14 
H. T. FERRAR. 
an area of some 20G square feet. The spheres are all planed off to an even surface, 
and there is no change in the slope of the hill to correspond with the junction of the 
two rocks. 
Turtle Back Island. 
Turtle Back Island, low and insignificant in aspect, lies in the bay between the 
Winter Quarters peninsula and the ice-tongue in Erebus Bay. It is less than a 
quarter of a mile long and about 100 yards broad, is rectangular in plan, and rises to a 
height of 50 feet. The loose rock-material on the surface of the island is bedded, and 
the layers of dark rock form a small anticline, of which the axis is the longer or 
N.E.-S.W. diameter of the island. Two boulders of kenyte (trachydolerite) with 
lenticular crystals of felspar (447 and 484) were found on this island. They are similar 
to the rock-specimens brought from the lower slopes of Mount Erebus, but are more 
glassy and of a black colour. Black augite-olivine nodules (448 and 451) are 
common, but the mass of the island consists of fine-grained fragments of olivine- 
basalt (449). 
Black Island. 
In point of size Black Island comes next to Ross Island. It lies south of 
latitude 78°, and is roughly triangular in plan, having a side about 15 miles long 
(Fig. 32, p. 58). It shows two central peaks, each over 3000 feet high, and appears to 
be composed entirely of volcanic rock. It is quite surrounded by glacier-ice, and is 
therefore almost a nunatak. It is probably connected with White Island, situated to 
the eastward, by an isthmus rising about 200 feet above sea-level. Specimens from 
rock in situ were obtained from a hill, 900 feet high, near the north end of the island. 
Compact and vesicular basalt-lavas (593, 594, 595) were obtained high up, but no 
specimens of rock in situ could be obtained from the lower slopes, which were 
completely covered with rock-debris. At the south-east end is a yellow trachytic 
rock (609, 610); it appeared to be a dyke nearly a quarter of a mile wide breaking 
through the black basaltic rock. The rock forms a bold headland nearly 400 feet 
high. The major joints, which are vertical, strike north-w T est and south-east, and 
notable variations in the appearance of the rock occur on either side of the joints. 
There are two other apparently similar rock-exposures near this spot, but time did 
not permit their examination. 
White Island. 
This island is 20 miles long, but is less than 5 miles broad. Its longer axis is 
nearly north-and-south ; the island lies between the longitudes 167° and 168° E., and 
is south of latitude 78° S. The land rises very suddenly out of the ice which surrounds 
it, and attains a height of 2000 feet. The only rock in situ obtained from it is a 
