512 
Proceedings of the Royal Society 
principally of the frustules of Diatoms. When dry it is a dirty 
white siliceous hour, soft to the touch, taking the impression of the 
fingers, and contains gritty particles which can be recognised by the 
touch. It coDtains on an average about 25 per cent, of carbonate 
of lime, which exists in the deposit in the form of small Glohigerina 
shells, fragments of Echinoderms and other organisms. The residue 
is pale white and slightly plastic ; minerals and fragments of rocks 
are in some cases abundant ; these are volcanic, or, more frequently, 
fragments and minerals coming from continental rocks and trans- 
ported by glaciers. T\iq fine washmgs consist essentially of particles 
of Diatoms along with argillaceous and other amorphous matter. 
We estimate that the frustules of Diatoms and skeletons of siliceous 
organisms make up more than 50 per cent, of this deposit. 
Radiolarian Ooze. — It was stated, when describing a Globigerina 
ooze, that Eadiolarians were seldom, if ever, completely absent from 
marine deposits. In some regions they make up a considerable 
portion of a Globigerina ooze, and are also found in Diatom ooze 
and in the terrigenous deposits of the deeper water surround- 
ing, however, the land. In some regions of the Pacific, the 
skeletons of these organisms make up the principal part of the 
deposits, and to these we have given the name “ Eadiolarian ooze.” 
The colour is reddish or deep brown, due to the presence of the 
oxides of iron and manganese. The mineral goarticles consist of 
fragments of pumice, lapilli, and volcanic minerals, rarely exceed- 
incy 0’07 mm. in diameter. There is not a trace of carbonate of 
O 
lime in the form of shells in some samples of Eadiolarian ooze, 
but other specimens contain 20 per cent, of carbonate of lime 
derived from the shells of pelagic Foraminifera. The clayey 
matter and mineral particles in this ooze are the same as those 
found in the red clays, which we will now proceed to describe. 
Red Clay. — Of all the deep-sea deposits this is the one which is 
distributed over the largest areas in the modern oceans. It might be 
said that it exists everywhere in the abysmal regions of the ocean 
basins, for the residue in the organic deposits which have been 
described under the names Globigerina, Pteropod, and Eadiolarian 
ooze, is nothing else than the red clay. However, this deposit 
only appears in its characteristic form in those areas where the terri- 
genous minerals and calcareous and siliceous organisms disappear to 
