The Hubbard and Dalton glaciers are fine examples of another class of ice-streams which flow into the sea and end in ice-cliffs, and which for convenience we call tide-water glaciers. Nowhere can finer or more beautiful examples of this type be found than those in view from Haenke island. The formation of icebergs from the undermining and breaking down of the ice-cliffs of the tide-water glaciers has already been mentioned. But there is another method by which bergs are formeda process even more remarkable than the avalanches that occur when portions of the ice-cliffs topple over into the sea. The ice-cliffs at the foot of the tide-water glaciers are really sea-cliffs formed by the waves cutting back a terrace in the ice. The submerged terrace is composed of ice, and may extend out a thousand feet or more in front of the visible part of the ice-cliffs. These conditions are represented in the accompanying diagram (figure 1), which exhibits a longitudinal section of the lower end of a tide-water glacier where it pushes out into the sea. As the sea-cliff of ice recedes and the submerged terrace increases in breadth there comes a time when the buoyancy of the ice at the bottom exceeds its strength, and pieces- break off and rise to the surface. The water about the ends of the glaciers is so intensely muddy that the submerged ice-foot is hidden from view, and its presence -would not, be suspe, ted were it not for the fragments occasionally rising from it. The sudden appearance of these masses of bottom ice at the surface is always startling. While watching the ice-cliffs and admiring the play of colors in the deep crevasses which penetrate them in every direction, or tracing in fancy the strange history of the silent river and wondering in what age the snows fell on the mountains, which are now returning to their parent, the sea, one is frequently awakened by a commotion in the waters below, perhaps several hundred feet in front of the ice-cliffs. At first it seems as if some huge sea-monster had risen from the deep and was lashing the waters into foam; but soon the waters part, and a blue island rises to the surface, carrying hundreds of tuns of water, which flows down its sides in cataracts of foam. Some of the bergs turn completely over on emerging, and thus add to the tumult and confusion that attends their birth. The waves roll away in widening circles, to break turf on the adjacent shores, and an island of ice of the most lovely blue floats serenely away to join the thousands of similar islands that have preceded it. The fragments of the glacier rising from the bottom in this Manner are usually larger than those broken from the faces of the ice-cliffs, sometimes measuring 200 or 300 feet in diameter. Their size and the suddenness with which they rise would insure certain destruction of a vessel venturing too near the treacherous ice-walls.
