1909-10.] Composition and Character of Oceanic Red Clay. 193 
Outside of the South Pacific the contents of iron in Red Clay tend to 
run fairly uniform — surprisingly so, since the supply of iron to the floor of 
the ocean would be expected to be not less variable than that of manganese. 
Of the specimens here dealt with the only ones exceptional as to iron are 
No. 9 (South Pacific), where it is very high, and No. 10 (off Australia), 
where it is very low. 
The origin of the iron in Red Clays of the Southern Hemisphere, where 
the mother-substances are mainly basic and highly ferruginous, is evident ; 
but the 8 per cent, or so of Fe 2 0 3 found in specimens from the northern 
oceans (Nos. 1, 2, 4, 5) are not so easily accounted for. The mother-substance 
in these regions is mainly white, acid (liparitic) pumice, which usually con- 
tains less than 1 per cent, of iron oxide. It seems probable, therefore^ 
that this iron has been imported from the waters of the ocean and is 
ultimately of terrigenous origin. Much iron is undoubtedly carried into 
the sea by rivers in a soluble form, as carbonate or humate. It may well be 
that some of this finds its way into pelagic waters and deposits, though it 
is not known with certainty that any dissolved iron exists in sea-water, and 
we have no evidence to explain by what processes it is carried into the 
deposits. 
It may be remarked that the figures now found for iron are in general 
rather lower than those of the older analyses, and agree fairly well with 
the average value stated by Clarke. 
In No. 2 the ignition loss is known to be too high, as there was far 
more extraneous organic (carbonaceous) matter present that in ordinary Red 
Clay. No. 8 is a highly phillipsitic deposit, and the exceptional content of 
alkalies is thus accounted for. No. 9 also contains phillipsite, but it scarcely 
betrays itself in the analysis. 
The hydrous or argillaceous portion of Red Clay, which not only pre- 
ponderates in amount but imparts to the deposit its characteristic plastic 
properties, is also interesting as representing the typical degradation-product 
of igneous minerals under submarine weathering. It is well, therefore, to 
compare the percentage composition of the several secondary portions by 
themselves. To this end Table B has been drawn up. The comparatively 
accidental items Mn0 2 and BaO have been omitted, and so much has in 
each case been subtracted from the ignition loss as corresponds to the con- 
version of Mn0 2 . JH 2 0 into Mn 3 0 4 . 
[Table. 
