OF SEA-WATER IN THE DIFFERENT PARTS OF THE OCEAN. 
238 
certain that the ice in spring sinks. I could, however, not find a single one of them who 
had in spring fished the ice up in his nets, while they very often in autumn and the 
beginning of the winter find it at the bottomland see it rise to the surface*. It was 
evident that the sudden disappearance of the ice in spring was the fact which they had 
observed, and that the sinking of the ice was the popular explanation of the fact. 
The natural philosopher will not allow ice to sink in sea-water, and it seems neces- 
sary to find another explanation. In order to give that I must first mention another pecu- 
liarity with the under-current of Elsinore. I observed on the 2nd of March, 1850, the 
temperature of the under-current with a maximum thermometer to be +2'6 C. (36 0, 8F.) 
at the depth of 108 feet, while the temperature at the surface was +1'6 G. (34 0, 9 F.). 
Early in the next spring a friend of mine repeated the observation, and found likewise 
the higher temperature in the under-current, the difference being about 2° C. A third 
observation made in summer gave no difference. To explain this, I must observe that the 
Water of the Kattegat, at least in its depth, is a branch of that great part of the Gulf- 
stream that passes along the western shores of Norway, and that the under-current at 
Elsinore necessarily must be less affected by the cold which reigns over the Baltic in winter 
time. Thus the under-current has in spring a higher temperature than the water of the 
surface, and at the same time contains a greater quantity of salt. Suppose, now, that the 
ice towards spring has begun to thaw and has become porous, as is generally the case, the. 
warmer and more saline water will come in contact with it from below, and will melt it,, 
partly on account of its temperature above freezing-point, partly on account of the greater 
quantity of salt which it contains. Thus without any apparent greater changes on the- 
surface the ice will melt quickly and almost imperceptibly, and disappear. This effect 
of the under-current will be increased by the peculiarity of sea-water, that its point of 
greatest density lies below the freezing-point of pure water, and a constant series of 
small vertical currents will be formed where the warmer water rises, and that which is 
refrigerated by the contact with the ice sinks, which motion always will increase the 
melting of the surface-ice. 
Besides at Elsinore and at Copenhagen, it has been observed at Kiel, near Stockholm, 
and in the Bay of Finland, that the deeper water is more saline than that of the surface. 
At Svartklubben, near Stockholm, water from the surface contained 3 - 256 chlorine 
'=5-919 salt, and from a depth of 720 feet 3-912 chlorine =7T82 salt (coefficient 
T836); in the Bay of Finland, between the islands Nervoe and Sukjeld, the surface- 
water contained 3-552 per 1000 salt, while in a depth of 180 feet it contained 4*921. 
It was only for the two larger salt-water basins of Europe, the Mediterranean and 
* This formation of the bottom ice is very frequently observed on our shores. There is a fishing bank a little 
to the north of Elsinore, where the fishermen often in the beginning of the winter find themselves suddenly 
surrounded by ice, which they see rise through the water, containing numerous pieces of Fucus inclosed in its 
• mass. The same fact has also been observed not. far from Copenhagen, and off Nyborg in the Great Belt. It 
seems, in fact, a phenomenon peculiar to such places where a strong current runs over a place that is not very 
deep. 
