22 THE DEPTH AND MARINE DEPOSITS OE THE PACIFIC OCEAN. 



A very interesting fact brought to light by the cruises of the " Albatross " 

 and the " Nero " is that the presence of manganese nodules in a deposit is 

 not at all incompatible with a high percentage of calcium carbonate, and 

 especially if many volcanic minerals are at the same time present in the 

 deposit, as indeed was indicated in the description of Station 297 in the 

 Challenger Report on Deep-Sea Deposits. Nodules were found in one deposit 

 containing 33 per cent of calcium carbonate, and in eight typical Globigerina 

 Oozes containing respectively 77, 62, 78, 54, 60, 75, 50, and 65 per cent of 

 calcium carbonate. We have here a large proportion of the total number 

 of stations where nodules were dredged, so that we may infer that 

 manganese nodules are by no means exclusively characteristic of Red Clay. 

 Their origin depends more on a ready supply of manganese and iron than 

 on depth, and is not dependent on the presence or absence of calcareous 

 organisms.^ 



The nodules, and specially those that are in course of formation, are often 

 associated with palagonitic tuffs, on which the oxides form a coating of 

 variable thickness ; the oxides also form irregularly distributed nuclei within 

 the cakes of palagonitic tuffs. We may mention here the peculiar forma- 

 tion of Station 4693 (lat. 26° 30' S., long. 105° 45' W.), where the oxides 

 are deposited within, and on the surface of, consolidated cakes of Globigerina 

 Ooze. This is the only instance met with during the cruise of a deposit being 

 dredged as consolidated lumps. During the cruise of the " Challenger " a 

 large piece of consolidated Globigerina rock was dredged between Arrou and 

 Banda at a depth of 129 fathoms ; this rock differs from the hardened ooze 

 described here in being quite hard, requiring a sharp blow of the hammer to 

 break it, and, moreover, it is not associated with manganese oxide. The 

 formation most nearly resembling this one appears to be a Globigerina Ooze 

 dredged by the S. S. " Britannia " in the year 1901 in lat. 14° 32' S. and 

 long. 175° 55' W. According to the report by Sir John Murray and Mr. 

 Peake, the material came up perfectly hard and dry, and required a liammer 

 to knock it out of the tubes. Nevertheless, the phenomenon is of rare 

 occurrence, and is worth mentioning. 



PhilUpsite is by no means rare in the Globigerina Ooze of this part of the 

 Pacific Ocean. It was met with in five typical samples containing respec- 



1 Reference to "A Contribution to the Oceanography of the Pacific," by James M. Flint (Bull. 

 U. S. Nat. Mus., No. 55, 1905), will show that, in that part of the ocean traversed by the " Nero," man- 

 ganese concretions are generally present, and sometimes quite numerous, in Globigerina Ooze. 



