Thus it is that floes from a few inches to twenty feet thick go voyaging out to join the belt of ice which is known as the pack.  Scott seems to have thought that the whole Ross Sea freezes over.[52] I myself think this doubtful, and I am, I believe, the only person living who has seen the Ross Sea open in mid-winter.  This was on the Winter Journey undertaken by Wilson, Bowers and myself in pursuit of Emperor penguin eggs—­but of that later.

It is clear that winds and currents are, broadly speaking, the governing factors of the density of pack-ice.  By experience we know that clear water may be found in the autumn where great tracts of ice barred the way in summer.  The tendency of the pack is northwards, where the ice melts into the warmer waters.  But the bergs remain when all traces of the pack have disappeared, and, drifting northwards still, form the menace to shipping so well known to sailors rounding the Horn.  It is not hard to imagine that one monster ice island of twenty miles in length, such as do haunt these seas, drifting into navigated waters and calving into hundreds of great bergs as it goes, will in itself produce what seamen call a bad year for ice.  And the last stages of these, when the bergs have degenerated into ‘growlers,’ are even worse, for then the sharpest eye can hardly distinguish them as they float nearly submerged though they have lost but little of their powers of evil.

There are two main types of Antarctic berg.  The first and most common is the tabular form.  Bergs of this shape cruise about in thousands and thousands.  A less common form is known as the pinnacled berg, and in almost every case this is a tabular berg which has been weathered or has capsized.  The number of bergs which calve direct from a mountain glacier into the sea is probably not very great.  Whence then do they come?

The origin of the tabular bergs was debated until a few years ago.  They have been recorded up to forty and even fifty miles in length, and they have been called floe bergs, because it was supposed that they froze first as ordinary sea-ice and increased by subsequent additions from below.  But now we know that these bergs calve off from the Antarctic Barriers, the largest of which is known as the Great Ice Barrier, which forms the southern boundary of the Ross Sea.  We were to become very familiar with this vast field of ice.  We know that its northern face is afloat, we guess that it may all be afloat.  At any rate the open sea now washes against its face at least forty miles south of where it ran in the days of Ross.  Though this Barrier may be the largest in the world, it is one of many.  The most modern review of this mystery, Scott’s article on The Great Ice Barrier, must serve until the next first-hand examination by some future explorer.

A berg shows only about one-eighth of its total mass above water, and a berg two hundred feet high will therefore reach approximately fourteen hundred feet below the surface of the sea.  Winds and currents have far more influence upon them than they have upon the pack, through which these bergs plough their way with a total disregard for such flimsy obstacles, and cause much chaos as they go.  For the rest woe betide the ship which is so fixed into the pack that she cannot move if one of these monsters bears down upon her.