DEEP-SEA EXPLORATION. 
401 
homogeneous; at other times the aspect is heterogeneous, owing to the presence of large fragments of 
rocks anil sliells and small i'ragments of calcareous organisms. When wet the deposit may he jilastic 
and behave like a true clay, hut as a rule these muds may he described rather as earthy than as clayey. 
The ChaUem/er samples ranged in de|)th from 125 to 2,800 fathoms, the average depth being 1,411 
fathoms. The percentage of carbonate of lime varies from a more trace to over 30 jier cent, consisting 
mainly of pelagic and bottom-living foramiuifera along with other calcareous fragments. 
The shells of pelagic species of foramiuifera, which make up so largo a part of a globigerina 
ooze, are not abundant nor universally distributed in the Idue muds, the remains of shallow-water or 
bottom-living organisms predominating in many cases. The remains of siliceous organisms are usually 
present in small quantity, sometimes making up 15 per cent of the whole dejiosit, and consist of dia- 
toms, radiolarians, 8)ionge s[>icules, arenaceous foramiuifera, and casts of the calcareous organisms in 
glauconite or some allied silicate. The mineral jtarticles are mostly derived from 1 he adjacent lands, 
and consist largely of the fragments and minerals of the various rocks forming the continents. The 
size of the mineral and rock particles varies much with the position ; they are as a rule larger near 
the shore and smaller as the dee|) sea is approached, except in those regions alfectcd by lloatiug ice. 
More than half of the deposit is in many cases made up of the mineral particles, consisting largely of 
rounded grains of ipiartz, along with particles of older crystalline or schisto-crystalliue rocks, quartzite, 
sandstones, and limestones. Among minerals, besides quartz, are orthoclase and jdagioclase, green 
hornblende, aiigite, mica, epidote, etc. ; glauconite can not be considered characteristic of liluo muds, 
but is to be found in Jiearly all of them, though in limiteil (piantity compared with the green muds. 
Averaf/e composition of the Challenger samples of blue mud. 
Carbonate of lime : 
Pelagic foraniinifera 7. 52 
Bottom-living foramiuifera 1.75 
Other organisms 3. 21 
12.48 
Residue : 
Siliceous m-gani.sms 3.27 
Mineral.s 22. 48 
Fine washings Cl. 77 
87. 52 
lOU 
7. lied mud . — Along the Brazilian coast of South America the terrigenous deposits offshore are 
different from the deposits found in similar positions along other continents in that they are all of a 
red-brown or red-brick color, apparently due to the largo iiuantity of ocherons matter carried into the 
ocean by the Amazon, Orinoco, and other South American rivers, and distributed by oceanic currents 
along these coasts. Similar red deposits are formed iu the Yellow Sea off the Chinese coast near the 
month of the Yang tse Kiang. Although organic matters are probably as abundant as in the deposits 
along other coasts, still they do not seem to be sufficient to reduce the whole of the peroxide of iron 
to the state of protoxide, nor does sulphide of iron accumulate here as in the blue muds. 
It is a remarkable fact that there is no trace of the green-colored glauconitic casts of foram- 
inifera and other calcareous organisms, nor of any of the glauconite grains which usually accompany 
these casts iu other terrigenous deposits. There are a few spicules of siliceous sponges, but Iriistules 
of diatoms and the remains of radiolarians arc exceedingly rare or wholly absent. In other respects 
this deposit resembles a blue mud. The Challenger samples varied in dei)th from 120 to 1,200 fathoms, 
the average de])th being 623 fathoms. The |)crcentage of carbonate of lime varies from 5 to 60 per 
cent, apparently depending more on jiroximity to the monlhs of rivers than on depths. The shells of 
pelagic and bottom-living foramiuifera are the most almndant of the calcareous organisms. The 
mineral particles range from 10 to 25 per cent, ([uartz being the most abundant. 
Average composition of the Challenger samples of red mud. 
Carbonate of lime; 
Pelagic f'oraminifera 13. 44 
Bottom-living foraniinifera 3.33 
Other organiams 15.51 
32. 28 
Residue: • 
Siliceons organisms 1 
Minerals 21.11 
Fine washings 45. 61 
67.72 
F. C. B. 1896—26 
100 
