NOTES ON A ROCK FROM NEW ZEALAND. 
211 
composition, but very indefinite and confused. It lias some 
similarity with the spherulites before mentioned, but occurs 
in too great quantity for this explanation to be probable. 
On the whole it is evident that a solid rock, which, how¬ 
ever, varied from a pumice to such an obsidian as we have 
considered in the early portion of this paper, has been blown 
into small fragments by the explosion. 
Unfortunately my specimen was far too small to permit 
of an analysis, and I have not seen any in the New Zealand 
papers which have reached me.* 
It may be worth while to mention that at the time of the 
disturbance Tongariro became somewhat explosive, and even 
the snow-clad Ruapehu began to emit smoke. At the other 
end of the line of fissure White Island had been unusually 
active for some time. It is worked for sulphur, and the 
workmen had been unable to get to it on account of increased 
violence in its eruptions. Since June it has been in eruption 
to an extent sufficient to be reported in the English papers. 
As the country all round Auckland is volcanic and many 
of the hills are craters—Mount Eden, for instance, which 
closely overlooks the city and forms, in fact, a suburb of it— 
there has naturally been some anxiety felt as to the probability 
of another outbreak of these hills. This set of volcanoes, 
however, is much older than the Taupo series—indeed, we 
may consider it likely that the latter replace the former as 
safety valves. The fissure has opened in a slightly different 
position, as is not unfrequent. 
* Since this note was communicated to the Society I have been 
able, through the kindness of Mr. W. J. Harrison, F.G.S., to make an 
analysis of another specimen of the dust, with the following result:— 
I. 
II. 
Silica 
.. 61-9 
58-07 
Titanic acid 
.. 1-0 
Alumina 
.. 12-9 
13-22 
Ferrous oxide 
..3-8 
10-10 
Ferric oxide 
..2-8 
Lime 
.. 7-1 
7-04 
Magnesia.. 
.. 2-7 
4-46 
Potash 
.. 2-0 
1-58 
Soda 
.. 3-8 
2-59 
Loss on ignition.. 
2-2 
1-50 
100-2 98-56 
In column II. I have copied for purposes of comparison an analysis 
of the Armatliwaite dyke as given by Mr. Teall in his paper on “ Some 
North of England Dykes,” Q.J.G.S. for May, 1884, p. 224, from which 
it will be seen that the principal difference consists in the much larger 
proportion of iron present in the English rock from which the darker 
character and more basaltic look follow. 
