THE VOYAGE OF H.M.S. CHALLENGER. 
]GS 
by a simple filling of the shell, but seem to be due to a chemical combination. There 
were in these deposits none of the smooth pale yellow and green casts so abundant in the 
Green ]\Iuds along continental shores. If these red coloured casts be treated with warm 
hydrochloric acid and the iron thus extracted, a number of colourless globules are 
obtained, which have resisted the action of the acid. It has been found that these casts 
consist of hydrated silicate containing alumina, lime, magnesia, and alkalies. The mean 
diameter of the minerals rarely exceeded OTO mm., and were usually much smaller; 
these were felspars, black mica, augite, hornblende, and magnetite. The great bulk of 
the residue after removal of the carbonate of lime, however, consisted of pumice stone in 
a fine state of division, wdth amorphous matter. Eadiolaria and Diatoms made up about 
1 per cent, of the whole deposit. 
The trawhng at 1350 fathoms gave many rounded fragments of pumice, from 6 to 8 
cm. in diameter, covered with oxide of manganese, and the branch of a tree several feet 
in length which was carbonised in some places (see Diagram 13). 
There were many very productive hauls with the surface nets between the Fiji Islands 
and the New Hebrides — Pteropods, Hetcropods, and pelagic Foraminifera being specially 
abundant. With the exception of a very large cylindrical species of Coscinodiscus, 
Diatoms were very rare both on the surface and at the bottom. It was observed that the 
larger Foraminifera, such as S'pliseroidina dehiscens, Pidvinulina menardii, and thick- 
shelled OrhidinaB, were procured in greatest abundance when the tow-net was dragged at 
a depth of 80 or 100 fathoms. 
New Hebrides to Raine Island. — The deposits between the New Hebrides and Raine 
Island (see Chart 27 and Diagram 13) varied greatly with depth, and were very in- 
teresting. At 2G50 fathoms not a trace of carbonate of lime could be detected either by 
the microscope, or by treating the Red Clay with weak acid. At 2450 fathoms there 
Avas 1 or 2 per cent, of carljonate of lime, consisting of a few broken fragments of Fora- 
minifera. At 2440 fathoms there was a Red Clay on the surface with 5 per cent, of 
carbonate of lime, but three inches beneath the surface a much lighter coloured deposit 
containing a very large number of Foraminifera, and 32 per cent, of carbonate of lime. 
At 2325 fathoms there was 32 per cent, of carbonate of lime, consisting of the dead shells 
of pelagic Foraminifera and a few Coccoliths and Rhabdoliths. The condition of things 
at 2440 fathoms Is worthy of special remark. It very frequently happened during the 
cruise that the deeper layers contained less lime than the surface ones, but only on 
two or three occasions did it happen that there were more calcareous shells in the deeper 
layer of the deposit as in this case. The surface layer, it will be observed, was the same 
in nearl}" all respects as the deposit in 2450 fathoms 80 miles to the eastward, and the 
deeper layer resembled that at 2325 fathoms still farther to the eastward, or the deposits 
in a lesser depth towards Raine Island, which contained over 50 per cent, of carbonate of 
lime, so that possibly a subsidence of the bottom had taken place subsequent to the 
