404: Transactions. — Geology. 



the level of the land, and alterations in the courses of the 

 river in the Lower Waikato basin, are numerous and interest- 

 ing from the surface-geologist's point of view, and a great deal 

 might be written about them, but it is not my intention to 

 enter fully into a description of this basin at present. One of 

 the most interesting features of the Lower Waikato basin is 

 the Matahura-Whangamarino Valley, which lies to the west- 

 ward of the wooded Hapuakohe Eanges. The Matahura and 

 Whangamarino Elvers rise in the centre of it, the former 

 flowing to the south and the latter to the north-west. Their 

 sources are a very short distance apart, and are separated by a 

 low saddle. This has evidently been the valley of a large river 

 at some period, and does not owe its erosion to the small 

 streams which now occupy it. There are evidences of vast 

 erosion high up on the sides of the valley, the remains of ancient 

 river-terraces now worn and wasted by the elements. This 

 was probably the course of the Waipa Eiver when the Waikato 

 flowed into the sea in the Hauraki Gulf. The alluvium of the 

 valley is quite different from that of the Waikato ; it is an 

 argillaceous deposit, free from pumice or the rhyolite sands 

 which characterize the deposits of the Waikato. It is very 

 fertile. The lands in the Matahura and Waerenga Valleys 

 derive their rich qualities from it, the latter being some of the 

 most fertile in the Waikato district. It is the same alluvium 

 which characterizes the rich lower terraces of the Waipa 

 Eiver, from Ngaruawahia up into the limestone land in the 

 King-country, and is traceable along the Mangawhara Eiver 

 into the Matahura Valley. 



Passing now from the Waikato to the Piako basin, we find 

 again evidences of changes, as shown by the raised beaches, 

 ancient terraces, and the river-alluvium. The level, swampy 

 plain extending from the Hauraki Gulf to Te Aroha is plainly 

 a combination of the bed of the gulf : the base of the hills on 

 the western side of the valley shows distinctly the remains of 

 the former coast-line. At Maukoro, twenty miles inlaiid from 

 the sea, close to the western bank of the Piako, and near the 

 confluence of the Waitoa and Piako Elvers, an old raised beach, 

 standing about 17ft. above high-water mark, is to be seen. 

 There is a consolidated slag or marl deposit containing shells 

 and unmistakable crab-holes, such as we see on the soft 

 beaches at present. Along the banks of the Piako there are 

 numerous sand-banks and banks of sea-shells, clearly showing 

 that at no very remote time the Lower Piako Valley was a 

 shallow bay of the sea. The immense quantity of pumice and 

 other detritus from the volcanic districts laid down as river- 

 alluvium in this large valley shows that it was the valley of a 

 great river flowing through a volcanic country ; and I have no 

 doubt but the Waikato brought down the alluvium seen in the 



