What is considered as salt-water-ice appears blackish in the water, but in the air is of a white or grey colour, porous, and in a great measure opaque, (except when in very thin pieces,) yet transmits the rays of light with a blue or blueish green shade. When dissolved, it produces water sometimes perfectly fresh, and at others saltish. This depends, in a great measure, on the situation from whence it is taken; such parts as are raised above the surface of the sea, in the form of hummocks, or which, though below the surface, have been long frozen, appear to gain solidity, and are commonly _fresh_; whilst those pieces taken out of the sea, that have been recently frozen, are somewhat salt. Fresh-water-ice of the sailors is distinguished by its black appearance when floating in small pieces in the sea, and by its transparency when removed into the air. Fresh-water-ice is fragile, but hard; the edges of a fractured part are frequently so keen as to inflict a wound like glass. The most transparent pieces are capable of concentrating the rays of the sun, so as to produce a considerable intensity of heat. With a lump of ice, of by no means regular convexity, I have frequently burned wood, fired gunpowder, incited lead, and lit the sailors’ pipes, to their great astonishment, all of whom, who could procure the needful articles, eagerly flocked around me, for the satisfaction of smoking a pipe ignited by such extraordinary means. Their astonishment was increased by observing that the ice remained firm and pellucid, while the solar rays emerging from it were so hot, that the hand could not be kept longer in the focus than for the space of a few seconds. In the formation of these lenses, I roughed them out with a small axe, and then scraped them with a knife, polishing them merely by the warmth of the hand, supporting them during the operation in a woollen glove. I once procured a piece of the purest ice, so large that a lens of sixteen inches diameter was obtained out of it; unhappily, however, the sun became obscured before it was completed, and never made its appearance again for a fortnight, during which time, the air being mild, the lens was spoiled. All young ice, such as bay-ice and light-ice, which form a considerable part of drift and pack-ice in general, is considered by Greenland sailors salt-water-ice; while fields, floes, bergs, and heavy-ice, chiefly consist of fresh-water-ice. Brash-ice likewise affords fine specimens of the latter, which, when taken out of the sea, are always found crowded on the surface with sharp points and conchoidal excavations.