4. Drift-ice consists of pieces less than floes, of various shapes and magnitudes.
5. Brash-ice is still smaller than drift-ice, and may be considered as the wreck of other kinds of ice.
6. Bay-ice is that which is newly-formed on the sea, and consists of two kinds, common bay-ice and pancake-ice; the former occurring in smooth extensive sheets, and the latter in small circular pieces, with raised edges.
7. Sludge consists of a stratum of detached ice crystals, or of snow, or of the smaller fragments of brash-ice, floating on the surface of the sea.
8. A hummock is a protuberance raised upon any plane of ice above the common level. It is frequently produced by pressure, where one piece is squeezed upon another, often set upon its edge, and in that position cemented by the frost. Hummocks are likewise formed by pieces of ice mutually crushing each other, the wreck being heaped upon one or both of them. To hummocks, principally, the ice is indebted for its variety of fanciful shapes, and its picturesque appearance. They occur in great numbers in heavy packs, on the edges, and occasionally in the middle of fields and floes, where they often attain the height of thirty feet or upwards.
9. A calf is a portion of ice which has been depressed by the same means as a hummock is elevated. It is kept down by some larger mass, from beneath which it shows itself on one side.
10. A tongue is a point of ice projecting nearly horizontally from a part that is under water. Ships have sometimes run aground upon tongues of ice.
11. A pack is a body of drift-ice, of such magnitude that its extent is not discernible. A pack is open when the pieces of ice, though very near each other, do not generally touch, or close when the pieces are in complete contact.
12. A patch is a collection of drift or bay-ice, of a circular or polygonal form. In point of magnitude, a pack corresponds with a field, and a patch with a floe.
13. A stream is an oblong collection of drift or bay-ice, the pieces of which are continuous. It is called a sea-stream when it is exposed on one side to the ocean, and affords shelter from the sea to whatever is within it.