218 THE ATLANTIC. [ CHAP. II. 
position of these tissues in contact with sea-water and the sun- 
dry matters which it holds in solution and suspension, these 
salts may pass into the more stable compound of which the 
red clay is composed. 
Our dredgings in the Atlantic, and a subsequent careful ex- 
amination of the soundings, certainly give us the impression 
that the siliceous bodies, including the spicules of sponges, the 
spicules and tests of Radiolarians, and the frustules of diatoms, 
which oceur in appreciable proportion in the globigerina ooze, 
diminish in number, and that the more delicate of them disap- 
pear in the transition from the calcareous ooze to the red clay ; 
and it is only by the light of subsequent observations that we 
are now aware that this is by no means necessarily the case. 
I think it may be well to anticipate here these later results in 
order to make the nature of the deep-sea deposits more clear. 
On the 23d of March, 1875, in the Pacific, in lat. 11° 24’ N., 
long. 143° 16’ E., between the Caroline and the Ladrone groups, 
we sounded in 4575 fathoms. The bottom was such as would 
naturally have been marked on the chart, from its general ap- 
> it was a fine deposit, reddish brown in 
pearance, “red clay: 
color, and it contained scarcely a trace of lime. It was some- 
what different, however, from ordinary red clay—more grit- 
ty; and the lower part of the contents of the sounding-tube 
seemed to have been compacted into a somewhat coherent cake, 
as if already a stage toward hardening into stone. When 
placed under the microscope, it was found to contain so large 
a proportion of the tests of Radiolarians, that Mr. Murray pro- 
posed for it the name “ radiolarian ooze.” 
The Raprotarta, whose name recurs so frequently in these 
pages, and which play so important a part in supplying materi- 
al for these new geological formations, are not very familiar to 
British naturalists. It seems that a very insignificant current 
of cold water passing southward from the Arctic Sea divides 
against the north of Scotland, the main body of it flowing into 
