, 
Hawea, and others, to the south of the Waitaki River. N ow, it has never 
been doubted that all these lakes owe their existence as such, more or less, to 
the action of glaciers ; those which occur to the north of the Waitaki, at all 
events, all lying in valleys above the lines of huge terminal moraines which 
have been deposited across them, and which have formed dams in many 
instances several miles in length and several hundred feet in depth. 
It is, moreover, a matter of extreme interest that many of the larger 
valleys which, during the former extension of the glaciers, were occupied by 
ice, and are now filled with ordinary alluvial deposits, must for a long period 
after the disappearance of the ice have been filled with water to the height at 
which the glacier streams had then cut through the terminal moraines. In 
this condition they resembled, in every respect, the great majority of the 
existing valley lakes to the northward of the Waitaki River. An admirable 
example indicating the former existence of such a lake, in which the water 
has been replaced by alluvium, is to be seen in the upper part of the valley 
of the Dillon. In this case the moraine which stretches across the valley has 
an average width of about a mile, and extends down it for upwards of three 
miles, the fall from the point at which the river has cut through it on the 
upper side to that at which it discharges itself on the lower side being fully 
180 feet, whilst the average slope of the valley for several miles above the 
moraine is less than 20 feet to the mile, but increases to at least 35 feet below 
it, indicating the great depth to which the moraine deposit extends below the 
present general level of the valley. The moraine itself rises, at its greatest 
height, about 100 feet above the level of the upper valley, and exhibits, in the 
angle which it forms with the mountains on the eastern side, and at a height 
of about 30 feet, a former lake margin, as fresh and clean, and as Sree from 
vegetation and all other marks (except the recent tracks of cattle and sheep), 
as if the lake had been emptied only a week ago. I have designated margins of 
this kind, which are usually composed of sub-angular shingle, as wave-margins, 
