278 
Proceedings of the Royal Society of Edinburgh. [Sess. 
The smaller fragments would not sink so deep as the larger ones, and would 
therefore be the sooner exposed. 
The material distributed by human agency consists of seventy pieces of 
furnace clinker and cinder, ten fragments of coal, the largest of which is 
only 1 J inches in greatest diameter, which seems to indicate that this locality 
is in the direct route of steamboats. 
Station 48. 31st May 1910. 
Lat. 28° 54' N., long. 24° 14' W. ; depth 5000-5500 m. 
Globigerina Ooze (?). 
Among the material from this Station there are two chips of dark 
chalk-flint with white crust denoting the original outside of the nodules 
from which they were derived. The edges of the chips are rubbed, which is 
suggestive of their having been glaciated. 
Metamorphic rocks are represented by one small specimen of foliated 
epidiorite or hornblende schist (1 x f X J inch), which has been ice-moulded, 
but is now covered with manganese oxide. 
The igneous rock fragments are volcanic, four of which are thoroughly 
decomposed basalt rocks (the largest 1J x f X \ inch); but the chief feature 
of the material consists of sixty-seven fragments of rolled oceanic pumice. 
The foliated epidiorite and the chalk flints, and in a less degree the 
basalt fragments, appear to connect up this material with that from Stations 
10 and 95, as if this Station were still within the influence of the northern 
drift ice. The pumice fragments, which are of the rolled type so widely 
distributed over the bed of the ocean, as is shown by the work of former 
expeditions, more especially by that of the Challenger , must have had 
quite another history. A study of them brings out many points of interest. 
They are all small and more or less rounded, but in the process of attrition 
to which they have been obviously subjected, the harder portions, such as 
the sanidine crystals, have been left projecting above the more fragile 
cellular parts. Hence it is clear that the shape of the fragments has been 
greatly determined by the projecting crystals as shown in PL VIII. 
figs. 1 and 2. 
Some of the pumice fragments enclose pieces of glassy rock with 
porphyritic crystals, evidently representing portions of the cooled crust 
of the lava-flow broken up and involved in the still liquid scum. The 
pumice must have emanated from some volcanic centre producing acid 
lavas, probably an oceanic island which, like Krakatoa, during violent 
eruption, sent off great floes of floating pumice, the fragments of which 
