The “birth” of such oceanic hills has been watched by travellers, at the moment of their breaking off from a glacier-foot, with no small interest, and also with no small danger, if they chanced to be within reach of the terrific billows started by such an event.
Sometimes icebergs come into existence differently. If the glacier comes to an end, not in but above the sea, the mass breaks off above with its own weight, and plunges downward, to float away on its new career. This was lately witnessed in far southern seas, and the travellers barely escaped with their lives, so tremendous was the rush of the ocean-wave following the plunge of the new mountain.
A great deal of carrying work is done by icebergs. Many and many a block of stone or rock—not to speak of supplies of gravel and sand and mud—is borne by them to mid-ocean, and there dropped. In the Atlantic they seldom get further south than the neighbourhood of Newfoundland. As they journey, they slowly weep and trickle out of existence.
In the Antarctic both glaciers and icebergs are abundant. The northern bergs are generally higher and more sharply peaked; the southern bergs of a flatter shape, but much larger and of a deeper blue.
Sea-water does not freeze so quickly as fresh water. On account of the salt which it contains, it does not become solid until it is four degrees colder than fresh water needs to be. The freezing-point of fresh water is 32° F.; that of salt water is 28° F. As ocean-water freezes, most of the salt is separated from it; and the ice formed is practically fresh, though often it holds unfrozen salt water in tiny hollows.
CHAPTER X.
RECEIVING—TO GIVE AGAIN
“O end to which our currents tend,
Inevitable Sea!”—A. H. Clough.
“ALL the rivers run into the sea; yet the sea is not full.”
So wrote the wisest of men, long centuries ago; and the words are true in a world-wide sense, which the writer with all his wisdom could not then have fully grasped.