400 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
about 50 per cent of the whole deposit. The siliceous remains of radiolarians, diatoms, and sjiouge 
spicules are nearly always present, but usually in small (|uantity. lu the purest samples of 
globigerina ooze mineral particles are exceedingly rare, and consist for the most part of, a few minute 
fragments of feldspar, augite or hornblende, magnetite, volcanic glass, sometimes more or less altered, 
with which are associated a small (piantity of clayey matter and the oxides of iron and manganese. 
In the less pure samples the mineral particles become. more numerous, feldspar, augite, olivine, 
hornblende, and more rarely mica, broiizite, actinolite, chromite, glauconite, quartz, and cosmic dust 
being met with. The terms pulvinulina ooze, orbulina ooze, and biloculina ooze have arisen through 
a misconception, the samples examined having been passed through sieves and only the larger particles 
preserved. They are all really globigerina oozes. 
Average conqMsition of the Challenger samjilea of glohigerina ooze. 
Carbonate of lime: 
Pelagic foraminif'era 5!!. 10 
Kottom-living forauiinilera 2. lii 
Other organisms <J. 24 
64. 47 
Kesidue: 
Siliceous organisms 1. 64 
Minerals...' a. 3:1 
Fine •u asliiiigs 30.56 
35. 53 
100 
5. rteropod ooze. — This deposit resembles the globigerina ooze in nearly all particulars, differing 
mainly in the greater abundance of the shells of jielagicmollusks (pterojiods and heteropods principally), 
which sometimes nmkes up over 30 per cent of the deposit. In oceanic regions the dejiosit approaches in 
constitution a globigerina ooze, being, however, more friable and granular and less homogeneous and 
uniform Irom the 2>resence of these larger shells, but the mineral particles are the same as in a globi- 
gerina ooze from the same region. Ne.ar the coast line the pteroiiod deposits resemble the terrigenous 
deposits in the large number of shore materials and organisms which enter into their comiiosition, or 
fragments from coral reefs and calcareou.s organisms from shallow water may make iq) a large jiart of 
the ileposit. The Challenger samples range in depth from 390 to 1,525 fathoms, the average depth being 
1,011 fathoms. The iievcentage of carbonate of lime varies from over 50 to nearly 100 per cent, princi- 
pally due to shells of pelagic foramiuifera and pelagic mollusks. The remains of siliceous organisms 
are usually present in small (piantity. Sometimes, however, they may make up nearly 20 per cent of 
the whole deposit. They are princi))ally sponge spicules, radiolarians, diatoms, along with a few casts 
of foramiuifera and arenaceous foraminifera. Mineral ^(articles, i)rinci](ally magnetite, augite, feldspar, 
hornblende, etc., make up from about 1 to 10 ])er cent. 
Average composition of the Challenger samjdes of pteropod ooze. 
Carbonate of lime: 
Pelagic foraminifera 
Bottom living foraminifera 
Other organisms 
Kesidue : 
Siliceous organisms 
Minerals 
Fine washings 
47. 15 
3. 15 
28. 05 
70. 25 
2. 89 
2. 85 
15. 01 
20.75 
B. Tekrigenocs Deposits. 
lOU 
6. Blue mud. — This name has been adopted for the deposits most frequently met with in the deeper 
waters surrounding continental laud, and in all inclosed or partially inclosed seas more or less cut off 
from free communication with the open ocean. The materials of which the blue muds are principally 
composed are derived from the disintegration of continental land, and are very complex in character. 
AVhen collected this deposit is blue or slate-colored, with an upper red or brown layer which had been in 
immediate contact with the water. The blue color is due to organic matter and sulphide of iron in a 
line state of division, and these muds have, as a rule, when taken from the sounding tube, a smell of 
sulphuretted hydrogen. 
The red or brown color of the thin watery upper layer is evidently due to the presence of ferric 
oxide or ferric hydrate, but as the deposit accumulates this oxide is transformed into sulphide and 
ferrous oxide in the presence of organic matter in the underlying layers. When dried the deposit 
becomes gray or brown, owing to the oxidation of the sulphide of iron. Sometimes the samples are 
