42 MR. W. В. В. OLIVER ON THE 
detachable material. The pink colouring matter which gives the island its 
unique appearance is contained in a surface-deposit. 
Probably the chief factor which determines the peculiarities of the 
vegetation is the poisonous steam which rises from the surface of the crater- 
lake. The analysis of samples of the water from this lake taken at different 
times gives slightly different results, but the amount of free hydrochloric 
acid present averages over five per cent. 
The following by Dr. Maclaurin is taken from Professor Park’s ‘ Geology 
of New Zealand’ (Wellington, 1910). 
Grains per gallon. Per cent. 
Sodium sulphate ........ e eee eee 620 0:88 
Ammonium sulphate .............. T 1788 248 
Potassium sulphate .................. 101 0-14 
Ferrous and ferric sulphates .......... 346 0:49 
Calcium sulphate ..... een nhe 351 0°50 
Magnesium sulphate.......... e 182 0:26 
Hydrochloric acid (free) .............. 3832 5:47 
7165 10:22 
Also present, silica (9 grains per gallon), and heavy traces of boric acid, 
arsenic, and copper. 
The presence of hydrochloric-acid fumes in the atmosphere has the effect 
of contaminating all fresh water on the island, so that the sulphur-workers 
resident there have to procure their supplies in jars from the mainland. In 
foggy weather the air becomes particularly unpleasant, and it may then be 
said to rain dilute hydrochloric acid. Gannets (Sula serrator), which breed 
in large numbers on the island, are frequently disturbed by noxious fumes 
from the crater. No vegetation occurs within or on the upper slopes of the 
outside of the crater. The vegetation occurs near the coast only, and usually 
in three definable belts :—(1) The sea-cliffs and coastal slopes support a low 
growth of grasses and herbaceous plants; (2) next follows a belt of dense 
scrub ; (3) followed by an open low shrub-formation. It is a significant 
fact that serub occurs mainly on the southern and western sides of the 
island, for the prevailing winds being from the south-west, would usually 
earry the steam-clouds in a north-easterly direction. There can be little 
doubt also, that, in addition to the distribution of the vegetation on White 
Island, the paucity of species and the stunted character of the dominant 
plants are due to the harmful effects of hydrochloric-acid fumes. 
No meteorologieal observations have been made on White Island, but, 
situated in S. lat. 37° 30', its climate will be similar to that of Te Kaha and 
