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1911-12.] Report on Rock Specimens. 
All the igneous rocks have been examined microscopically by Dr Flett, 
who has kindly supplied the following description : — 
“ Of the igneous rocks that were sliced for microscopic examination 
one much decomposed specimen may be a basaltic tuff, and several belong 
undoubtedly to the quartz-dolerite group, but the remainder are olivine 
basalts and olivine-free basalts. Some of them are rich in olivine, but in 
most that mineral is rather scarce, and it is never in a good state of pre- 
servation. As a rule the specimens are somewhat decomposed, and none of 
them is absolutely fresh, so that there is no probability that they are of Re- 
cent age ; this practically excludes the possibility that they have been derived 
from the modern volcanoes of Iceland. Taking the series as a whole, they 
have many features that make it unlikely that they have been derived from 
the volcanic rocks of Carboniferous age in the west of Scotland (Clyde 
Valley, etc.). On the other hand, they have marked affinities with the 
Tertiary volcanic rocks of the Inner Hebrides and the north of Ireland. The 
quartz-dolerites are no exception to this, for members of this class occur as 
intrusive sills and dykes among the Tertiary volcanic rocks. This conclu- 
sion rests only on the general characters of the collection, for among these 
rocks there is not one that shows peculiarities by which its source can be 
established beyond doubt.” 
The table on the next page shows the number and condition of the 
rock specimens from this Station. A glance at this table makes it at once 
apparent that such a range of formations as our collection represents could 
hardly occur in place within the small space swept by the trawl. 
Mode of Occurrence of the Rock Specimens . — A close study of the 
specimens shows that at the time they were dredged all, without exception, 
had been only partially embedded in the ooze of the sea-floor. This is 
apparent from the disposition of the attached organisms, such as siliceous 
sponges, serpulse, and horny worm-tubes and hydroids and arenaceous 
foraminifera, as well as from a slight coating of manganese oxide, which 
occur on the exposed parts, but are absent from the embedded surfaces. 
The manganese coating is most pronounced near the junction of the two 
areas. 
The examination in the “ Challenger ” office of the deposit from the floor of 
the ocean at this locality shows it to be a “globigerina ooze” with 63T7 
per cent, of calcium carbonate, leaving a residue of 36 - 83 per cent. In 
the calcareous part the remains of pelagic and bottom-living foraminifera, 
echinoid spines, ostracods, and coccoliths have been observed, but it is 
evident that warm-water surface foraminifera have been its chief source. 
The residue is shown to be made up of 1 per cent, of siliceous organisms 
