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Polar Distance of any celestial object, is an arc of a meridian, contained between the centre of that object and the pole of the equinoctial ; or, in other words, it is the distance of the object from ihe elevated pole.
Refraclion.-Refraction is a quantity by which a body appears above its true place in the heavens.
Right Ascension. - The Right Ascension of a celestial body is that portion of the equinoctial which is intercepted by a celestial meridian passing through the centre of the body and the first point of the ecliptic. It is generally given in time.
Right Ascension of the Meridian.—The Right Ascenson of the Meridian is that part of the equinoctial that comes to the Meridian with the object measured from the first point of Aries.
Terrestrial an 1 Celestial Equators.- The Terrestrial Equator is a great circle (supposed to be described) around the earth, at an equal distance, or 90 degrees from the poles, dividing the globe into two equal parts; the part to the southward of the equator being called the southern hemisphere, and that to the northward the northern hemisphere.
The Celestial Equator, commonly called the Equinoctial, is an imaginary circle described in the heavens, corresponding to and coinciding with the terrestrial equator.
Time. -Time is measured by the apparent motion of a celestial body over the surface of the globe, and is called Solar, Lunar, or Sidereal, according to the body with which it is referred ; a full revolution of either of these objects is called its apparent day, and begins when the object comes to the meridian; but for the convenience of civil and commercial business, that of the sun, called solar or civil time, is from midnight to midnight, the first twelve hours of which are marked A. M., signifying ante meridian, and the last twelve hours P. M., signifying post meridian. In this and the following mode of keeping time, the day is dated as soon as it commences.
Astronomical Day.—This day is also measured by the apparent motion of the sun, but for the convenience of astronomical computations, it is taken to begin at noon, that is, 12 hours after the beginning of the civil day, and end at noon of the following day. Astronomers generally reckon the hours of this day up to 24 hours, without any distinction of ante or post meridian, which they call astronomical time ; hence the first 12 hours of which are the P. M. hours of the civil day on which it begins, and the last 12 hours of it are the A. M. hours of the day on which it ends.
The Nautical Day.—This day, as well as the civil and astronomical day, is measured by the apparent motion of the sun. It begins just with the astronomical day, but it is dated with the noon on which it ends; hence it is 24 hours in date later than the astronomical day, the first 12 hours of which are marked in the journal with P. M., and the last 12 hours with A. M., so that occurrences which happen on the afternoon of the civil day on which it begins, come in the journal under the date of the civil day in which it ends. The Log Book is generally kept in nautical or Sea Time, but it may be kept in Common or Civil Time.
Tropics. - The Tropics are two circles (supposed to be described) parallel to the equator, at the distance of about 23° 28', equal to the highest declination. The northernmost is called the Tropicof Cancer, and the other the Tropic of Capricorn.
Twilight.—The Twilight is that duration of light which is apparent in the absence of the sun. It generally continues whilst he is traversing about 18 degrees below the horizon. It is caused by the column of atmosphere which surrounds the earth receiving the rays, or light, of the sun, and from which that light is transmitted to those parts of the surface of the globe opposite the sun at its rising and setting
Vertical Circles.-Vertical Circles are circles (supposed to be described in the heavens) perpendicular to the horizon, and meeting at the Zenith. They are sometimes called circles of altitudes, circles of azimuths, and prime vertical circles.
Zenith and Nadir.-The Zenith is that point in the heavens which is directly over the observer's head; and the Nadir that which is opposite to it.
Zenith Distance. — The Zenith Distance of a celestial object is equal to that portion of the vertical circle which is intercepted between the centre of the object and the observer's zenith. It is always equal to the complement of the altitude to a quadrant, or 90 degrees.
EXPLANATION OF COMPASS TERMS. Variation of the Compass is the angle between the True North and the Magnetic North. This difference or error arises from the Magnetic Poles not coinciding with the Terrestrial ones, and is due entirely to the influence of the earth ,on Magnetic Needles, which is the same at few parts of the world.
Deviation of the Compass is the angle included between the Magnetic North and the Compass North,
This error is due to the disturbing influences of the iron of which the ship is built, as rudderposts, masts, chains, funnel, &c. ; her position when building, her cargo, or other causes within the ship.
Local Attraction is the error caused by some disturbing force outside the ship, and belonging entirely to the locality at which a ship may be--as mooring posts or chains, dock cranes, another iron vessel alongside, volcanic or magnetic influences, &c.
Heeling Error is the effect produced on the Compass by the heeling of an iron or composite ship, the angle increasing with the amount of Heel.
Leeway is the angle between the ship's course by Compass and the direction which she makes through the water, as shown by her wake.
Compass Course is the course steered by ship's Compass.
Magnetic Course is the Compass Course corrected for Deviation and Leeway.
The True Course of a ship is the Compass Course corrected for Deviation, Leeway, and Variation. EXPLANATION OF ASTRONOMICAL CHARACTERS. © The Sun.
? Ceres. ( The Moon.
# Juno. 8 Mercury
2 Jupiter. Ő Venus.
Saturn. # The Earth.
Uranus. 8 Mars.
Neptune. 8 Ascending Node.
8 Descending Node.
SIGNS OF THE ZODIAC, &c. o Aries (the Ram), oo
* Sextile, when two signs dis8 Taurus (the Bull), 30°
tant, or differing 60° in I Gemini (the Twins), 60°
Longitude or Rt. Ascension. Cancer (the Crab), 90° - Quartile, when three signs S. Leo (the Lion), 120°
distant, or differing 90° in me Virgo (the Virgin), 150° Longitude or Rt. Ascension. A Libra (the Balance), 180° 8 Opposition, when six signs m Scorpio (the Scorpion), 210° distant, or differing 180° in † Sagittarius (the Archer), 240° Longitude or Rt. Ascension.
Capricornus (the Goat), 270°
Aquarius (the Waterbearer), * Pisces (the Fishes), 330° (300 N. North. Mins, of Arc.
S. South. Secs. of Arc. ó Conjunction, in the saine de E. East. h. Hours.
gree or sign, or having the W. West. m. Mins. of Time
same Longitude or Rt. Ascn. Degrees. S. Secs. of Time.
Ad valorem.-According to value.
cargo ; an average of the loss insured for the benefit of
all concerned, to be made good proportionately. Award.--The decision in arbitration. Banco.- A continental term for bank money at Hamburg and other
places. Barratry.-A fraudulent act on the part of the master or crew of a
vessel, against the interest of the owners. Insurances
are effected against barratry: Bill of Health.—A certificate granted by Consuls and Customs
Officers as to health of port. Bill of Lading.-A master's acknowledgment and undertaking as
to receipt and delivery of goods or cargo. Bottomry.-Money' borrowed on a ship’s bottom or hull, to be
repaid with interest if the ship return in safety, but if not to be lost or forfeited. Sometimes it is raised on the
lading and master's personal security ; see Respondentia. Brokerage.—The commission charged by merchants and brokers for
securing and transacting business for ships. Charter Party. A contract with the owner, agent, or master for
the service of his vessel. Consul. – The commercial representative of one country residing
officially in another,
Credit, Letter of.-A letter written by one party to another,
requesting the party addressed to advance the bearer or
person named a certain sum of money. Days of Grace. - Days allowed by law or custom for payment of
Bills of Exchange (except those payable at sight or on demand) after specified day of payment; thus, when three days are allowed, as usual in England, a bill due on the
5th of the month is payable on the 8th. Dead Freight.- The damage payable by one who engages to load
a ship fully, and fails so to do. Debenture.- An instrument of the nature of a bill or bond, by
which a debt is claimable. May bear interest or conser some peculiar advantage. It is given at the Custom
House to claim a drawback. Derelict.-Goods cast away or relinquished by wreck or otherwise.
Reductions in duty are also made proportionate to the
damage on them. Deviation is a divergence from the voyage insured which may
release the underwriter from his risk. Drawback. ---An allowance granted by Government to encourage
exportation of an article, or a return of duties paid upon
certain articles on exportation. Discount.- An allowance made for money paid before it is due.
To discount a Bill is to buy from the holder the right
to receive the money upon it when due. Dunnage.—Articles used in stowing a cargo or trimming a ship. Embargo.-An order issued by Government to prevent vessels sailing. Flotsam.-Goods floating after a wreck. Jelsam are those sunk.
Lagan are those sunk but secured by a buoy. Groundage.-Money paid in some parts for permission to anchor. Insurance. -A contract whereby, for a stipulated consideration,
called a premium, one party undertakes to indemnify the
other against certain risks. Invoice.-A document enumerating goods sold from A to B.
Where the goods are exported by A to be sold on his own account, the document is a specification, and not,
strictly speaking, an invoice. Lay Days.-Days allowed by charter for loading or unloading ships. Lighterage. — The expense of a lighter or barge. Manifest.— The specification of a cargo made out and signed by
the master of a ship. Policy. -A document containing the contract of insurance. A Valued
Policy is when the interest insured is valued. An Open Policy is one in which the amount is left for subsequent proof. In an open policy, where the value shipped does not equal the value insured, the difference is termed over insurance; and the proportionate amount of premium re
turnable to the insurer is called a return for short interest. Frimage. -A small allowance for the shipmaster's care of goods
now generally included in the freight. Pro rata.—Payment in proportion to the interests concerned. Quid pro quo. -Giving one thing for another. Řespondentia. A contract of loan by which goods in a ship ar
hypothecated to the lender, as in bottomry. Super Cargo. -A person sent with a vessel to dispose of its cargo
to the best advantage.
EDUCATIONAL STANDARD REQUIRED BY VARIOUS MARITIME POWERS FOR MASTERS AND MATES.
77 per cent.
The percentage of oxygen varies as follows:---
21 per cent.
20'50 do. Confined Houses..
20*75 do. Air travels in England in healthy years at the rate of about 41 miles per hour, and in unhealthy years about 34 miles per hour. Each adult inhales a gallon of air per minute, and consumes daily 30 oz. of oxygen. For the conversion of this oxygen a certain amount of food is required-say 13 oz. of carbon for a male and 11 oz. for a female-equivalent to 3lb. and 2 lb. of bread respectively.
THE POWER OF THE WIND.
Figures to denote the Force Description of of the Wind. Wind.
POWER OF THE WIND
the Wind as regards a well-conditioned Man-of-War per Hour
or First-class Clipper Ship. in Miles,
(5 to 6
o to Just sufficient to give steerage way
3-10 With which the above Ship
I to 2 knots .. 11 with all sail set and clean
16 - 20 full would go in smooth 3 to 4
25 Royals, &c.
30 Single Reefs and In which she could T.G. Sails.
- 36 just carry in chase Double Reefs and full and by.. Jib, &c....
37 44 "Triple Recfs, &c. 45 52
Close Reefs & Courses 53 -60 In which she could just bear close-reefed
Main Topsail and reefed Foresail 61 69 Under Storm Staysail
70 80 Bare Poles