As we had now successfully accomplished the ascent of the two great mountains, I determined to leave the tapued district as soon as possible, and strike a south-easterly course across the Onetapu Desert to the southern base of the Kaimanawa Mountains, in order to examine the geological formation of that region. I had noticed when examining the western banks of the Waikato River, that on its opposite side, where the mountains rose in all their grandeur, the geological aspect of the country was entirely different from that of the Rangipo table-land, the geological formation of which was principally composed of fluvial drift, with a deep superimposed stratum of pumice, and over which again was a final stratum of volcanic earth, formed principally by the decomposition of the trachytic rocks forming the numerous volcanic cones which bounded the table-land on the west. Owing, however, to the flooded state of the Waikato, it was impossible to reach its opposite side, where the Kaimanawa Mountains rose in the form of a stupendous wall. I therefore resolved to head the river at its upper waters, in order to get into the Kaimanawa country in that way. On the day following our ascent of Ruapehu, we started across the plains in the direction indicated above, and as the day was fine we rode leisurely along, coaxing our half-starved horses on their way by occasional feeds from the luxuriant growth of native grasses which covered that part of the Rangipo. In this portion of the plains there was a great variety of native grasses, and among them were those known to the natives as the _parakerake_ and _pekipeki_, while the tussock grass grew in clumps often three feet in height. Dotted all over the plain likewise was a curious spiked plant, which our horses carefully avoided whenever they came in its way. This singular plant grew at the bottom, in the form of a widespreading circular tuft, composed of narrow sword-edged leaves, the ends of which were as pointed and as sharp as a lancet. From the centre of the tuft rose a stem varying from a foot to two feet in height, which bristled at the top with a spike-like thorn, while clustering all over its sides were long thin thorns, pointed, and as sharp as needles. So strong and sharp are the thorns of this plant, that the natives often use them as spurs.