Hamrton.—On Formation of Quartz Pebbles of Southland Plains. 415 
water-worn pebbles in our diluvium. On closer examination, however, it is 
found that this hypothesis cannot be the true one. In all the mountains 
which surround the plains in question, such as Longwood, the Takitimos, 
the Hokonuis, and the mountains to the east of Wyndham, quartz veins are 
of rare occurrence, and form a quite insignificant part of the whole. It is 
also seen that the detritus or gravel formed at the base of these ranges is 
of quite a different character to that under our notice. The gravel of the 
beds of the Oreti and Mataura formed from these mountains is, for the 
most part, blue in colour and composed of very hard sandstone or slate. 
The upper plains of Southland, such as the Waimea, Mararoa, Otapiri, 
and Lora Plains, are composed of gravel of this kind, while the lower plains 
near thé sea-level are composed of heavy beds of milk-white quartz of the 
kind we are speaking of; and it is further found by the bores that have 
been made, that these beds alternate with heavy beds of clay and seams of 
lignite to the depth of more than 200 feet. These beds of quartz could not, 
‘therefore, have been deposited from the mountains behind our plains on the 
landward side. 
Similar difficulties stand in the way, if we suppose them to have been 
derived from the seaward side. The syenite of the Bluff hill contains 
plenty of quartz, but only as a component of a rock as hard as quartz itself; 
and which water wears into round balls remarkable for their great elasticity 
and hardness. 
The Stewart Island granites could not account for the deposition of 
these beds anything more easily ; nor the sandstones of Ruapuke, or the 
Greenhills. 
The only remaining possible supposition is, that there were mountains 
of quartz in siti, which were degraded on the spot, and left these beds to 
mark the place where they stood. This is so unlikely that it can hardly be 
entertained, as mountains of this kind occur nowhere else in the neighbour- 
hood, and even if such had been the case here, the great hardness of such 
mountains must have resisted the denuding forces as much as the sand- 
stones and the granites in their neighbourhood. No vestige or evidence of 
such mountains is anywhere seen, while the beds of clay and lignite would 
have to be otherwise accounted for. 
However much geologists may object to it, the true theory of the forma- 
tion of these pebbles seems to be, that they are silicified wood ; and the more 
they are examined, the more convincing does the proof become that these 
beds represent, in one condition, the remains of ancient forests, just as the 
coal beds represent the same thing in another condition. On examining 
these pebbles closely, it is seen that, in almost every case, the appearance 
of wood structure can be detected. In some cases it is quite perfect ; the 
