356 Transactions. — Geology. 



From the sources of the Waipa the limestone, with the 

 underlying coal - measures, extend southward almost un- 

 interruptedly to Totaro, in the middle Mokau Valley, and 

 westward to Kawhia Harbour and the west coast. On the 

 slopes of Pirongia and the Hauturu Eange they are much 

 obscured by a covering of trachyte tuffs and lavas, which 

 occupy all the higher parts of this watershed, and descend in 

 some places to the sea. 



In the months of March and April, 1859, Dr. Von Hoch- 

 stetter explored the valleys of the Waipa, Mangapu, and Upper 

 Mokau. In his narrative of the journey he describes the 

 pumice terraces in the Lower and Upper Waipa Valley, and 

 makes a number of interesting observations relating to the 

 physical and geological features of the country he passed 

 through. The time at his disposal did not permit him to 

 make a close examination of the geological structure of this 

 district, and his route along the course of the Waipa and 

 Mangapu Eivers carried him to the eastward of the rich lime- 

 stone and papa country already described. 



In the month of January, 1885, under the direction of Sir 

 James Hector, I geologically examined the whole of the coun- 

 try lying between Alexandra and the slopes of Pirongia, in- 

 cluding the district around Hikurangi and the north end of 

 the Hauturu Eange, which was the most southern point I 

 reached on that occasion, on account of the obstruction of the 

 natives. I defined the boundaries of the limestone and asso- 

 ciated marly greensands, and examined the coal-outcrops in the 

 Okoka and Moakurarua Valleys. In my report I also de- 

 scribed the occurrence of hard argillaceous and siliceous sand- 

 stones in the bed of the Ngutunui Stream, at the point where 

 the road to Kawhia begins the ascent of Pirongia. 



Proceeding up the banks of the Mangaone Stream from the 

 point where it joins the Turitea Eiver, the rocks first met with 

 are tough, grey, vesicular trachytes, which were found by a 

 subsequent examination to occupy the narrow ridge dividing 

 this stream from the Maokurarua Eiver, presenting on both 

 sides a long line of steep escarpment varying from 20ft. to 

 80ft. in height. At a point some 20 chains higher up the tra- 

 chytes are cut off by the underlying calcareous sandstones, which 

 appear first in the bed and then on the banks of the stream. 

 Still proceeding up the valley, the calcareous sandstones are 

 found tilted to the north-west at a low angle, and are seen to 

 pass downwards into an impure limestone, which in its turn 

 becomes first gritty, then pebbly, and immediately passes into 

 a coarse conglomerate composed principally of large rounded 

 or subangular boulders of granite and hard somewhat flaggy 

 argillaceous sandstone. The granitic element reaches its 

 greatest development a few chains above the impure limestone 



