W. Travers. — O71 Extinct Glaciers in the South Island. 301 



indicating, as they do in all the existing lakes, the dit-ection of the most 

 prevalent ^inds, and usually running across the valleys in which the lakes are 

 situated. 



The moraine above referred to is about 24 miles below the main source of 

 the river, and the lake which succeeded the ice could not have been less than 

 14 miles in length in the principal valley, with a branch at least five miles 

 long in the tributary valley of the Ada. Of course it is impossible to deter- 

 mine the actual depth of the moraine deposit at its upper face, but even 

 assuming it not to exceed 150 feet below the lake margin, we have an area of 

 19 miles in length and a mile in width, with an average depth of 60 feet, 

 which has been filled with river alluvium (independently of the immense 

 quantity of matter which must at the same time have been carried below the 

 moraine) within the period which the river has occupied in cutting down the 

 comparatively loose material of this dam, to a depth of 35 feet only. 



It may, in view of such a fact, appear remarkable that the beds of the 

 lakes on the northern side of the Spencer Mountains — which present on that 

 side precisely similar conditions — should not also have been filled up ; but 

 I attribute the rapid accumulation of alluvium in the case of the Dillon Valley 

 to the facts that the mountains bounding it are much steeper, are composed of 

 more easily disintegrated rock, are in their vipper parts very bare of vegetation, 

 and therefore exposed to the alternate action of frost and heat, and moreover 

 present in many places, for thousands of feet in height and for miles in length, 

 little else than continuous slopes of broken stone ; whilst those on the 

 opposite side of the range are in a great measure densely wooded, and are 

 chiefly composed of hard, crystalline rocks. I ought, however, to state that 

 in assuming the moraine of the Dillon glacier to have a depth of only 150 feet 

 below the lake margin above referred to, and in further assuming that the bed 

 of the valley rises gradually from that depth to 0', I am doing so without any 

 ascertained facts. 



I am not aware whether any measurements have been made in order to 

 ascertain the depth of any of the lakes between the Spencer and Mount Cook 

 ranges, with reference to the fall of the rivers flowing from them below the 

 lines of their moraine dams ; but the depth of Lakes Arthur and Ho wick, on 

 the northern side of the Spencer Mountains, is very great as compared with 

 the apparent depth of the bed of the valley of the Duller ; whilst that of some 

 of the larger lakes in the Otago Province, and notably of the Wakatipu, 

 exceeds 1,100 feet, their beds, indeed, extending below the present level of 

 the sea. 



From a consideration of these facts, and of others which I have not thought 

 it necessary to mention in so general a sketch, I think we are justified in 

 concluding that these extinct glaciers originated during an upheaval of the 



