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 mammillge. 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. ^, 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, i. 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. 



