Speight. — The Geology of Banks Peninsula. 369 



the names of the valleys which they head. Their heights are as follows : 

 Gebbie's Pass, 360 ft. ; ' and McQueen's Pass, 350 ft. 



Immediately to the east of McQueen's Valley the crater-ring rises to 

 1,843 ft. in Dyke Hill, so called from two prominent dykes on its northern 

 slope, and this is succeeded by Kaituna Pass, on the eastern side of 

 which rises like a bastion the steep slopes of Mount Herbert (2.805 ft.) ; 

 this passes into Herbert Peak, from whose summit a long gentle slope 

 according with the angle of the lava-streams which form it reaches 

 down to the harbour. This is cut off on the eastern side by the valley 

 which leads down to Purau Harbour, and is then succeeded by the 

 remnants of the crater-ring which lie between it and the southern side of 

 the entrance. 



At the head of the harbour there are two well-marked peninsulas which 

 determine the position of three considerable indentations of the shore-line — 

 viz., Governor's Bay, Head of the Bay, and Charteris Bay— the first known 

 as Manson's Peninsula and the second as Potts Point ; while on the eastern 

 side of the Mount Herbert slope there lies Purau Bay, another deep in- 

 dentation. These are all instances of depression topography, and the bays 

 are drowned valleys with their lower reaches prolonged beneath sea-level 

 at the same grade as the exposed floors of the valleys. In the middle of the 

 harbour, in practically the centre of the crater-ring, lies Quail Island, 184 

 acres in area, seven-eighths of a mile long by half a mile broad, and its 

 highest point 282 ft. above sea-level, with steep cliffs 200 ft. high facing the 

 harbour, but with gentler slope on the other sides. It lies off the end of the 

 peninsula dividing Charteris Bay from the Head of the Bay, and at low tide 

 it is possible by wading to cross the space between the two. About half-way 

 over there is a rise in the connecting ridge which is permanently above sea- 

 level and is known as Little Quail Island. 



The harbour is very shallow in its upper parts, and at low water there 

 are extensive mud-flats, the water gradually deepening towards the entrance, 

 where it is about 10 fathoms deep ; the floor is almost flat, the deep water 

 continuing right up to the rocky wall-like shores. In one place, just opposite 

 to the entrance to the breakwater, a rocky area rises above high-water mark, 

 and at another place, about a mile nearer the heads, opposite Ripa Island, 

 a solid rock rises to about 10 ft. of the surface. With these two excep- 

 tions the floor, of the harbour is entirely covered with mud and any irregu- 

 larities are completely masked. 



Lyttelton Harbour was described by Haast as a caldera, the entrance 

 between the heads forming the barranco, and his explanation was 

 adopted by Hutton. Allowing for the modification of the southern wall 

 by the slope reaching down from Mount Herbert Peak, the name, as used 

 in its widest sense, is applicable. It has, however, been considerably 

 modified by stream action : the crater-wall has been broken down com- 

 pletely at Gebbie's Pass, and the majority of the topographic features are 

 due to stream erosion and not to the effects of a paroxysmal explosion. 

 This point will be dealt with more fully when the geological history is 

 considered. 



2. Akaroa Harbour. (Plate XXVI, figs. 1 and 2.) 



Akaroa Harbour is of characteristic ealdera-like form, with the entrance 

 at the heads forming the barranco. It is fiord-like in some of its features, 

 eleven miles in length and three miles wide in its widest part. The entrance 

 is a mile wide, and flanked by perpendicular cliffs, the southern being 525 ft. 

 in height and the northern about 300 ft. Inside the northern entrance, 



