36 THE DEPTH AND MARINE DEPOSITS OF THE PACIFIC OCEAN. 



varied amounts of manganese grains and a few undeterminable crystalline 

 particles, and coated with a thin film of manganese. Palagonite largely pre- 

 dominates over manganese, and has all its usual characters : yellow color, 

 low specific gravity, and hardness. Besides palagonite proper there are 

 also angular yellow grains, which exhibit crypto-crystalline structure, but it 

 is not possible to say what is the mineral they are derived from. One of 

 the slabs is eight inches in length, four inches in breadth, and one and one- 

 half inches in thickness, and is in the same state as it was in at the bottom 

 of the sea, as the coating of oxides extends all over it. One side is still cov- 

 ered with mud, whilst the other is free from it. Both surfaces are very 

 uneven, being full of hollows and protuberances, which resemble worm- 

 tracks in many instances. No organisms have been observed on either 

 surface of the slabs. 



Referring to the description of the Globigerina Ooze from which the slabs 

 were dredged, it will be remarked that curiously enough the minerals had to 

 be estimated as traces; the only deduction that can be made is that the vol- 

 canic material which formed the slabs was deposited during a phase of volcanic 

 activity which had nearly ceased when the ooze itself was laid down. 



Disturbances of the sea-bottom might be indicated by the regular shape 

 of some of the slabs, which are coated with manganese on their ivhole sur- 

 face, after having probably been broken off some much larger flags, as their 

 shape indicates, and that very likely through volcanic action or movement 

 of the earth's crust. There is mention of a similar phenomenon in the 

 Challenger Report on Deep-Sea Deposits, p. 124, Station 281, Oct. 6, 1875. 



Station 4695, 23rd December, 1904. Lat. 25° 22.4' S. ; long. 107° 45' W.; 

 depth, 2020 fathoms. 



By far the greater part of the solid material brought up at this station is 

 represented by large, irregular fragments of palagonitic tuff, up to five 

 inches in length, and coated with oxides of manganese and iron. The ex- 

 ternal surfaces have a distinctly mammillated structure, more pronounced 

 on one side than on the other ; worm-tubes may be seen on both surfaces. 



The tuii has a very low specific gravity, and is easily crushed between 

 the fingers. It is formed of yellow palagonite, with a waxy lustre, in frag- 

 ments from a fraction of a millimeter up to five or more millimeters in di- 

 ameter, cemented by a brown amorphous matter, which represents, most 

 likely, a further product of the decomposition of the palagonite. 



