ii8 



NATURE 



[Dec. lo, 1874 



In tlie Globigcrina ooze siliceous bodies, including the spicules 

 of sponges, tlie spicules and tests of radiolarians, and tlie fmstules 

 of diatoms occur in appreciable proportion ; and these algo 

 diminish in number, and the more delicate of them disappear in 

 the transition from the calcareous ooze to the red clay. 



I have already alluded to the large quantity of nodules of the 

 peroxide of manganese which were brought up by the trawl from 

 ihe red-clay area on the 13th of March. Such nodules seem to 

 occur universally in this formation. No manganese can be 

 detected in the Olobigcrina ooze j but no sooner has the removal 

 of the carbonate of lime commenced than small black grains 

 make their appearance, usually roumled and mamniiUated on 

 the surface, miniatures, in fact, of the larger nodules which 

 abound in the clay ; and at the same time any large organic 

 body, such as a shark's tooth, that may happen to be in the ooze 

 is more or less completely replaced by manganese ; and any 

 inorganic body, such as a jiebble or a piece of pumice, is coated 

 with it as a fine bkack mammillatcd Layer. It is not easy to tell 

 what the proportion of manganese in the red clay may be, but it 

 is very considerable. At station 160, on the 13th of March, the 

 trawl brought up nearly a bushel of nodules from the size of a 

 walnut to that of an orange, but these were probably the result 

 of the sifting of a large iiuantity of the cl.iy. The manganese is 

 doubtless .set free like the iron by the decomposuion of the 

 organic bodies and tests. It is known to exist in the ash of 

 some algre to the amount of four per cent. 



The interesting <iuestion now arises as to the cause and 

 method of the removal of the carbonate of lime from the cre- 

 taceous deposit, and on this matter we arc not yet in a position 

 to form any definite conclusion. 



One possible explanation is sufficiently obvious. All sea- 

 water contains a certain proportion of free carbonic acid, and 

 Mr. liuchanan believes that he finds it rather in excess in bottom- 

 water from great depths. At all events the quantity present is 

 sufficient to convert into a soluble compound, and thus remove a 

 considerable amount of carbonic lime. If the balance of supply 

 be very delicately adjusted, it is just conceivable that the lime in 

 the shells in its fine state of subdivision having been attacked by 

 the sea-water from the moment of the death ol the animal, may 

 be entirely dissolved during its retarded passage through the half 

 mile or so of water of incria^ing density. The bottom-water in 

 these deep troughs has been lost at the surface, a great deal of it 

 in the form ol circumpolar freshwater ice ; and tliough fully 

 charged with carbonic acid, it is possible that it may be com- 

 paratively free from carbonate of lime, and that its solvent power 

 may thus be greater. 



The red clay, or more probably the circumstances which lead 

 to its deposition, seem on the whole unfavourable to the develop- 

 ment of animal life. Where its special characters are most 

 marked, no animals which require much carbonate of lime for 

 the development of their tissues or their habitations appear to 

 exist. Our growing experience is, that although animal life is 

 possible at all depths alter a certain depth, say 1,500 fathoms, its 

 abundance diminishes. This would seem to indicate that the 

 extreme conditions of vast depths are not favourable to its deve- 

 lopment : and one might well imagine that the number of shell- 

 building animals might decrease until the supply of lime was so 

 far reduced as to make it difficult (or them to hold their own 

 against the scjlvent power of the water of the sea — just as in 

 many districts where there is little lime, the shells of land and 

 freshwater molluscs are light and thin, and the animals them- 

 selves are stunted and scarce. 



It seems, however, that neither the extreme depth at which 

 the red clay is found, nor the conditions under which it is sepa- 

 rated and laid down, are sufficient entirely to negative the 

 existence of living animals, even of the higher invertebrate orders. 

 In several of the hauls we brought up holothurids of consider- 

 able size, with the calcareous neck-rings very rudimentary, anl 

 either no calcareous bodies in the test or a mere trace of sucn. 

 Nearly every haul gave us delicate branching Bryozua with the 

 zooecium almost membranous. One fortunate cast, about 150 

 miles from Sombrero, brought up from a depth of 2,975 fathoms 

 ■ very well-marked red mud, which did not effervesce with hydro- 

 chloric acid. Entangled in the dredge, and imbedded iu the 

 mud, were m.iny of the tubes of a tube-building annelid, several 

 ol them 3 in. to 4 in. long, and containing the worm, a species of 

 Myriochele, still living. The worm-tubes, like all the tests of 

 foraminilera from the same dredging, were made up of particles 

 of the red clay alone. 



It seems evident, from the observations here recorded, tha 

 r/rt;', which wc have hitherto looked upon as cssenti.xlly the pro 



duct of the disintegration of older rocks, may be under certain 

 circumstances an organic formation like chalk ; that as a matter 

 of fact, an area on the surface of the globe, whic h we have shown 

 to be of vast extent, although we are still far from having ascer- 

 tained its limits, is being covered by such a deposit at the present 

 day. 



it is impossible to avoid associating .such a formation with the 

 fine, smooth, homogeneous clays and schists, poor in fossils, but 

 showing worm-tubes and tracks, and bunches of doubtful 

 branching things, such as Oldhamia, siliceous sponges, and thin- 

 shelled peculiar .shrimps. Such formations more or less meta- 

 morphosed are very lamiliar, especially lo the student of 

 pahx-ozoic geology, .and they olten attain a vast thickness. One 

 is inclined, from this great resemblance between them in compo- 

 sition and in the general character of the included fauna, to 

 suspect that these may be organic formations, like the modem 

 red clay of the Atlantic and .Southern Sea, accumulations of the 

 insoluble ashes of shelled creatures. 



The dredging in the red clay on the 13th of March was 

 unusually rich. The bag contained examples, those with cal- 

 careous shells rather stunted, of most of the characteristic deep- 

 water groups of the Southern Sea, including Umbellularia, 

 Kuplectella, Pterocrinus, Urising.a, Ophioglypha, I'ourtalesia, 

 and one or two Mollusca. This is, however, very rarely the 

 case. Generally the red clay is barren, or contains only a very 

 small number of forms. 



On the nth of February, lat. 60° 52' S., long. 80° 20' E., and 

 March 3, ht. 53' 55' S., long. loS" 35' E., the sounding instru- 

 ment came up filled with a very fine cream-coloured paste, which 

 scarcely effervesced with acid, and dried into a very light 

 impalpable white powder. Thi.s, when examined under the 

 microscojie, was found to condst almost entirely of the frustules 

 of diatoms, some of them wonderfully perfect in all the details of 

 their ornament, and many of them broken up. The species of 

 diatoms entering into this deposit have not yet been worked up, 

 but they appear to be referable chiefly to the genera Fragilaria, 

 Coscinodiscus, Ch;etoceros, Asteromphalus, and Diclyoeha, with 

 fragments of the separated rods of a singular siliceous organisnti, 

 with which wc were unacquainted, and which made up a large 

 proportion of the finer matter of this deposit. Mixed with the 

 diatoms there were a few small Globigerina;, some of the tests 

 and s))icules of radiolarians, and some .sand particles ; but these 

 foreign bodies were in too small proportion to affect the formation 

 as consisting practically of diatoms alone. On the 4th of February, 

 in lat. 52° 29' S., long. 71° 36' E. , a little to the north of the 

 Meard Islands, the tow-net, dr.igging a few fathoms below the 

 surface, came up nearly filled with a pale yellow gelatinous 

 mass. This was found to consist entirely of diatoms of the 

 same species of that found at the bottom. By far the most 

 abundant was the little bundle of siliceous roils, fastened 

 together loosely at one end, separating from one another at the 

 other end, and the whole bundle loosely twisted into a spindle. 

 The rods arc hollow, and contain the characteristic endochrome 

 of the iJiatoinacea-. Like the Globigerina ooze, then, which 

 it succeeds to the southward in a band apparently of no great 

 width, the materials of this siliceous deposit are derived entirely 

 from the surface and intermediate depths. It is somewhat 

 singular that diatoms did not appear to be in such large numbers 

 on the surface over the diatom ooze as they were a little further 

 north. This may perhaps be accounted for by our not having 

 struck their belt of depth with the tow-net ; or it is possible that 

 when we found it on the nth ol February the bottom deposit 

 was really shifted a little to the south by the warm current, the 

 excessively fine llocculent debris of the diatoms taking a certain 

 time to sink. The belt of diatom ooze is certainly a little 

 further lo the southward in long. 80" E. in the path of the reflux 

 of the Agullins current than in long. 108° E. 



All along the edge of the ice-pack — everywhere, in fact, 

 to the south of the two stations, on the nth of February 

 • n our southward voyage, and on the 3rd of March on our 

 retLi 1. we brought up fine sand and greyish mud, with small 

 pebble.' of quartz and felspar, and small fr.igments of mica- 

 slate, chlorite-.slate, chiy-slate, gneiss, and granite. This 

 deposit, I have no doubt, was derived from the surface like the 

 others, but in this case by the melting of icebergs and the pre- 

 cipitation of foreign matter contained in the ice. 



We never saw any trace of gravel or sand, or any material 

 necessarily derived from land, on an iceberg. .Several showed 

 vertical or irregular fissures filled with discoloured ice or snow ; 

 but when looked at closely the discoloration proved usually to 

 be very slight, and the effect at a distance was usually due to the 



