400 Transactions. — Geology. 



drift-pumice and light sands, enclosing the trunks of trees and 

 carbonised wood. The worn shore-like sides which surrounded 

 these pumice-beds, cliffs of tufaceous rock, often plainly water- 

 worn, aiid the stratified horizontal layers of light drift pumice, 

 leave but little doubt that a large area in this part of the Wai- 

 kato basin was occupied by a lake through which the river 

 flowed. In my opinion, deposits of light pumice sands such 

 as are here found could only be laid down in still water. 



The elevation of the outlet through the range was at first 

 300ft. above the present bed. A steep narrow channel was 

 formed through the pass, the successive stages in the process 

 of low'ering being marked by horizontal terraces round the 

 south end of the gorge and the lake - basins in the valleys 

 above. These terraces are of immense proportions, ranging 

 to 200ft. above the present river-bed. An excellent example of 

 these terraces may be seen near Ateamuri Bridge, where the 

 Rotorua-Taupo Eoad crosses the river. Below the gorge 

 the river eroded a deep and narrow channel through the loose 

 tufa countr}^ along the base of the wooded mountains of the 

 King-country. Here one looks in vain for the characteristic 

 features which mark an ancient valley. The country through 

 which the river flows has the appearance of an old plateau, 

 along the bases of the ridges and hills of which the water cuts 

 its channel, and there is nothing to mark its course as an 

 ancient feature of the landscape — no prolonged area of de- 

 pression along the course of the river, and very little terrace 

 formation. 



Another remarkable deflection from its natural course 

 w^ould seem to have taken place in the Waikato at Hinuwera, 

 fourteen miles above Cambridge. Here we have a broad, well- 

 defined valley, bordered on either side by waterworn cliffs, 

 from 30ft. to 40ft. in height, sloping down through Hinuwera 

 in a north-easterly direction towards Matamata. It is con- 

 fluent with the valley of the Waikato above. The trend and 

 height of the river-terraces, the character of the alluvium, the 

 waterworn cliffs, and the general topographical features of the 

 land all point to the conclusion, I think, that this was its old 

 natural valley, and that the Waikato once flowed down 

 through it to the sea in the Hauraki Gulf. For the causes 

 which brought about the change in the Waikato's course here 

 we seek in vain amongst the topographical featm'es of the 

 land. There is nothing to show why its natural course was 

 impeded, and why it is not now flowing down the Hinuwera 

 Valley to the Hauraki Gulf, instead of taking the unnatural 

 course it has through the ridges of the Maungatautari and 

 Hinuwera Eanges. 



Here, again, we have the same sequence of events recorded 

 that took place at the Whakamaru. It would appear that the 



