210 
NOTES ON A KOCK FROM NEW ZEALAND. 
Mount Tarawera is described by travellers as presenting 
tlie appearance of a glassy dome, no doubt a rock sucli as 
that just described and the mountain was one of the most 
strictly tabooed of all the district, for on its summit were 
exposed the bodies of the chief men of one of the most 
powerful of the tribes. It had been their cemetery for the 
whole of their traditional history, and it is certain that it 
had never been in eruption since the Maoris entered New 
Zealand. Whether this furious outburst has exhausted the 
forces below, or whether, as in the case of Vesuvius, in 79 
a.d., it is but the re-establishment of an active crater, must be 
left for the future to determine. The celebrated Dr. Hocli- 
stetter, who made a geological survey of New Zealand in 
1859, expressed his opinion that the whole country w,s so 
completely undermined by the decomposing and removing 
action of the hot springs, that eventually an explosion would 
occur by the falling in of the crust. It is probable that 
something of this sort happened. So far as any accounts 
which I have seen relate, there was no flow of any lava. 
Showers of stones and mud have done the damage, and dust 
has been so distributed over the district as to completely 
cover the vegetation and in many places destroy even the 
trees. 
A microscopical examination of a specimen of the dust 
collected on the steamer ‘‘Southern Cross,'’ in the Bay of 
Plenty, which has been placed at my disposal by my friend, 
J. E. Clark, B.A., of York, shows the same relation of 
things. There are very few portions which can be referred 
to the ejection of a fluid lava, and probably these are really 
fragments of a pumice which has been shattered by the ex¬ 
plosion. There are glass fragments of all degrees of porosity 
—in some the pores are approximately spherical, while others 
again are drawn out into mere threads and twisted about most 
confusedly. Other pieces of glass contain microliths similar 
to those previously mentioned as occurring in the Tarawera 
obsidian, and also the globulites, both singly and in strings. 
The felspar is mostly orthoclase, but one cleavage fragment 
which is well twinned gives the extinction of oligoclase. 
This fragment also contains some inclusions of a brownish 
glass, which have apparently the same crystalline shape as 
the enclosing crystals—so-called negative crystals. I have 
found no hornblende, but there are a few grains of the 
rhombic pyroxene, with strong dichroism. 
There are also a number of fragments of a lightest brown 
almost opaque substance, which when quite thin can be 
examined in polarised light and shows a doubly refracting 
