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kind in the courts of the United States; his right of action, however, revives on the declaration of peace. See INTERNATIONAL LAW.

Alignment. An imaginary line to regulate the formation of a squadron.

Alioth. The star e Ursa Majoris.

All.

The whole; quite.

ALL AGOG. In a flurry of excitement. ALL AHOO. Confused; awry; aslant. ALL-A-TAUNT-0. Fully rigged with masts an-end, yards crossed, and rigging rove.

ALL HANDS. The whole ship's company. ALL HANDS! The boatswain's summons for the whole crew, in distinction from the watch.

ALL READY FORWARD, ALL READY THE MAIN, etc. The notice that a particular part of the ship is ready for the next order.

ALL STANDING. Fully equipped. To be brought up all standing is to be suddenly stopped without any preparation.

ALL'S WELL. The sentry's call as each bell is struck, from tattoo to reveillé.

ALL TO PIECES. Out-and-out; excessively. ALL WEATHERS. All times and all seasons. ALL IN THE WIND. The sails shivering. ALL OF A HEAP. Dumfounded; confused. STERN ALL. The shout of the harpooner when the fish is struck.

HAUL OF ALL. To swing all the yards at the same time.

ALL UP AND AFT. The report of the officer of the deck when the officers and men are assembled on the quarter-deck ready for muster.

Allan. A piece of land nearly surrounded by

water.

Allege. (Fr.) A ballast-boat.

Allegiance. The tie which binds the citizen to his sovereign or country. Its full consideration involves an examination of the right of a citizen to expatriate himself, a matter about which there is a conflict of theories. The common law of England denies the right of the subject to throw off his allegiance to the country of his birth, and European nations generally have taken the same position, while in the United States we require of persons seeking naturalization the renunciation of their former allegiance. The inherent difficulties of the subject make it improbable that any solution will ever be attained by legislative action, but it may be assumed that the sense of humanity of enlightened nations at this day will prevent being treated as criminals, persons who, by the silent acquiescence, and, therefore, the presumed consent of the country of their birth, have removed to other countries and assumed a new allegiance, even if they should be taken in arms against their native country. Many of the questions growing out of the subject have been disposed of by treaties between the United States and foreign nations. See NATURALIZATION.

Alley. A passage-way between the tiers of tanks in a magazine. (See MAGAZINE.) A passage-way affording means of access to the propeller-shaft.

Alliance. A league between two or more friendly powers, either offensive and defensive, or defensive only.

Alligator. The American crocodile. Alligator Water. The muddy, brackish water near the mouth of tropical rivers.

Allision. Synonymous with collision, but is

sometimes used to mark a distinction between one vessel running into another, and two vessels striking each the other.

Allotment. That part of the pay of a person on duty in a United States vessel which is paid during his absence to some person on shore. Allotments may be granted by any officer, or, with the approval of the commanding officer, by any man or petty officer in a vessel in commission. They are paid by navy pay agents to the allottees on the last day of every month, and the paymaster of the vessel at the same time deducts the amount of the allotment from the allottor's pay. The allottee must be a member of the allottor's family, or some person who receives the money for the benefit of said family. Allotments cannot exceed one-half the allottor's monthly pay. It is the duty of the paymaster having charge of the allottor's account to deduct as much from his pay as is paid on the allotment, and, in case of death, desertion, or discharge of the allottor, to give notice to the navy pay agent to cease payments to the allottee. The Fourth Auditor keeps a register of all allotments, the amounts paid to the allottees, and the amounts checked from the pay of the allottors. In case more is deducted from the pay of an allottor than is paid to the allottee, the difference will be paid to the former on application to the Fourth Auditor.

Allowance. Reimbursement of incidental expenses or losses incurred in the performance of duty; as, traveling allowance, allowance to paymasters for loss on clothing, small stores, etc. A gratuity or bounty; as, allowance of additional pay on re-enlistment. A commutation; as, allowance for the subsistence of pilots in officers' messes. A ration or fixed quantity of food. It is double, full, two-thirds, half, or short, according to circumstances. (Commercial.) A customary deduction from the gross weight of goods, varying in different countries.

Alloy. A combination of metals by fusion. The term is also applied to the metal that is mixed with gold or silver. The properties of the alloy are very different from the mean of the properties of the constituents, the alloy being harder, more tenacious, less ductile, fusing at a lower temperature, and more easily oxidized. Its density may be either greater or less than this mean, and its power of conducting electricity is less. If mercury enter into a combination, it is known as an amalgam.

Alluvion, or Alluvium. A deposit of earth, gravel, etc., along shores or banks, caused by the washing of the water, or by the precipitation of substances held in solution. Sea alluvions differ from those of rivers in that they form a slope toward the land.

Ally. A confederate. A prince or state united to another by treaty. See ALLIANCE.

Almacantars. Circles parallel to the horizon, and passing through every meridian.

ALMACANTARS STAFF. An old instrument of 15° of arc to observe the amplitude.

Almady. A canoe made of bark, used by the natives of Africa for war purposes. The name is also applied to a boat in use at Calcutta, often measuring from 80 to 100 feet in length, and generally from 6 to 7 feet in breadth.

Almafadas. Large dunnage cut on the coast of Portugal.

Almanac. A calendar of the days and months of the year, to which is generally added a record of the feast-days and celestial phenomena.

Almanac, The Nautical. As the astronomical ephemeris had its origin in the necessity for easy and accurate prediction of the phenomena and configurations of the heavenly bodies, so the nautical almanac originated in connection with the necessity for safe and speedy navigation. So soon as out of sight of land the navigator has but one sure means of information as to his position at sea; his compass gives him only the direction in which his ship lies or is sailing; he must rely upon the heavens alone for the precise determination of his position; and the problem of longitude and latitude is capable of solution only in connection with some prediction (a suitable period in advance) of the absolute positions of the bodies observed at the time when the ob

servations are made upon them. This annual volume of such predictions of the positions of the heavenly bodies as are necessary in the navigation of ships constitutes the nautical almanac. In general, these predictions are given for equidistant intervals of time, so that by interpolation the position of a single body, or the relative position of two bodies, may be readily computed for any intermediate epoch. Long before the publication of the first nautical almanac, books of predictions, known as ephemerides, had been issued from time to time, at irregular intervals, mostly for the convenience of astronomers. It required simply a regulation and extension of the idea of these volumes to make up a nautical almanac. The nautical almanac proper had its origin with the English nation about the middle of the 18th century. It owes its existence to a

memorial presented to the Commissioners of Longitude, on February 9, 1765, by Dr. Maskelyne, in which, after stating many facts and experiments to prove the utility of the lunar method of obtaining the longitude at sea, he concludes, that "nothing is wanting to make this method generally practicable at Sea but a Nautical Ephemeris." Dr. Maskelyne proposed the construction of such a "Nautical Ephemeris" from the "New and Correct Tables of the Motions of the Sun and Moon," by Tobias Mayer. The first volume issued was that for the year 1767. Gradually additions were made to the nautical almanac, and improvements introduced, mostly, however, in the direction of such predictions and ephemerides as were of more service to the astronomer than to the navigator, and the volume assumed the name of "The Nautical Almanac and Astronomical Ephemeris," which title it retains to the present day. The most important era in the history of the nautical almanac is marked by the " Report of the Committee of the Astronomical Society of London relative to the Improvement of the Nautical Almanac," adopted November 19, 1830. One very great improvement consisted in the abolition of the use of apparent time in all the computations of the nautical almanac, and the substitution of mean time therefor. (See EPHEMERIS, THE ASTRONOMICAL.) The entire almanac was remodeled by this committee; and the new arrangement of the several ephemerides therein contained has formed the basis of all subsequent nautical almanacs, and has remained unchanged in the "British Nautical Almanac" up to the

"The

latest volume,-that for the year 1883. American Nautical Almanac" had its origin nearly a century after the "British Nautical Almanac." On March 3, 1849, an act of Congress was approved providing for the preparation of such a work. The preparation of the first volume-that for the year 1855-was begun in the latter part of 1849, and the series of volumes is unbroken down to the present time, the volume for 1883 having just been issued. By act of Congress, "The meridian of the observatory at Washington shall be adopted and used as the American meridian for astronomical purposes, and the meridian of Greenwich shall be adopted for all nautical purposes." This law was the occasion of the subdivision of "The American Ephemeris and Nautical Almanac" into two distinct parts, and the publication of two separate volumes. Part the first is substantially identical with that portion of the "British Nautical Almanac" intended for the special use of navigators, and is likewise computed for the meridian of Greenwich. This part contains all the data necessary in the navigation of ships, and is published three years in advance of the year for which it is computed. "The American Nautical Almanac" likewise contains accounts of the transits of Mercury and Venus, and of eclipses of the sun and moon, with engraved diagrams of the solar eclipses. Each volume contains also an article on the arrangement and use of the various ephemerides, and a selection of subsidiary tables, of frequent use to the navigator.-D. P. Tod.

Almath. The star in Aries whence the first mansion of the moon takes its name.

Almeria. A city and port of Spain, in Andalusia, on the Mediterranean, 104 miles E. of Malaga. In the bay there is a good anchorage, in 12 and 14 fathoms. Pop. 30,000. Almirante. (Sp.) Admiral.

Almury. The upright part of an astrolabe. Almy, John J., Rear-Admiral U.S.N. Born in Rhode Island in the year 1815. Appointed from that state as midshipman, February 2, 1829; attached to the "Concord," Mediterranean, 183032; "Ontario," coast of Brazil, 1833-34; promoted to passed midshipman July 3, 1835; receiving-ship at New York, 1836-37; "Cyane," Mediterranean, 1838-41.

Commissioned as lieutenant, March 8, 1841; brig "Bainbridge," West Indies, 1842; frigate "Macedonian," coast of Africa, 1843-45; lineof-battle ship "Ohio," Gulf of Mexico and Pacific Ocean during the Mexican war and after the war, 1846-50; participated in the siege and capture of Vera Cruz and the capture of Tuspan; latter part of the war-1848-on the Pacific coast, and commanded one of the forts at Mazatlan during the naval occupation of that place; coast survey in 1851-56, on the survey of Chesapeake Bay and the sea-coast of Virginia and North Carolina; commanding "Fulton," on the coast of Central America, in 1857, when General Walker and his filibustering party surrendered to Rear-Admiral Paulding, on board of that vessel, at Nicaragua. Commanded the "Fulton" in the expedition to Paraguay in 1858-59; at navy-yard, New York, 1860–61.

Commissioned as commander, April 24, 1861; commanded "South Carolina," South Atlantic Squadron, 1862-63; "Connecticut," North At

lantic Squadron, 1864; "Juniata," South Atlantic Squadron, 1865.

While in command of the "Connecticut," captured and sent in four noted blockade-running steamers with valuable cargoes; ran ashore and destroyed four others.

Commissioned as captain, March 3, 1865; commanded "Juniata" in a cruise to the South Atlantic (coast of Brazil and south coast of Africa), 1865-67. While on the coast of Brazil rescued the Brazilian brig "Americo" and crew from shipwreck, attended with great danger, for which service received the thanks of His Imperial Majesty the Emperor of Brazil. Ordnance duty at the navy-yard, New York, 1868-69.

Commissioned as commodore, December 30, 1869; chief signal-officer of the navy at Washington, 1870-72.

Commissioned as rear-admiral, August 24, 1873, and the following month took command of the United States naval forces in the Pacific Ocean. While at Panama, in October, 1873, a serious and violent revolution broke out, characteristic of that country, which continued for three weeks. The city of Panama and the Panama Railroad were in imminent danger of being destroyed. A force of seamen and marines numbering 200, under competent officers, was landed from the ships and kept on shore until the revolution terminated, affording efficient protection to the railroad, to American and to European interests. Two United States vessels, the flag-ship "Pensacola" and the "Benicia," were the only men-of-war in port. Passengers, freight, and specie continually passed over the road in safety and without interruption.

For these services Rear-Admiral Almy received the thanks of the Panama Railroad Company, the Pacific Mail Steamship Company, and of all the consuls and the foreign merchants at Pa

nama.

Was in command of the United States naval forces in the Pacific for two years and ten months.

Has performed altogether twenty-seven years and ten months' sea service; shore, or other duty, fourteen years and eight months.

In April, 1877, was retired, having reached the age prescribed by law for retirement.

Alnus Caver. Early English transports, so called from the wood of which they were made.

Aloft. Overhead; on high; anywhere about the upper masts, yards, or rigging. See ALOW. LAY ALOFT! The command to the men to run up to their stations.

ALOFT THERE! The hail to men on the yards and in the rigging.

ALOFT is used in a figurative sense for heaven. Alonde. An old word for ashore; on land. Along. Lengthwise.

ALONG OF. With.

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marks symbols on paper, in contradistinction to those whose signals are made by a needle, mirror, or sound.

Alphard. The star a Hydræ.
Alpheratz. a Andromeda.
Altair. a Aquila.

Altar. A step of a dry-dock.

Alternate. To happen or act by turns.

ALTERNATING WINDS. Blow for a time in one direction, and suddenly, from an alteration of the temperature, change and blow in the opposite directions. See MONSOON and BREEZE.

Altiscope. An instrument which enables an observer to look over an intervening object. This instrument has been applied, not very successfully, to pointing guns, the observer being on the deck below.

Altitude. Height. Angular distance of a heavenly body above the horizon measured on a great circle.

ALTITUDE, CIRCLES of. Great circles of the celestial concave perpendicular to the horizon, and so called because "altitudes" are measured on them. They all pass through the poles of the horizon, of which the superior is the "vertex" of the visible heavens, and hence they are also called " Vertical Circles," or simply " Verticals." In a polar system of horizon co-ordinates they are termed "Circles of Azimuth," as marking out all points that have the same "azimuth."

ALTITUDE, CIRCLES OF EQUAL. Circles on the earth's surface, from every point of each of which a given heavenly body is observed to have the same altitude at any given time. The circle of equal altitude is a great circle of the sphere when the body is in the horizon, or its altitude 0; the circle is reduced to a point when the body is in the zenith, or its altitude 90°; and between these two limits the parallels are small circles whose radii correspond to the complements of the altitude. A small are of a circle of equal altitude, when projected on a Mercator's chart, will be approximately a straight line, especially if the altitude of the body be low. Such a line is called "A Line of Equal Altitude." The determination of one or two such lines intersecting each other forms the basis of what is called "Sumner's Method" of finding a ship's position at sea.

ALTITUDE, CORRECTION IN. The total correction to be applied to the apparent altitude to deduce the true altitude. In the case of the stars, it is due solely to refraction, but for appreciably near bodies to the combined effects of refraction and parallax.

ALTITUDE, A DOUBLE. Two altitudes taken for the solution of the same problem. The ordinary problems for which the method furnishes the data are finding the latitude, and rating a chronometer. These altitudes may le of the same body, taken at different times, either both on the same side or on opposite sides of the meridian; or of different bodies similarly situated observed at the same time; or, lastly, of different bodies similarly situated observed at different times.

ALTITUDE, MERIDIAN. The altitude of a celestial body when on the meridian. In the case of a circumpolar star, whose whole diurnal circle is completed above the horizon, the body comes to the meridian twice, when its altitudes are spoken of respectively as "the Meridian Altitude below the Pole," and "the Meridian Altitude above the Pole"; the former is the lowest altitude the body

has in its revolution, the latter the highest. The meridian altitude is easily observed at sea with a sextant, and furnishes the simplest and most satisfactory method of determining the latitude, the declination of the body only being required in addition.

ALTITUDE, MOTION IN. An instrument is said to move in altitude" when it is turned on a horizontal axis; in contradistinction, it is said to move in azimuth" when it is turned on a vertical axis. An azimuth and altitude instrument admits of both motions.

ALTITUDE, OBSERVED, APPARENT, AND TRUE. The altitudes of heavenly bodies are observed from the deck of a ship at sea with the sextant. Such an altitude is called the "Observed Altitude." There are certain instrumental and circumstantial sources of error by which this is affected: the sextant (supposed otherwise to be in adjustment) may have an index error; the eye of the observer being elevated above the surface of the sea, the horizon will appear to be depressed, and the consequent altitude in reality too great; and one of the limbs of the body may be observed instead of its centre. When the corrections for these errors and method of observing are applied-the "index correction," "correction for dip," and "semi-diameter"the observed is reduced to the "Apparent Altitude." But again, for the sake of comparison and computation, all observations must be transformed into what they would have been had the bodies been viewed through a uniform medium, and from one common centre,-the centre of the earth. The altitude supposed to be so taken is called the "True Altitude"; it may be deduced from the apparent altitude by applying the corrections called "correction for refraction" and "correction for parallax." "Correction for refraction": when a body is viewed through the atmosphere, refraction will cause the apparent to be greater than the true altitude; hence the correction for refraction is subtractive in finding the true from the apparent altitude. "Correction for parallax": the position of the observer on the surface, especially for near bodies, will cause the apparent to be less than the true altitude; hence the correction for parallax is additive in finding the true from the apparent altitude.

ALTITUDE, PARALLELS OF. Lesser circles of the celestial sphere parallel to the horizon. They mark all the points of the heavens which have the same altitude. The Arabic term for this system was "Almacantars."

ALTITUDE, REDUCTION OF, TO ANOTHER PLACE OF OBSERVATION. See RUN.

ALTITUDES, CIRCUMMERIDIAN. When the body is near the meridian, and altitudes are observed with a view of solving problems by first finding from these the meridian altitude, such altitudes are conveniently distinguished as Circummeridian Altitudes.

ALTITUDES, EQUAL. Double altitudes of the sun, when at the same altitude in the forenoon and afternoon.

ALTITUDES, EQUATION OF EQUAL. In equal altitudes of the sun, its declination changes slightly in the interval between the forenoon and afternoon observation, and therefore the hourangles corresponding to the two altitudes are not exactly equal. Hence half the interval added

to the time of the first observation requires a correction in order to give the time shown by chronometer when the sun is on the meridian. This correction is called "The Equation of Equal Altitudes." It is given in tables.

ALTITUDES, SIMULTANEOUS. Double altitudes of different bodies taken at the same time. Altometer. The theodolite.

Altona. A city and free port of Prussia, in Holstein, on the right bank of the Elbe, a little below Hamburg. It is accessible to sea-going vessels, and has a large trade. Pop. 90,000.

Aluffe, or Aloof. A very old form for luff. Alveus. An ancient boat made of a single trunk; a dug-out.

Amadas (or Amidas), Philip, b. Hull, 1550; d. England, 1618. A commander of one of the vessels sent out by Sir Walter Raleigh, with Barlow, to take possession of lands on the eastern shore of America. He discovered Ocracoke Inlet, and landed on Wocoken Island, in Florida, subsequently exploring Pamlico and Albemarle Sounds and Roanoke Island. The title of admiral was conferred upon him, and he was united with Lane in the settlement of North Carolina, afterwards called Virginia.

Amain. With force or vigor; all at once; as, lower amain. An old word for yield. The lowering of the topsail was called striking amain, and it was demanded by the wave amain, or the brandishing of a sword.

Amalfi. A city and seaport of Italy, in the Gulf of Salerno, and 23 miles S. E. of Naples. Lat. 40° 38′ N.; lon. 14° 37' 10 E. A naval school is located at Amalfi. Pop. 6500.

Amalgam. A compound of mercury with another metal. See ALLOY.

Amalphitan Code. The oldest code of modern sea laws, compiled during the first Crusade by the people of Amalfi, in Italy.

Amaye. Sea-marks on the French coast. Ambassador. A diplomatic officer of the highest rank. A practical joke, in which the victim is unmercifully ducked.

Amber. A hard, resinous, vegetable substance, generally of a bright yellow color, and translucent.

Ambergris. A fragrant substance, the origin of which was long a matter of dispute. It is now known to be a morbid product developed in the intestines of the sperm whale. It is of a grayish color, very light, and fusible, and is used as a perfume and as a cordial.

Amelioration. An allowance made to the neutral purchaser, on reclaiming a ship improperly condemned, for the repairs she has undergone at his expense.

America. See CONTINENTS.

Americus Vespucci. See VESPUCCI.

Amidships. The middle part of a ship, whether in regard to her length or breadth, but more generally applied to the axis or fore-andaft line.

Ammen, Daniel, Rear-Admiral U.S.N. Born in Ohio, May 15, 1820. Appointed midshipman, July 7, 1836; attached to the Exploring Expedition, 1837-38; sloop " Levant" and "Vandalia," in the West Indies, 1838-39; sloop "Preble," on the coast of Labrador and in the Mediterranean, 1840-41; returned to the United States on board ship-of-the-line "Ohio," 1841, and to Naval School; passed examination, June, 1842,

and received warrant of passed midshipman; store-ship "Lexington," as navigator, 1843-44, to the Mediterranean; sloop "Vincennes," as navigator, East India Squadron, 1845-47; coast survey, 1848-49.

Commissioned as lieutenant, November 4, 1849; frigate "St. Lawrence," Mediterranean Squadron, 1850; coast survey, 1851; attached to a commission for selecting a naval station in the Bay of San Francisco, Cal., 1852; scientific expedition of steamer "Water Witch," Paraguay River, 1853-54; brig "Bainbridge," Brazil Squadron, 1854-55; Naval Observatory, Washington, 1856-57; steam-sloop "Saranac," Pacifle Squadron, 1858; steam-frigate" Merrimac," Pacific Squadron, 1859-60; steam-frigate "Roanoke," as executive-officer, North Atlantic Blockading Squadron, 1861; commanding "Seneca," South Atlantic Blockading Squadron, 1861-62, at battle of Port Royal, November 7, 1861; the day following hoisted our flag over Fort Beauregard, and made formal delivery to the army, by order of Rear-Admiral Du Pont; Tybee Island, December, 1861; commanded forces entering by way of Whale Branch in attack on Port Royal Ferry, January 1, 1862; engaged in the operations against Fernandina through St. Andrew's Sound and in St. John's River.

Promoted to commander, February 21, 1863; commanding monitor "Patapsco," South Atlantic Blockading Squadron, against Fort McAllister, March, 1863, and in the attack on Fort Sumter, April 7, 1863; had charge of a draft of 220 seamen on board of the California passenger steamer "Ocean Queen," May, 1864, bound to Aspinwall; two days after leaving New York suppressed an open and organized mutiny, with the assistance of Boatswain Thomas G. Bell, who was the only aid assigned, receiving in doing so the excellent co-operation of Captain Tinklepaugh,—who commanded the "Ocean Queen,”his officers, and several of the passengers; commanding steam-sloop "Mohican," North Atlantic Blockading Squadron, 1864-65; in the bombardment of Fort Fisher, December, 1864, and again when it was carried by assault by the army, January, 1865; commanding ironclad "Miantonomah," special service, 1866.

Commissioned as captain, July 25, 1866; special duty, Hartford, Conn., 1866-67; commanding flag-ship "Piscataqua," Asiatic Squadron, 1867-68; Chief of Bureau of Yards and Docks, 1869-71.

Commissioned as commodore, 1872. Chief of Bureau of Navigation, 1871-78. Commissioned as rear-admiral, 1877; retired at his own request, 1878. July, 1878, appointed chairman of a board for the re-location of the Naval Observatory. April, 1879, ordered to attend the convocation at Paris, France, known as the Interoceanic Ship-Canal Congress. Had constructed on his design a cask "balsa," or life-boat, which is now at the navy-yard, Portsmouth, N. H., at which place are built life-boats on this design for all of our vessels of war. Total sea-service 21 years and 1 month; other duty, 17 years and 3

months.

Ammunition. In early times this word sig nified every description of warlike stores and provisions for attack or defense.

In modern usage its signification is limited to

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Amnesty. An act of oblivion or general pardon for all acts committed in time of war, or the proclamation of such pardon.

Amok. Slaughter. The practice, of Malays under the influence of bang, of running about the streets, attacking anybody and everybody.

TO RUN A-MUCK. To make an indiscriminate assault.

Amorce. (Fr.) Priming powder.

Amoy. A seaport town of China, on an island of the same name. Lat. 24° 10′ 3′′ N.; lon. 118° 13′ 5′′ E.; nearly opposite to the centre of the island of Formosa. The population, mostly employed in the coasting trade, is about 300,000.

Amperes. An ancient vessel in which the rowers pulled two oars each.

Amphibia. A class of animals which can live either in the water or on the land.

Amphiproræ. Ancient vessels, both ends of which were prow-shaped, so that in narrow channels they need not turn; the prototypes of the double-enders.

Amphiscii. The inhabitants of the torrid zone are thus denominated from their shadow being turned one part of the year to the north and the other to the south.

Amplitude. The angular distance of a heavenly body in the horizon from the east or west point. The magnetic amplitude is the angular distance of the body from the east or west point as indicated by the compass. The difference be tween the true and the magnetic amplitude is the variation of the compass.

At a given latitude the amplitude depends on the declination of the object. Amplitude is sometimes used to denote the horizontal distance to which a projectile is expelled from a gun, or what is more frequently called the range.

AMPLITUDE, OBSERVATION OF. The usual instructions for taking amplitudes are laid down with the view that the body shall be observed at the moment when its centre is really in the rational horizon. Thus the bearing of the sun is directed to be taken when its lower limb appears half-way between the horizon and its centre; the bearing of a star is to be taken at an altitude of 34: the amplitude of the moon cannot be thus directly observed with accuracy, especially in high latitudes, by reason of her great depression by parallax, but may be found approximately by observing her bearing when her upper limb is in the horizon. In all cases, however, the better plan is to obtain by observation the bearing when the centre of the body appears on the horizon, and apply the necessary corrections (for dip, refraction, and parallax) taken from a table. For the sun, when rising, observe the bearing of the upper limb as it appears on the horizon, and continue to take the bearings of the centre, bi

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