Ancient Glaciers of JVeiv Zealand. 259 



The glaciers around Mt. Earnslaw are still at work, as 

 they have been for ages, in extending the valley. The 

 streams that are formed by the melting of the ice — the riv- 

 ers Dart and Rees — are all the year turbid with silt, which 

 is the rock that has been ground fine by the glacier — the 

 flour from the mill — which they deposit in the upper end of 

 the lake. In this manner some six or eight miles of the val- 

 ley have been filled up to a height of a few feet above the 

 present level of the lake. We have but to extend the forces 

 now in operation on Mt. Earnslaw to the whole valley of 

 Lake Wakatipu, to have an accurate and satisfactory explan- 

 ation of its formation. 



There is another feature of great interest in the history of 

 this valley. On the shore of the lake, about twelve miles 

 above Queenstown,* is a limited deposit of Tertiary lime- 

 stone ; containing as fossils, Ostrea Wullerstorfii, Cucullcea 

 alta, (J. Wort/tingtoni, Panopwa plicata, and many others. 

 The junction of the limestone with the crystalline rocks be- 

 neath, can be seen but a few feet below the surface of the 

 lake. The limestone being at the present level of the Avater, 

 the valley must have been eroded to that depth before the 

 limestone was formed. As its deposition took place beneath 

 the waters of the ocean, the valley was at one time an arm 

 of the sea, and was afterwards upheaved to its present eleva- 

 tion or higher, and the wearing-down of the valley contin- 

 ued. We have, therefore, in the sequence of events that 

 resulted in the formation of Lake Wakatipu, the follow- 

 ing series of stages. 



(1. ) The Southern Alps existed as a sloping table-land, the 

 highest remaining point of which is Mt. Cook. On this high 

 table-land were deposited immense amounts of ice and snow, 

 brought by the warm, moist winds from the ocean, and form- 

 ins: the glaciers that flowed oft' in various directions towards 

 the sea. One of these ancient rivers of ice had its source 



* At T on the accompanying map. 



