This iceberg was full of rents as high as any of our people ascended upon it, extending in a direction perpendicularly downward, and dividing it into innumerable columns. The surface was very uneven, being furrowed and cracked all over. This roughness appeared to be occasioned by the melting of the snow, some streams of water being seen running over the surface; and others, having worn away the superficial ice, could still be heard pursuing their course through subglacial channels to the front of the iceberg, where, in transparent streams, or in small cascades, they fell into the sea. In some places, chasms of several yards in width were seen, in others they were only a few inches or feet across. One of the sailors, who attempted to walk across the iceberg, imprudently stepped into a narrow chasm, filled up with snow to the general level. He instantly plunged up to his shoulders, and might, but for the sudden extension of his arms, have been buried in the gulf. Icebergs are, probably, formed of more solid ice than glaciers, but, in every other respect, they are very similar. The ice of which they consist is, indeed, a little porous, but considerable pieces are found of perfect transparency. Being wholly produced from rain or snow, the water is necessarily potable. Icebergs have, probably, the same kind of origin as glaciers, and the time of their first stratum is nearly coeval with the land on which they are lodged. Though large portions may be frequently separated from the lower edge, or, by large avalanches from the mountain summit, be hurled into the sea, yet the annual growth replenishes the loss, and, probably, on the whole, produces a perpetual increase in thickness.