30 THE DEPTH AND MARINE DEPOSITS OF THE PACIFIC OCEAN, 
spectively dome-shaped and cone-shaped. Looking normally at one of the 
surfaces, the wider portion is circular, so that there is practically an axis of 
symmetry passing through the apex of both surfaces. The dome-shaped 
one is due to the aggregation of a few smoothly undulating bosses or pro- 
tuberances of large radius. It is very smooth and black, with a metallic 
lustre, and has a distinctly scaly structure. The other surface is mammil- 
lated, has a dull color, and is incoherent, breaking up with little exertion of 
the fingers. A certain amount of clay is, moreover, mixed with the oxides, 
filling the cavities between the mammille. The important point is that living 
organisms are implanted on that surface, arenaceous Foraminifera and Poly- 
zoa, all of them in their natural state, and not containing the oxides of 
manganese and iron. In one case the apex is formed by a well-preserved 
ear-bone, also quite free from these oxides.! 
A section across a nodule shows it to be formed of successive concentric 
layers following exactly in their distribution the contours of the smooth 
surface. The innermost layer has absolutely the same shape as the outer 
one. The difference between the alternate layers is mainly one of hardness. 
In the samples cut, it has not been possible to find what was originally the 
centre of accretion; it probably consisted of some material which has since 
been transformed, or rather, replaced, by the oxides. 
This particular kind of nodule does not appear to have been described 
before; the nearest approach to it, as regards shape, is one represented in 
fig. 4, Plate 3, of the Challenger Report on Deep-Sea Deposits. 
Station 4660, 15th November, 1904. Lat. 9° 55.6’ S.; long. 87° 30’ W. ; 
depth, 2425 fathoms. 
No deposit is at hand from this station, but three large manganese ~ 
nodules were received, on the surfaces of which some of the deposit, a 
Red Clay, is still adhering. These nodules have a massive, irregular shape, 
and the largest one is no less than seven inches in diameter. They are 
characterized by a kind of non-homogeneity, 7. e. they are not formed of 
one solid lump of manganese-iron oxides, but rather of numerous smaller 
nodules grafted the one on the other. There is no metallic lustre, but 
1 Dr. Lee holds that the logical conclusion is that the cone-shaped mammillated surface is the 
upper surface, the smooth shining one being embedded in the clay, whereas Sir John Murray takes 
the view from his ‘‘ Challenger” experience that the smooth surface was the upper one, and points to 
figure 1, Plate IX, of the Challenger Report on Deep-Sea Deposits as confirmation of this, the smooth 
surface in his opinion being formed above the level of the deposit. 
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