THE DEPTH AND MARINE DEPOSITS OF THE PACIFIC OCEAN. 29 



two other stations where the deposit is a Red Clay. The nodules are of low 

 specific gravity, with no shining lustre, and are rather incoherent, being 

 always mixed with a large proportion of foreign elements. 



The first stage towards the formation of nodules is represented by cakes 

 of palagonite and other decomposed minerals (chloritic minerals and decom- 

 posed felspar, besides palagonite formed by decomposed glass), in which the 

 mineral particles are coated with a thin layer of the oxides ; the whole cake 

 may also be coated with the oxides. The more perfect nodules are not 

 formed of solid oxides, but round a core of palagonite comes a layer of 

 oxides, then another layer of palagonite, and the latter is again covered 

 with oxides, and so on. 



The most interesting point about this station is that it contains remark- 

 able examples of deposition of manganese-iron oxides round very different 

 centres of accretion : we have here some curiously shaped pseudo-nodules 

 which are undoubtedly silicons sponges iTnpregnated with manganese and iron 

 oxides. The entire sponge is not always wholly preserved, but the siliceous 

 skeleton can always be detected, unaltered, in the midst of the oxides in 

 which it is embedded. 



Organisms, sometimes of large size (Hydroids), are specially abirndant, 

 and can be seen attached in their original position on the surface of nearly 

 all the specimens. They are often distributed on the whole of the surface 

 of the nodule, so that the latter was either not deeply buried in the mud, or 

 had its position shifted. 



The lack of metallic lustre alluded to is very likely due to the large pro- 

 portion of palagonite and other products of decomposition, taking part in the 

 formation of the nodules. 



It may be added that it was possible to observe on certain grains of 

 palagonite the gradual transformation of brown volcanic glass into that 

 mineral, but such instances are of rare occurrence. It was also found, in 

 studying this material, that certain crystalline minerals, possibly felspar, 

 form products of decomposition very similar to that of volcanic glass. 



Station 4658, 14th November, 1904. Lat. 8° 29.5' S. ; long. 85° 35.6' W, ; 

 depth, 2370 fathoms. 



The nodules from this station (see PI. 1, figs. 1, 2) are as remarkable for 

 their large size as for their constant shape, which is on a definite pattern. 

 These nodules have each two surfaces, which are, roughly speaking, re- 



