Thomas. — Geology of Tongariro and Tauvo. 345 



extent all round the lake ; they are thickest, however, near 

 the northern end, reaching the thickness of 300ft. in one of 

 the cliffs. Throughout the district, indeed, the pumice is 

 widely spread over the surface of the ground, especially to the 

 east, north-east, and north of the lake. It is found even on 

 the summits of the highest mountains — here, however, merely 

 as a sprinkling, whilst at the bases of the hills and in the 

 valleys it may reach the depth of hundreds of feet. The 

 manner in which the river-valleys have been filled up with 

 pumice, out of which the water has excavated terraces, is 

 sufficient evidence of the influence of running water in dis- 

 tributing the pumice. There are, however, many facts which 

 shov^ that much of the pumice has travelled through the air 

 and fallen in showers in its present position. 



Popular belief ascribes this pumice to the great volcanic 

 mountains Euapehu, Ngauruhoe, and Tongariro, which lie to 

 the south of the lake, the showers of pumice being supposed to 

 have been brought by the prevailing south-west winds. Any 

 one who will examine the distribution of the ash from the 

 Tarawera eruption* will see that the explanation has a prima 

 facie probability, for in that case the ash was spread out in 

 just such a manner. But the examination of the neighbour- 

 hood of Tongariro shows that such an explanation is not 

 applicable to the distribution of the pumice in the Taupo 

 district. The pumice is less abundant in the neighbourhood 

 of the great mountains thaii elsewhere in the district, and, as 

 will be shown further on, the rocks of Tongariro belong to a 

 different group. The pumice around Lake Taupo contains 

 considerable quantities of rhyolite - fragments other than 

 pumice, especially of the perfectly-laminated variety which 

 has been termed lithoidite. Near Ouaha, on the east side of 

 the lake, I found angular blocks of lithoidite 3ft. and more in 

 diaiaieter, and weighing two tons or more, imbedded in the 

 pumice-deposits. It is obvious that blocks of this size cannot 

 have travelled any great distance, whether by the agency of 

 water or the force of volcanic explosions, but must have been 

 derived from some source near at hand. The only localities 

 near Taupo that I am acquainted with where this variety of 

 rock is found in sitil in lava-streams are at Motutaiko, the 

 island in the lake, and Hamaria, three or four miles distant, 

 on the shores of the lake. We might perhaps not unnaturally 

 look to Tauhara, the volcanic cone at the north end of the 

 lake, as a source of part of the pumice. This mountain has 

 the height of 3,603ft., and the country at its base on both 



* A map showing the distribution and depth of the ashes from the 

 Tarawera eruption will be found in the " Keport of the Eruption of 

 Tarawera and Eotomahana," by the writer. 



