414 Transactions. — Geology. 



Moa bones are also found, in the deposit at Oamaru in the position 

 figured on page 71 of the report just named. Dr. von Haast also says, in 

 his Beport on the Timaru District (1865), that this silt deposit is underlaid 

 by fine clay or gravel, sloping up from the sea to a height of 686 feet, and 

 containing recent marine shells near the sea ; (see also Eeport on the Can- 

 terbury Plains, 1864, p. 8). The difficulty here is to explain the presence 

 of marine shells at Timaru and at Oamaru, in the latter place in beds of 

 gravel distinctly interbedded with the silt. 



All these facts are explained on the hypothesis that this silt deposit is 

 due to the fine mud brought down by the great rivers and deposited on the 

 bottom of the sea when the land stood some 1,000 feet or so lower than it 

 does at present. Two other difficulties, however, now present themselves. 

 First, the absence of marine fossils in the upper part of the deposit ; and, 

 secondly, the absence of sea-cliffs at high levels in Banks Peninsula. Both 

 these are cases of negative evidence and of no great weight. Many un- 

 doubted marine formations are devoid of fossils, and in our case this may 

 be due to the rapid deposition of the silt, or to the unfavourable nature of 

 the sea-bottom for marine Mollusca. The moa bones, of course, offer no 

 difficulty ; they are the remains of birds floated down the large rivers. 

 With regard to the absence of sea-cliffs on Banks Peninsula — which, how- 

 ever, cannot yet be said to be certainly established — we must remember 

 that sea-cliffs are formed only when the land is stationary, and that, if the 

 movements of depression and elevation were continuous, no sea-cliffs would 

 be formed, or only such small ones as would be easily obliterated. 



It appears to me, therefore, that the evidence in favour of the marine 

 origin of this deposit preponderates enormously over the evidence in favour 

 of its subaerial origin. 



Art. LI. — On the Formation of the Quartz Pebbles of the Southland Plains. 



By W. S. Hamilton. 



[Read before the Southland Institute, 9th May, 1882.] 

 The great abundance of white quartz pebbles about Invercargill, and all 

 over the seaward portion of the Southland Plains, is quite a feature of its 

 geology. To strangers visiting the district, the first question that suggests 

 itself is, where has all that quartz come from ? 



The usual hypothesis entertained is, that great mountain masses have 

 been washed down by the action of the sea, or by the great annual rainfall, 

 and that the quartz reefs or dykes in these mountains, being harder than 

 the adjoining btrata, have withstood the action of the water, and appear as 



