their Relation to Geological Formations. 201 
gradations apparently consequent on occupying intermediate 
depths, and often represented by the grey ooze. It would 
also appear that at the greatest ascertamed depths conditions 
prevail unfavourable to the existence of organisms with calci- 
ferous tissues or calcareous skeletons. Life, however, still 
exists in the abyssal basins where the grey and red clays are 
formed. In several hauls, in one instance from 2975 fathoms, 
there were brought up :—holothurids of considerable size with 
rudimentary calcareous neck-rings; delicate branching, almost 
membranous Bryozoa; tube-building annelids, and tests of 
Foraminifera, the two latter being made up of particles of the 
red clay alone. And on one occasion, between Kerguelen Island 
and Melbourne, the ‘red clay,” at the depth of 2600 fathoms, 
yielded Holothurias, starfishes, Actinias, Palliobranchs, Huplec- 
tella-sponges, &c.: those with calcareous parts were rather 
stunted. 
Considering the existence in the ocean of vast numbers o 
diatoms, polycystines (these, there is no doubt, habitually live 
at or near the surface), sponges, and other organisms, whose 
skeletons consist of silica—also that rock-particles in the 
finest state of division, from their occurrence everywhere im 
the atmosphere, must be scattered over the sea-bottom by 
the distributive action of currents, it was to be expected that 
the foraminifer-ooze would not be purely calcareous. The 
analyses published by Messrs. David Forbes and John Hunter 
(late of the Queen’s College, Belfast) show that such is actually 
the fact—the former having found, in a specimen from the 
depth of 2435 fathoms, 23°34 silica, 5-91 ferric oxide, 5°35. 
alumina*; the latter, in a specimen taken in 1443 fathoms, 
26°77 fine insoluble gritty sand (rock-débris), 1°33 alumina 
(soluble in acids), and 2°17 sesquioxide of iron (soluble in 
acids) +. Mr. Buchanan, of the ‘Challenger, has found 1 per 
cent. of a reddish mud, consisting of silica, alumina, and red 
oxide of iron, after washing and subjecting samples of the ooze 
to the action of weak acid. These results seem to have satis- 
fied the scientific Director of the Survey that, allowing certain 
difficulties as mere matters of detail, the question as to the 
origin of the red clay is in the main solved. Grant sufficient 
free carbonic acid in the water of deep ocean-basins to dissolve 
all calcareous bodies, such as foraminifer-shells, that fall into 
them, the insoluble constituent alone will remain as a deposit. 
Professor W.C. Williamson proposed a similar hypothesis 
many years ago to account for the absence of calcareous shells 
in the siliceous (Diatomaceous) deposits of Bermuda and Vir- 
* Proc. Royal Soc. vol. xviil. p. 490. + 1b. p. 428. 
