THE DErTH AND MARINE DEPOSITS OF THE PACIFIC OCEAN. 31 



under the pressure of a hard smooth body, such as an agate pestle, they take 

 on a very shining metallic lustre. The nature of the surface does not vary, 

 so that the part embedded in the clay does not differ from the uppermost 

 one. 



The smallest nodule (four inches in diameter) exhibits well the non-homo- 

 geneous character alluded to ; it is formed of a flat slab, one inch thick, on 

 ■which is grafted another nodule, hemispherical in shape, the surface of sepa- 

 ration being marked by a thin layer of clay. The slab is broken, and the 

 fracture shows that no nucleus is present, or, if one has been present, it has 

 been replaced by the oxides. 



After treatment with hydrochloric acid there remains but very little 

 residue, which is very light and formed of palagonite and other decomposed 

 minerals, and of pumice very much altered. 



Station 4662, 16th November, 1904. Lat. 11° 13.8' S. ; long. 89° 35' W. ; 

 depth, 2439 fathoms. 



No deposit is at hand from this station, but many manganese nodules 

 were received (see PI. 2, fig. 3). There is much difference between the 

 various nodules; they do not appear to have been built on a constant 

 pattern, and have not the general family likeness that one sees, as a rule, in 

 nodules collected in one station. According to their nature and appearance, 

 they may be divided into three groups: (1) imperfect nodules — cakes of 

 palagonite and volcanic ash, more or less impregnated with oxides and 

 covered with a coating of the latter; (2) perfect nodules — very similar to 

 those of Station 4658, that is, having a circular section and two surfaces, 

 the one dome-shaped, the other practically level ; the dome-shaped surface 

 has no mammillae or protuberances, but has the appearance of shagreen, 

 whilst the other surface is furnished with mammillag which have a metallic 

 lustre; (3) the third category is represented by nodules similar to those 

 of Station 4660 ; they have a massive, irregular shape, and look more like 

 clusters of smaller nodules than like one solid lump of the oxides. One of 

 them shows the presence of a good deal of fine-grained, decomposed volcanic 

 ash, forming a kind of nucleus, round which the oxides are deposited, more 

 thickly in some parts than in others, so as to form pronounced mammillse. 



Even the more perfect of these nodules (No. 2) can often be broken in 

 the hands by the exertion of a little strength, and the fracture always 

 appears to take place along cracks which had existed for a long time when 



