758 SCIENCE. 
shows that the percentage of carbonate of 
lime in the deposits falls off much more 
rapidly at depths between 2,200 and 2,500 
fathoms than at other depths. 
The Red Clay which occurs in all the 
deeper stretches of the ocean far from land, 
and covers nearly half of the whole sea-floor, 
contains—in addition to voleanic débris, 
clayey matter, the oxides of iron and manga- 
nese—numerous remains of whales, sharks, 
and other fishes, together with zeolytic crys- 
tals, manganese nodules, and minute mag- 
netic spherules, which are believed to have 
a cosmic origin. One haul of a small trawl 
in the Central Pacific brought to the surface 
on one occasion, from a depth of about two 
anda half miles, many bushels of manganese 
nodules, along with fifteen hundred sharks’ 
teeth, over fifty fragments of earbones and 
other bones of whales. Some of these or- 
ganic remains, such as the Carcharodon and 
Lamna teeth and the bones of the Ziphioid 
whales, belong apparently to extinct species. 
One or two of these sharks’ teeth, earbones 
or cosmic spherules, may be occasionally 
found in a Globigerina Ooze, but their oc- 
currence in this or any deposits other than 
Red Clay is extremely rare. 
Our knowledge of the marine deposits is 
limited to the superficial layers; as a rule 
the sounding tube does not penetrate more 
than six or eight inches, but in some positions 
the sounding-tube and dredge have been 
known to sink fully two feet into the de- 
posit. Sometimes a red clay is overlaid by 
a Globigerina Ooze, more frequently a Red 
Clay overlies a Globigerina Ooze, the transi- 
tion between the two layers being either 
abrupt or gradual. In some positions it is 
possible to account for these layers by re- 
ferring them to changes in the condition of 
the surface waters; but in other situations 
it seems necessary to call in elevations and 
subsidences of the sea-floor. 
If the whole of the carbonate of lime 
shells be removed by dilute acid from a 
[N. 8. Von. X. No. 256. 
typical sample of Globigerina Ooze, the in- 
organic residue left behind is quite similar 
in composition to a typical Red Clay. This. 
suggests that possibly, owing to some hypo- 
gene action, such as the escape of carbonic 
acid through the sea-floor, a deposit that 
once was a Globigerina Ooze might be 
slowly converted into a Red Clay. How- 
ever, this is not the interpretation which 
commends itself after an examination of all 
the data at present available; a considera- 
tion of the rate of accumulation probably 
affords a more correct interpretation. It 
appears certain that the Terrigenous De- 
posits accumulate much more rapidly than 
the Pelagic Deposits. Among the Pelagic 
Deposits the Pterapodand Globigerina Oozes- 
of the tropical regions, being made up of the 
calcareous shells of a much larger number 
of tropical species, apparently accumulate 
at a greater rate than the Globigerina Oozes. 
in extra-tropical areas. Diatom Ooze being 
composed of both calcareous and siliceous 
organisms has again a more rapid rate of 
deposition than Radiolarian Ooze. In Red 
Clay the minimum rate of accumulation 
takes place. The number of sharks’ teeth, 
of earbones and other bones of Cetaceans,. 
and of cosmic spherules in a deposit may 
indeed be taken as a measure of the rate 
of deposition. These spherules, teeth and 
bones are probably more abundant in the 
Red Clays, because few other substances 
there fall to the bottom to cover them up, 
and they thus form an appreciable part of 
the whole deposit. The volcanic materials. 
in a Red Clay having, because of the slow 
accumulation, been for a long time exposed 
to the action of the sea-water, have been 
profoundly altered. The massive manga- 
nese-iron nodules and zeolitic crystals pres- 
ent in the deposit are secondary products. 
arising from the decomposition of these vol- 
canic materials, just as the formation of 
glauconite, phosphatic, and calcareous and 
barytic nodules accompanies the decompo- 
