1879.] 1 61 [Crosby. 
The globigerina-ooze extends from the ordinary shore deposits to a 
depth of 2000 or 2500 fathoms, where it shades off gradually into 
the other distinct abyssal deposit, commonly designated as “red 
clay,” which is found at nearly all points where the depth exceeds 
2500 fathoms. Although quite homogeneous to the naked eye, under 
the microscope this material is resolved into three distinct portions: 
first, and principally, an amorphous and impalpable red clay, which 
is essentially a hydrous silicate of aluminum colored with the red 
oxide of iron; secondly, inorganic particles, which are easily proved 
to be minute flakes of pumice and exceedingly small crystalline frag- 
ments of volcanic minerals, including quartz, feldspar, mica, augite, 
hornblende, olivine, magnetite and titanic iron; thirdly, organic 
particles, which are mainly the silicious remains of Radiolaria and 
Diatoms, with now and then a partially decomposed fragment of 
some calcareous shell, either foraminiferous or molluscan. 
Over the entire area, estimated by Prof. Wyville Thomson at not 
less than ten millions of square miles, where this red clay is accum- 
ulating, and especially in the deep water of the Pacific, the dredge 
brings up large numbers of nodules of very irrecular forms and vary- 
ing in size from minute grains to masses weighing several pounds, 
and consisting chiefly of the iron and manganese per-oxides ar- 
ranged in concentric layers in the matrix of clay, around a nucleus 
formed by a shark’s tooth, or a piece of bone, or an otolith, or a 
piece of siliceous sponge, or more frequently a fragment of pumice. 
Prof. Wyville Thomson has shown that we have in these nodules, and 
in some of their nuclei, ‘‘ample evidence that this abyssal deposit is 
taking place with extreme slowness; for the nodules are evidently 
formed in the clay, and the formation of the larger ones and the 
seoregation of the material must have required a very long time ; 
while many of the sharks’ teeth forming the nuclei of the nodules, 
and which are frequently brought up uncoated with foreign matter, 
belong to species which we have every reason to believe to be extinct. 
Some teeth of a species of Carcharodon are of enormous size, four 
inches across the base, and are scarcely distinguishable from the 
huge teeth found in the Tertiary beds. On this point Mr. John 
Murray, also of the Challenger scientific staff, says: “‘ When there 
has been no reason to suppose that the trawl has sunk more than 
one or two inches in the clay, we have had in the bag over a hundred 
sharks’ teeth and between thirty and forty ear-bones of cetaceans. 
While in the globigerina, radiolarian, and diatom oozes, we have 
PROCEEDINGS B.S. N. H.— VOL. XX 11 JULY, 1879. 
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