Now it will be obvious that, as the glacier continues to press further and further into the sea, the natural equilibrium of the ice must ultimately become disturbed,--that is, the end of the glacier is forced further down into the water than it would be were it free from restraint, and at liberty to float according to the properties acquired by congelation. The moment that more than seven eighths of its front are below the water line, the glacier will, like an apple pressed down by the hand in a pail of water, have a tendency to rise, until it assumes its natural equilibrium. Now it will be remembered that the glacier is a long stream of ice, many miles in extent, and, although the end may have this tendency to rise, yet it is, for a time, held down firmly by the continuity of the whole mass. At length, however, as the end of the glacier buries itself more and more in the water, the tendency to rise becomes stronger and stronger, and finally the force thus generated is sufficient to break off a fragment, which, once free, is buoyed up to the level that is natural to it. This fragment may be a solid cube half a mile through, or even of much greater dimensions. The disruption is attended with a great disturbance of the waters, and with violent sounds which may be heard for many miles; but, floating now free in the water, the oscillations which the sudden change imparted to it gradually subside; and, after acquiring its natural equilibrium, the crystal mass drifts slowly out to sea with the current, and is called an Iceberg.[6] [Footnote 6: It was formerly supposed that the icebergs were discharged by the force of gravity, but this error, as well as the true theory of berg discharge, was pointed out by Dr. H. Rink, now Royal Inspector of South Greenland. Some fragments are, however, detached from the face of the glacier and fall into the water, but these are always necessarily of comparatively small dimensions, and can scarcely be called bergs.] [Sidenote: THE LAW OF CIRCULATION.] And thus the glacier has fulfilled its part in the great law of _Circulation_ and change. The dew-drop, distilled upon the tropic palm-leaf, falling to the earth, has reappeared in the gurgling spring of the primeval forest, has flown with the rivulet to the river, and with the river to the ocean; has then vanished into the air, and, wafted northward by the unseen wind, has fallen as a downy snow-flake upon the lofty mountain, where, penetrated by a solar ray, it has become again a little globule of water, and the chilly wind, following the sun, has converted this globule into a crystal; and the crystal takes up its wandering course again, seeking the ocean. But where its movement was once rapid, it is now slow; where it then flowed with the river miles in an hour, it will now flow with the glacier not more in centuries; and where it once entered calmly into the sea, it will now join the world of waters in the midst of a violent convulsion.