Page:The open Polar Sea- a narrative of a voyage of discovery towards the North pole, in the schooner "United States" (IA openpolarseanarr1867haye).pdf/183

 steady course, it finally reaches many miles beyond the original shore-line.

And now it has attained the climax of its progress.

When, long ages ago, after pouring over the sloping land, it finally reached the coast and looked down the bay which it was ultimately to fill up, its face was many hundreds of feet high. Gradually it sank below the line of waters as it moved outward, and finally its front has almost wholly disappeared.

In a former chapter I have mentioned that a block of fresh-water ice floating in sea water rises above the surface to the extent of one eighth of its weight and bulk, while seven eighths of it are below the surface. The cause of this is too well known to need more than a passing explanation. Every school-boy is aware that water, in the act of freezing, expands, and that in the crystal condition fresh water occupies about one tenth more space than when in a fluid state; and hence, when ice floats in the fresh water from which it was formed, one tenth of it is exposed above, while the remaining nine tenths are beneath the surface. When this same fresh-water ice (which it will be remembered is the composition of the glacier) is thrown into the sea, the proportion of that above to that below being changed from one and nine to one and seven, is due to the greater density of the sea-water, caused by the salt which it holds in solution.

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