4.8 



Kysten — ikke er større, end at vi i Overensstemmelse 

 med tidligere Erfaringer kan tænke os, at Bølgernes Virk- 

 ninger forplanter sig helt ned til Bunden. 



I Overensstemmelse med de foregaaende Analyser 

 synes det rimeligt at antage. at Rhabdammina-Leret — 

 saaledes som vi tinder det pna de østligste Stationer - - maa 

 have sin Oprindelse fra stærkt kvartskoldige Bergarter. 

 For at linde saadanne behøver vi ikke at lede længe i de 

 omgivende Lande : vi moder mægtige Sandstenlag paa Nord- 

 kysten af Norge, paa Beeren Eiland og Spidsbergen, lige- 

 som ogsaa taMge Brudstykker af den samme Bergart blev 

 fundne ved de fleste Dybdemaalinger og Skrabninger i Øst- 

 havet. 



Men selv om vi med nogen Grad af Sandsynlighed 

 kan tænke os. at denne Bergart har været den oprindelige 

 Kilde for Dannelsen af Rhabdammina-Leret, saaledes som 

 vi findér det paa de tvende ovennævnte Stationer. bliver 

 det imidlertid et andet og vanskeligere Spørgsmaal at af- 

 gjøre, fra hvilken Kant Materialet er hentet, og hvorledes 

 dette er blevet fordelt over den jevne og grunde Havbund. 



Jeg skal ber blot indskramke mig til at nævne, at 

 den omtalte lille Beeren Eiland har særegne Betingelser 

 for at kunne forsyne den nærliggende Havbund med stadig 

 nye Bidrag til dens Aneiriuger. Beeren Eiland har alle- 

 rede i Løbet af -en Menneskealder undergaaet betydelige 

 Forandringer ved Isens og Bølgernes ødelæggende Virknin- 

 ger. De løse itufrosne Bergslag, bvoraf Øen tildels bestaar, 

 ligger ved Kysterne blottede for Havet,' hvis Kraft, her ikke 

 bliver afdæmpet ved Holmer eller Skjær. Geologen Prof. 

 Keilhau 1 giver i sin Beskrivelse af denne. følgende Skil- 

 dring af. hvorledes Ødelæggelsen foregaar: "Ved saadanne 

 vertikale Revner, og ved de ydre Stykkers derpaa følgende 

 Fraløsning gaar Øen lidt etter lidt sin fuldkomne Forsvin- 

 den imøde ; allerede i Mands Minde er Kysterhes Forandring 

 mærkelig, og at slutte efter de ældste Erfaringer, maa alle- 

 rede betydelige Stykker være undergaugne". 



Vi maa saaledes være lierettigede til at formode, at 

 Beeren Eiland stadig kan gi ve Anledning til sedimentære 

 Vi/dannelser. Hvis Rhabdammina-Leret kan henregnes 

 blandt saadanne. eller hvis det altsaa er et Depositum af 

 senere Oprindelse end Nordhavets øvrige Sedimenter, kunde 

 dette maaske være en Grund for den mindre oxyderte Til- 

 stand, hvori det befinner sig. 



Hvor vi i den vestlige hel af Nordhavet træffer et 

 lignende porøsl og st;erkt sandholdigt Ler. er dette som 

 oftest al' en brun Farve, eller altsaa stærkere oxyderet. 

 Man kunde altsaa tænke siu. ,-it Slammets Oxydationsgrad 

 var aftiængig af den Tid. i hvilken det har befundet sig i 

 Havet. Denne Antagelse bestyrkes, naar man ser hen til 



1 Reise til Vest- og Østfinmarken samt iil Beeren Eiland og 

 Spidsbergen. 



— at a considerable distance from the coast — isnotgreater 

 than will, we know. in conformity with experience. admit 

 of the influence of the waves being transmitted from the 

 surface to the bottom. 



From the resiilts of the foregoing analyses, it would 

 appear that the origin of Rbabdanunina clay. as that depos- 

 it occurs in the most easterly localities of the' North At- . 

 lantic, may be traced to the disintegration of quarzitic 

 rocks, — an assumption borne out by the geological char- 

 acter of the surrounding countries. Along the north coast 

 of Norway, and on Beeren Eiland and Spitzbergen. we meet 

 with vast masses of sandstone; and numerous fragments of 

 that rock came up when sounding and dredging in the 

 East Sea. 



But even admitting that disintegrated . sandstone has 

 chiefly contributed to the formation of Rhabdammina clay 

 as found at the two above-mentioned Stations. another and 

 more difticult question remains to decide from what quarter 

 the siliceous particles are. derived, and how thev an- distri- 

 buted over the level and shallow bottom. 



On this head I shall merely observe here, that Beeren 

 Eiland has peculiar facilities for constantly furnishing the 

 adjacent portions of the sea-b.ed with the material compos- 

 ing their surface-layer of deposit. Within the memory of 

 man, the combined action of the waves and glaciérs have 

 caused that island to undergo very considerable changes. 

 The porous, frost-riven rocks of which this island in great 

 part consists, are everywhere on the coast exposed to the 

 full sweep of the ocean, no islets or skerries being here to 

 break its force. The following extract from Professor Keil- 

 hau's description of Beeren Eiland 1 will show in what 

 manner the work of destruction is proceeding: — "From 

 the repeated occurrence of such vertical fissures and the 

 subsequent dislocation of the outer fragments, the slow but 

 total demolition of the island may be surely foreseen; even 

 within the memory of man, a remarkable change has tåken 

 place in the coastal outline, and to judge from the oldest 

 accounts considerable portions of the island must have 

 already disappeared." 



"We have accordingly every i;easou to assume. that 

 Beeren Eiland, so 1-ong as it exists, will still continue the 

 source of sedimentary new formations. Now, regarding 

 Rhabdammina clay as oue of such- layers, and therefore as 

 of later origin than any other of the deposits distributed 

 over the- bed of the North- Atlantic, this may possibly serve 

 to account for the low degree ol' oxidation by which that 

 shbstance is distinguished, 



A porous and highly sahulous clay is also met with 

 in the western tract of the North Atlantic, but its colour 

 is genérally brown, indicating a more advanced stage of oxi- 

 dation. "We might therefore not unfeasonably infer that the 

 greater or less extent to which a deposit is oxidi/.ed mainly 

 depends on the length of the pefiod during which it has 



' Reise til Vest- og Østfinmarken samt til Beeren Biland og 

 Spitzbergen. 



