52 



Overgangsleret, der ofte er saa gjennemvævet af disse tine 

 Kiselnaale, at man ved at berøre den tørrede Bundprøve 

 faar Huden fuld af dem. 



Vi er berettigede til at antage, at Havets fysiske For- 

 hold maa have en stor Betydning for Dyrelivets Udbredelse 

 eller Fordeling over Havbunden; især gjælder dette om 

 Globigerinerne, der som pelagiske Foraminiferer maa være 

 udsatte for de forskjellige Strømningers Virkning — hvad 

 enten de nu i død eller levende Tilstand synker ned i 

 Slammet. Ved mine kemiske Undersøgelser af Biloculin- 

 leret har jeg, som senere skal sees, tåget Hensyn til disse 

 Sporgsmaal. 



Betragter man forskjellige Prover af Biloculinleret 

 under Mikroskopet, vil man linde. at. Blandingsdelenes Fin- 

 hed ikke altid er den samme. Mangensteds kan man neppe 

 selv med eu stærk Forstørrelse adskille de enkelte Partik- 

 ler, men i Almindelighed ser man dog en Del krystallinske 

 Korn, der tildels er af forskjellig Farve. De fleste af disse 

 er imidlertid farveløse og gjennemsigtige og synes for den 

 største i lei at beståa af Kvarts. At dette Mineral kan 

 udgjøre en væsentlig Bestanddel af Dybvandsslammet, har 

 allerede Ehrenberg 1 paavist ved sine Undersøgelser af tre 

 Prøver fra Atlanterhavets Bund (Dybde: 10,800, L2,000 

 og 12,900 Kod). 



Slammets fineste krystallinske Partikler er i Alminde- 

 lighed temmelig skarpkantede ; grovere for det ubevæbnede 

 Øie synlige Korn forekommer næsten aldrig i Biloculinleret, 

 men er derimod ikke ualmindelige i Overgangsleret og har 

 da som oftest en afrundet Form. I det sidstnævnte Ler 

 ser man ofte talrige Gliminerblade ; disse forekommer ogsaa 

 i Biloculinleret. men er her saa yderst smaa, at de vanske- 

 lig kan opdages. 



Pimpsten eller amorft, vulkansk Glas synes ikke at 

 udgjøre nogen væsentlig Del af Biloeulinlerets mikroskopi- 

 ske Bestanddele. I 10 — 15 Prover fra forskjellige Partier 

 af Havbunden fandtes vulkansk Glas blot paa et Par Sta- 

 tioner. Kogle større Stykker (2x2x2 Cm.) blev op- 

 tagne paa Station 4< I. Her gjordes forøvrigt et eiendomme- 

 ligt Fund. der fortjener nærmere l (mtale. Sammen med 

 Pimpstenstykkerne fandtes nemlig i Skraben en Mængde 

 faste Klumper eller Knoller, der var af forskjellig Udseende 

 og Art, liggende nldeles for sig selv, ligesom Stene i Ler- 

 massen. De største af disse ((i X (i X li Cm.) var af en 

 meget forskjellig og uregelmæssig Form; den haarde og 

 furede ( tverfiade var tildels bedækket af et tyndt sort Lag, 

 der væsentlig var dannet a f Manganoxyder, medens det 

 indvendige bestod af en brunrød, porøs Substans, der inde- 

 holdt en temmelig betydelig Mængde vulkansk (ilas. 



Disse Klumper var temmelig faste, men tillige megel 

 sprøde og kunde med Lethed brydes istykker; de havde en 



1 Berliner acad. Berichte von 1854, S. 54, SM',. 305, von 185." 

 S. 17.;. Nærmere beskrevet i ; 'Mierogeologie" von Ehrenberg. Leip- 

 zig 1854. 



bers in transition clay. which is absolutely interwoveu with 

 these minute siliceous needles, so. that. ou touching the 

 dried bottom-sample. the hand gets covered with them. 



We have reason to believe that the physical condi- 

 tions of the sea exert very considerable influence on the 

 distribution of animal life over its bed; and in particular 

 as regards Olobk/erinæ, which, as pelagic Fbraminifera, 

 must be exposed to the action of currents. in whichever 

 state they reach the bottom — living or dead. To these 

 questions, as will afterwards appear, I bad due regard when 

 analysing samples of Biloculina clay. 



On examining under the microscope Biloculina clay 

 (rom different localities, the fineness of its constituents is 

 not always found to be the same. In some samples, even 

 when highly magnitied, it is hardly possible to distinguish 

 the individual particles of which they consist: a number of 

 crystalline granules, here and there varying in colour, may 

 however be generally detected with a powerful lens; but 

 the majority of such are colourless and translucent. con- 

 sisting apparentlv in greater part of quartz. a. mineral the 

 occurrence of which as one of the principal constituents of 

 deep-sea surface-layers has been already shown by Ehren- 

 berg, 1 who submitted to analysis three samples of such 

 deposit from the lied of the Atlantic. - - depth. respectively 

 1(1.800. 12.000. and 12,9.00 feet. 



The finest crystalline particles of deep-sea deposit are 

 as a rule compåratively sharp-edged; coarser granules occur 

 very rarely if ever in Biloculina clay. whereas in transition 

 clay such particles, of a rounded form, are not infrequently 

 met with. The latter deposit is often found to contain 

 numerous laminæ of mica .schist. which also occur in Bilo- 

 culina clay, but so delicate and minute as to be with diffi- 

 culty detected. 



Pumice or scori;e does not appear to be one of the 

 chief microscopic constituents of Biloculina clay. Of 10 to 

 15 samples from different parts of the sea-bed, scoriæ oc- 

 curred in one or two only. A few larger pieces (2x2 

 X 2 tn ') came up at Station 40, where the deposit was found 

 to be characterized by a peculiar feature, which I must 

 not omit to record. Along with the fragments of pumice, 

 but Lying apart and imbedded like stones or pebbles in the 

 clay, the dredge brought up a number of nodules or con- 

 cretions, varying in character and appearance. The lar- 

 gest, measuriug 6 X 6 X 6 cm > were very different and irre- 

 gular in form; the hard, furrowed surface had in some a 

 thin coating of black oxide of manganese, whereas the inner 

 portion consisted of 'a brownish-red, vesicular substance, 

 containing a considerable proportion of scoriæ. 



These concretions are compåratively firm, but at the 

 same time exceedingly brittle; their weight too is very 



1 Berliner acad. Berichte von 1854, pp. 54, 236, 305, von 1855 

 p. 17:'.. The subjeot ia treated more a1 large in "Microgeologie" von 

 Ehrenberg. Leipzig 1854, 



