506 Tranaactions. — Geology. 



III. EUAPEHU. 



Euapehu I ascended on the 4th April, 1897, from the 

 saddle between Ngauruhoe and Euapehu. I am greatly 

 indebted to E. T. Batley, Esq., at Moawhango, for having 

 provided me vpith good horses, an excellent companion, and 

 good advice. The most important thing is to camp out as 

 high as possible, in order to arrive at the top early the next day, 

 and to have plenty of time for exploring the extensive summit. 



We succeeded in finding, far above the apparent line of 

 good camping-ground, a detached patch of bush, where there 

 were also water in some pools of a lava-gully and tussock- 

 grass for the horses. From that place, the next day, we 

 reached the north summit, Te Heuheu, in 3 hours 35 minutes, 

 partly riding and partly walking. The slope was in many 

 places free from snow, and we walked mostly on a ridge, 

 skirting a small ?ieve on our left (in ascending). The slope I 

 estimate to be about 20° only. 



The summit of Euapehu is, roughly speaking, a vast, 

 oblong, almost level plain, covered with neve — viz., hard 

 snow — and surrounded by a number of rocky peaks, the most 

 prominent of which are in the south, south-west, and north. 



Before entering into a further description a few more 

 general remarks may not be out of place. Euapehu surpasses 

 the snow-line considerably — i.e., that height above which 

 more snow falls than can be melted. On mountains like this 

 the excess of snow is counterbalanced, as we know, in that 

 a part of the snow travels to lower altitudes — partly as 

 avalanches, partly as glaciers— to be melted down below. 

 Now, suppose a volcano surpassing the snow-line, and pro- 

 vided with a crater right on its top : if the crater-rim be intact, 

 of even height all round, and no internal heat existent, the 

 snow is bound to fill up the whole crater, and to overtop or, as 

 it were, overflow its rim on all sides. In this case the crater 

 must be obliterated entirely ; one would find a snow-dome on 

 its top, without any trace of a pit or hole. But as soon as we 

 suppose the crater-rim to have one or more gaps the streams 

 of neve, or glacier ice, can escape ; and the upper parts of the 

 inner slopes of the crater, which generally are very steep, and 

 therefore do not hold much snow, will become visible. The 

 drainage of frozen water, which in the former case will occur 

 evenly all over the rim indiscriminately, in the latter case will 

 be confined to the gaps, if they are of any extent. Instead of 

 a complete gap, it would be also sufficient if the rim were 

 lower on some parts than on others : the lower parts would 

 be overflowed by the neves and the upper ones become free 

 from snow. Anyhow, the deeper part of the crater-bottom 

 must be covered by everlasting snow. 



