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44
tioner (omkring den 38te Længdegrad), hvor det
fremtræder som et ensartet, temmelig fint Slam af en eiendommelig
mørkgrøn Farve, Efter Tørring opnaar det kun en
ubetydelig Fasthed eller Sammenhængskraft og kan mellem
Fingrene knuse§ til et Pulver, der er at føie paa som et
meget fint Sand.
Under Mikroskopet viser det sig for en væsentlig
Del at bestaa af smaa Kyartskorn, der i Almindelighed ér
temmelig skarpkantede.
Af Dyrelevninger indeholder Slammet kun faa.
Almindeligst finder man Kør af Annelider (udelukkende
Spio-chetopterus), Kiselspikujer af Svampe og Skaller af Slægten
Astarte. foruden den omtalte Foraminifer Eh’dbäamjnina,
der synes at være meget almindelig.
Det fremgaar af Bundprøverne fra Expeditionens
østligste Stationer, at Rhabdammina-Leret her er af en ringe
Mægtighed, da jeg nemlig paa flere Steder har fundet et
underliggende Lag af mørkgraat. finkornigt og mindre
sandholdigt Ler.
Paa de vestligere Stationer taber Rhabdammina-Leret
lidt efter lidt sine karakteristiske Egenskaber: det bliver
mere plastisk og Farven mifidre udpræget grønlig, ligesom
heller jkke nogen Lagdannelse viser sig i Bundprøverne —
indtil vi i Syd for Beeren Eiland (under 20—25° 0. L.)
gjenfinder det graa Ler. Nordenom denne 0 gaar
Rhabdammina-Leret længere ud i Havet i vestlig Retning og
naar her op til Spidsbergens Sydkyst.1
I kemisk Retning udmærker det grønlige Ler sig ved
sin store Kiselsyremængde og ved clen mindre oxyderte
Tilstand, hvori det befinder sig. Jeg- har troet at iagttage,
at flere af Bundprøverne, ved at henligge i Luften (paa
Laboratoriet)’, forandrer sit Udseende, og i en enkelt har
jeg ad kemisk Vei konstateret, at den i pulveriseret
Tilstand efter nogen Tids Forløb har tiltaget i Jernoxydgehalt,
idet Farven samtidig er blevet brunlig. I Bundprøven fra
Station 264 fandt, jeg nemlig i det saltsure Udtræk ved
den første Analyse: 2.48 pCt. FeO og blot 0.24 pCt.
Fe203,2 et halvt Aar senere erholdt jeg derimod: 1.00 pCt.
FeO og 1.39 pCt. Fe,.03.
Da jeg har kontrolleret den sidste Bestemmelse og
heller ikke har nogen Grund til at tvivle paa Rigtigheden
af den første, synes dette mig at være et Fænomen, der er
vel værd at’ lægge Mærke til.
I Rhabdammina-Leret har jeg udført fuldstændige
Analyser af to Bundprøver fra Expeditionens østligste Rute,
1 Rundt om Beeren Eiland vil man paa Kortet, finde et aabent
Kum. Her har Expeditionen foretaget flere Dybdemaalinger, der
viser, at Bunden ikke ligger dybere end 100 Favne. Da Loddet
næsten altid stødte mod Sten, blev ingen Bundprøve, optaget.
"’ Den samlede .fernmængde er bestemt med Kamæleon efter.
Reduktion med Zink.
extreme eastern section of the tract (near the 38th parallel
of latitude), where this deposit occurs as a homogeneous,
comparatively fine mud of a peculiar dark-green colour.
Friable when dried, it possesses very little cohesive power,
admitting of being crushed between the fingers to powder,
which has a gritty feel, like fine sand.
Examined under the microscope, it is minute, and, as. a
. rule, comparatively sharp-edged particles of quartz are found
to form its chief. constituent.
Of animal remains this deposit contains but few.
Those most frequently met with are tubes of Annelids
(exclusively Spiochet opt ents). siliceous spicules of sponges,
and shells of the genus Astmie, as also of the previously
mentioned Foraminifer’ Rhabdammina, which would appear
to be comparatively numerous.
The deposit brought up at the most easterly of the
. observing-stations shows the surface-layer of Rhabdammina
clay in that locality to be of trifling thickness; several of
the samples had.an under layer of dark-grey, finely
granulated, and somewhat sabulous clay.
Throughout the western part of the tract, the
Rhabdammina clay gradually loses its distinctive features,
becoming more plastic in substance and in colour less
characteristically green, with no appearance of stratification in
the samples, — till, south of Beeren Eiland (long. 20" to
25° E.) we again meet with the grey clay. North of that
island, the Rhabdammina clay extends farther seaward,
reaching up to the south coast of Spitzbergen.1-
Regarded chemically, the chief characteristics of this
greenish clay are its large proportion of silica and the
slight extent to which it is oxidized. On exposure to
atmospheric influence (in the laboratory), several of the
samples underwent, I feel pretty sure, a change of aspect.;
and in one, which had been pulverized and allowed to
stand over for some time, I proved by direct analysis an
increase in the amount of oxide, of iron; its colour, too,
had become brownish.- Again, in the sample brought up
at Station 264, I found in the hydrochloric acid decoction
as the result of a first analysis, 2.48 per cent of FeO and
only 0.24 per cent of Fe^O^;2 but six months later the
proportion determined was 1.00 per cent of FeO and 1.39
per cent of FeL>0^.
Having tested the results of the latter analysis and
seeing no. reason to doubt the accuracy of the first, I call
attention to this phenomenon as one that should, I think,
by no means pass disregarded.
Of the Rhabdammina clay met with on the eastern
route of the Expedition. I have submitted to rigorous ana-
1 Round the shores of Beeren Eiland a blank space has been
left in the map. From several soundings taken here at ’different
points, the depth was found not to cxeeed 10.0 fathoms; and the lead
having almost invariably struck against rock or stone, no sample of
the bottom could of coarse be obtained.
- The total amount of iron was determined with permanganate
of potash, after desoxidat.ion with zinc.
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