hed, der giver dem en ganske anden Betydning end de 

 foregaaende. 



Imidlertid kan der efter Forchhammers eget Udsagn 

 gjøres nogle Indvendinger med Hensyn til Indsamlingen af 

 disse Vandprøver, der for den største Del blev medbragt 

 af forskjellige Søfarende, hvorved man ikke altid kunde 

 have den nødvendige Garanti for deres omhyggelige Opta- 

 gelse og Opbevaring. De Feilkilder, der paa denne Maade 

 kunde opstaa. er maaske for en Del Skyld i de Uoverens- 

 stemmelser, der hist og her forekommer i Forchhammers 

 Tabeller, hvor den overveiende Del af Tallene kun viser 

 smaa og ialmindelighed let forstaaelige Differentser. 



Foråt skaffe Vand op fra Dybet har Forchhammer 

 betjent sig af en tilproppet tom Finske, som firedes ned til 

 det bestemte Dyb, hvorved Våndet trykkede Proppen ind 

 og fyldte Flasken. Ved Opbringelsen bragtes paa Grund 

 af den tiltagende Varme og det aftagende Tryk Proppen 

 atter paa sin Plads i Flaskens Munding. Man kan indse, 

 at denne Fremgangsmaade ikke yder nogeu tilstrækkelig 

 Garanti for. at det optagne Vand virkelig stammer fra de 

 bestemte Dybder; og Forchhammer indrømmer ogsaa villig 

 dens Mangelfuldhed. De Dybvandsiagttagelser, Forchham- 

 mer paa denne Maade har anstillet, er ogsaa temmelig faa- 

 tallige og indskrænker sig ialmindelighed til de hoierelig- 

 gende Vandskikter. saa at man ikke deraf kan drage nogen 

 Slutning med Hensyn til det Vand. der befinder sig i næ»- 

 mere Berørelse med Havbuuden. Der var jo en Mulighed 

 for, at der her kunde gjøre sig andre Kræfter gjældende, 

 f. Ex. Dyrelivet eller Havbundens Beskaffenhed, som kunde 

 frembringe Forandringer i Havets Sammensætning. 



Andre Kemikere har vistnok' i den senere Tid be- 

 handlet dette Emne, og enkelte har ogsaa fundet, at Vån- 

 det fra Bunden har en noget anden Sammensætning end 

 Våndet fra Overfladen, men disse Iagttagelser ere dog i 

 nere Retninger saa ufuldstændige. at noiere Undersøgelser 

 maa være af Interesse. 



Da den norske Nordhavsexpedition i Aarene 1876, 

 1877 og 1878 udgik paa sine forskjellige Togter fornt 

 undersøge Havet mellem Norge, Færøerne, Island, .lan 

 Mayen og Spidsbergen i fysisk, zoologisk og kemisk Retning, 

 var den rigelig udrustet med Redskaber til Indsamlingen 

 af det respektive videnskabelige Materiale. 



Til Opbevaring af Vandprøver var medtaget omkring 

 L00 med Glasproppe forsynede Flasker (hvoraf de fleste 

 rummede '2. nogle 5 Liter). I 'roverne bleve dels tagne fra 

 Overfladen. dels hentede fra Bunden og de mellemliggende 

 Dyb ved Hjælp af en af Hr. Kaptain Wille konstrueret 

 Vandhenter 1 . Ved Optagelsen af Våndet, saavelsom ved 



' Tegning og Beskrivelse afdette Apparat findes i Tornøe's Af- 

 handling em den i Søvandel opløste Luft. 



in different parts of the ocean, performing his analyses with 

 a thoroughness and rigorous precision that entitle them, as 

 scientific results, to a far higher rank than can be claimed 

 for any preceding obseryations. 



Meanwhile, as Forchhammer himself admits. objections 

 may be urged to the mode in which these samples of sea- 

 watér were drawn, the greater part having been brought 

 home by seamen; and hence it was not always possible to 

 obtain the uecessary assurance. that due care had been 

 tåken in collecting and preserving them. To errors that 

 may possibly have arisen from tliis source, we must, per- 

 haps, partly ascribe the want of agreement met with hére 

 and there throughout Fbrchhammer's Tables, in which the 

 figures general ly exhibit but small differences easily ac- 

 counted for. 



To obtain deep-sea water. Forchhammer made use ol 

 a corked bottle, which was sunk to a depth at which the 

 water, by reason of its greater pressure, forced in the cork 

 and filled the bottle. On hauling in the line, the increased 

 temperatur-e and diminished pressure brought back the cork 

 to its original position in the neck of the bottle. Now it 

 is obvious. that, with this mode of drawing sea-water, there 

 can be no absolute certainty of the sample ohtained origin- 

 ating at the required depth; and Forchhammer readily 

 grants its defectiveness. Indeed, the observations he has 

 instituted with water drawn in this manner are compara- 

 tively few. and chiefly contined to the higher of the deep- 

 sea strata; and hence nothing can be inferred from them 

 respecting the water which is in close proximity to the 

 bottom. Possibly, other agencies may he at work there : 

 such, for instance, as depend on the presence of animal 

 lite or on the nature of the bottom, and which. in some 

 way or other. might influeiice the composition of ocean-water. 



Other chemists, too. have of late years investigated 

 this subject; and, according to some, water from the 

 bottom does differ slightly in composition from surface- 

 water. Meanwhile, their results are in many respects so 

 defective. that a record of more trustworthy observations." 

 adapted to the present state of chemical science, will. it 

 is believed, be found sijecially opportune. 



The Norwegian North-Atlantic Expedition despatched 

 in the years 1876, 1877, and 1878, for the physical, zoo- 

 logical, and chemical investigation of the tracts of ocean 

 stretching between Norway, the F^aroe Islands, IcelaruK 

 .lan Mayen, and Spitzbergen, was fltted out with the great- 

 est care, being furnished with every aid and appliance 

 deémed even remotely requisite for the attainment of the 

 end proposed. 



Among the chemical desiderata were comprised 

 about 100 pbials, with ground glass stoppers (some contain- 

 ing 2. and some 5 bitres), in which to preserve samples of 

 sea-water. The samples collected on the Expedition were 

 ohtained partly from the surface, partly from intermediate 

 depths, and partly from the bottom, in an instrument 1 de- 



1 This apparatus is figured and described in Tornøe's Memoir on 

 the air in sea-water. 



