Hill. — Tempo Plateau and Lake. 463 



valley of the Wai-o-tapu. Elevation and depression are comple- 

 mentary events in the history of volcanic phenomena, and one 

 cannot exist without the other. Probably ever since the water- 

 shed from Ruapehu and Tongariro presented the same general 

 slope as at present a river has flowed towards the north, but, as 

 explained already, its direction appears to have been into the 

 Bay of Plenty. The present Waikato River could only have 

 flowed after the filling-up of Taupo ; and if the greater Taupo 

 is considered, not less than twelve hundred years would have 

 been required to fill the lake. During that time there could have 

 been no Waikato River. Nor does it appear as if the Waikato 

 had flowed for a long period. The rift through which the river 

 flows is made up in many places of loose pumice, and yet the 

 sides are steep and denudation has done but little, there being 

 as yet no valley formation as usually understood. 



Pumice. 



The Taupo Lake and the rift appear to have supplied the 

 pumice which has covered so much country in the North Island ; 

 but how long ago cannot be stated. A glance at the country 

 suggests a period that is comparatively recent. The freshness 

 of the pumice, the absence of denudation, the limitation of 

 vegetation, all show that no other volcanic event has taken place 

 since the pumice was deposited. Maunganamu is composed of a 

 fine trachyte almost similar in appearance to pumice, and 

 resembles it in many respects. A similar deposit is met with 

 along the northern portion of the lake. The great depression in 

 which Taupo is situated might easily lead us to understand that 

 extensive areas have been covered to a great depth with the 

 debris that was thrown out, and so hidden volcanic orifices. 

 Travellers have wondered at the extensive distribution of pumice 

 over the Island, and every visitor to the volcanic district is struck 

 with the everlasting sterility of the country where the pumice is 

 found. The Napier hills a few feet below the surface are covered 

 with it to the depth of several feet, and it is found, sometimes 

 below a capping of black light soil, and sometimes as a surface 

 deposit, over all the stratified-rock country to the westward as 

 far as Tarawera. Further west the pumice-deposit increases, and 

 the whole country is covered to the depth of many feet, the 

 varieties being numerous. Beyond the Rangitaiki River the 

 pumice is mixed with volcanic grits and angular and partly 

 rounded stones such as are found on the strand at Taupo. As 

 you descend towards the lake from Opepe every exposure by the 

 roadside shows an increasing cmantity of stones and rock-masses, 

 and the latter increase in size, some being tons in weight. The 

 distribution of the pumice, however, is not limited to the east- 



