300 Transactions. — 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 

 moutonn^es, blocs perches, etc., 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 Arthu]-, to the north of the Spencer 

 Mountains ; Lakes Tennyson and Guyon, on the eastern side of the same 

 group ; Lakes Sumner and Tayloi'j lying between the Provinces of Nelson and 

 Canterbury ; Lakes Coleridge, Lyndon, Heron, Acland, Tripp, and others, in 

 the latter Province ; and the more extensive Lakes Wanaka, "Wakatipu, 

 Hawea, and others, to the south of the Waitaki River. Now, 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 iii length and several hundi-ed 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 has been replaced by alluvium, is to be seen in the upper jjart of the valley 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 free 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, us wave-margins, 



