The accumulation upon elevated situations of frozen snow, produces those moving masses of ice called glaciers. (See Glaciers.) In the Alps, and in Norway, these glaciers coming down to a mild region melt away; but in the arctic regions, they often flow into the sea and produce icebergs. While floating about, these masses may increase indefinitely in size, from receiving fresh accessions of snow, or by the freezing of the water continually splashed against them, as well as by the sudden freezing of the water which falls as rain. They are of all sizes, from mere fragments to upwards of half a mile in diameter, and of all weights, from a few pounds to a hundred thousand tons. They rise sometimes 150 feet above the water, and this is but an eighth of the whole mass. They float about in hundreds, and are often driven by winds far into the ocean, and become exceedingly dangerous to navigation. Icebergs from each pole have approached nearer the equator than 40° N. and S. Lat.; they have been met with in the neighbourhood of the Cape of Good Hope. Many of these icebergs, originating on land, present the same phenomena Iceland, as glaciers. Hence, upon near inspection, they are found to be loaded with the debris which, as glaciers, they scraped off the mountain sides, past which they flowed to the sea. This debris contains masses of greenstone, clay-slate, gneiss, granite, &c. In the polar circle, where the floating masses reach to many hundreds of miles in length, they are called ice islands. When two of these approach each other, any vessel which happens to be between them is almost certain to be crushed to pieces. The larger of the two, by its greater momentum, urges itself beneath the smaller, which is thus tilted up on the shoulders of the larger, whose mass it goes to increase. The iccblikk is an appearance produced on the horizon by these ice islands when stationary, and which indicates the existence of an ice island before it is itself visible.