Chapter XVIII: Act 1895: , No. 20 of 1895) (4)

[5] See further J. Wellhausen, _Prolegomena_, pp. 342 sqq.; G.F.
Moore, Ency. Bib. col. 1443; S.A. Cook, _Jew. Quart. Rev._ (1906),
pp. 741 sqq. (1907), p. 122, and art. MOSES. Ex. xiii. 17-19 forbids
the compromise which would place Sinai-Horeb in the neighbourhood of
Kadesh (A.E. Haynes, _Pal. Explor. Fund, Quart. Statem._ (1896), pp.
175 sqq.; C.F. Kent [see _Lit._ below], p. 381).

[6] So B. Stade, Steuernagel, Guthe, G.F. Moore, H.P. Smith, C.F.
Kent, &c. See CALEB; JERAHMEEL; JUDAH; KENITES; LEVITES; and JEWS:
_History_, SS 5, 20 (end).

[7] An instructive parallel to the last-mentioned is afforded by
Dissard's account of the migration of Arab tribes into Palestine in
the 18th century A.D. (_Revue biblique_, July 1905).

EXOGAMY (Gr. [Greek: exo], outside; and [Greek: gamos], marriage), the term proposed by J.F. McLennan for the custom compelling marriage "out of the tribe" (or rather "out of the totem"); its converse is endogamy (q.v.). McLennan would find an explanation of exogamy in the prevalence of female infanticide, which, "rendering women scarce, led at once to polyandry within the tribe, and the capturing of women from without." Infanticide of girls is, and no doubt ever has been, a very common practice among savages, and for obvious reasons. Among tribes in a primitive stage of social organization girl-children must always have been a hindrance and a source of weakness. They had to be fed and yet they could not take part in the hunt for food, and they offered a temptation to neighbouring tribes. Infanticide, however, is not proved to have been so universal as McLennan suggests, and it is more probable that the reason of exogamy is really to be found in that primitive social system which made the "captured" woman the only wife in the modern sense of the term. In the beginnings of human society children were related only to their mother; and the women of a tribe were common property. Thus no man might appropriate any female or attempt to maintain proprietary rights over her. With women of other tribes it would be different, and a warrior who captured a woman would doubtless pass unchallenged in his claim to possess her absolutely. Infanticide, the evil physical effects of "in-and-in" breeding, the natural strength of the impulse to possess on the man's part, and the greater feeling of security and a tendency to family life and affections on the woman's, would combine to make exogamy increase and marriages within the tribe decrease. A natural impulse would in a few generations tend to become a law or a custom, the violation of which would be looked on with horror. Physical capture, too, as soon as increasing civilization and tribal intercommunication removed the necessity for violence, became symbolic of the more permanent and individual relations of the sexes. An additional explanation of the prevalence of exogamy may be found in the natural tendency of exogamous tribes to increase in numbers and strength at the expense of those communities which moved towards decadence by in-breeding. Thus tradition would harden into a prejudice, strong as a principle of religion, and exogamy would become the inviolable custom it is found to be among many races. In Australia, Sir G. Grey writes: "One of the most remarkable facts connected with the natives is that they are divided into certain great families, all the members of which bear the same name ... these family names are common over a great portion of the continent and a man cannot marry a woman of his own family name." In eastern Africa, Sir R. Burton says: "The Somal will not marry one of the same, or even of a consanguineous family," and the Bakalahari have the same rule. Paul B. du Chaillu found exogamy the rule and blood marriages regarded as an abomination throughout western Equatorial Africa. In India the Khasias, Juangs, Waralis, Otaons, Hos and other tribes are strictly exogamous. The Kalmucks are divided into hordes, and no man may marry a woman of the same horde. Circassians and Samoyedes have similar rules. The Ostiaks regard endogamy (marriage within the clan) as a crime, as do the Yakuts of Siberia. Among the Indians of America severe rules prescribing exogamy prevail. The Tsimsheean Indians of British Columbia are divided into tribes and totems, or "crests which are common to all the tribes," says one writer. "The crests are the whale, the porpoise, the eagle, the coon, the wolf and the frog.... The relationship existing between persons of the same crest is nearer than that between members of the same tribe.... Members of the same tribe may marry, but those of the same crest are not allowed to under any circumstances; that is, a whale may not marry a whale, but a whale may marry a frog, &c." The Thlinkeets, the Mayas of Yucatan and the Indians of Guiana are exogamous, observing a custom which is thus seen to exist throughout Africa, in Siberia, China, India, Polynesia and the Americas.

AUTHORITIES.--J.F. McLennan, _Primitive Marriage_ (1865), and _Studies
in Anc. Hist._ (1896); Lord Avebury, _Origin of Civilization_ (1902);
Westermarck, _History of Human Marriage_ (1894); A. Lang, _Social
Origins_ (1903); L.H. Morgan, _Ancient Society_ (1877); J.G. Frazer,
_Totemism and Exogamy_ (1910); see also TOTEM.

EXORCISM (Gr. [Greek: exorkizein], to conjure out), the expulsion of evil spirits from persons or places by incantations, magical rites or other means. As a corollary of the animistic theory of diseases and of belief in Possession (q.v.), we find widely spread customs whose object is to get rid of the evil influences. These customs may take the form of a general expulsion of evils, either once a year or at irregular intervals; the evils, which are often regarded as spirits, sometimes as the souls of the dead, may be expelled, according to primitive philosophy, either immediately by spells, purifications or some form of coercion; or they may be put on the back of a scapegoat or other material vehicle. Among the means of compelling the evil spirits are assaults with warlike weapons or sticks, the noise of musical instruments or of the human voice, the use of masks, the invocation of more powerful good spirits, &c.; both fire and water are used to drive them out, and the use of iron is a common means of holding them at bay.

The term exorcism is applied more especially to the freeing of an individual from a possessing or disease-causing spirit; the means adopted are frequently the same as those mentioned above; in the East Indies the sufferer sometimes dances round a small ship, into which the spirit passes and is then set adrift. The patient may be beaten or means may be employed whose efficiency depends largely on their suggestive nature. Among the Dakota Indians the medicine-man chants _hi-le-li-lah!_ at the bed of the sick man and accompanies his chant with the rattle; he then sucks at the affected part till the possessing spirit is supposed to come out and take its flight, when men fire guns at it from the door of the tent. The Zulus believe that they can get rid of the souls of the dead, which cause diseases, by sacrifices of cattle, or by expostulating with the spirits; so too the _shaman_ or magician in other parts of the world offers the possessing spirit objects or animals.

The professional exorcist was known among the Jews; in Greece the art was practised by women, and it is recorded that the mothers of Epicurus and Aeschines belonged to this class; both were bitterly reproached, the one by the Stoics, the other by Demosthenes, with having taken part in the practices in question. The prominence of exorcism in the early ages of the Christian church appears from its frequent mention in the writings of the fathers, and by the 3rd century there was an order of exorcists (see EXORCIST). The ancient rite of exorcism in connexion with baptism is still retained in the Roman ritual, as is also a form of service for the exorcising of possessed persons. The exorcist signs the possessed person with the figure of the cross, desires him to kneel, and sprinkles him with holy water; after which the exorcist asks the devil his name, and abjures him by the holy mysteries of the Christian religion not to afflict the person possessed any more. Then, laying his right hand on the demoniac's head, he repeats the form of exorcism as follows: "I exorcise thee, unclean spirit, in the name of Jesus Christ; tremble, O Satan, thou enemy of the faith, thou foe of mankind, who hast brought death into the world, who hast deprived men of life, and hast rebelled against justice, thou seducer of mankind, thou root of evil, thou source of avarice, discord and envy." Houses and other places supposed to be haunted by unclean spirits are likewise to be exorcised with similar rites, and in general exorcism has a place in all the ceremonies for consecrating and blessing persons or things (see BENEDICTION).

See Tylor, _Primitive Culture_; Skeat, _Malay Magic_, p. 427 seq.;
Frazer, _Golden Bough_, vol. iii. 189; Krafft, _Ausfuhrliche Historie
von Exorcismus_; Koldeweg, _Der Exorcismus im Herzogthum
Braunschweig_; Brecher, _Das Transcendentale, Magie, etc. im Talmud_,
pp. 195-203: _Zeitschr. fur Assyriologie_ (Dec. 1893, April 1894);
Herzog, _Realencykl., s.v._ "Exorcismus"; Waldmeier, _Autobiography_,
p. 64; L.W. King, _Babylonian Magic_; Maury, _La Magie_; R.C.
Thompson, _Devils and Evil Spirits of Babylonia_.

EXORCIST (Lat. _exorcista_, Gr. [Greek: exorkistes]), in the Roman Catholic church, the third grade in the minor orders of the clergy, between those of acolyte and reader. The office, which involves the right of ceremonially exorcising devils (see Exorcism), is actually no more than a preliminary stage of the priesthood. The earliest record of the special ordination of exorcists is the 7th canon of the council of Carthage (A.D. 256). "When they are ordained," it runs, "they receive from the hand of the bishop a little book in which the exorcisms are written, receiving power to lay hands on the _energumeni_, whether baptized or catechumens." Whatever its present position, the office of exorcist was, until comparatively recent times, by no means considered a sinecure. "The exorcist a terror to demons" (Paulinus, _Epist._ 24) survived the Reformation among Protestants, with the belief, expressed by Firmilianus in his epistle to St Cyprian, that "through the exorcists, by the voice of man and the power of God, the devil may be whipped, and burnt and tortured."

EXOTIC (Gr. [Greek: exotikos], foreign, from [Greek: exo], outside), of foreign origin, or belonging to another country. The term is now used in the restricted sense of something not indigenous or native, and is mostly applied to plants introduced from foreign countries, which have not become acclimatized. Figuratively, "exotic" is used to convey the sense of something rare, delicate or extravagant.

EXPATRIATION (from Late Lat. _expatriare_, to exile, and _patria_, native land), a term used in a general sense for the banishment of a person from his own country. In international law expatriation is the renunciation or change of allegiance to one's native or adopted country. It may take place either by a voluntary act or by operation of law. Some countries, as France and England, disclaim their subjects if they become naturalized in another country, others, again, passively permit expatriation whether a new nationality has been acquired or not; others, as Germany, make expatriation the consequence of continued absence from their territory. (See ALIEN; ALLEGIANCE; NATURALIZATION.)

EXPERT (Lat. _expertus_, from _experiri_, to try), strictly, skilled, or one who has special knowledge; as used in law, an expert is a person, selected by a court, or adduced by a party to a cause, to give his opinion on some point in issue with which he is peculiarly conversant. In Roman law questions of disputed handwriting were referred to experts; and in France, whenever the court considers that a report by experts is necessary, it is ordered by a judgment clearly setting forth the objects of the _expertise_ (Code Proc. Civ. art. 302). Three experts are then to be appointed, unless the parties agree upon one only (art. 303). The experts are required to take an oath (art. 305), but in practice this requirement is frequently dispensed with. They may be challenged on the same grounds as witnesses (art. 310). The necessary documentary and other evidence is laid before them (art. 317), and they make a single report to the court, even if they express different opinions: in that case the grounds only of the different opinions are to be stated, and not the personal opinion of each of the experts (art. 318). If the court is not satisfied with the report, new experts may be appointed (art. 322); the judges are not bound to adopt the opinion of the experts (art. 323). "This procedure in regard to experts is common to both the civil and commercial courts, but it is much more frequently resorted to in the commercial court than in the civil court, and the investigation is usually conducted by special experts officially attached to each of these courts" (Bodington, _French Law of Evidence_, London, 1904, p. 102). A similar system is to be found in force in many other European countries; see e.g. Codes of Civil Procedure of Holland, arts. 222 et seq.; Belgium, arts. 302 et seq.; Italy, arts. 252 et seq.; as well as in those colonies where French law has been followed (Codes of Civil Procedure of Quebec, arts. 392 et seq.; St Lucia, arts. 286 et seq.). In Mauritius the articles of the French law, summarized above, are still nominally in force; but in practice each side calls its own expert evidence, as in England.

There is some evidence that in England the courts were in early times in the habit of summoning to their assistance, apparently as assessors, persons specially qualified to advise upon any scientific or technical question that required to be determined. Thus "in an appeal of maihem (i.e. wounding) ... the court did not know how to adjudge because the wound was new, and then the defendant took issue and prayed the court that the maihem might be examined, on which a writ was sent to the sheriff to cause to come _medicos chirurgieos de melioribus London, ad informandum dominum regem el curiam de his quae eis ex parte domini regis injungerentur_" (Year Book, 21 Hen. VII. pl. 30, p. 33). The practice of calling in expert assistance in judicial inquiries was not confined to medico-legal cases. "If matters arise," said Justice Saunders in _Buckley_ v. _Rice Thomas_ (1554, Plowden, 124 a), "which concern other faculties, we commonly apply for the aid of that science or faculty which it concerns." English procedure, however, being _litigious_, and not, like continental European procedure, _inquisitorial_, in its character, the expert soon became, and still is, simply a witness to speak to matters of opinion.

There is a considerable body of law in England as to expert evidence. Only a few points can be touched upon here. (1) An expert is permitted to refresh his memory in regard to any fact by referring to anything written by himself or under his direction at the time when the fact occurred or at a time when it was fresh in his memory. This is also law generally in the United States (see e.g. New York Civil Code, s. 1843). In Scotland, medical and other scientific reports are lodged in process before the trial, and the witness reads them as part of his evidence and is liable to be examined or cross-examined on their contents. (2) In strictness, an expert will not be allowed, in cases of alleged insanity, to say that a litigating or incriminated party is insane or the reverse, and so to usurp the prerogative of the court or jury. But he may be asked whether certain facts or symptoms, _assuming them to be proved_, are or are not indicative of insanity. But in practice this rule is relaxed both in England and in Scotland, and (where it exists) to a still greater extent in America. (3) Foreign law can only be proved in English courts--and the same rule applies in Scotland--(a) by obtaining an opinion on the subject from a superior court of the country whose laws are in dispute under the Foreign Law Ascertainment Act 1861 or the British Law Ascertainment Act 1859, or (b) by the evidence of a lawyer of the country whose law is in question, or who has studied it _in that country_, or of an official whose position requires, and therefore presumes, a sufficient knowledge of that law. (4) The weight of authority both in England and in America supports the view that an expert is not bound to give evidence as to matters of opinion unless upon an undertaking by the party calling him to pay a reasonable remuneration for his evidence.

Statutory provision has been made in England for the summoning of expert assistance by the legal tribunals in various cases. In the county courts the judge may, if he thinks fit, on the application of either party, call in as assessor one or more persons of skill and experience as to the matters in dispute (County Courts Act 1888, s. 103), and special provision is made for calling in an assessor in employers' liability cases (act of 1880, s. 6) and admiralty matters (see County Courts Admiralty Jurisdiction Acts of 1868 and 1869). In the High Court and court of appeal one or more specially qualified assessors may be called in to assist in the hearing of any cause or matter except a criminal proceeding by the crown (Judicature Acts 1873, s. 56), and a like power is given to both these courts and the judicial committee of the privy council in patent cases (Patents, &c., Act 1883., s. 28). Maritime causes, whether original or on appeal from county courts, are usually taken in the presence of Elder Brethren of the Trinity House, who advise the judge without having any right to control or any responsibility for his decision (see the "Beryl," 1884, 9 P.D. 1), and on appeal in maritime causes nautical assessories are usually called in by the court of appeal, and may be called in by the House of Lords (Judicature Act 1891, s. 3); a like provision is made as to maritime causes in Scottish courts (Nautical Assessors [Scotland] Act 1894). The judicial committee of the privy council, besides its power to call in assessors in patent cases, is authorized to call them in in ecclesiastical causes (Appellate Jurisdiction Act 1876, s. 14).

In addition to the authorities cited in the text, see Taylor, _Law of
Evidence_ (9th ed., London, 1895); J.D. Lawson, _Law of Expert and
Opinion Evidence_ (1900).

EXPLOSIVES, a general term for substances which by certain treatment "explode," i.e. decompose or change in a violent manner so as to generate force. From the manner and degree of violence of the decomposition they are classified into "propellants" and "detonators," but this classification is not capable of sharp delimitation. In some cases the same substance may be employed for either purpose under altered external conditions; but there are some substances which could not possibly be employed as propellants, and others which can scarcely be induced to explode in the manner known as "detonation." A propellant may be considered as a substance that on explosion produces such a disturbance that neighbouring substances are thrown to some distance; a detonator or disruptor may produce an extremely violent disturbance within a limited area without projecting substances to any great distance. Time is an important, perhaps the most important, factor in this action. A propellant generally acts by _burning_ in a more or less rapid and regular manner, producing from a comparatively small volume a large volume of gases; during this action heat is also developed, which, being expended mostly on the gaseous products, causes a further expansion. The noise accompanying an explosion is due to an air wave, and is markedly different in the case of a detonator from a real propellant. Some cases of ordinary combustion can be accelerated into explosions by increasing the area of contact between the combustible and the oxygen supplier, for instance, ordinary gas or dust explosions. Neither temperature nor quantity of heat energy necessarily gives an explosive action. Some metals, e.g. aluminium and magnesium, will, in oxidizing, produce a great thermal effect, but unless there be some gaseous products no real explosive action.

Explosives may be mechanical mixtures of substances capable of chemical interaction with the production of large volumes of gases, or definite chemical compounds of a peculiar class known as "endothermic," the decomposition of which is also attended with the evolution of gases in large quantity.

All chemical compounds are either "endothermic" or "exothermic." In
endothermic compounds energy, in some form, has been taken up in the
act of formation of the compound. Some of this energy has become
potential, or rather the compound formed has been raised to a higher
potential. This case occurs when two elements can be united only under
some compulsion such as a very high temperature, by the aid of an
electric current, or spark, or as a secondary product whilst some
other reactions are proceeding. For example, oxygen and nitrogen
combine only under the influence of an electric spark, and carbon and
calcium in the electric furnace. The formation of chlorates by the
action of chlorine on boiling potash is a good instance of a complex
compound (potassium chlorate), being formed in small quantity as a
secondary product whilst a large quantity of primary and simpler
products (potassium chloride and water) is forming. In chlorate
formation the greater part of the reaction represents a running down
of energy and formation of exothermic compounds, with only a small
yield of an endothermic substance. Another idea of the meaning of
endothermic is obtained from acetylene. When 26 parts by weight of
this substance are burnt, the heat produced will warm up 310,450 parts
of water 1 deg. C. Acetylene consists of 24 parts of carbon and 2 of
hydrogen by weight. The 24 parts of carbon will, if in the form of
pure charcoal, heat 192,000 parts of water 1 deg., and the 2 parts of
hydrogen will heat 68,000 parts of water 1 deg., the total heat
production being 260,000 heat units. Thus 26 grams of acetylene give
an excess of 50,450 units over the amount given by the constituents.
This excess of heat energy[1] is due to some form of potential energy
in the compound which becomes actual heat energy at the moment of
dissolution of the chemical union. The manner in which a substance is
endothermic is of importance as regards the practical employment of
explosives. Some particular endothermic state or form results from the
mode of formation and the consequent internal structure of the
molecule. Physical structure alone can be the cause of a relative
endothermic state, as in the glass bulbs known as Rupert's drops, &c.,
or even in chilled steel. Rupert's drops fly in pieces on being
scratched or cut to a certain depth. The cause is undoubtedly to be
ascribed to the molecular state of the glass brought about by chilling
from the melted state. The molecules have not had time to separate or
arrange themselves in easy positions. In steel when melted the carbide
of iron is no doubt diffused equally throughout the liquid. When
cooled slowly some carbide separates out more or less, and the steel
is soft or annealed. When chilled the carbides are retained in solid
solution. The volume of chilled glass or steel differs slightly from
that in the annealed state.

Superfused substances are probably in a similar state of physical
potential or strain. Many metallic salts, and organic compounds
especially, will exhibit this state when completely melted and then
allowed to cool in a clean atmosphere. On touching with a little of
the same substance in a solid state the liquids will begin to
crystallize, at the same time becoming heated almost up to their
melting-points. The metal gallium shows this excellently well, keeping
liquid for years until touched with the solid metal, when there is a
considerable rise of temperature as solidification takes place.

All carbon compounds, excepting carbon dioxide, and many if not all
compounds of nitrogen, are endothermic. Most of the explosives in
common use contain nitrogen in some form.

Exothermic compounds are in a certain sense the reverse of
endothermic; they are relatively inert and react but slowly or not at
all, unless energy be expended upon them from outside. Water, carbon
dioxide and most of the common minerals belong to this class.

The explosives actually employed at the present time include mixtures, such as gunpowders and some chlorate compositions, the ingredients of which separately may be non-explosive; compounds used singly, as guncotton, nitroglycerin (in the form of dynamite), picric acid (as lyddite or melinite), trinitrotoluene, nitrocresols, mercury fulminate, &c.; combinations of some explosive compounds, such as cordite and the smokeless propellants in general use for military purposes; and, finally, blasting and detonating or igniting compositions, some of which contain inert diluting materials as well as one or more high explosives. Many igniting compositions are examples of the last type, consisting of a high explosive diluted with a neutral substance, and frequently containing in addition a composition which is inflamed by the explosion of the diluted high explosive, the flame in turn igniting the actual propellant.

_Explosive Mixtures._--The explosive mixture longest known is undoubtedly gunpowder (q.v.) in some form--that is, a mixture of charcoal with sulphur and nitre, the last being the oxygen provider. Besides the nitrates of metals and ammonium nitrate, there is a limited number of other substances capable of serving in a sufficiently energetic manner as oxygen providers. A few chlorates, perchlorates, permanganates and chromates almost complete the list. Of these the sodium, potassium and barium chlorates are best known and have been actually tried, in admixture with some combustible substances, as practical explosives. Most other metallic chlorates are barred from practical employment owing to instability, deliquescence or other property.

Of the chlorates those of potassium and sodium are the most stable, and mixtures of either of these salts with sulphur or sulphides, phosphorus, charcoal, sugar, starch, finely-ground cellulose, coal or almost any kind of organic, i.e. carbon, compound, in certain proportions, yield an explosive mixture. In many cases these mixtures are not only fired or exploded by heating to a certain temperature, but also by quite moderate friction or percussion. Consequently there is much danger in manufacture and storage, and however these mixtures have been made up, they are quite out of the question as propellants on account of their great tendency to explode in the manner of a detonator. In addition they are not smokeless, and leave a considerable residue which in a gun would produce serious fouling.

Mixtures of chlorates with aromatic compounds such as the nitro- or dinitro-benzenes or even naphthalene make very powerful blasting agents. The violent action of a chlorate mixture is due first to the rapid evolution of oxygen, and also to the fact that a chlorate can be detonated when alone. A drop of sulphuric acid will start the combustion of a chlorate mixture. In admixture with sulphur, sulphides and especially phosphorus, chlorates give extremely sensitive compositions, some of which form the basis of friction tube and firing mixtures.

Potassium and sodium perchlorates and permanganates make similar but slightly less sensitive explosive mixtures with the above-mentioned substances. Finely divided metals such as aluminium or magnesium give also with permanganates, chlorates or perchlorates sensitive and powerful explosives. Bichromates, although containing much available oxygen, form but feeble explosive mixtures, but some compounds of chromic acid with diazo compounds and some acetylides are extremely powerful as well as sensitive. Ammonium bichromate is a self-combustible after the type of ammonium nitrate, but scarcely an explosive.

_Explosive Compounds._--Nearly all the explosive compounds in actual use either for blasting purposes or as propellants are nitrogen compounds, and are obtained more or less directly from nitric acid. Most of the propellants at present employed consist essentially of nitrates of some organic compound, and may be viewed theoretically as nitric acid, the hydrogen of which has been replaced by a carbon complex; such compounds are expressed by M.O.NO2, which indicates that the carbon group is in some manner united by means of oxygen to the nitrogen group. Guncotton and nitroglycerin are of this class. Another large class of explosives is formed by a more direct attachment of nitrogen to the carbon complex, as represented by M.NO2. A number of explosives of the detonating type are of this class. They contain the same proportions of oxygen and nitrogen as nitrites, but are not nitrites. They have been termed nitro-derivatives for distinction. One of the simplest and longest-known members of this group is nitrobenzene, C6H5NO2, which is employed to some extent as an explosive, being one ingredient in rack-a-rock and other blasting compositions. The dinitro-benzenes, C6H4(NO2)2, made from it are solids which are somewhat extensively employed as constituents of some sporting powders, and in admixture with ammonium nitrate form a blasting powder of a "flameless" variety which is comparatively safe in dusty or "gassy" coal seams.

Picric acid or trinitrophenol, C6H2.OH.(NO2)3 is employed as a high explosive for shell, &c. It requires, however, either to be enclosed and heated, or to be started by a powerful detonator to develop its full effect. Its compounds with metals, such as the potassium salt, C6H2.OK.(NO2)3, are when dry very easily detonated by friction or percussion and _always_ on heating, whereas picric acid itself will burn very quietly when set fire to under ordinary conditions. Trinitrotoluene, C6H2.CH3.(NO2)3, is a high explosive resembling picric acid in the manner of its explosion (to which in fact it is a rival), but differs therefrom in not forming salts with metals. The nitronaphthols, C10H6.OH.NO2, and higher nitration products may be counted in the list. Their salts with metals behave much like the picrates.

All these nitro compounds can be reduced by the action of nascent hydrogen to substances called amines (q.v.), which are not always explosive in themselves, but in some cases can form nitrates of a self-combustible nature. Aminoacetic acid, for instance, will form a nitrate which burns rapidly but quietly, and might be employed as an explosive. By the action of nitrous acid at low temperatures on aromatic amines, e.g. aniline, C6H5NH2, diazo compounds are produced. These are all highly explosive, and when in a dry state are for the most part also extremely sensitive to friction, percussion or heat. As many of these diazo compounds contain no oxygen their explosive nature must be ascribed to the peculiar state of union of the nitrogen. This state is attempted to be shown by the formulae such as, for instance, C6H5.N : N.X, which maybe some compound of diazobenzene. Probably the most vigorous high explosive at present known is the substance called hydrazoic acid or azoimide (q.v.). It forms salts with metals such as AgN3, which explode in a peculiar manner. The ammonium compound, NH4N3, may become a practical explosive of great value.

Mercuric fulminate, HgC2N2O2, is one of the most useful high explosives known. It is formed by the action of a solution of mercurous nitrate, containing some nitrous acid, on alcohol. It is a white crystalline substance almost insoluble in cold water and requiring 130 times its weight of boiling water for solution. It may be heated to 180 deg. C. before exploding, and the explosion so brought about is much milder than that produced by percussion. It forms the principal ingredient in cap compositions, in many fuses and in detonators. In many of these compositions the fulminate is diluted by mixture with certain quantities of inert powders so that its sensitiveness to friction or percussion is just so much lowered, or slowed down, that it will fire another mixture capable of burning with a hot flame. For detonating dynamite, guncotton, &c., it is generally employed without admixture of a diluent.

_Smokeless Propellants._--Gunpowders and all other explosive mixtures or compounds containing metallic salts must form smoke on combustion. The solids produced by the resolution of the compounds are in an extremely finely-divided state, and on being ejected into the atmosphere become more or less attached to water vapour, which is so precipitated, and consequently adds to the smoke. The simplest examples of propellants of the smokeless class are compressed gases. Compressed air was the propellant for the Zalinski dynamite gun. Liquefied carbon dioxide has also been proposed and used to a slight extent with the same idea. It is scarcely practical, however, because when a quantity of a gas liquefied by pressure passes back again into the gaseous state, there is a great absorption of heat, and any remaining liquid, and the containing vessel, are considerably cooled. Steam guns were tried in the American Civil War in 1864; but a steam gun is not smokeless, for the steam escaping from the long tube or gun immediately condenses on expansion, forming white mist or smoke.

At the earliest stage of the development of guncotton the advantage of its smokeless combustion was fully appreciated (see GUNCOTTON). That it did not at once take its position as _the_ smokeless propellant, was simply due to its physical state--a fibrous porous mass--which burnt too quickly or even detonated under the pressure required in fire-arms of any kind. In the early eighties of the 19th century it was found that several substances would partly dissolve or at least gelatinize guncotton, and the moment when guncotton proper was obtained as a colloid or jelly was the real start in the matter of smokeless propellants.

Guncotton is converted into a gelatinous form by several substances, such as esters, e.g. ethyl acetate or benzoate, acetone and other ketones, and many benzene compounds, most of which are volatile liquids. On contact with the guncotton a jelly is formed which stiffens as the evaporation of the gelatinizing agent proceeds, and finally hardens when the evaporation is complete. Whilst in a stiff pasty state it may be cut, moulded or pressed into any desired shape without any danger of ignition. In fact guncotton in the colloid state may be hammered on an anvil, and, as a rule, only the portion struck will detonate or fire. Guncotton alone makes a very hard and somewhat brittle mass after treatment with the gelatinizing agent and complete drying, and small quantities of camphor, vaseline, castor oil and other substances are incorporated with the gelatinous guncotton to moderate this hard and brittle state.

All the smokeless powders, of which gelatinized guncottons or nitrated celluloses are the base, are moulded into some conveniently shaped grain, e.g. tubes, cords, rods, disks or tablets, so that the rate of burning may be controlled as desired. The Vieille powder, invented in 1887 and adopted in France for a magazine rifle, consisted of gelatinized guncotton with a little picric acid. Later a mixture of two varieties of guncotton gelatinized together was used. In addition to guncottons other explosive or non-explosive substances are contained in some of these powders. Guncotton alone in the colloid state burns very slowly if in moderate-sized pieces, and when subdivided or made into thin rods or strips it is still very mild as an explosive, partly from a chemical reason, viz. there is not sufficient oxygen in it to burn the carbon to dioxide. Many mixtures are consequently in use, and many more have been proposed, which contain some metallic salt capable of supplying oxygen, such as barium or ammonium nitrate, &c., the idea being to accelerate the rate of burning of the guncotton and if possible avoid the production of smoke.

The discovery by A. Nobel that nitroglycerin could be incorporated with collodion cotton to form blasting gelatin (see DYNAMITE) led more or less directly to the invention of ballistite, which differs from blasting gelatin only in the relative amounts of collodion, or soluble nitrated cotton, and nitroglycerin. Ballistite was adopted by the Italian government in 1890 as a military powder. Very many substances and mixtures have been proposed for smokeless powder, but the two substances, guncotton and nitroglycerin, have for the most part kept the field against all other combinations, and for several reasons. Nitroglycerin contains a slight excess of oxygen over that necessary to convert the whole of the carbon into carbon dioxide; it burns in a more energetic manner than guncotton; the two can be incorporated together in any proportion whilst the guncotton is in the gelatinous state; also all the liquids which gelatinize guncotton dissolve nitroglycerin, and, as these gelatinizing liquids evaporate, the nitroglycerin is left entangled in the guncotton jelly, and then shares more or less its colloidal character. In burning the nitroglycerin is protected from detonation by the gelatinous state of the guncotton, but still adds to the rate of burning and produces a higher temperature.

_Desirable Qualities._--Smokelessness is one only of the desirable
properties of a propellant. All the present so-called smokeless
powders produce a little fume or haze, mainly due to the condensation
of the steam which forms one of the combustion products. There is
often also a little vapour from the substances, such as oils, mineral
jelly, vaseline or other hydrocarbon added for lubrication or to
render the finished material pliable, &c. The gases produced should
neither be very poisonous nor exert a corrosive action on metals, &c.
The powder itself should have good keeping qualities, that is, not be
liable to chemical changes within ordinary ranges of temperature or in
different climates when stored for a few years. In these powders
slight chemical changes are generally followed by noticeable ballistic
changes. All the smokeless powders of the present day produce some
oxide of nitrogen, traces of which hang about the gun after firing and
change rapidly into nitrous and nitric acids. Nitrous acid is
particularly objectionable in connexion with metals, as it acts as a
carrier of oxygen. The fouling from modern smokeless powders is a
slight deposit of acid grease, and the remedy consists in washing out
the bore of the piece with an alkaline liquid. The castor oil, mineral
jelly or camphor, and similar substances added to smokeless powders
are supposed to act as lubricants to some extent. They are not as
effective in this respect as mineral salts, and the rifling of both
small-arms and ordnance using smokeless powders is severely gripped by
the metal of the projectile. The alkaline fouling produced by the
black and brown powders acted as a preventive of rusting to some
extent, as well as a lubricant in the bore.

_Danger in Manufacture._--In the case of the old gunpowders, the most
dangerous manufacturing operation was incorporation. With the modern
colloid propellants the most dangerous operations are the chemical
processes in the preparation of nitroglycerin, the drying of
guncotton, &c. After once the gelatinizing solvent has been added, all
the mechanical operations can be conducted, practically, with perfect
safety. This statement appears to be correct for all kinds of nitrated
cellulose powders, whether mixed with nitroglycerin or other
substances. Should they become ignited, which is possible by a rise of
temperature (to say 180 deg.) or contact with a flame, the mixture
burns quickly, but does not detonate.

As a rule naval and military smokeless powders are shaped into flakes,
cubes, cords or cylinders, with or without longitudinal perforations.
All the modifications in shape and size are intended to regulate the
rate of burning. Sporting powders are often coloured for trade
distinction. Some powders are blackleaded by glazing with pure
graphite, as is done with black powders. One object of this glazing is
to prevent the grains or pieces becoming joined by pressure; for rods
or pieces of some smokeless powders might possibly unite under
considerable pressure, producing larger pieces and thus altering the
rate of burning. Most smokeless powders are fairly insensitive to
shock. All these gelatinized powders are a little less easily ignited
than black powders. A slightly different cap composition is required
for small-arm cartridges, and cannon cartridges generally require a
small primer or starter of powdered black gunpowder.

It is desired that a propellant shall produce the maximum velocity
with the minimum pressure. The pressure should start gently so that
the inertia of the projectile is overcome without any undue local
strain on the breech near the powder chamber, and more especially that
as more and more space is given to the gases by the movement of the
projectile up the gun to the muzzle, gas should be produced with
sufficient rapidity to keep the pressure nearly uniform or slightly
increasing along the bore. The leading idea for improvements in
relation to propellants is to obtain the greatest possible pressure
regularly developed, and at the same time the lowest temperatures.
(W. R. E. H.)

_Law._--In 1860 an act was passed in England "to amend the law concerning the making, keeping and carriage of gunpowder and compositions of an explosive nature, and concerning the manufacture and use of fireworks" (23 & 24 Vict. c. 139), whereby previous acts on the same subject were repealed, and minute and stringent regulations introduced. Amending acts were passed in 1861 and 1862. In 1875 was passed the Explosives Act (38 & 39 Vict. c. 17), which repealed the former acts, and dealt with the whole subject in a more comprehensive manner. This act, containing 122 sections, and applying to Scotland and Ireland, as well as to England, constitutes, with various orders in council and home office orders, a complete code. The act of 1875 was based on the report of a committee of the House of Commons, public opinion having been greatly excited on the subject by a terrible explosion on the Regent's Canal in 1874. Explosives are thus defined: (1) Gunpowder, nitroglycerin, dynamite, guncotton, blasting powders, fulminate of mercury or of other metals, coloured fires, and every other substance, whether similar to those above-mentioned or not, used or manufactured with a view to produce a practical effect by explosion or a pyrotechnic effect, and including (2) fog-signals, fireworks, fuses, rockets, percussion caps, detonators, cartridges, ammunition of all descriptions, and every adaptation or preparation of an explosive as above defined. Part i. deals with gunpowder, providing that it shall be manufactured only at factories lawfully existing or licensed under the act; that it shall be kept (except for private use) only in existing or new magazines or stores, or in registered premises, licensed under the act. Private persons may keep gunpowder for their own use to the amount of thirty pounds. The act also prescribes rules for the proper keeping of gunpowder on registered premises. Part ii. deals with nitroglycerin and other explosives; part iii. with inspection, accidents, search, &c.; part iv. contains various supplementary provisions. By order in council the term "explosive" may be extended to any substance which appears to be specially dangerous to life or property by reason of its explosive properties, or to any process liable to explosion in the manufacture thereof, and the provisions of the act then extend to such substance just as if it were included in the term "explosive" in the act. The act lays down minute and stringent regulations for the sale of gunpowder, restricting the sale thereof in public thoroughfares or places, or to any child apparently under the age of thirteen; requiring the sale of gunpowder to be in closed packages labelled; it also lays down general rules for conveyance, &c. The act also gives power by order in council to define, from time to time, the composition, quality and character of any explosive, and to classify explosives, and such orders in council are frequently made including new substances; those in force will be found in the _Statutory Rules and Orders_, tit. "explosive substance." The Merchant Shipping Act 1894 imposes restrictions on the carriage of dangerous goods in a British or foreign vessel, "dangerous goods" meaning aquafortis, vitriol, naphtha, benzine, gunpowder, lucifer matches, nitroglycerin, petroleum and any explosive within the meaning of the Explosives Act 1875. The act is administered by the home office, and an annual report is published containing the proceedings of the inspectors of explosives and an account of the working of the act. Each annual report gives a list of explosives at the time authorized for manufacture or importation, and appendices containing information as to accidents, experiments, &c.

Practically every European country has legislated on the lines of the English act of 1875, Austria taking the lead, in 1877, with an explosives ordinance almost identical with the English act. The United States and the various English colonies also have explosives acts regulating the manufacture, storage and importation of explosives. (See also PETROLEUM.) (T. A. I.)

BIBLIOGRAPHY.--M. Berthelot, _Sur la force des matieres explosives_
(Paris, 1883); P.F. Chalon, _Les Explosifs modernes_ (Paris, 1886);
W.H. Wardell, _Handbook of Gunpowder and Guncotton_ (London, 1888);
J.P. Cundill, _A Dictionary of Explosives_ (London, 1889 and 1897); M.
Eissler, _A Handbook of Modern Explosives_ (London, 1896, new ed.
1903); J.A. Longridge, _Smokeless Powder and its Influence on Gun
Construction_ (London, 1890); C. Napier Hake and W. Macnab,
_Explosives and their Power_ (London, 1892); G. Coralys, _Les
Explosifs_ (Paris, 1893); A. Ponteaux, _La Poudre sans fumee et les
poudres anciennes_ (Paris, 1893); F. Salvati, _Vocabolario di polveri
ed explosivi_ (Rome, 1893); C. Guttmann, _The Manufacture of
Explosives_ (London, 1895 and later); S.J. von Romocki, _Geschichte
der Sprengstoffchemie, der Sprengtechnik und des Torpedowesens bis zum
Beginn der neusten Zeit_ (Berlin, 1895); _Geschichte der
Explosivstoffe, die rauchschwachen Pulver_ (Berlin, 1896); P.G.
Sanford, _Nitro-explosives_ (London, 1896); L. Gody, _Traite theorique
et pratique des matieres explosives_ (Namur, 1896); R. Wille, _Der
Plastomerite_ (Berlin, 1898); E. Sarrau, _Introduction a la theorie
des explosifs_ (1893); _Theorie des explosifs_ (1896); O. Guttmann,
_Manufacture of Explosives_ (London, 1895); E.M. Weaver, _Notes on
Military Explosives_ (New York, 1906); M. Eissler, _The Modern High
Explosives_ (New York, 1906); _Treatise on Service Explosives_,
published by order of the secretary of state for war (London, 1907).
Most of the literature on modern explosives, e.g. dynamite, &c., is to
be found in papers contributed to scientific journals and societies.
An index to those which have appeared in the _Journal of the Society
of Chemical Industry_ is to be found in the decennial index (1908)
compiled by F.W. Renant.

FOOTNOTE:

[1] Not necessarily heat energy entirely. A number of
substances--acetylides and some nitrogen compounds, such as nitrogen
chloride--decompose with extreme violence, but _little heat_ is
produced.

EXPRESS (through the French from the past participle of the Lat. _exprimere_, to press out, by transference used of representing objects in painting or sculpture, or of thoughts, &c. in words), a word signifying that which is clearly and definitely set forth or represented, explicit, and thus used of a meaning, a law, a contract and the like, being specially contrasted with "implied." Thus in law, malice, for which there is actual evidence, as apart from that which may be inferred from the acts of the person charged, is known as "express." The word is most frequently used with the idea of something done with a definite purpose; the term "express train," now meaning one that travels at a high speed over long distances with few intermediate stoppages, was, in the early days of railways, applied to what is now usually called a "special," i.e. a train not running according to the ordinary time-tables of the railway company, but for some specific purpose, or engaged by a private person. About 1845 this term became used for a train running to a particular place without stopping. Similarly in the British postal service, express delivery is a special and immediate delivery of a letter, parcel, &c., by an express messenger at a particular increased rate. The system was adopted in 1891.

In the United States of America, express companies for the rapid transmission of parcels and luggage and light goods generally perform the function of the post office or the railways in the United Kingdom and the continent of Europe. Not only do they deliver goods, but by the cash on delivery system (see CASH) the express companies act as agents both for the purchaser and seller of goods. They also serve as a most efficient agency for the transmission of money, the express money order being much more easily convertible than the postal money orders, as the latter can only be redeemed at offices in large and important towns. The system dates back to 1839, when one William Frederick Harnden (1813-1845), a conductor on the Boston and Worcester railway, undertook on his own account the carrying of small parcels and the performance of small commissions. Obliged to leave the company's service or abandon his enterprise, he started an "express" service between Boston and New York, carrying parcels, executing commissions and collecting drafts and bills. Alvin Adams followed in 1840, also between Boston and New York. From 1840 to 1845 the system was adopted by many others between the more important towns throughout the States. The attempt to carry letters also was stopped by the government as interfering with the post office. In 1854 began the amalgamation of many of the companies. Thus under the name of the Adams Express Company the services started by Harnden and Adams were consolidated. The lines connecting the west and east by Albany, Buffalo and the lakes were consolidated in the American Express Company, under the direction of William G. Fargo (q.v.), Henry Wells and Johnston Livingston, while another company, Wells, Fargo & Co., operated on the Pacific coast. The celebrated "Pony Express" was started in 1860 between San Francisco and St Joseph, Missouri, the time scheduled being eight days. The service was carried on by relays of horses, with stations 25 m. apart. The charge made for the service was $2.50 per 1/2 oz. The completion of the Pacific Telegraph Company line in 1861 was followed by the discontinuance of the regular service.

The name "express" is applied to a rifle having high velocity, flat trajectory and long fixed-sight ranges; and an "express-bullet" is a light bullet with a heavy charge of powder used in such a rifle (see RIFLE).

EXPROPRIATION, the taking away or depriving of property (Late Lat. _expropriare_, to take away, _proprium_, i.e. that which is one's own). The term is particularly applied to the compulsory acquisition of private property by the state or other public authority.

EXPULSION (Lat. _expulsio_, from _expellere_), the act of driving out, or of removing a person from the membership of a body or the holding of an office, or of depriving him of the right of attending a meeting, &c. In the United Kingdom the House of Commons can by resolution expel a member. Such resolution cannot be questioned by any court of law. But expulsion is only resorted to in cases where members are guilty of offences rendering them unfit for a seat in the House, such as being in open rebellion, being guilty of forgery, perjury, fraud or breach of trust, misappropriation of public money, corruption, conduct unbecoming the character of an officer and a gentleman, &c. It is customary to order the member, if absent, to attend in his place, before an order is made for his expulsion (see May, _Parliamentary Practice_, 1906, p. 56 seq.). Municipal corporations or other local government bodies have no express power to expel a member, except in such cases where the law declares the member to have vacated his seat, or where power is given by statute to declare the member's seat vacant. In the cases of officers and servants of the crown, tenure varies with the nature of the office. Some officials hold their offices _ad vitam aut culpam or dum bene se gesserunt_, others can be dismissed at any time and without reason assigned and without compensation. In the case of membership of a voluntary association (club, &c.) the right of expulsion depends upon the rules, and must be exercised in good faith. Courts of justice have jurisdiction to prevent the improper expulsion of the member of a voluntary association where that member has a right of property in the association. In the case of meetings, where the meeting is one of a public body, any person not a member of the body is entitled to be present only on sufferance, and may be expelled on a resolution of the body. In the case of ordinary public meetings those who convene the meeting stand in the position of licensors to those attending and may revoke the licence and expel any person who creates disorder or makes himself otherwise objectionable.