804 MR D. FERGUSON ON 



volcanic tuffs. There are rounded and angular felspathic grains in the greywacke, 

 and their prevailing grey colour, contrasted with the black of the shales, gives a 

 distinguishing shade to the rocks of this division. . 



The total thickness of the rocks of the lower division is not disclosed in any of 

 the exposures seen, as they invariably descend below sea-level ; and when we do find 

 rocks unquestionably underlying them, they are covered unconformably by the rusty- 

 brown rocks. The lower division may also end downward in an unconformity. 



The unconformity between the oldest rocks and the rusty-brown rocks, which 

 are apparently conformable with the dark shales and greywacke division, shows also 

 that the dark shales and greywackes filled up the hollows in the old land surface 

 on which they were laid down. The higher ground of the old land surface was 

 sufficiently elevated to be only completely covered when the lower portion of the 

 rusty-brown division was being deposited. 



The greatest thickness of the dark shales and greywackes will be above the 

 deepest hollows of the old land surface on which it was deposited. So far as present 

 observation has been made these are not exposed, and we cannot therefore state 

 definitely the full thickness. It is not likely, however, to exceed greatly the thick- 

 ness exposed in Cumberland Bay, about 1200 feet. 



Diabase. — In the black shales of this division in Moraine Fiord, Cumberland Bay, 

 there is a sill of diabase. It was probably intruded during the deposition of the 

 rocks of the middle division, and was contemporaneous with volcanic eruptions which 

 took place when the lower beds of that division were laid down. There are much 

 volcanic debris and some tuffs in the beds of the middle division, and their red rusty- 

 brown colour is very probably due to the decomposition of the trachytic lavas. 



Cape George Series (Greenish- Grey Rocks). 



These rocks occupy the lowest geological horizon on the island. They are 

 separated, as already noted, from the rocks overlying them by an unconformity. 

 The irregularities of their upper surface form the heights and hollows of an old land 

 surface. They were tilted and probably folded before the beginning of the denuda- 

 tion which shaped the old land surface. 



They are of a glistening greenish-grey colour, thinly banded, and intensely hard. 

 The banding is a secondary cleavage which shows " Augen " structure, and both this 

 and the indurated character of the rocks are due to crustal or folding movements, 

 producing pressure-metamorphism. 



They were only seen in two detached small masses, one on the south-east shore of 

 Cumberland Bay, adjacent to Moraine Fiord, and the other in the harbour of Cape 

 George and the glacier glen leading into it from the north-west. They descend below 

 sea-level in both cases, and do not rise 500 feet above it. We never find them on 

 the higher slopes of the central range. 



