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THE DEPTH AND MARINE DEPOSITS OF THE PACIFIC OCEAN. 33 
side there are worm-tracks and arenaceous Foraminifera, together with 
some egg-like white capsules. The flat side is, therefore, in this case the 
upper one. 
Station 4685, 10th December, 1904. Lat. 21° 36.2’S.; long. 94° 56’ W. ; 
depth, 2205 fathoms. 
Numerous pieces of manganese slabs and a few manganese nodules 
were brought up at this station. The slabs, which may be as much as 
six inches in length and one and one-fourth inches in thickness, are essen- 
tially cakes of volcanic ash more or less impregnated with the oxides of 
manganese and iron, with formation of an actual crust of the oxides on 
both surfaces. The volcanic ash is made up of particles of augite, some 
of which belong to the violet variety, of basic felspar, and of volcanic 
glass, more or less decomposed. The particles have a diameter of 0.01 to 
0.02 mm., and are often even smaller. 
The nodules are not so abundant as the slabs. They are discoidal, 
their shape recalling that of a broad bean, and their diameter is from one- 
half of an inch to three-fourths of an inch. They sometimes occur in 
clusters of two or three individuals. The structure is scaly, due to the 
concentric arrangement of the layers; the centre of the nodule is occu- 
pied by a nucleus formed of an aggregate of loose mineral particles, at- 
taining a diameter of 0.08 mm., which are the same as those occurring 
in the slabs, 7 ¢. a great quantity of augite, with volcanic glass and 
plagioclase. Magnetite is also present. There is no marked transition 
between the nucleus and the body of the nodule proper, so that it is 
difficult to say what is the relative proportion of the diameter of the 
nucleus to that of the nodule; yet it appears to be not more than about 
one-fifth in the case of a typical nodule. 
Station 4711, 31st December, 1904. Lat. 7° 47.5’ S.; long. 94° 5.5’ W. ; 
depth, 2240 fathoms. 
The Globigerina Ooze from this station contains numerous typical 
manganese nodules (see Pl. 2, fig. 4), some of which rival those from 
Station 4658. About half a dozen are of very large size, one measur- 
ing six inches in diameter. As they all have a distinctly mammillated 
structure, the mammille breaking off easily, many of the smaller nodules 
must be considered as having formed part of the larger ones. 
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