Chapter M: M. J. SUTHERLAND, D.Sc., F.I.C (3)

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.

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_.

ACIERAGE ([=a]'s[=e]-[.e]r-[=a]j), (Fr. _acier_, steel), a process by which an engraved copper-plate or an electrotype from an engraved plate of steel or copper has a film of iron deposited over its surface by electricity in order to protect the engraving from wear in printing. By this means an electrotype of a fine engraving, which, if printed directly from the copper, would not yield 500 good impressions, can be made to yield 3000 or more; and when the film of iron becomes so worn as to reveal any part of the copper, it may be removed and a fresh coating deposited so that 20,000 good impressions may be got.

ACIPENSER (as-i-pen's[.e]r), the genus of cartilaginous ganoid fishes to which the sturgeon belongs.

ACI REALE ([:a]'ch[=e] r[=a]-[:a]'l[=a]), a seaport of Sicily, north-east of Catania, a well-built town, with a trade in corn, wine, fruit, &c. Pop. 35,587.

A'CIS, according to Ovid, a beautiful shepherd of Sicily, loved by Galatea, and crushed to death by his rival the Cyclops Polyphemus. His blood, flowing from beneath the rock which crushed him, was changed into a river bearing his name, and renowned for the coldness of its water. It has been identified as the Fiume di Jaci.

ACLIN'IC LINE (Gr. priv. _a, klin[=o]_, to incline), the magnetic equator, an irregular curve in the neighbourhood of the terrestrial equator, where the magnetic needle balances itself horizontally, having no dip. See _Magnetism_.

ACNE (ak'n[=e]), a skin disease, consisting of small hard pimples, usually on the face, caused by congestion of the follicles of the skin.

ACOLYTES (ak'o-l[=i]ts), in the ancient Latin and Greek Churches, persons of ecclesiastical rank next in order below the subdeacons, whose office it was to attend the officiating priest. The name is still retained in the Roman Church. Cf. Duchesne, _Christian Worship, its Origin and Evolution_.

ACONCAGUA ([.a]-kon-k[:a]'gw[.a]), a province, a river, and a mountain of Chile. The peak of Aconcagua, whose summit is just within the Argentine Republic, rises to the height of 23,080 feet, and is probably the highest mountain of the western hemisphere. Area of province, 5406 sq. miles. Pop. (1919), 132,165.

AC'ONITE (_Acon[=i]tum_), a genus of hardy herbaceous plants, nat. ord. Ranunculaceae, represented by the well-known wolf's-bane or monk's-hood, and remarkable for their poisonous properties and medicinal qualities, being used internally as well as externally in rheumatism, gout, neuralgia, &c.

ACON'ITINE, an alkaloid extracted from monk's-hood and some other species of aconite; used medicinally, though a virulent poison.

ACONQUIJA ([.a]-kon-k[=e]'_h_[.a]), a range of mountains in the Argentine Republic; the name also of a single peak, 17,000 feet high.

A'CORN, the fruit of the different kinds of oak. The acorn-cups of one species are brought from the Levant under the name of _valonia_, and used in tanning.

ACORN-SHELL. See _Balanus_.

AC'ORUS, a genus of plants, including the sweet-flag. See _Sweet-flag_ and _Calamus_.

ACOS'TA, Gabriel, afterwards Uriel, a Portuguese of Jewish descent, born at Oporto in 1590, died by his own hand 1640. Brought up a Christian, he afterwards embraced Judaism. Having gone to Amsterdam, where he attacked the practices of the Jews, and denied the divine mission of Moses, he suffered much persecution at the hands of the Jews. He left an autobiography, published in 1687, under the title _Exemplar Humanae Vitae_. He is the hero of a novel, _Die Sadducaeer von Amsterdam_, and of a tragedy, _Uriel Acosta_, both by Gutzkow.

ACOTYLE'DONS, plants not furnished with cotyledons or seed-lobes. They include ferns, mosses, seaweeds, &c., and are also called flowerless plants or cryptogams.

ACOUSIMETER, or ACOUMETER (Gr. _akouein_, to hear, and _metron_, measure), an instrument used to determine the acuteness of hearing. It consists of a small bar which gives a uniform sound when struck by a hammer.

ACOUSTICS (a-kou'stiks), the science of sound. It deals with the production of sound, its propagation and velocity in various media; the reflection, refraction, and interference of sound waves; the properties of musical notes; and the general phenomena of such vibrations of elastic bodies as affect the organ of hearing.

In order that a sound may be heard, it is necessary that an uninterrupted series of particles of elastic matter should extend from the sounding body to our ear. Sound is propagated by a longitudinal wave-motion in the medium (gaseous, liquid, or solid), that is, the particles oscillate along the line in which the wave is travelling, giving rise to regular series of condensations and rarefactions.

The velocity of sound varies directly as the square root of the elasticity, and inversely as the square root of the density, of the medium in which it is propagated. The velocity of sound in air at 0deg C. is 330.6 metres per second, or 1085 feet per second; in water 1.49 kilometres per second, or 0.926 mile per second; in copper 5.01 kilometres per second, or 3.12 miles per second.

The intensity of sound varies inversely as the square of the distance from the sounding body. Recently sound-ranging instruments have been produced by means of which the position of a gun can be determined.

A note produced by a musical instrument consists of a _fundamental_ of a certain frequency, together with a number of _overtones_ of various higher frequencies and much smaller amplitude. The _timbre_ of a note depends on the overtones present, the _loudness_ depends on the amplitude of the vibrations, and the _pitch_ depends on the frequency. The musical scale consists of eight notes, C D E F G A B C, whose frequencies are in the proportion of the numbers 24, 27, 30, 32, 36, 40, 45 and 48. The interval between two notes is the ratio of the frequency of the higher note to the frequency of the lower note. In order that the intervals may be the same in all keys, a tempered scale is used in music. (See Table, p. 25.)

BIBLIOGRAPHY: Lord Rayleigh, _Theory of Sound_; H. Smith, _The Making of Sound in the Organ and Orchestra_; J. W. Capstick, _Sound_ (Cambridge Natural Science Manuals); E. H. Barton, _Text-book of Sound_.

ACQUI ([.a]k'w[=e]), a town of Northern Italy, 18 miles S.S.W. of Alessandria, a bishop's see. It has warm sulphurous baths, which were known to the Romans, and which still attract a great many visitors. Pop. 16,500.

ACRE, a standard British measure of land, also used in the colonies and the United States. The imperial statute acre consists of 4840 sq. yards, divided into 4 roods. The old Scotch acre contains 6146.8 sq. yards, the old Irish acre 7840 sq. yards.

ACRE ([=a]'k[.e]r) (ancient ACCHO and PTOLEMAIS), a seaport of Syria, in Northern Palestine, on the Bay of Acre, early a place of great strength and importance. Taken from the Saracens under Saladin in 1191 by Richard I of England and Philip of France; bravely defended by the Turks, assisted by Sir Sidney Smith, in 1799 against Napoleon; in 1832, taken by Ibrahim Pasha; in 1840, bombarded by a British, Austrian, and Turkish fleet, and restored to the Sultan of Turkey. The town was occupied by British troops under General Allenby in September, 1918. Pop. 10,000.

* * * * *

MUSICAL INTERVALS.--See _Acoustics_

Intervals in Intervals in
Perfect Diatonic Diatonic Scale. Tempered Scale--
Scale. Perfect on System of Mean tone.
Diatonic Scale Equal (2^{1/6} = 1.123).
Temperament. Semitone.
(2^{1/12}= 1.059).
---------------------------------------------------------------------
C 1 1.000
9/8 major tone tone.
D 9/8 = 1.125 2-2/12 = 1.123
10/9 minor tone tone.
E 5/4 = 1.250 2-4/12 = 1.260
16/15 limma semitone.
F 4/3 = 1.333 2-5/12 = 1.335
9/8 major tone tone.
G 3/2 = 1.500 2-7/12 = 1.498
10/9 minor tone tone.
A 5/3 = 1.667 2-9/12 = 1.682
9/8 minor tone tone.
B 15/8 = 1.875 2-11/12 = 1.888
16/15 limma semitone.
C' 2 2.000

Major tone ratio = 9/8 = 1.125 Limma tone ratio = 16/15 = 1.067
Minor " " = 10/9 = 1.111 Semitone " = 2^{1/12} = 1.059
Mean " " = 2^{2/12} = 1.123

NOTES OF PERFECT DIATONIC SCALE (WITH THEIR FREQUENCIES)

C,, 64. Ut_1 C, 128. Ut_2 C 256. Ut_3 C' 512. Ut_4
D,, 72 D, 144 D 288 D' 576
E,, 80 E, 160 E 320 E' 640
F,, 85.3 F, 170.7 F 341.3 F' 682.7
G,, 96 G, 192 G 384 G' 768
A,, 106.6 A, 213.3 A 426.7 A' 853.2
B,, 120 B, 240 B 480 B' 960
C'' 1024. Ut_5

PERFECT DIATONIC SCALES (TRANSITION TO KEY OF DOMINANT)

_Example_--Key of C to Key of G