142 
stillede jeg paa følgende Maade. —Fordunstningsskaalen 
holdtes tør. Et lidet Glas sattes op 1 den. og den belaste- 
des forresten med tørre Vægter, Sand og Hagel, til den 
kom paa Merke. Det ydre Vand var ved Forsøgets Be- 
gyndelse varmest. tildels opvarmet over Luftens Tempera- 
tur. Dets Temperatur noteredes, hvorpaa jeg lod det af- 
kjøle, enten 1 Luften eller ved Hjelp af Sne omkring det 
ydre Kar. 
aflæstes Vandets Temperatur og Bøjen bragtes ned paa 
Merke ved at helde rent Vand fra en Burette i det lille 
Glas. Efter hvert saadant Forsøg aftørredes Glasset om- 
hyggeligt. Den i Glasset heldte Vandmængde udviser For- 
skjellen mellem Værdien af x, ved den oprindelige højeste 
og ved de senere noterede lavere Temperaturer af det ydre 
Vand. Jeg gjorde to saadanne Forsøgsrækker med hver 
af Fordunstningsmaalerne. Af disse hidsættes de med B 
gjorte, den første 1 Christiania før Rejsen 1 1877, den an- 
den i Tromsø samme Sommer. 
Christiania. 
Kubikeentimeter. 
( Cubic Centimetres). 
t jt Gyo, Om. IDG: 
HO AIS G00 OO 
200 210 1.08 1.2 += 0.1 
it © 2080 1.38 1.5 4 0.1 
it © 203 40 106 = oi 
OG 203 2158 282 + 0.05 
9.5 tO 228 22 Gi 
Forskjellerne mellem de observerede og beregnede 
Verdier ere, som man ser, mindre end den Nøjagtighed. 
som man kan opnaa 1 Sen. 
4. Under Fordunstmngen voxer Vandets Saltholdig- 
For at 
vise Virkningen heraf vil jeg tage et Exempel. Lad Van- 
dets specifiske Vægt være ved Forsøgets Begyndelse 1.027. 
Vandet 1 Skaalen 1 Å udgjør 623 cbem.. altsaa dets Vægt 
623 x 1.027 eller 640 Gram. Til en specifisk Vægt af 
1.027 svarer efter Prof. Karstens Tabeller 3.54 Procent Salt. 
640 Gram Vand indeholder altsaa 22.65 Gram Salt. Den største 
Fordunstningsmængde, der maaltes med A er 125 cbem., 
eller 125 Gram rent Vand. Ved Forsøgets Slutning var 
der åltsaa 640 minus 125 eller 515. Gram Vand i Skaalen. 
I disse 515 Gram Vand indeholdes den hele Saltmængde, 
22.65 Gram, eller Saltholdigheden er 4.40 Procent. Van- 
dets specifiske Vægt er voxet fra 1.027 til 1.0336. 
hed, hvorved Fordunstningen bliver langsommere. 
Paa forskjellige Stadier under denne Afkjøling. 
object in view, I proceeded as follows: — The evaporating 
dish was kept dry. A small glass vessel was put into the 
dish, which, besides, was loaded with dry weights, sand 
and shot, till the buoy had become depressed to the mark 
on the stem.. At the beginning of the experiment, the 
outer water was warmest, being sometimes heated to a 
higher temperature than that of the air. Its temperature 
was noted, after which I let it cool, either by exposure to 
the air or with snow surrounding the outer vessel. At 
successive stages of the cooling, the temperature of the 
water was read off, and the buoy brought down to the 
mark on the stem by pouring fresh water from a burette 
into the small glass vessel. After each experiment the 
glass vessel was carefully dried. The quantity of water 
poured into the glass vessel represents the difference be- 
tween the value of x, at the original (maximum) tempera- 
ture of the outer water and at the subsequently noted 
(lower) temperatures. I made two such series of experi- 
ments, with each of the atmometers. The following Table 
gives the series with atmometer B, the first of which was 
made in Christiania, previous to our departure on the 
cruise in 1877, the second in Tromso during the course of 
the same summer. 
Tromso. 
Kubikcentimeter. 
(Cubie Centimetres). 
t i. Foyt (Olus, Diff. 
Ole ILO OG OG | 
da mo 70 7 0.0 
Bok O67 O08 OG 0.0 
4.6 0.56 106 0.4 —07 
too Oto 1.46 Koil — 0.4 
Moff Ol 1.50 0.8  —0.7 
The differences between the observed and the computed 
values are much below the limit of accuracy attainable 
at sea. 
4. During evaporation the saltness of the water in- 
creases, thus retarding the evaporating process. To show 
the effect of this phenomenon, I will give an instance in 
point. Let the specific gravity of the water at the begin- 
ning of the experiment be 1.027. The volume of the wa- 
ter in the evaporating dish A amounts to 623 cubic centi- 
metres, and its weight is accordingly 623 x 1.027, or 640 
erammes. To a specific gravity of 1.027 correspond, ac- 
cording to Professor Karstens’s Tables, 3.54 per cent of 
salt; hence, 640 grammes of water contain 22.65 grammes 
of salt. The greatest evaporation found, in any one ex- 
periment with atmometer A, was 125 cem., or 125 grammes 
of water. At the end of the experiment, there was con- 
sequently 630 minus 125. or 515 grammes of water in the 
