But ice naturally floats. The upward pressure of the sea becomes increasingly great, fighting against the tenacity of the ice, and in the end old Ocean has the best of the contest. A huge mass of ice snaps off from the glacier-foot and springs to the surface, making the waters seethe and swirl with the shock, and sending heavy waves in all directions. Then the buoyant mass floats away as a newly made Iceberg. Some Icebergs, broken thus from a Greenland glacier, are two or three hundred feet high. That is to say, a sailor on board a ship can see two or three hundred feet of solid ice above the surface of the sea. But this is by no means the true iceberg height. When we talk of ice “floating,” we do not mean that the whole piece of ice rests upon the top of the water. It floats _in_ the water. Only about one-eighth of it is visible above, and the other seven-eighths are hidden below. So in the case of an iceberg rising two or three hundred feet above the sea, we may be sure that at least seven times as much ice is underneath the ocean-surface. This shows what an enormous mass the whole of a floating ice-mountain must be. [Illustration: AN ICEBERG, SHOWING THE SECTION UNDER WATER For every cubic foot of ice above water there are seven cubic feet below _Face page 86_ ] No wonder that a certain iceberg, which held its head one hundred and fifty feet high, should have run aground in water five hundred feet deep! No wonder, either, that when two such bergs come together, and an unfortunate ship happens to lie between, it should be smashed like an egg-shell. In Baffin’s Bay Dr. Kane once counted a pack of two hundred and eighty bergs, most of them being between two and three hundred feet high. 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.