16 
H. T. FERRAR. 
lie on the surface and in the small crateriform hollow at the centre of the island. 
There are one or two dykes which project slightly above the loose scoriaceous 
matter of the general surface. 
The Dellbridge Islands. 
These four islands lie three or four miles south-west of the base of Mount Erebus 
and twelve miles north of Winter Quarters ; although the nearest together are two 
miles apart, they are probably all remnants of a once continuous land-mass. 
Inaccessible Island, the most northerly of the group, is elongated in an east-and- 
west direction, and has an almost sheer cliff facing the south. Its north side slopes at 
about 40°, and is therefore too steep in places to hold the disintegration-products of 
the rocks which form its higher peaks. The dimensions of the island are, roughly, 
length two miles, breadth half a mile, and height 500 feet. Mr. Hodgson collected 
specimens here, and tells me that the rocks are much confused, but generally dip to the 
north. The specimens include a red vesicular trachytic lava (802), porphyritic basalts 
(805), yellow trachytes (803), and trachydolerite of intermediate character (804) ; on 
the south-east end there are many irregularly bedded chrome-yellow bands. Tent 
Island is nearly rectangular in plan, and has sides about a mile long. Its greatest 
height is about 400 feet, and the highest point is close above the steep north-west cliff. 
The upper surface of the island slopes to the south-east and agrees with the dip of the 
lava-beds. The lowest rock exposed is a basalt-agglomerate (817) which occupies the 
lowest 100 feet on the north-west cliff. It is covered by sheets of a vesicular glassy 
kenyte (463-466), with lenticular porphyritic crystals of felspar, like the rock of Cape 
Royds. These sheets have a dip of about 20°, are parallel, and are each about 20 
feet thick. Razor Back Island is merely a ridge of rock rising 100 feet above the 
water. Its sides meet to produce a central ridge of which the angle is not much 
greater than a right angle. The long axis is perhaps half a mile long, and along the 
same straight line is the Little Razor Back Island. The specimens obtained are 
vesicular lavas of olivine-basalt (470, 471) and of trachytic rocks (473, 476). 
