470 
TECHNICAL TEH MS. 
[APP. N° IX. 
Crow's Nest . —A circular box, like a small pulpit, fixed at 
the mast-head, for the accommodation of the captain or 
officer, when employed in navigating the ship through 
ice, or looking out for whales. This structure, which 
is extremely commodious, was the invention of Captain 
Scoresby senior, and is now universally used by the 
northern whalers. 
Drift-ire .— Masses of floating ice, of the sheet kind, of va¬ 
rious shapes and magnitudes, up to, perhaps, a quarter 
of a mile in diameter. 
Field .— A sheet of ice so extensive, that its limits cannot be 
discerned from a ship’s mast-head. 
Floe .—A large sheet of ice, whose extent can he seen from 
a ship's mast-head. This term is seldom applied to 
pieces of ice of less diameter than a quarter of a mile. 
Frost-rime .—A sort of fog that appears on the surface of 
the sea, in severe frosts, produced by the condensation 
of the vapour arising from the water, in consequence of 
its bein;r much warmer than the air. 
Heavy ice . — A term applied to thick ponderous ice, in con¬ 
tradistinction to “ light,” or thin ice. 
Hummock .—A protuberance, the effect of pressure, raised 
upon any plain of ice above the common level. 
Iceberg .—The polar glacier. The same term is also applied 
to large elevated floating masses, sometimes called ice- 
islands, which are merely dismemberments of the land 
icebergs. 
Ice-blink .—The same as blink. 
Lunil-icc. — Grounded ice, or ice attached to the land, 
whether in floes, or closely aggregated drift-ice, some¬ 
times extending several miles from the shore. 
Lane, or vein .—A narrow opening, in which a ship may 
conveniently sail, in a pack or other large collection of 
