THE DEPTH AND MARINE DEPOSITS OF THE PACIFIC OCEAN. 27 
of this mineral was based ' came from the eastern shores of the Pacific in the 
neighborhood of the track of the “ Albatross.” 
The oaides of iron and manganese are widely distributed in the pelagic 
deposits, either as grains or as nodules. There is hardly a Red Clay or a 
Globigerina Ooze that does not contain manganese grains, or, at least, 
minute particles diffused in the “ fine washings.” The grains average 0.1 mm. 
in diameter, and have generally a botryoidal shape and shining surface; the 
minute particles found in the “fine washings” have no sharply defined out- 
lines, and appear to be mixed with more or less clayey matter, giving them 
a flocculent appearance. : 
Phillipsite is of frequent occurrence and has been observed in Globigerina 
Ooze as well as in Red Clay, but not in such large amount as is the case with 
some of the Red Clays dredged further south by the “Challenger.” Isolated 
crystals are much more frequent than clusters; their breadth is relatively 
larger than in the case of those found by the “ Challenger,” the proportion 
of breadth to length being generally from 1 to 3 to 1 to 4. As it often 
happened that only little material was available, it is quite possible that 
phillipsite may have escaped observation more than once, and, therefore, may 
be more abundantly distributed than it appears to be from the descriptions. 
Methods used for Determination. Examination in reflected light with the 
binocular microscope was always made of the mineral particles as they 
stood after removal of the carbonate of calcium and the washing away of 
the finer material. This examination gives indications as to the weathering 
of the minerals, and as to their mutual relations, that is, a particle of mag- 
netite, for instance, may be quite free, or, on the other hand, firmly attached 
to some other mineral. 
After this preliminary examination the particles are measured with a 
graduated ocular micrometer, and then, if sufficiently thin, directly exam- 
ined under the mineralogical microscope. For all purposes one can dispense 
with actual slides mounted in balsam ; if the particles are too thick, they are 
ground in an agate mortar to the requisite thinness; the diameter will, of 
course, correspondingly decrease, but with a high power and an ocular fur- 
nished with an iris diaphragm, the figures of interference in convergent light 
can still easily be observed. This method saves much of the time that would 
be required in order to make thin slices, and allows the studying of different 
1 See Collet et Lee, “ Recherches sur la Glauconie.”” Proc, Roy. Soc. Edin., Vol. XXVL., p. 238, 
1906. 
sii, st 
