260 Ancient Glaciers of JVew Zealand. 



in the region of Mi; Earnslaw — then, however, greatly dif- 

 ferent from its present form — and flowed over what is now 

 the valley of Lake Wakatipu. This old-time glacier contin- 

 ued its slow motion towards the sea for unknown ages, until 

 it had ground out the solid rock to a depth of 5,000 or 6,000 

 feet in vertical thickness and for over 100 miles' in length. 



(2.) The work of this mighty glacier was finally termin- 

 ated by a sinking of the land, which caused the valley to 

 become an arm of the sea, similar in every respect to the 

 deep narrow fiords that form such a characteristic feature of 

 the wild West Coast of New Zealand at the present day. 

 What was before an Alpine valley, filled with hundreds of 

 feet of ice, then became the home of huge oysters and many 

 other forms of marine life, whose remains we now find in the 

 limestone. We know that the sea filled the valley for a long 

 time, since the compact gray limestone that it left behind 

 was not formed rapidly, as sandstone and conglomerate may 

 be, but the material had to be first gathered from the waters 

 to form the shells of mollusks and foraminifera, or the hard 

 parts of corals, crinoids, etc., and these worn down to a fine 

 detritus by the waves, and spread out as a calcareous sedi- 

 ment, before the hardening process of rock-making could 

 commence. Together with the limestone are beds of fine 

 shale, and masses of conglomerate composed of both angular 

 and rounded pebbles, and containing fossil shells ( Crassatella 

 ampla) ; these deposits speak of other, although minor 

 changes, during the time that the sea occupied the valley. 



(3.) In the third stage the land was again upheaved to 

 the dignity of a mountain chain, whose lofty summits became 

 covered with fields of snow and ice, which, seeking an equi- 

 librium, again flowed as a glacier down the valley of Lake 

 Wakatipu. This second extension of the ice-stream down 

 the old valley resulted in the removal not only of most of 

 the limestone that had been deposited, but also of 1,400 

 feet of the crystalline rocks beneath. The limestone on the 

 shore of the lake is thus shown to be an inter-glacial deposit, 



