PHYSIOGRAPHY OF EASTERN NEW GUINEA, ETC. 93 
(ut) SUBMARINE ActTiviry.—In many places in the 
vicinity of the craters, the water of the harbour is very hot. 
The temperature of the water rises and falls rhythmically. 
This seems to indicate the presence of submarine fumaroles. 
Submarine eruptions of considerable intensity and in 
deep ocean water have been reported by the naval 
authorities off the south coast of New Britain. 
(1v) AsH-BEDS.—As mentioned previously, the whole 
of the Rabaul area is built up of ash-beds extending for a 
considerable distance south and west. Good sections may 
be seen in the deep and narrow ravines near Bita Paka, 
about fifteen miles south-west of Rabaul. Sections may also 
be seen in the road cuttings on the Namanula Road at 
Rabaul. The different eruptions and stages of eruptions 
ean be clearly marked at Bita Paka in the varying features 
of the ash. Numerous beds of yellow and brown ash and 
pumice are interspersed by beds of black scoria. Occasion- 
ally, large lumps of consolidated ash, similar to the 
agglomerate at the craters, are found embedded in the ash. 
The observed thickness is at least about 400 ft. It is 
impossible to state the total depth, as the base level of the 
streams is still in ash. The writer regrets that circum- 
stances did not permit the making of a permanent record 
of the Bita Paka section. Judging by the presence of 
quantities of pumice and yellow ash, the original lava 
would seem to belong to the acid group. 
(v) Seismic FEATURES.—The present activity of the 
area is further evidenced by continual tremors and oeea- 
sional shocks of considerable violence. There has never 
been any accurate record kept, and needless to state there 
were no recording instruments. The area is not altogether 
suitable for recording instruments, on account of the soft 
nature of the ground. The facts recorded in this section 
are those observed by the writer and others who have been 
compelled to share many strange experiences of seismic 
energy. 
Distinction must be made between the different classes 
of shoeck— 
(1) The violent shocks of some amplitude affecting 
wide areas ; 
(2) The less intense shocks and tremors of medium 
amplitude affecting only loeal areas: 
