72 
være uforholdsmessig store, en Anskuelse, som ved de 
senere Undersøgelser fuldstæudig er bleven modbevist. Rig- 
tignok er det paa den engelske Cliallengerexpedition iagt- 
taget, at de i den hede Zone fra Havbunden optagne A and- 
prøver ved at henstaa nogen Tid vise Overmætningsphæno- 
mener. men dette vil jo ikke være vanskeligt at forklare, 
naar man erindrer, at Våndet i de store Dyb selv iÆqta- 
toregnene er meget nær iskoldt. Det følger nemlig at sig 
selv. at de til en saa lav Temperatur svarende Luftmæng - 
der ikke kunne holdes opløste, naar Vandprøverue ved læn- 
gere Tids Henstand antager de tropiske Egnes liøie Luft- 
temperatur. Stærkest taler de paa den norske Expedition 
udførte Luftbestemmelser for. at Tryktilvæxten med Dyb- 
den ikke kan have nogen Indflydelse paa Mængden af den 
i Sovandet opløste Luft. Tager man nemlig Middelet af 
Dybder. Temperaturer og Kvælstofmængder for .alle de fra 
Puncter under Overfladen stammende Våndprøver, hvori 
der paa denne Expedition er foretaget Luftbestemmelser. 
erholder man til et Middeldyb 693 Favne (1267 Meter) en 
Middeltemperatur — 0."05 og en midlere Kvælstofgehalt 
13.99 CC. per Litre, det vil sige. Våndet i Dybet indeliol- 
der gjeunemsnitlig næsten 0.5 CO. Kvælstof mindre, end 
det ved sin Temperatur vikle kunne holde opløst under eli 
Atmosphæres Tryk. 
Naar man erindrer, at Trykket i Havdybene ikke 
dreier sig om Atmosphærer men om Hundreder af Atmo- 
sphærer. saa maatte man dog vente, at dets Indflydelse 
(om det havde nogen) vikle give sig tilkjende ved Uregel- 
mæssigheder a f pa a viselig Størrelse, og man er, da dette 
ikke i mindste Maade er Tilfæklet, berettiget til den Slut- 
ning, at Trykket ikke besidder nogen Evne til i mærkbar. 
(i rad at opkobe Luftmængderne i de store Dyb. Paa den 
anden Side maa det fomuftigvis antages, at Våndet i de 
dybere liggende Lag ikke kan afgive rioget af sin Luft. da 
det jo paa Grund af det der herskende Tryk vil kunne 
holde opløst overveiende større Mængder end de, der nogen- 
sinde ere forefundne. 
Den rimeligste Slutning af de senere Tiders Obser- 
vationer over disse Gjenstande vil saaledes være den, at en 
Yandprøve, saahenge den befinder sig under Overfladen. 
uforandret vil beholde den samme Luftmængde eller rig- 
tigere Kvælstofmængde 1 , som den havde absorberet. da den 
sidste Gang befandt sig i Overfladen udsat for Luftens frie 
Indvirkning. 
Nu er den Luftmængde. som Sovandet absorberer af 
Atmosphæren, hovedsagelig afhængig af Vaudets Temperatur, 
idet Barometerstandens Variationer ligeoverfor støi-re Tem- 
peraturdiffcrentser kun har en underordnet Betydning. Heraf 
følger, at de Vandmasser, der have absorberet sin Luft- 
mængde under varmere Himmelstrøg. maa være forholdsvis 
1 Den absorberede Surstofmængde er nemlig i nogen Grad af- 
luvugig af Dyrelivet «g andre Tilfældigheder, saaledes at det her lige- 
Kom i den tidligere Afhandling vil viere det Rigtigste at anvende 
Kvælstofmængden som Maal for den samlede Luftmængde. 
vailing there, has been wholly refuted by the results of 
later observations. True, the samples of water obtained 
at great depths within the tropics on the “Challenger 
Expedition were found to exhibit the phenomena of super- 
saturation when allowed to stand over some time; this, 
however, is easily explained, il we call to mind that the 
water at great depths, even in equatorial regions, lias a 
temperature but little above zero. Hence it naturally fol- 
lows. that the quantity of air corresponding to so low a 
temperature cannot be retained on the samples ol water 
having stood over sufficiently long to acquire the high tem- 
perature of the atmosphere in tropical climates. The air- 
determinations performed on the Norwegian Expedition 
afford the strongest proof ol' the fact, that the increase of 
pressure with the depth does not exert any appreciable 
influence on the proportion of air in sea-water. Now. it 
we compute the mean depth, temperature, and amount of 
nitrogen for all the samples of water from below the sur- 
face examined for air-rdetermiuations, the result will be as 
follows: mean depth 693 fathoms (1267 metres); mean 
temperature — 0.° 05 ; mean amount of nitrogen 13.99 cc 
per litre, which shows that in the depths of the ocean the 
proportion of nitrogen averages 0.5 cc less than could be 
absorbed by sea-water ol the temperature prevailing there 
with the pressure of one atmosphere. 
If we call to mind that the pressure in the depths 
of the sea is not computed even by tens, hut by hundreds 
of atmospheres, its influence, if any. must surely, one would 
imagine, occasion irregularities of appreciable magnitude; and 
we may therefore safely conclude, since no such disturbance 
can be detected, that pressure does not perceptibly increase 
the amount of air at great depths. On the other hand, there 
is every reason to infer, that the water in the lower strata, 
owing to the immense pressure, cannot part with any of 
its air. the quantity actually absorbed never being even 
approximately so great as such a pressure would enable it 
to retain. 
From the latest observations throwing light on this 
question, we may therefore reasonably infer, that all sea- 
water below the surface retains undiminished the quantity 
of air. or rather of nitrogen. 1 which it absorbed when last 
at the surface, in direct contact with the atmosphere. 
Now. the quantity of air absorbed by sea-water is 
mainly dependent on the temperature of the latter, tile 
rise or fall of the barometer, as compared with consider- 
able differences in temperature, being in this case of hut 
little moment. Hence it follows, that the proportion of air 
absorbed by sea-water in warm climates is small compared 
1 The amount of oxygen absorbed by sea-water depending to a 
certain extent on the presence of animal life and other accidental 
causes, the amount of nitrogen may. with greater precision, be as- 
sumed to represent the total amount of air — a standard' of measure- 
ment adopted in the proceeding Memoir. 
