60 The N.Z. Journal of Science and Technology. [April 
very small catchment area behind them are said to persist all the year 
round, a tribute to the high and steady rainfall of this part of Samoa. 
The three falls on the east side, above the village of Lono, are all from 
hanging valleys of about the same height, 300 ft. or 400 ft., probably hung 
on a hard lava-bed. That behind Masina is at a higher level, about 500 ft. 
A still higher fall lies behind Salimu. There is considerable variety of 
rock in the shore exposures and the beach boulders. At Samanea there 
is a dense basalt dyke through a coarser and lighter rock of andesitic 
appearance. The point at the west end of Masina Village is composed 
of a coarse picritic basalt, very similar in appearance to that described by 
Cross from Haleakala, in Maui, Hawaiian Islands. The beach boulders 
include, besides, dense basalts and a highly feldspathic type. At Salimu 
some of the beach boulders are zeolitized. 
Falifa Bay is not so steep-walled, and receives on its south side a fairly 
large river, falling over a low but wide waterfall. This river appears to 
drain an extensive flat plain behind, which I am informed is very steep- 
walled, and is possibly a very large crater. If so, it rivals Haleakala in 
size, and is one of the largest craters of the world. The attention of future 
visiting geologists may be directed to the desirability of confirming or 
disproving this information. 
The upper parts of the numerous creeks on TJpolu are noted for their 
waterfalls, and probably present good sections of the rocks. The only one 
I had an opportunity to examine was Leapuna Creek, near Falemauga, 
a locality supposed to be a likely place for gold. The creek flowed in a 
steep gorge, and contained nothing but basalt boulders. The walls were 
composed of fairly fine-grained basalt, separated by a thin layer of red 
clayey rock, which appeared to represent an old erosion surface. There 
is said to be much red clay in the neighbourhood of Lanoto’o, a high crater- 
lake to the south-west of Apia. 
The relatively flat and fertile country between Apia and Mulifanua 
looks from the distance as if it were composed of sedimentary or alluvial 
rocks or volcanic ash, and Friedlander states that ash enters into its 
composition. I cannot believe, however, that there is any extent of ash- 
beds, since I am informed that there is no extent of ploughable land 
suitable for sugar-growing, and this would certainly be expected if such 
flat ground were composed mainly of this material. 
Very few of the lavas of Upolu have been examined petrographicaliy. 
Jensen describes only two, an olivine basalt from Vailima Plantation, and 
an olivine basalt-porphyrite from Papaseea Falls, both near Apia. Weber 
describes feldspar basalts (with olivine) from the Tapatapa Boad and from 
Malata, trachydolerite from six miles south of Apia, and nepheline basanites 
from Fale o le Fee and Suionu. He mentions determinations by Mohle 
of limburgite from Malifa Bathing-pool and from Vailee, and plagioclase 
basalts from these and many other places. 
Lava-tunnels and Water-supply. 
The formation of lava-tunnels in the Matavanu eruption has already 
been mentioned. Such tunnels are a characteristic of basaltic eruptions 
of the Kilauea type, and have an almost circular cross-section while the 
flow is active, but when the supply of lava ceases that in the tunnel drains 
out, leaving only a little in the bottom, so that a cooled tunnel has an 
almost circular section except for a flat bottom. In any tunnel the height 
and breadth are remarkably constant, except when branching takes place. 
