Part 5

instances of acceleration.--_Acceleration of the Moon_, the increase of the moon's mean angular velocity about the earth, the moon now moving rather faster than in ancient times. This phenomenon has not been fully explained, but it is known to be partly owing to the slow process of diminution which the eccentricity of the earth's orbit is undergoing, and from which there results a slight diminution of the sun's influence on the moon's motions.--_Diurnal acceleration of the fixed stars_, the apparent greater diurnal motion of the stars than of the sun, arising from the fact that the sun's apparent yearly motion takes place in a direction contrary to that of his apparent daily motion. The stars thus seem each day to anticipate the sun by nearly 3 minutes 56 seconds of mean time.

AC'CENT, a term used in several senses. In English it commonly denotes superior stress or force of voice upon certain syllables of words, which distinguishes them from the other syllables. Many English words, as _as'pi-ra"tion_, have two accents, a secondary and primary, the latter being the fuller or stronger. Some words, as _in-com'pre-hen'si-bil"i-ty_, have two secondary or subordinate accents. When the full accent falls on a vowel, that vowel has its long sound, as in _vo'cal_; but when it falls on a consonant, the preceding vowel is short, as in _hab'it_. This kind of accent alone regulates English verse, as contrasted with Latin or Greek verse, in which the metre depended on _quantity_ or length of syllables. In books on elocution three marks or accents are generally made use of, the first or _acute_ (') showing when the voice is to be raised, the second or _grave_ (`), when it is to be depressed, and the third or _circumflex_ (^) when the vowel is to be uttered with an undulating sound. In some languages there is no such distinct accent as in English (or German), and this seems to be now the case with French.--In music, accent is the stress or emphasis laid upon certain notes of a bar. The first note of a bar has the strongest accent, but weaker accents are given to the first notes of subordinate parts of the bars, as to the third, fifth, and seventh in a bar of eight quavers.

ACCEN'TOR (_Accentor modul[=a]ris_), or HEDGE ACCENTOR, a British bird of the warbler family. See _Hedge Warbler_.

ACCEP'TANCE, in law, the act by which a person binds himself to pay a bill of exchange drawn upon him. (See _Bill_.) No acceptance is valid unless made in writing on the bill, but an acceptance may be either absolute or conditional, that is, stipulating some alteration in the amount or date of payment, or some condition to be fulfilled previous to payment.

AC'CESSARY, or AC'CESSORY, in law, a person guilty of an offence by connivance or participation, either before or after the act committed, as by command, advice, concealment, &c. An accessary _before the fact_ is one who procures or counsels another to commit a crime, and is not present at its commission; an accessary _after the fact_ is one who, knowing a felony to have been committed, gives assistance of any kind to the felon so as to hinder him from being apprehended, tried, or suffering punishment. An accessary before the fact may be tried and punished in all respects as if he were the principal. In high treason, all who participate are regarded as principals.

ACCIDEN'TALS, notes introduced in the course of a piece of music in a different key from that in which the passage where they occur is principally written. They are represented by the sign of a sharp, flat, or natural immediately before the note which is to be raised or lowered.

ACCIPITRES (ak-sip'i-tr[=e]z), the name given by Linnaeus and Cuvier to the rapacious birds now usually called Raptores (q.v.).

ACCLIMATIZA'TION, the process of accustoming plants or animals to live and propagate in a climate different from that to which they are indigenous, or the change which the constitution of an animal or plant undergoes under new climatic conditions, in the direction of adaptation to those conditions. The systematic study of acclimatization has only been entered upon in very recent times, and the little progress that has been made in it has been more in the direction of formulating anticipative, if not arbitrary hypotheses, than of actual discovery and acquisition of facts. The best-known society founded, for the purpose of naturalizing animals and plants, is the Societe d'Acclimatation in Paris. It opened the Jardin d'Acclimatation in 1860. See _Tropical Hygiene_. The term is sometimes applied to the case of animals or plants taking readily to a new country with a climate and other circumstances similar to what they have left, such as European animals and plants in America and New Zealand: but this is more properly _naturalization_ than acclimatization.--In agriculture the word is used with reference to stock, principally sheep, 'acclimatized' to a

## particular area, a special allowance being made by the landlord on

transference of the farm and stock in respect of the acclimatization of the sheep. The value assigned to the advantages resulting from acclimatization of stocks varies considerably. In Argyllshire, for instance, Dumbartonshire, and the western portion of Perthshire the rates are high, while in the south of Scotland and the north of England they are much lower.

ACCOLADE (ak-o-l[=a]d'; Fr., from Lat. _ad_, to, _collum_, the neck), the ceremony used in conferring knighthood, anciently consisting either in the embrace given by the person who conferred the honour of knighthood or in a light blow on the neck or the cheek, latterly consisting in the ceremony of striking the candidate with a naked sword.

ACCOL'TI, Benedetto, an Italian lawyer, born at Arezzo in Tuscany in 1415, died at Florence in 1466. He was secretary to the Florentine republic, 1459, and author of a work on the Crusades which is said to have furnished Tasso with matter for his _Jerusalem Delivered_.

ACCOMMODA'TION BILL, a bill of exchange drawn and accepted to raise money on, and not given, like a genuine bill of exchange, in payment of a debt, but merely intended to accommodate the drawer: colloquially called a _wind bill_ and a _kite_.

ACCOMMODA'TION LADDER, a light ladder hung over the side of a ship at the gangway to facilitate ascending from, or descending to, boats.

ACCOM'PANIMENT, in music, is that part of music which serves for the support of the principal melody.

ACCOR'DION, a keyed musical wind-instrument similar to the concertina, being in the form of a small box, containing a number of metallic reeds fixed at one of their extremities, the sides of the box forming a folding apparatus which acts as a bellows to supply the wind, and thus set the reeds in vibration, and produce the notes both of melody and harmony. The accordion was invented by Damian of Vienna in 1829.

ACCOUNTANT, a person whose chief business is with accounts and the drawing up of financial statements and balance-sheets. An accountant is an important official in banks, railways, and certain other institutions, and many persons carry on the business of accountant as a distinct profession, auditing the books of merchants, joint-stock companies, &c. There are several bodies of accountants in the United Kingdom incorporated by royal charter, and hence specially distinguished as 'chartered accountants' (C.A.). Since 1919 women are admitted as members of the Society of Incorporated Accountants.--BIBLIOGRAPHY: L. R. Dicksee, _Advanced Accounting_; G. Lisle, _Encyclopaedia of Accounting_ (8 vols.).

AC'CRA, a British settlement in Africa, in a swampy situation, capital of Gold Coast, about 75 miles east of Cape Coast Castle. Exports gold-dust, ivory, gums, palm-oil; imports cottons, cutlery, &c. Pop. 20,000.

AC'CRINGTON, a municipal borough of England, Lancashire, 5 miles east of Blackburn, with large cotton factories, print-works and bleaching-greens, and coal-mines. Pop. 43,610. Accrington was created a parliamentary borough in 1918.

ACCU'MULATOR, a name applied to a kind of electric battery by means of which electric energy can be stored and rendered portable. In the usual form each battery forms a cylindrical leaden vessel, containing alternate sheets of metallic lead and minium wrapped in felt and rolled into a spiral wetted with acidulated water. On being charged with electricity the energy may be preserved till required for use.

ACCU'SATIVE CASE, in Latin and some other languages, the term applied to the case which designates the object to which the action of any verb is immediately directed, corresponding, generally speaking, to the _objective_ in English.

ACE, in aviation the name 'ace' is given to a flying-man who has distinguished himself by bringing down a large number (sometimes given as ten) of enemy machines. The word is used colloquially, and was borrowed from the French Air Force during the European War.

ACEPH'ALA, in zoology, the headless Mollusca or those which want a distinct head, corresponding to those that have bivalve shells and are also called _Lamellibranchiata_.

A'CER, the genus of plants (nat. ord. Aceraceae) to which belongs the maple.

ACERRA ([.a]-cher'[.a]), a town in South Italy, 9 miles north-east of Naples, the see of a bishop, in a fertile but unhealthy region. Pop. 17,878.

ACETAB'ULUM, an anatomical term applied to any cup-like cavity, as that of a bone to receive the protuberant end of another bone, the cavity, for instance, that receives the end of the thigh-bone.

ACETATES (as'e-t[=a]ts), salts of acetic acid. The acetates of most commercial or manufacturing importance are those of aluminium and iron, which are used in calico-printing; of copper, which as verdigris is used as a colour; and of lead, best known as sugar of lead. The acetates of potassium, sodium, and ammonium, of iron, zinc, and lead, and the acetate of morphia, are employed in medicine.

ACET'IC ACID, an acid produced by the oxidation of common alcohol, and of many other organic substances. Pure acetic acid has a very sour taste and pungent smell, burns the skin, and is poisonous. From freezing at ordinary temperatures (58deg or 59deg) it is known as _glacial acetic acid_. Vinegar is simply dilute acetic acid. Acetic acid is largely used in the arts, in medicine, and for domestic purposes. See _Vinegar_.

ACET'IC ETHERS, or ACETIC ESTERS, acetates of alcohol radicals. The common ester--ethyl acetate--is a volatile colourless liquid, manufactured by distilling a mixture of alcohol, oil of vitriol, and acetic acid, and used for flavouring purposes.

ACETONE (as'), a constituent of ordinary wood spirit, a colourless volatile liquid used as a solvent, the simplest of the _ketones_.

ACET'YLENE, C_2H_2, is a substance composed of two elements, carbon and hydrogen, and belonging to a class of compounds known as hydrocarbons. It is formed in the incomplete combustion of many hydrocarbons and also of coal-gas, and may be produced in a variety of ways, but is now made almost entirely from calcium carbide. Acetylene has been known for a long time, but only since 1870 has it been produced in any quantity. After the development of the electric furnace it was found that calcium oxide, quicklime, heated with carbon to the high temperature possible in such a furnace, is transformed into calcium carbide, and this compound reacts with water, generating acetylene. A great deal of heat is developed on adding water to calcium carbide, so that care has to be taken in generating acetylene. Various devices are in use for bringing the two substances in contact slowly, and for keeping the temperature low. When carbon and hydrogen combine to form acetylene a large amount of heat is used up, so that much heat is evolved when acetylene decomposes again, and once decomposition starts sufficient heat is developed to decompose the whole volume of gas.

Acetylene is a colourless gas slightly soluble in water and very sparingly soluble in brine. When pure it has little or no odour, but as ordinarily prepared it has a strong unpleasant odour due to traces of impurities such as sulphuretted hydrogen, phosphine, &c. The gas can be liquefied easily, and in the liquid state is highly explosive. It burns with an exceedingly sooty flame, but if it is allowed to pass through a very small orifice the carbon liberated becomes incandescent and acetylene burns with an intense white flame. It is largely used as an illuminant and for the production of great heat. As an illuminant the gas is produced in specially-constructed generators. It is led through iron pipes and burned from an acetylene burner, or it may be used with special types of incandescent mantles. Acetylene readily combines with copper and with silver to form metallic acetylides which are very explosive, hence pipes through which acetylene is passing must not be made of brass or copper. Acetylene mixed with air and brought in contact with an ignited body explodes even more violently than a mixture of air and coal-gas.

Large quantities of acetylene are generated and stored for oxy-acetylene welding. Acetylene, burning in oxygen, gives an intensely hot flame (about 2000deg-3000deg C.), sufficiently hot to melt iron. Although liquid acetylene is unstable, and even the gas, under slight pressure, is also unstable, it may be transported safely if dissolved in acetone. Acetone dissolves a large volume of acetylene, and this solution is quite stable and may be stored in iron cylinders and used for various purposes. If it is to be stored it must be carefully purified from phosphine, which is apt to cause sudden decomposition. Recently, numerous patents have been taken out for the preparation of compounds such as acetaldehyde, acetic acid, acetic anhydride, &c., using acetylene as starting-point, so that many substances may be prepared from acetylene just as many substances may be prepared from benzene.

ACHAEANS (a-k[=e]'anz), one of the four races into which the ancient Greeks were divided. In early times they inhabited a part of Northern Greece and of the Peloponnesus. They are represented by Homer as a brave and warlike people, and so distinguished were they that he usually calls the Greeks in general Achaeans. Afterwards they settled in the district of the Peloponnesus, called after them Achaia, and forming a narrow belt of coast on the south side of the Gulf of Corinth. From very early times a confederacy or league existed among the twelve towns of this region. After the death of Alexander the Great it was broken up, but was revived again, 280 B.C., and from this time grew in power till it spread over the whole Peloponnesus. It was finally dissolved by the Romans, 147 B.C., and after this the whole of Greece, except Thessaly, was called Achaia or Achaea. Achaia with Elis now forms a nomarchy of the kingdom of Greece. Pop. 254,728. Cf. Freeman, _History of Federal Government in Greece and Italy_, London, 1893.

ACHAEMENIDAE (ak-[=e]-men'i-d[=e]) a dynasty of ancient Persian kings, being that to which the great Cyrus belonged.

ACHAIA (a-k[=a]'ya). See _Achaeans_.

ACHALZIK. See _Akhalzik_.

ACHARD ([.a]_h_'[.a]rt), Franz Karl, a German chemist, born 1753, died 1821, principally known by his invention (1789-1800) of a process for manufacturing sugar from beetroot. In 1801 the first beet-sugar factory ever established was started by him in Silesia.

ACHARD ([.a]-sh[:a]r), Louis Amedee Eugene, born 1814, died 1875, French journalist, novelist, and playwright. He was best known as a novelist; wrote the novels _Belle Rose_, _La Chasse royale_, _Chateaux en Espagne_, _Robe de Nessus_, _Chaines de fer_, &c. His _Lettres Parisiennes_ were published in 1838 under the pseudonym of Grimm.

ACHATES (a-k[=a]'t[=e]z), a companion of Aeneas in his wanderings subsequent to his flight from Troy. He is always distinguished in Virgil's _Aeneid_ by the epithet _fidus_, 'faithful', and has become typical of a faithful friend and companion.

ACHEEN, or ATCHIN ([.a]-ch[=e]n') (Du. _Atjeh_), a native State of Sumatra, with a capital of the same name, in the north-western extremity of the island, now nominally under Dutch administration. Though largely mountainous, it has also undulating tracts and low fertile plains. By treaty with Britain the Dutch were prevented from extending their territory in Sumatra by conquest; but this obstacle being removed, in 1871 they proceeded to occupy Acheen. It was not till 1879, however, after a great waste of blood and treasure, that they obtained a general recognition of their authority. But they have not been able to establish it firmly, and have had to put down many determined risings, sometimes costing them losses both in men and guns. In the seventeenth century Acheen was a powerful State, and carried on hostilities successfully against the Portuguese, but its influence decreased with the increase of the Dutch power. The principal exports are rice and pepper. Area, 20,471 sq. miles; pop. 789,664.

ACHELOUS (ak-e-l[=o]'us) (now ASPROPOT[)A]MO), the largest river of Greece, rising on Mount Pindus, separating Aetolia and Acarnania, and flowing into the Ionian Sea. In Greek legend, Achel[=o]us, the son of Oceanus and Tethys, was the river-god.

ACHENBACH ([.a]'_h_en-b[.a]ch), Andreas, was a distinguished German landscape and marine painter, born in 1815, died in 1910.

ACHENBACH, Oswald, born 1827, died 1905, brother of above, was also a distinguished landscape painter. Both are of the Duesseldorf school, and pupils of the famous painter Schadow.

[Illustration: Achene of Buttercup (magnified)

E, Embryo. En, Endosperm. T, Testa and pericarp.]

ACHENE, or ACHENIUM (a-k[=e]n', a-k[=e]'ni-um), in botany, a small, dry carpel containing a single seed, the pericarp of which is closely applied but separable, and which does not open when ripe. It is either solitary, or several achenia may be placed on a common receptacle as in the buttercup.

ACHENSEE, a lake in Tyrol, 20 miles north-east of Innsbruck and 3018 feet above sea-level. On its shores are beautiful villas and hotels frequented as summer resorts.

ACHERON (ak'e-ron) (modern FANARIOTICOS), the ancient name of several rivers in Greece and Italy, all of which were connected by legend with the lower world. The principal was a river of Thesprotia in Epirus, which passes through Lake Acherusia and flows into the Ionian Sea. Homer speaks of Acheron as a river of the lower world, and late Greek writers use the name to designate the lower world.

ACHEULIAN, a term applied by archaeologists to the late stage of Chellean civilization in the Pleistocene Age. It is named after St. Acheul in the Somme valley, where relics of it were found. The geological horizon, according to Professor James Geikie, is late Second Interglacial and Third Glacial periods.

ACH'IAR, or AT'CHAR, an Indian condiment made of the young shoots of the bamboo pickled.

ACHIEVEMENT (a-ch[=e]v'ment), in heraldry, a term applied to the shield of armorial bearings generally, or to a hatchment (q.v.).

ACHILL (ak'il), the largest island on the Irish coast, separated from the mainland of Mayo by a narrow sound, now bridged over. The chief occupation is fishing. The island is mountainous, has fine scenery, and is visited by many tourists, there being now a railway terminus here, and many recent improvements. Pop. nearly 7000.

ACHILLAE'A, the milfoil genus of plants.

ACHILLEION, famous castle at Corfu, which used to belong to the Empress Elizabeth of Austria. It was acquired by the ex-Kaiser William II, who bought it from the Archduchess Gisela, wife of Prince Leopold of Bavaria.

ACHILLES (a-kil'[=e]z), a Greek legendary hero, the chief character in Homer's _Iliad_. His father was Peleus, ruler of Phthia in Thessaly, his mother the sea-goddess Thetis. When only six years of age he was able to overcome lions and bears. His guardian, Cheiron the Centaur, having declared that Troy could not be taken without his aid, his mother, fearing for his safety, disguised him as a girl, and introduced him among the daughters of Lycomedes of Scyros. Her desire for his safety made her also try to make him invulnerable when a child by anointing him with ambrosia, and again by dipping him in the River Styx, from which he came out proof against wounds, all but the heel, by which she held him. His place of concealment was discovered by Odysseus (Ulysses), and he promised his assistance to the Greeks against Troy. Accompanied by his close friend, Patroclus, he joined the expedition with a body of followers (Myrmidons) in fifty ships, and occupied nine years in raids upon the towns neighbouring to Troy, after which the siege proper commenced. On being deprived of his prize, the maiden Briseis, by Agamemnon, he refused to take any further

## part in the war, and disaster attended the Greeks. Patroclus now persuaded

Achilles to allow him to lead the Myrmidons to battle dressed in his armour, and he having been slain by Hector, Achilles vowed revenge on the Trojans, and forgot his anger against the Greeks. He attacked the Trojans and drove them back to their walls, slaying them in great numbers, chased Hector, who fled before him three times round the walls of Troy, slew him, and dragged his body at his chariot-wheels, but afterwards gave it up to Priam, who came in person to beg for it. He then performed the funeral rites of Patroclus, with which the _Iliad_ closes. He was killed in a battle at the Scaean Gate of Troy by an arrow from the bow of Paris which struck his vulnerable heel. In discussions on the origin of the Homeric poems the term _Achilleid_ is often applied to those books (i, viii, and xi-xxii) of the _Iliad_ in which Achilles is prominent, and which some suppose to have formed the original nucleus of the poem. See _Iphigenia_.

ACHILLES' TENDON, or TENDON OF ACHILLES, the strong tendon which connects the muscles of the calf with the heel, and which may be easily felt with the hand. The origin of the name will be understood from the above article.

ACHILLES TATIUS (a-kil'[=e]z t[=a]'shi-us), a Greek romance writer of the fifth century A.D., belonging to Alexandria; wrote a love story in 8 books called _Leucipp[=e] and Cleitophon_.

ACHIMENES (a-kim'e-n[=e]z), a genus of tropical American plants, with scaly underground tubers, nat. ord. Gesneraceae, now cultivated in European greenhouses on account of their white, blue, and red flowers.

ACHLAMYDEOUS (ak-la-mid'i-us), in botany, wanting the floral envelopes, that is, having neither calyx nor corolla, as the willow.

ACHOR ([=a]'kor), a disease of infants, in which the head, the face, and often the neck and breast become incrusted with thin, yellowish or greenish scabs, arising from minute, whitish pustules, which discharge a viscid fluid.

ACHROMAT'IC (Gr. _a_, priv., and _chr[=o]ma, chr[=o]matos_, colour), in optics, transmitting colourless light, that is, not decomposed into the primary colours, though having passed through a refracting medium. A single convex lens does not give an image free from the prismatic colours, because the rays of different colour making up white light are not equally refrangible, and thus do not all come to a focus together, the violet, for instance, being nearest the lens, the red farthest off. If such a lens of crown-glass, however, is combined with a concave lens of flint-glass--the curvatures of both being properly adjusted--as the two materials have somewhat different optical properties, the latter will neutralize the chromatic aberration of the former, and a satisfactory image will be produced. Telescopes, microscopes, &c., in which the glasses are thus composed are called _achromatic_.

ACID (Lat. _acidus_, sour), a name applied to a number of compounds, having more or less the qualities of vinegar (itself a diluted form of acetic acid). Their general properties are sour taste, the power of changing vegetable blues into reds, of evolving hydrogen in presence of magnesium, of decomposing chalk with effervescence, and of being in various degrees neutralized by alkalies. An acid has been defined as a compound of hydrogen, the whole or a part of which is replaceable by a metal when this is presented in the form of a hydroxide; being _monobasic_, _dibasic_, or _tribasic_, according to the number of replaceable hydrogen atoms in a molecule. See _Chemistry_.