previously, when the surface of the sea is being frozen over, the salt in that part of the water which is changed into ice is thrown out and must therefore make the neighbouring water more saline; on the other hand, when that ice melts during the following summer it adds a considerable amount of fresh water to the sea in its neighbourhood.
The salter water would naturally have a higher specific gravity than the fresher water but it is not unlikely that the fresher water produced from melting ice may, by virtue of its being colder than the neighbouring more saline water, actually have a higher specific gravity. The presence of icebergs, which in the south are of enormous size and very numerous, and which even in the north are very numerous in certain districts, must produce an enormous amount of fresh water during the summer and quite sufficient to affect the salinity of the sea where they occur. One of the most interesting features of Arctic waters, especially between Greenland and Spitsbergen and to the north of Spitsbergen well into the Polar Basin, is the existence of an intermediate layer of comparatively warm water in the Arctic Ocean between the surface colder water and the colder water beneath. This was observed as far back as the beginning of the nineteenth century by Scoresby and sub-
