88 PROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND. 
peaks rising to 7,000 ft. New Britain, as far as is known, 
is entirely volcanic, and there are many craters both active 
and quiescent throughout its length. To the north of New 
Britain is a small group of islands known as the French 
Group. The main island is a great crater, partly 
submerged, known as Johann Albrecht. As observed inside, 
from the deck of a steamer, the crater must have a diameter 
of three miles. The walls are perfectly perpendicular to a 
height of about 600 ft., while the water in the crater is 
over 400 fathoms or 2,400 ft. deep. To the south of New 
Britain is one of the great deeps of the Pacifie, known as 
the Planet Deep. Depths up to 4,000 fathoms have been 
recorded. Fringing the east coast of New Ireland is a 
series of volcanic islands roughly parallel to the coast-line. 
St. John Island is noted for its mud-springs and fumaroles, 
and contains at least one active geyser known as Balamus- 
son. These islands rise out of deep water over 1,000 
fathoms. The Rabaul voleanic system is situated at the 
extreme eastern end of the island of New Britain, surround- 
ing the harbour known variously as Blanche Bay, Simpson- 
haven, or Rabaul Harbour. 
III—_HISTORY AND DEVELOPMENT OF THE 
RABAUL VOLCANIC SYSTEM. 
The original crater of the Rabaul voleanie system is 
undoubtedly the depression known as Simpsonhaven. The 
definite walls surrounding the harbour, though now much 
weathered, composed of vast beds of yellow ash, pumice, 
and scoria, and the general shape, indicate this fact 
(text-fig. 2). Even in its original condition it must have 
been of considerable extent. At present the depression has 
a length of five miles and a breadth of two. The other 
craters are marginal to Simpsonhaven. The oldest seems 
to be Mount Mother, 2,500 ft. high, whose tall, steeply 
sloping sides indicate a typical tuff-cone (Plate III, fig. 1). 
This erater is quite extinct. Two further marginal craters 
were formed later, one at the foot of Mount Mother and 
the ether on the South Daughter. These two craters appear 
much alike and no apparent distinction as to age is obsery- 
able. They are both plugged, but contain active fumaroles. 
When Dampier visited Blanche Bay in 1699 he observed an 
active voleano on the north side of the bay. This probably 
refers to one of these craters. An eruption is reported to 
