The Sailor's Word-Book Part 133

HYDRAULIC PRESS. The simple yet powerful water-press invented by Bramah, without which it would have been a puzzle to float the enormous _Great Eastern_.

HYDRAULIC PURCHASE. A machine for drawing up vessels on a slip, in which the pumping of water is used to multiply the force applied.

HYDRAULICS. _See_ HYDROLOGY.

HYDROGRAPHER. One who surveys coasts, &c., and constructs true maps and charts founded on astronomical observations. The hydrographer to the admiralty presides over the hydrographical office.

HYDROGRAPHICAL CHARTS OR MAPS. Usually called _sea-charts_, are projections of some part of the sea and its neighbouring coast for the use of navigation, and therefore the depth of water and nature of the bottom are minutely noted.

HYDROGRAPHICAL OFFICE. A department of the admiralty where the labours of the marine surveyors of the Royal Navy are collected and published.

HYDROGRAPHY. The science of marine surveying, requiring the princ.i.p.al points to be astronomically fixed.

HYDROLOGY. That part of physics which explains the properties of water, and is usually divided into hydrostatics and hydraulics. The former treats of weighing water and fluids in general, and of ascertaining their specific gravities; the latter shows the manner of conveying water from one place to another.

HYDROMETER. An instrument constructed to measure the specific gravities of fluids. That used at sea for testing the amount of salt in the water is a gla.s.s tube containing a scale, the bottom of the tube swelling out into two bulbs, of which the lower is laden with shot, which causes the instrument to float perpendicularly, and as it displaces its own weight of water, of course it sinks deeper as the water is lighter, which is recorded by the scale.

HYGRE. (_See_ BORE and EAGRE.) An effect of counter-currents.

HYGROMETER. An instrument for ascertaining the quant.i.ty of moisture in the atmosphere.

HYPERBOLA. One of the conic sections formed by cutting a cone by a plane which is so inclined to the axis, that when produced it cuts also the opposite cone, or the cone which is the continuation of the former, on the opposite side of the vertex.

HYPOTHECA. A mortgage. In the civil law, was where the thing pledged remained with the debtor.

HYPOTHECATION. An authority to the master, amounting almost to a power of the absolute disposal of the ship in a foreign country; he may hypothecate not only the hull, but his freight and cargo, for necessary and urgent repairs.

HYTHE. A pier or wharf to lade or unlade wares at [from the Anglo-Saxon _hyd_, coast or haven].

I.

I. The third cla.s.s of rating on Lloyd's books, for the comparative excellence of merchant ships. (_See_ A.)

ICE-ANCHOR. A bar of round iron tapered to a point, and bent as a pot-hook; a hole is cut in the ice, the point entered, and the hawser bent to the shorter hook; by this vessels ride safely till any motion of the ice capsizes it, and then it is hauled in. The ice is usually entered by a lance, which cuts its hole easily.

ICE-BEAMS. Strengtheners for whalers. (_See_ FORTIFYING.)

ICEBERG. An insulated mountain of ice, whether on Arctic lands or floating in the sea. Some have been known to be aground in 120 fathoms water, and rise to the height of 150 feet above it. Cook's obtaining fresh water from floating icebergs was not a new discovery. The Hudson's Bay ships had long made use of it; and in July, 1585, Captain Davis met with ice "which melted into very good fresh water."

ICE-BIRDS. Small sea-fowl in the polar regions.

ICE-BLINK. A streak or stratum of lucid whiteness which appears over the ice in that part of the atmosphere adjoining the horizon, and proceeds from an extensive aggregation of ice reflecting the rays of light into the circ.u.mambient air.

ICE-BOAT. A peculiar track-schuyt for the Dutch ca.n.a.ls in winter.

ICE-BOUND. A vessel so surrounded by ice as to be prevented from proceeding on her voyage.

ICE-CHISEL. A large socket-chisel into which a pole is inserted, used to cut holes in the ice.

ICE-CLAWS. A flat claw with two p.r.o.ngs spread like a can-hook; the same as a single span or claw-dog.

ICE-FENDERS. Fenders of any kind, used to protect a vessel from injury by ice; usually broken spars hanging vertically where the strain is expected.

ICE LANE OR VEIN. A narrow temporary channel of water in the packs or other large collections of ice.

ICE-MASTER. A pilot, or man of experience, for the Arctic Sea.

ICE-PLANK. _See_ SPIKE-PLANK.

ICE-QUAKE. The rending crash which accompanies the breaking of floes of ice.

ICE-SAW. A huge saw for cutting through ice; it is made of 2/8 to 3/8 inch plates of iron, and varies in length from 10 to 24 feet.

ICE-SLUDGE. Small comminuted ice, or bay-ice broken up by the wind.

ICE-TONGUE. _See_ TONGUE.

ICHNOGRAPHY. A ground plot or plan of a fortification, showing the details of the construction as if cut horizontally through.

ICK. An Erse or Manx term for a creek or gullet.

IDLER. A general designation for all those on board a ship-of-war, who, from being liable to constant day duty, are not subjected to keep the night-watch, but must go on deck if all hands are called during the night. Surgeons, marine-officers, paymasters, and the civil department, are also thus denominated.

IDOLEERS. The name by which the Dutch authorities are known in their oriental colonies, the designation being a corruption of _edle herren_.

IGNORANCE. If a loss happen through the ignorance of the master of a ship, it is not considered as a peril of the sea; consequently the a.s.surers are not liable. Nor is his ignorance of admiralty-law admissible as an excuse.

IGUANA. A large lizard used for food in tropical climates.

ILAND. The Saxon _ealand_ (_See_ ISLAND.)

ILDE, AND ILE. Archaic terms for _island_.

ILET. Lacing holes. (_See_ EYELET-HOLES.)

ILLEGAL VOYAGE. (_See_ VOYAGE.)

IMMER. A water-fowl (_See_ EMBER-GOOSE). The _Colymbus immer_ of Linn., the great plunger of Buffon.

IMMERSION. The prismatic solid carried under water on the lee-side of a ship by its inclination.--_Centre of immersion_, the mean centre of the part immersed. (_See_ CENTRE OF CAVITY.) Astronomically, immersion means the disappearance of a heavenly body when undergoing eclipse.

IMP. One length of twisted hair in a fishing-line.

IMPEDIMENTA. The ancient term for the baggage of an army.