Chapter 9

Excavating the Panama CanalExcavating the Culebra Cut, Panama Canal

Excavation, the process of removing soil or rock in engineering or exploration works, such as for docks, retaining-walls, railway cuttings, canals, foundations, &c. On a small scale, or in situations unsuitable for machinery, it is performed by hand, the soil being first loosened by the pick, and then shovelled into barrows. In rocky soils, drilling and explosives may be employed. In large works power shovels or 'steam-navvies' are employed, which are essentially cranes carrying a large shovel, or a system of steel buckets of the dredger type. These carry their own means of propulsion, and run on temporary rails laid down as the work proceeds. They work against the face of the excavation, and load directly into bogies or wagons.

Excavations.The forgotten history of the remote past has been reconstructed by thosescientists who have explored the sites of ancient seats of civilization. Egyptian and Babylonio-Assyrian investigations date from the middle of the eighteenth century, but it was not until the middle of the nineteenth century, when modern scholars first penetrated the secrets of the lost languages (seeCuneiform WritingandHieroglyphics) that the ancient civilizations were rendered more or less articulate. As the texts were being deciphered with increasing ease and accuracy, a basis was provided for archæology, and it became possible to frame chronological systems. During the latter years of the nineteenth and the early years of the present century, excavators, philologists, and ethnologists have provided a fairly continuous and detailed history of man from 3000B.C.till classical times, thus bridging a gulf which used to be misty with doubtful legends and traditions. The most dramatic excavations were those begun by Heinrich Schliemann in 1871 at Hissarlik, the site of ancient Troy. On the hillock he dug through nine successive settlements. He afterwards excavated at Mycenæ and Tiryns in Greece and found evidence of a high pre-Hellenic culture. Following up the clues thus afforded, Sir Arthur Evans and others, excavating in Crete during the opening years of the present century, discovered abundant relics, including palaces and towns, of the earliest Ægean civilization now referred to as Minoan (seeCrete). Of late years Central and Western Europe have yielded evidence of the 'drift' of Minoan culture to outlying parts. Excavations in Russian Turkestan and Chinese Turkestan have revealed traces of ancient culture centres dating back beyond 2000B.C.In the Americas the excavators have thrown considerable light on the pre-Columbian civilizations of Peru, Central America (Maya), and Mexico, but the picture-writings have not been deciphered. SeeBabylonia;Crete;Egypt;Troy.

Ex´cellency, a title given to ambassadors and plenipotentiaries, governors of colonies, the President of the United States, of France, &c.

Excess Profits Duty, devised in 1915 to meet the extraordinary expenditure occasioned by the war, is a tax upon the profits of certain trades and businesses carried on in the United Kingdom, or owned or carried on abroad by persons resident in the United Kingdom, in so far as these profits, after deduction of a specified allowance, exceed a pre-war standard. The main exceptions are agriculture, offices and employments, and professions where personal qualifications predominate and only small capital is necessary. In some cases, e.g. estate agencies, where a portion of the profits arises from professional skill, only the portion otherwise arising falls into charge. The pre-war standard is an alternative one at the option of the taxpayer. Firstly, it may be a profits standard—the average of the profits of any two of the last three pre-war years, or if there have been only two pre-war years, then the average profits of those years, or the actual profits of the last year, or if there has been only one pre-war year, then the actual profits of that year. Where the average profits of the last three pre-war years are 25 per cent less than the average of the three years immediately preceding them, the taxpayer may take the average of any four of those six years. Secondly, it may be, and as a general rule where the business has not had one full pre-war year must be, a percentage standard, calculated at the appropriate rate on the capital in the business at the end of the last pre-war trade year, or where there has not been one pre-war year, then on the average amount of capital employed (a) during the year or accounting period in question, or (b) in respect of periods ending after 31st Dec., 1919, during the first accounting period. The percentage standard of sole traders, partnerships, and private companies may in respect of accounting periods ending after that date be increased by £500 per annum for each working proprietor, but not so as to exceed £750 per annum each. The general free allowance is £200, increased in 1920 to £500 for new or re-opened businesses of ex-service men. A further abatement is now granted where profits do not exceed £4000, with the result that liability cannot arise unless profits exceed £832.

The rate of duty, at first 50 per cent, was raised to 60 per cent in 1916, and to 80 per cent in 1917. Reduced to 40 per cent in 1919, it was again increased to 60 per cent by the Finance Act, 1920. It was abolished in 1921. Undoubtedlyit was injurious to trade and an incentive to wasteful expenditure, but an effective substitute for supplying the unparalleled financial needs of the State resulting from the war apparently could not be devised.

'Munitions Levy' is the counterpart of Excess Profits Duty in its application to Government-controlled establishments for the production of munitions of war.

In the fiscal year 1919-20 the tax produced £290,045,000, while the estimate for the year 1920-1 was £220,000,000.

Exchange, a place in large commercial towns where merchants, agents, bankers, brokers, and others concerned in commercial affairs meet at certain times for the transaction of business. The institution of exchanges dates from the sixteenth century. They originated in the important trading cities of Italy, Germany, and the Netherlands, from which last-named country they were introduced into England. The Royal Exchange of London was established by Sir Thomas Gresham in 1556. In some exchanges only a special class of business is transacted. Thus there are stock exchanges, corn exchanges, coal exchanges, cotton exchanges.

Exchange, in commerce, that species of transactions by which the debts of individuals residing at a distance are cancelled by order, draft, or bill of exchange, without the transmission of specie. Thus, a merchant in London who owes £100 worth of cotton goods in Glasgow gives a bill or order for that amount which can be negotiated through banking agencies or otherwise against similar debts owing by other parties in Glasgow who have payments to make in London. The creditor in Glasgow is thus paid by the debtor in Glasgow, and this contrivance obviates the expense and risk of transmitting money. The process of liquidating obligations between different nations is carried on in the same way by an exchange of foreign bills. When all the accounts of one country correspond in value with those of another, so that there is an even balance, the exchange between the countries will beat par, that is, the sum for which the bill is drawn in the one country will be the exact value of it in the other. Exchange is said to beat parwhen, for instance, a bill drawn in New York for the payment of £100 sterling in London can be purchased there for £100. If it can be purchased for less, exchange isunder parand is against London. If the purchaser is obliged to give more, exchange isabove parand in favour of London. Although the numerous circumstances which incessantly affect the state of debt and credit prevent the ordinary course of exchange from being almost ever precisely at par, its fluctuations are confined within narrow limits, and if direct exchange is unfavourable between two countries this can often be obviated by the interposition of bills drawn on other countries where an opposite state of matters prevails. SeeBill of Exchange.—Bibliography: G. J. Goschen,Theory of Foreign Exchange; H. Withers,Money Changing.

Exchange, Deed of, in English law, an original common law conveyance for the mutual transfer of real estate. It takes place between two contracting parties only, although several individuals may be included in each party; and the parties must take an equal estate, as fee-simple for fee-simple, legal estate for legal estate, copyhold for copyhold of the same manor, and the like.

Excheq´uer(Fr.échiquier, chess-board), in Britain, the department which deals with the moneys received and paid on behalf of the public services of the country. The public revenues are paid into the Bank of England (or of Ireland) to account of the Exchequer, and these receipts as well as the necessary payments for the public service are under the supervision of an important official called the Comptroller and Auditor General, the payments being granted by him on receipt of the proper orders proceeding through the Treasury. The public accounts are also audited in his department. The Chancellor of the Exchequer, who must be a member of the House of Commons, is the head of the Treasury Department. When the Prime Minister is a member of the House of Commons, he sometimes holds the office of Chancellor of the Exchequer.

Exchequer, Court of, an ancient English court of record, established by William the Conqueror, and intended principally for the care and collection of the royal revenues. It was one of the supreme courts of common law, and is said to derive its name from the chequered cloth, resembling a chess-board, on which the sums were marked and scored with counters. The judges of this court were the chief baron and five junior orpuisnébarons. This court was abolished by the Judicature Act of 1873, and its jurisdiction transferred to the High Court of Justice. In Canada there is a Court of Exchequer for the Dominion.

Exchequer and Audit Department, a department of the English Civil Service charged with the functions of auditing the accounts of all other departments.

Exchequer Bills, bills of credit issued by authority of Parliament as a means of raising money for temporary purposes. They are of various sums—£100 or any multiple—and bear interest at a rate fixed for every half-year according to the rate ruling in the money-market at the time. These bills pass from hand to hand as money, and form part of the public unfundeddebt of Great Britain.Exchequer bondsare similar, but they run for a definite number of years (six at most) at a fixed rate of interest.

Excise´, an inland duty or impost laid on commodities produced and consumed within a country, and also on licences to manufacture and deal in certain commodities. Excise duties were introduced into England by the Long Parliament in 1643, being then laid on the makers and vendors of ale, beer, cider, and perry. Being found to be a convenient and productive source of revenue, they continued to gain ground, and in 1919 yielded £59,663,000. In Britain the excise includes duties on spirits and beer, licences on dogs, guns, carriages, servants, plate, railways, game, &c. In 1917 an excise duty was laid on entertainments, matches, and table waters. Spirits and beer yield over £44,000,000.

Exci´to-motor action, the action of nerves distributed to muscular organs, the stimulation of which leads to movement. Thus, irritation of a nerve supplying a muscle will lead to contraction of the muscle by excito-motor action, and irritation of certain nerves distributed to blood-vessels will lead to contraction of the vessel by acting on its muscular coat.

Exclusion, Bill of, a bill introduced into the British Parliament during the reign of Charles II for the purpose of excluding the Duke of York (afterwards James II), he being a Roman Catholic, from the throne.

Excommunication, the exclusion of a Christian from the communion and spiritual privileges of the Church. Excommunication was a recognized penalty among the Jews (John, ix, 22), and was practised early by the Christian Church. A distinction gradually arose between a lesser and a greater excommunication, the former being a suspension from Church privileges, the latter a formal expulsion excluding from all communion with the faithful. In the Middle Ages the Popes often excommunicated whole cities and kingdoms. In such a case all religious services ceased, and the grave inconveniences thus caused made excommunication a formidable weapon in the hands of the Pope, till with frequent abuse it lost its force. Besides excommunication an extreme degree of denunciation calledanathema, and cutting the offender off from all the hopes and consolations of the Christian faith, is used in the Roman Catholic Church. Both Luther and Calvin were in favour of the right of excommunication by the ministers of the Church. In the Church of England both the less and the greater excommunications are recognized.—Cf. E. Taunton,The Law of the Church.

Excre´tion, in physiology, the separation and carrying off of waste matter from some organ of an animal body, a function performed by the lungs, kidneys, and the skin, besides the action of the intestinal canal.

ExcubitoriumExcubitorium, St. Alban's Abbey

Excubito´rium, in mediæval churches, a gallery where public watch was kept at night on the eve of some festival, and from which the great shrines could be seen.

Exe, a river of England, which rises in Exmoor, in the county of Somerset, and after a southerly course of about 50 miles falls into the English Channel at Exmouth.

Execution, in law, is a judicial writ grounded on a judgment of the court by which the writ is issued, and is granted for the purpose of carrying the judgment into effect, by having it executed. Execution is granted by a court only upon the judgments given by the same court, not upon those pronounced by another. SeeElegit;Fieri facias.

Executioner, the official who carries into effect a sentence of death, or inflicts capital punishment in pursuance of a legal warrant. In England the duty of executing the extreme sentence of the law devolves upon the sheriff, and in Scotland on the civic magistracy, but in practice the duty is performed by another in presence of these functionaries. In the reign of James I Gregory Brandon was the executioner of London, and hence the name Gregory has often been employed to designate executioners. In France the executioner is styled Monsieur de Paris.

Exec'utive, that branch of the government of a country by which the laws are carried into effect or the enforcement of them superintended. The term is used in distinction from thelegislativeand thejudicialdepartments, and includes the supreme magistrate, whether emperor, king, president, or governor, his cabinet or ministers, and a host of minor officials.

Exec´utor, in law, is one appointed by a man's last will to carry its provisions into execution after the testator's death. The testator may, by the English law, appoint any person of sound mind and discretion, though otherwise under some legal disabilities as to contracting and transacting business in general, such as a married woman, or a minor. The duties of executors and of administrators are, in general, the same, the difference of the two depending mostly on the mode of appointment, the executor being nominated by the testator, the administrator being appointed by the Judge of Probate. In Scotland an executor appointed by will is styled executornominate, and by authority of the court executordative.

Exequa´tur(Lat., 'Let him accomplish'), a written recognition of a consul or commercial agent issued by the Government to which he is accredited, and authorizing him to exercise his powers.

Ex´eter, a city, river-port, parliamentary county, and municipal borough of England, county town of Devon, on the left bank of the Exe, 10 miles north-west of its outlet in the English Channel. It is pleasantly situated on the summit and slopes of an acclivity rising from the river, and has handsome squares, terraces, and streets. The chief architectural feature is the cathedral (founded in 1112), a long, low building with fine west front, unique in having two towers forming its transepts, and only these two. The city has remains of the old castle and old walls, Guildhall, Albert Memorial College, training college, and St. Michael's Church. There are iron-foundries, works for agricultural implements and paper, and 'Honiton' lace is made. By a canal vessels of 300 tons can reach the city. The largest vessels remain at Exmouth. Exeter is a place of remote antiquity, having been a British settlement long prior to the invasion of the Romans, by whom it was calledIsca Damnoniorum. It was taken by William the Conqueror in 1068. It long returned two members to Parliament, but lost one of them in 1885. Pop. 59,608.

Exeter College, Oxford, a college, originally called Stapledon Hall, founded in 1314 by Walter de Stapledon, Bishop of Exeter, who made a foundation for a rector and twelve fellows. In 1404 Edmund Stafford, Bishop of Exeter, added two fellowships and obtained leave to give the college its present name.

Exeter Hall, a large building on the north side of the Strand, London, opened in 1831, and capable of containing over 3000 persons. In it the 'May Meetings' of the several religious societies were held. It was sold in 1907 by the Young Men's Christian Association to a firm of caterers, who demolished it in 1908. The Strand Palace Hotel now stands on its site.

Exfoliationis the scaling off of dead tissues; thus there may be exfoliation of the skin, of bone, or of other parts from their living surroundings.

Exhibition, a fixed sum given for a term of years from the funds of a school, college, or university, generally upon the result of a competitive examination. An exhibition, no matter what its pecuniary value, is less of a distinction than a scholarship. At Cambridge an exhibitioner has no standing in his college different from that of the ordinary 'pensioner', while a scholar is on the Foundation of his college.

Exhibitions.The earliest recorded 'exhibition', in the modern acceptation of the word, is that in which, for one hundred and eighty days, Ahasuerus "shewed the riches of his glorious kingdom" at Shushan (Esther, i, 2-4). The first European exhibition was held at Venice in 1268; while the great fairs of Leipzig and Nijni-Novgorod partook of the same nature. But the real forerunner of the modern exhibition was that held in London by the Society of Arts in 1756, when carpets, china, and similar artistic objects were displayed. This was followed in 1761 by an exhibition of agricultural machinery. In 1797 France held a display ofobjets d'artat St. Cloud; there was another two years later at the Louvre; while a third in 1802 is memorable for the first issue of an official catalogue, and for the presence of Montgolfier the aeronaut, and Jacquard the inventor of the loom that bears his name, among exhibitors. Besides the exhibition of Irish industries, held at Dublin (1829), and the Birmingham exhibition of metal-work (1849), numerous displays were held in both Europe and America before the first International or 'Great' Exhibition of 1851. This memorable display was under the active patronage of Prince Albert, and for its accommodation the Crystal Palace was erected in Hyde Park. Its success gave the exhibition movement an impetus which produced examples at New York and Dublin (1853), both of which proved financial failures; at Munich and Melbourne (1854); Paris (1855); and at South Kensington, where was held the second International Exhibition (1862). Five years later, after Constantinople, Oporto, and Agra had, among other places, held displays, came the great Paris Exhibition, planned on a colossal scale; though the main building in the Champde Mars was stigmatized as 'a gasometer' by Napoleon III. Vienna had a magnificent but financially disastrous exhibition in 1873, and in 1876 Philadelphia celebrated the centenary of the Independence of the United States by a display. In 1878 Paris held another exhibition, for which the Trocadero was built. A series held at South Kensington (1871-4) had only a moderate success, but great popularity was attained by the 'Fisheries', 'Health', 'Inventions', and Colonial Exhibitions held in the years 1883-6. Edinburgh was the scene of a forestry display in 1884, and at the same time New Orleans opened an exhibition which continued till the following year. The Paris Exhibition of 1889 was notable for the 'side-shows', which included the Eiffel Tower; while the financial result of that held in 1900, which covered 550 acres of ground and admitted thirty-nine million people, was far from satisfactory. Meanwhile Chicago had in 1893 celebrated the four hundredth anniversary of Columbus's discovery of America by a huge 'World's Fair'. The present century opened inauspiciously with the assassination of President McKinley at the Pan-American Exhibition at Buffalo (1901); Glasgow had a thoroughly successful exhibition the same year; St. Louis was the scene of another in 1904; while London organized the Franco-British Exhibition in 1908. This last owed much to the late Imre Kiralfy, who had directed many previous displays, and was the designer of the 'White City' at Shepherd's Bush, where in 1914 was held the Anglo-American Exposition. After the conclusion of the European War various plans for new exhibitions were put forward, such as the British Empire Exhibition, which is to be held in London in 1923, and which is intended to foster imperial interests.

Ex´ile, a punishment by which a person is compelled to leave the city, province, or the country where he has previously resided. It is a punishment for State criminals.

Exmoor´, a wild and hilly district of England, in the extreme south-west of Somersetshire, extending also into Devonshire, formerly a forest.

Ex´mouth, a town of England, in Devonshire, 10 milesS.S.E.of Exeter, at the mouth of the Exe. It is picturesquely situated, and is one of the best-known sea-bathing places on the Devonshire coast. The chief industries are lace-making and the fisheries. Pop. 13,614.

Exmouth, Edward Pellew, Viscount, a British naval officer, born at Dover in 1757, died 23rd Jan., 1833. He went to sea at the age of thirteen, served as midshipman in theBlondefrigate during the American War, and greatly distinguished himself at Lake Champlain. In 1782 he was made a post-captain for a brilliant action in thePelican, and on the outbreak of the war in 1793 was appointed to the command of the frigateLa Nymphe. From this time till the peace in 1802 he was employed on active service. In 1804, on the resumption of hostilities, he was sent to take the chief command on the East India station, in theCulloden, of seventy-four guns; and here he remained till 1809, when he had attained the rank of vice-admiral. His next appointment was the command of the fleet blockading the Scheldt. In 1814 he was made Baron Exmouth with a pension of £2000 per annum. In 1816 he was sent with a fleet to punish the Dey of Algiers for outrages committed, and to force him to give up his Christian captives and abolish Christian slavery. Along with some Dutch war vessels he bombarded the city for eight hours, and inflicted such damage that the Dey agreed to every demand. Three thousand Christian slaves were thus restored to liberty. Lord Exmouth was made a viscount and received honours from several of the European sovereigns, and the freedom of the City of London. In 1821 he retired into private life.

Exoascineæ, a family of parasitic ascomycetous Fungi, distinguished by the absence of any definite fruit-body, the asci being produced in a layer on the surface of the host. The best known areExoascus Pruni, the cause of the mal-formed fruits called 'bladder-plums' or 'pocket-plums', andE. turgidus, which produces the abnormal tufts of branches on silver birch known as 'witches' brooms'.

Exobasidiineæ, a family of parasitic basidiomycetous Fungi, resembling the Exoascineæ in most respects, but producing basidia in place of asci, a remarkable instance of parallel evolution. The commonest British species isExobasidium Vaccinii,which is frequent on cowberry (Vaccinium Vitis-Idæa) in Scotland.E. vexansis the cause of a serious disease of the tea-plant called 'blister-blight', which is very destructive to the Assam plantations.

Ex´odus(Gr.exodos, a going out), the name given in theSeptuagintto the second book of thePentateuch, because it describes the departure of the Israelites from Egypt. The contents of the book are partly historical, describing the departure of the Israelites from Egypt, and partly legislative, describing the promulgation of the Sinaitic law. One of the difficulties connected with this book is that, according to Scriptural chronology, the residence of the Israelites in Egypt was only 215 years, and it seems incredible that in this time "the threescore and ten souls" who accompanied Jacob to Egypt could have become the two and a half millions who left with Moses.

Exogamy(Gr.exo, outside, andgamos, marriage), a term applied to the custom of allowing marriages only between members who do notbelong to the same group. The study of exogamy is practically a branch of ethnology. The opposite of exogamy is endogamy, or prohibition of marriage outside the tribe. Exogamy, which among other causes may be ascribed to a desire of forming useful alliances with hostile tribes, is practised among Australian aborigines, Mongols, and American Indians, and the custom is widely distributed in various forms in all stages of civilization.—Bibliography: Sir J. G. Frazer,Totemism and Exogamy; E. A. Westermarck,The History of Human Marriage.

Exogenous Plants(eks-oj´e-nus), orExogens, old names for Dicotyledons (q.v.).

Exogenous Structures, in botany, are those which arise from superficial tissues of the parent organ, as stem-branches and leaves. Opposed to endogenous structures.

Ex´orcism(Gr.exorkizein, to expel with an oath), the casting out of evil spirits by certain forms of words or ceremonies. An opinion prevailed in the ancient Church that certain persons, those particularly who were afflicted with certain diseases, especially madness and epilepsy, were possessed by evil spirits; this was calleddemoniac possession.Over such persons forms of conjuration were pronounced, and this act was calledexorcism. There were even certain men who made this a regular profession, and were calledexorcists. Exorcism still forms a part of the beliefs of some Churches. In the Roman Catholic Church exorcist is one of the inferior orders of the clergy.—Cf. Sir J. G. Frazer,The Golden Bough.

Exosto'sis, in medicine, an excrescence or growth from one of the bony structures of the body. It is generally found at the end of long bones near the joints, and in connection with the skull.

Exothermic Compoundsare compounds which evolve heat during their formation; these are usually stable compounds, as they must be supplied with a corresponding amount of heat for their decomposition.

Exot´ic, belonging to foreign countries; a term used especially of plants. Exotic plants are such as belong to a soil and climate entirely different from the place where they are raised. They are nearly always greenhouse or hothouse plants.

Expansion, in physics, the increase of the dimensions of a body caused by a change of temperature. In general, bodies expand with rise of temperature, solids expanding least and gases most. This change in the dimensions of solids with temperature is expansion in length, area, and volume. These changes are referred to a unit called the coefficient of expansion, or expansion of unit length, area, or volume for 1° rise. For example, the coefficient of linear expansion of iron is .000011; that is, a yard, say, of iron rod becomes longer by this fraction of a yard for each degree centigrade that its temperature is raised. The coefficient of volume expansion of a solid is three times its linear coefficient. Crystals have different rates of expansion along the three crystalline axes. Fused silica or quartz expands so slightly that it may be plunged when red-hot into water without being cracked. Invar, a nickel-steel alloy, which also has an extremely small coefficient of expansion, is used in making clock pendulums, which are unaffected by change of temperature. The observed expansion of liquids is affected by the expansion of the vessel containing them, and the apparent expansion of a liquid is thus always less than its real expansion. The expansion of water with rise of temperature is irregular; water contracts from 0° to 4°C., and thereafter expands at an increasing rate until the boiling-point is reached. The expansion of mercury and other liquids is employed in thermometry. Gases when kept at constant pressure expand by about1/273rd part of their volume at 0°C. for each degree rise.

Expectation, in the doctrine of chances, the value of any prospect of prize or property depending upon the happening of some uncertain event. A sum of money inexpectationupon a certain event has a determinate value before that event happens. If the chances of receiving or not receiving a hundred pounds, when an event arrives, are equal, then, before the arrival of the event the expectation is worth half the money.—Expectation of life, the number of years which a man or woman of any age may be expected to live. To calculate this with any reasonable degree of probability, it is necessary to have particulars of a large number of individuals. The earliest observations were based upon the records of the registers of certain towns. Out of a number of people alive at one date the numbers still living at the end of successive years were found, and an estimate of the probable duration of life was made. With increased facilities for collecting statistics of a larger number of lives, this estimate has since been modified. It is necessarily influenced by the progress of civilization, improved methods of sanitation, increased knowledge of the best methods of treating diseases, and other causes, but the collected statistics are now so numerous that the actuaries of life assurance offices have been able to prepare tables of mortality from which the cost of life premiums and the price of annuities are calculated.

Expec´torantsare drugs used to increase and liquefy the secretion in the lungs and air-passages. The most effective are ipecacuanha, squills, apomorphine, ammonium carbonate, andpotassium iodide. Some of these are usually present in the many cough mixtures so widely used.

Exper´iment, an operation designed to discover some unknown truth, principle, or effect, or to establish it when discovered. It differs from observation in the fact that the phenomena observed are, to a greater or less extent, controlled by human agency. Experiment distinguishes the modern method of investigating nature, and to it we owe the rapid strides made in chemistry and physics.

Expert´(Lat.experiri, to test), a person eminently skilled in any particular branch or profession; specifically, a scientific or professional witness who gives evidence on matters connected with his profession, as an analytical chemist or a person skilled in handwriting.

Exploits´, River of, a river which traverses nearly the whole of Newfoundland fromS.W.toN.E., and falls into the Bay of Exploits. It is about 150 miles long, and is navigable for steamers for 12 miles.

Explo´sion, a sudden violent outburst accompanied by a loud noise, and giving rise to an impulsive wave which spreads outwards from the place of explosion. Generally applied to the very rapid combustion of explosive substances which, under the influence of heat or shock, are resolved with extreme rapidity into gaseous form. Substances are termed low explosives or high explosives according as they are set off by combustion or detonation.

Explosive Mechanism, in botany, (1) in flowers, an arrangement for the transference of pollen to an insect-visitor by a sudden movement of floral organs. (2) In fruits, an arrangement for the forcible expulsion of seeds from a fruit brought about in various ways (seeSling-fruits). The spores of Ferns, ascospores, and some conidia are also liberated explosively.

Explosives.An explosive is a substance or mixture of substances which, by the action of a blow or of heat, can be converted very easily and suddenly into a more stable substance or substances, usually gaseous, with the simultaneous liberation of a large amount of heat. Explosives are divided into classes according to the uses to which they are put, but the line of demarcation is not always very clear. The industrial and blasting powders may be either low or high explosives. A 'low' explosive explodes by the application of heat, and burns more or less uniformly and slowly, and projects neighbouring objects to a distance. A 'high' explosive explodes under a blow, and the whole of the substance is instantly transformed, and instantly exerts its maximum pressure, creating a violent disturbance in a limited area without necessarily projecting substances to any great distance. Service explosives, for naval and military purposes, are divided into propellants and high explosives. Sporting powders are specially modified propellant powders. Examples of these classes of explosives, with notes on their composition, are given below.

Low Explosives.—The best examples of the low explosive are gunpowder and similar mixtures. The constituents of the 'gunpowder' explosives are generally not explosive alone, but only when mixed. A 'gunpowder' mixture contains carbon or carbonaceous matter like wood-meal, hydrocarbons, starches, and sugars, &c., which burn owing to the presence of highly oxygenated substances like peroxides, chlorates and perchlorates, nitrates, permanganates, chromates and dichromates, all of which convey the necessary oxygen. In addition, there usually is present some very easily ignited substance like sulphur or sulphides, or phosphorus or phosphides, &c. As compared with other explosives, gunpowder or black-powder has certain advantages. It is cheap, easily ignited, insensitive to shock, and stable at moderately high temperature; it burns regularly, and its residue is non-corrosive. But it is weak in power, and produces much smoke. It is excellent for armour-piercing shell and for rings of time-fuses. Gunpowder made in different countries varies in composition, but for rifle, cannon, and sporting powders it, usually contains 74 to 75 parts of saltpetre, 9 to 14 parts of sulphur, 12 to 16 parts of charcoal. For blasting powders less saltpetre and more charcoal is used. Charcoal is made by the carbonization of wood. In England dogwood, alder, and willow woods are used; in Germany alder and willow are used; in France black alder and also white alder, poplar, aspen, birch, and hazel; in Switzerland hazel wood; in Spain oleander, yew, willow, hemp stems, and vine; in Italy hemp stems. The wood is generally carbonized in iron retorts. The product is allowed to cool out of contact with air, else it may inflame. Wood burnt for ordnance powders gives a yield of 20 to 30 per cent charcoal; that for small-arms gives a yield of 40 per cent. The charcoal contains from 68 to 85 per cent carbon, from 2.8 to 3.7 per cent hydrogen, from 12 to 27 per cent oxygen, and may have up to 5 per cent ash. The saltpetre is found naturally in Chile, India, and in other countries, and is refined by crystallization from water. It is a colourless, crystalline solid. Sulphur, a pale-yellow solid, melting-point 113° C., boiling-point 444·5° C., is found in nature, and is refined to a purity of 99·5 per cent and over. It has a low ignition temperature of 261° C., and makes the powder burn more readily. Under the pressure of the press and the incorporating mill it flows and cements the minute particles of charcoal and saltpetre together. The threeingredients are ground, mixed, sieved, incorporated or mixed in drums or mills, broken down, and then pressed, corned or granulated, and glazed. Cannon powders receive an addition of graphite to reduce the rate of burning. The powder is then dried in a stove, finished in a reel to get rid of the last traces of dust, and blended. In the United States powder for blasting contains sodium nitrate instead of potassium nitrate. The powder is cheaper and stronger, but is hygroscopic. Sprengsaltpetre is largely used in Stassfurt salt-mines, where a mild explosive is required, and consists of 75 parts by weight of sodium nitrate, 10 parts by weight of sulphur, and 15 parts by weight of brown coal. It is cheap, and does not produce poisonous fumes. Bobbinite is largely used in coal-mines. It is black powder with ammonium and copper sulphates, possibly also starch and paraffin wax. When gunpowder explodes, the product consists of 43 per cent gases, 56 per cent solids, and the rest water. The composition of other industrial and blasting powders is given in the sequel.

Propellant Explosives.—The chief propellants arc nitrocellulose, also called nitrocotton or guncotton, and nitroglycerine.

Nitrocellulose.—The chief sources of cellulose are wood and cotton. When cotton is plentiful, nitrocellulose is made as follows. Cotton-waste is hand-picked to get rid of string, wood, &c.; it is opened out by a teasing-machine, which tears off small portions at a time, and the cotton is then dried to about 0.5 per cent moisture content. The cotton is then nitrated with 'mixed acid'—a mixture of about 16 per cent nitric and 75 per cent sulphuric acid and about 8 per cent water—at 15° to 25° C. After the nitration, the acid is removed and the nitrocotton boiled up in water to stabilize it. Generally nitrocotton contains about 12 to 13 per cent of nitrogen. Wet nitrocotton is quite safe although it can be detonated, but dry nitrocotton is very dangerous. To-day, paper is usually made from wood-pulp, and when the cotton supplies of Germany were stopped during the European War, nitrocellulose had to be made from wood-pulp via a form of paper crêpe prepared by the Germans from the pulp. For propellant purposes the nitrocotton is 'gelatinized', either alone or mixed with nitroglycerine, and is then worked up into different forms, such as wire, rods, grains, or tape, when it becomes controllable at will, so that the firing is not dangerous.

Nitroglycerine.—Mixed acid, containing 41 per cent nitric acid and 57.5 per cent sulphuric acid, is brought to 22° C. by cooling coils of brine, and pure glycerine is injected into the acid at such a rate that no glycerine accumulates unchanged, and that the temperature is kept between 15° and 22° C. When all the glycerine has been added, the liquid is allowed to stand, and the nitroglycerine rises to the surface. It is run off to the wash-house, where it is washed free from acid and settled. The process is a dangerous one, and great care must be taken at every stage of the manufacture. The floors of the plant must be free from grit and dirt, no accumulation of liquid should be allowed anywhere, special clothing and rubber boots must be worn, no metallic implements may be used, and the plant should not be handed over for repairs except under the supervision of a responsible person. Nitroglycerine, when absorbed in a porous earth called 'Kieselguhr', is called dynamite. Kieselguhr, or simply guhr, absorbs twice its weight of nitroglycerine; cork charcoal absorbs nine times its weight. Dynamite cartridges are generally exploded by detonators.

Preparation of Cordite; Nitrocellulose Tape (N.C.T.); Ballistite; &c.—For cordite, the nitrocotton, freed from moisture, is mixed with nitroglycerine, and the paste or the cotton itself, if N.C.T. is to be made, is incorporated into a uniform dough with ether and alcohol. Some mineral jelly is added to render the explosive more stable. The dough is pressed through different sizes of dies according to the product desired. For rifle powder fine cords are used; for artillery, thicker cords or flat ribbons of varying thicknesses are required. The cords or tapes from the dies are cut into suitable lengths, the solvents driven off, and the products blended to obtain uniform ballistic quality. For ballistite the nitrocellulose is beaten up with nitroglycerine in water. The paste is freed from water, dried, and worked into horn-like sheets by means of rollers.

High Explosives; Picric Acid.—At the outbreak of the European War the chief high explosive of the Entente Powers was lyddite (in France, mélenite), also called trinitrophenol or picric acid. It is a bright-yellow solid, melting-point 122° C., sparingly soluble in water, and forms easily exploded metallic salts. It is now displaced by trinitrotoluene. Picric acid is made from phenol or carbolic acid. Phenol is obtained from coal-tar, or made synthetically from benzene. The phenol is sulphonated with strong sulphuric acid, and the phenol-sulphonic acid resulting is nitrated with strong nitric acid at about 100° C. Picric acid separates, and is washed free from mineral acid and dried. It may also be made from benzene without converting it into phenol thus: The benzene is chlorinated and gives chlorbenzene. This is nitrated into dinitrochlorbenzene, and is then treated with caustic soda to give dinitrophenol. This is then further nitrated into trinitrophenol or picric acid. Picric acid has a high melting-point, it must be used pure, is dissolved by water, it attacks metalsforming dangerous compounds, and requires troublesome plant for its manufacture. Hence it has been displaced by more suitable substances, notably by trinitrotoluene.

Trinitrotoluene(T.N.T.).—This compound may now be made in a continuous plant. Mononitrotoluene is put in at one end of the plant and comes out as trinitrotoluene. Mixed nitric and sulphuric acid is put in at the end where the T.N.T. is obtained, and emerges, where mononitrotoluene is put in, as waste acid. T.N.T. in the past has also been made discontinuously thus: The toluene is nitrated by mixed acid into either mono- or dinitrotoluene, which is then trinitrated. The conversion into mononitrotoluene was used in the United Kingdom, France, Germany, Canada, and America; the conversion into dinitrotoluene was used in Italy. The T.N.T. emerges liquid, and is passed over a rotating drum internally cold water cooled. A knife strips the thin congealed skin of T.N.T. off. This T.N.T. is only grade 3, and for conversion into grade 1 it must be purified. Formerly this was done by means of an organic solvent, but this dangerous and expensive method has been displaced by treatment either with phenol or sodium sulphite, which gives a grade 1 product. T.N.T. is a very pale yellow solid, melting-point 80.2° C., and therefore, melted by hot water, almost insoluble in water, burns quickly in the air, is inert, and comparatively safe to handle. It has displaced picric acid owing to its superiority, physically and chemically, over that substance.

Tetryl or C.E.(Composition Exploding).—Tetryl, also called tetranitrodimethylaniline, or more correctly trinitrophenylmethylnitramine, is a powerful high explosive, and is thus obtained. One part of dimethylaniline is dissolved in 10 parts of strong sulphuric acid, and the solution allowed to flow into strong nitric acid. The temperature should be kept below 40° C., else decomposition may occur. After nitration the yellow tetryl separates out, and is filtered off and water-washed till free from acid. It is then dried in hot-air stoves. Tetryl is much more dangerous than T.N.T., and is also more poisonous to handle. No other nitro-bodies were made in England on the large scale during the European War, but on the Continent, owing to the scarcity of raw materials, dinitrobenzene, dinitrotoluene, and nitronaphthalenes, and even less important nitro-bodies, were made. Their manufacture is similar to that of those already described. Probably none of these nitro-bodies so pressed into use is as good as T.N.T.

Detonating Substances.—Though modern explosives are not easily exploded by a blow, they are sensitive to shock of given intensity, and lesser or different shocks will not suffice. The 'detonator' to produce the shock is set into the explosive. A complete shell carries two detonators. One, in the percussion cap, sets off the propellant charge which expels the projectile; the other, in the fuse in the nose of the shell, is ignited by the discharge of the gun, and detonates the high-explosive filling at a set interval after the discharge of the shell. Therefore, the shell can be exploded either in its flight when it is used as shrapnel shell, or on its arrival at its objective when it can be used for small-calibre artillery shell for field-guns, &c., or after its arrival when it is used for heavy howitzer and armour-piercing shell for destroying entrenched works, armoured forts, or ships. The manufacture of detonators is a very dangerous and delicate operation. Some substances (the copper acetylides) explode by a scratch, some (nitrogen iodide) by the touch of a feather or the tread of a fly, some explode even in solution when poured from one vessel into another (diazobenzeneperchlorates). Mercury fulminate is more often employed in the detonator, and is prepared from mercury, alcohol, and nitric acid. It is expensive, and most modern detonators consist of lead azide or salts of styphnic acid, with a layer of T.N.T. in a narrow aluminium cylinder.

The following is a list of the more important explosives, the different groups not being mutually exclusive:—

Coal-mine Explosives

American.

Aetna Coal-mine Powder A, B, C: nitroglycerine explosive.Black Diamond: 2A, 3A, 6L.F are nitroglycerine explosives; 5, 7, 8, ammonium nitrate explosives.Carbonite: nitroglycerine 26, barium nitrate 4, potassium nitrate 29, wood-meal or starch flour 40, calcium carbonate 0.25.Du Pont Permissible: nitroglycerine, ammonium nitrate, common salt.Eureka: nitroglycerine and hydrated salt.Monobel: ammonium nitrate, nitroglycerine, wood-meal, alkali chloride.Red H1-7: ammonium nitrate explosives.Trogan Coal Powder: contains nitrostarch.

Aetna Coal-mine Powder A, B, C: nitroglycerine explosive.

Black Diamond: 2A, 3A, 6L.F are nitroglycerine explosives; 5, 7, 8, ammonium nitrate explosives.

Carbonite: nitroglycerine 26, barium nitrate 4, potassium nitrate 29, wood-meal or starch flour 40, calcium carbonate 0.25.

Du Pont Permissible: nitroglycerine, ammonium nitrate, common salt.

Eureka: nitroglycerine and hydrated salt.

Monobel: ammonium nitrate, nitroglycerine, wood-meal, alkali chloride.

Red H1-7: ammonium nitrate explosives.

Trogan Coal Powder: contains nitrostarch.

Austrian and Hungarian.

Chloratit: during war was used in coal-mines.Dynammon: ammonium nitrate, potassium nitrate, red charcoal.Pannomite: nitroglycerine, collodion cotton, ammonium nitrate, dextrin, glycerine, nitrotoluene, alkali chloride.Titanite: Ammonium nitrate, trinitrotoluene, curcuma charcoal.

Chloratit: during war was used in coal-mines.

Dynammon: ammonium nitrate, potassium nitrate, red charcoal.

Pannomite: nitroglycerine, collodion cotton, ammonium nitrate, dextrin, glycerine, nitrotoluene, alkali chloride.

Titanite: Ammonium nitrate, trinitrotoluene, curcuma charcoal.

Belgian.

Alsilite: ammonium nitrate, trinitrotoluene, ferrosilicon-aluminium, salt.Baellnite: ammonium-nitrate, trinitrotoluene.Densite: alkaline nitrates, trinitrotoluene, dinitrotoluene, and ammonium chloride.Favier Explosives: mixtures in varying proportions containing ammonium nitrate, nitronaphthalene, paraffin, and resin; higher nitrated naphthalenes, potassium nitrate, and tetryl may be present. Manufactured by the French Government as Explosifs N or Favier or Grisounites. Grisounites-couche for coal-mines have theoretical explosion temperatures of 1500° C., Grisounites-roche of 1900° C. Ammonite, Westfalite, Bellite, Roburite are explosives of this type; other ammonites, Bellite Nos. 2 and 4, Faversham powder, and negro powder have ammonium or sodium chloride added.

Alsilite: ammonium nitrate, trinitrotoluene, ferrosilicon-aluminium, salt.

Baellnite: ammonium-nitrate, trinitrotoluene.

Densite: alkaline nitrates, trinitrotoluene, dinitrotoluene, and ammonium chloride.

Favier Explosives: mixtures in varying proportions containing ammonium nitrate, nitronaphthalene, paraffin, and resin; higher nitrated naphthalenes, potassium nitrate, and tetryl may be present. Manufactured by the French Government as Explosifs N or Favier or Grisounites. Grisounites-couche for coal-mines have theoretical explosion temperatures of 1500° C., Grisounites-roche of 1900° C. Ammonite, Westfalite, Bellite, Roburite are explosives of this type; other ammonites, Bellite Nos. 2 and 4, Faversham powder, and negro powder have ammonium or sodium chloride added.

British.

Ammonite: Favier type; ammonium nitrate 75, dinitronaphthalene or other nitro-body, salt 20.Bellite: ammonium nitrate and metadinitrobenzene; salt and starch may be added.Bobbinite: the only gunpowder explosive allowed in England, not allowed in foreign mines; alkali nitrate, carbohydrates, wax may be added. Shatters coal less than high explosives.Cambrite: a Nobel carbonite plus 8 per cent of a cooling agent.Denaby Powder: ammonium nitrate, alkali nitrate, T.N.T., ammonium chloride.Dynobel: nitroglycerine 15, collodion cotton 0.5, nitro-body 3, ammonium nitrate 46, wood-meal 5.5, salt 29.5, magnesium carbonate 0.5. Limit charge, 18 to 30 ounces. Swing of ballistic pendulum, 2.35 inches.Monarkite: ammonium and sodium nitrate, nitroglycerine, nitrocotton, starch, mineral jelly, salt.Monobel: ammonium nitrate, nitroglycerine, wood-meal, salt, alkali chloride, magnesium carbonate; nitro-body may be present.Negro Powder: Grisounite type; ammonium nitrate 88, T.N.T. 10, graphite 2.Rex Powder: nitroglycerine 12, salt 20, wood-meal 8, ammonium nitrate 60. Charge, 20 ounces. Swing of pendulum, 2.61 inches.Rippite (Super): nitroglycerine, nitrocotton, potassium nitrate, borax, alkali chloride.Roburite: ammonium nitrate 61, T.N.T. 16, salt 23.Stomonal: nitroglycerine, ammonium nitrate, sodium nitrate, wood-meal, wheat-flour, salt, ammonium oxalate.Thames Powder. Similar to above.

Ammonite: Favier type; ammonium nitrate 75, dinitronaphthalene or other nitro-body, salt 20.

Bellite: ammonium nitrate and metadinitrobenzene; salt and starch may be added.

Bobbinite: the only gunpowder explosive allowed in England, not allowed in foreign mines; alkali nitrate, carbohydrates, wax may be added. Shatters coal less than high explosives.

Cambrite: a Nobel carbonite plus 8 per cent of a cooling agent.

Denaby Powder: ammonium nitrate, alkali nitrate, T.N.T., ammonium chloride.

Dynobel: nitroglycerine 15, collodion cotton 0.5, nitro-body 3, ammonium nitrate 46, wood-meal 5.5, salt 29.5, magnesium carbonate 0.5. Limit charge, 18 to 30 ounces. Swing of ballistic pendulum, 2.35 inches.

Monarkite: ammonium and sodium nitrate, nitroglycerine, nitrocotton, starch, mineral jelly, salt.

Monobel: ammonium nitrate, nitroglycerine, wood-meal, salt, alkali chloride, magnesium carbonate; nitro-body may be present.

Negro Powder: Grisounite type; ammonium nitrate 88, T.N.T. 10, graphite 2.

Rex Powder: nitroglycerine 12, salt 20, wood-meal 8, ammonium nitrate 60. Charge, 20 ounces. Swing of pendulum, 2.61 inches.

Rippite (Super): nitroglycerine, nitrocotton, potassium nitrate, borax, alkali chloride.

Roburite: ammonium nitrate 61, T.N.T. 16, salt 23.

Stomonal: nitroglycerine, ammonium nitrate, sodium nitrate, wood-meal, wheat-flour, salt, ammonium oxalate.

Thames Powder. Similar to above.

Danish.

Aerolite: ammonium nitrate 78.1 per cent, potassium nitrate 7.5 per cent, sulphur 8.75 per cent, tar 2.5 per cent, sago-meal 1.25 per cent, manganese dioxide 1.25 per cent, resin 0.6 per cent.Poudre Blanche Cornil: ammonium nitrate, alkali nitrate, nitronaphthalene, lead chromate.

Aerolite: ammonium nitrate 78.1 per cent, potassium nitrate 7.5 per cent, sulphur 8.75 per cent, tar 2.5 per cent, sago-meal 1.25 per cent, manganese dioxide 1.25 per cent, resin 0.6 per cent.

Poudre Blanche Cornil: ammonium nitrate, alkali nitrate, nitronaphthalene, lead chromate.

French.

Favier Explosives. See underBelgianexplosives.Grisounite. As above.Grisoutine or Grisou Dynamite. It is a mixture of ammonium nitrate and blasting gelatine. It is the only explosive except Grisounite allowed in the more dangerous French mines.Naphthalite (Grisou): potassium chlorate 80 per cent, aryl hydrocarbons, 12 per cent nitrocompounds not trinitro-bodies, paraffin, fatty oils, flour and other organic substances. May contain alkali chlorides and up to 4 per cent blasting gelatine.

Favier Explosives. See underBelgianexplosives.

Grisounite. As above.

Grisoutine or Grisou Dynamite. It is a mixture of ammonium nitrate and blasting gelatine. It is the only explosive except Grisounite allowed in the more dangerous French mines.

Naphthalite (Grisou): potassium chlorate 80 per cent, aryl hydrocarbons, 12 per cent nitrocompounds not trinitro-bodies, paraffin, fatty oils, flour and other organic substances. May contain alkali chlorides and up to 4 per cent blasting gelatine.

German.

Albit (Wetter): a chlorate explosive replacing nitrates; scarce during the war.Astralit (Wetter): ammonium nitrate explosive containing some blasting gelatine. Many varieties, which may also contain rape-oil and potato-meal. Has been used in trench howitzers.Carbonit. Numerous compositions come under this name and are made in different countries. Consists chiefly of nitroglycerine and metallic nitrates. Arctic carbonite, a low-freezing mixture, contains 15.5 per cent nitroglycerine, 10.5 per cent nitrohydrocarbon, 42 per cent potassium nitrate, 31.7 per cent wood-meal, and 0.3 per cent calcium carbonate.Chloratzit: potassium chlorate or perchlorate, aryl nitro-bodies, resins, and carbohydrates. For coal-mines add cooling agents.Detonit: ammonium nitrate, charcoal, meal, 4 per cent blasting gelatine, neutral salts.Donarit: ammonium nitrate 80 per cent, trinitrotoluene 12 per cent, rye-flour 4 per cent, nitroglycerine 4 per cent. The standard in Germany for sensitiveness of ammonium nitrate explosives.Dorfit: ammonium nitrate, trinitrotoluene, flour, salt, alkali nitrate.Dynamit: nitroglycerine 75 per cent, Kieselguhr 25 per cent.Gehlingerit: ammonium nitrate, trinitrotoluene, flour.Permonit: a perchlorate explosive.Tremonit: contains gelatinized dinitroglycerine, pea-flour, and salt.

Albit (Wetter): a chlorate explosive replacing nitrates; scarce during the war.

Astralit (Wetter): ammonium nitrate explosive containing some blasting gelatine. Many varieties, which may also contain rape-oil and potato-meal. Has been used in trench howitzers.

Carbonit. Numerous compositions come under this name and are made in different countries. Consists chiefly of nitroglycerine and metallic nitrates. Arctic carbonite, a low-freezing mixture, contains 15.5 per cent nitroglycerine, 10.5 per cent nitrohydrocarbon, 42 per cent potassium nitrate, 31.7 per cent wood-meal, and 0.3 per cent calcium carbonate.

Chloratzit: potassium chlorate or perchlorate, aryl nitro-bodies, resins, and carbohydrates. For coal-mines add cooling agents.

Detonit: ammonium nitrate, charcoal, meal, 4 per cent blasting gelatine, neutral salts.

Donarit: ammonium nitrate 80 per cent, trinitrotoluene 12 per cent, rye-flour 4 per cent, nitroglycerine 4 per cent. The standard in Germany for sensitiveness of ammonium nitrate explosives.

Dorfit: ammonium nitrate, trinitrotoluene, flour, salt, alkali nitrate.

Dynamit: nitroglycerine 75 per cent, Kieselguhr 25 per cent.

Gehlingerit: ammonium nitrate, trinitrotoluene, flour.

Permonit: a perchlorate explosive.

Tremonit: contains gelatinized dinitroglycerine, pea-flour, and salt.

Some Blasting Explosives

Ammonal: ammonium nitrate 80 to 90 per cent, aluminium 4 to 18 per cent, charcoal 2 to 6 per cent. The more violent mixtures contain some trinitrotoluene in addition. Has been used in grenades and by Austrians in trench-howitzer bombs. Not suitable in underground workings owing to poisonous gases evolved.Astralit: a mixture of ammonium nitrate and blasting gelatine. May contain wood-meal, trinitrotoluene, paraffin-oil. Has been used for projectiles.Carbodynamite: nitroglycerine absorbed in cork charcoal instead of guhr.Gelignite: nitroglycerine 56 to 63 per cent, nitrocotton 4 per cent, wood-meal 7 per cent, potassium nitrate 27 per cent, calcium carbonate 0.2 per cent.Oxyliquit: liquid oxygen absorbed in a porous combustible material. Used in construction of Simplon Tunnel. Very cheap; safe after misfire because oxygen evaporates off.Perdit: German mining, demolition, and rifle grenade explosive. Ammonium nitrate 76 per cent, potassium perchlorate 6 per cent, wood-meal 2 per cent, dinitrotoluene 16 per cent.Rendarock: a brand of American dynamite.Sprengel Explosives: one or both of the substances to be liquid, and mixing to occur shortly before firing. Nitric acid, alkali chloride, nitrogen peroxide on nitrobenzene, nitronaphthalene, carbon bisulphide, petrol, picric acid. Panclastite, Prométhée, Rack-a-Rock, are examples of this class.Tonite: gun-cotton and barium nitrate.

Ammonal: ammonium nitrate 80 to 90 per cent, aluminium 4 to 18 per cent, charcoal 2 to 6 per cent. The more violent mixtures contain some trinitrotoluene in addition. Has been used in grenades and by Austrians in trench-howitzer bombs. Not suitable in underground workings owing to poisonous gases evolved.

Astralit: a mixture of ammonium nitrate and blasting gelatine. May contain wood-meal, trinitrotoluene, paraffin-oil. Has been used for projectiles.

Carbodynamite: nitroglycerine absorbed in cork charcoal instead of guhr.

Gelignite: nitroglycerine 56 to 63 per cent, nitrocotton 4 per cent, wood-meal 7 per cent, potassium nitrate 27 per cent, calcium carbonate 0.2 per cent.

Oxyliquit: liquid oxygen absorbed in a porous combustible material. Used in construction of Simplon Tunnel. Very cheap; safe after misfire because oxygen evaporates off.

Perdit: German mining, demolition, and rifle grenade explosive. Ammonium nitrate 76 per cent, potassium perchlorate 6 per cent, wood-meal 2 per cent, dinitrotoluene 16 per cent.

Rendarock: a brand of American dynamite.

Sprengel Explosives: one or both of the substances to be liquid, and mixing to occur shortly before firing. Nitric acid, alkali chloride, nitrogen peroxide on nitrobenzene, nitronaphthalene, carbon bisulphide, petrol, picric acid. Panclastite, Prométhée, Rack-a-Rock, are examples of this class.

Tonite: gun-cotton and barium nitrate.

Some High Explosives

Alumtol: ammonium nitrate, trinitrotoluene, aluminium powder. Used for trench mortars, bombs, &c.Amatol: a mixture of ammonium nitrate and trinitrotoluene, used for shell-filling. Called by Germans Füllpulver. The Germans did not develop this explosive as much as the Entente Powers, who effected great economy of trinitrotoluene.Blastine: ammonium perchlorate, sodium nitrate, dinitrotoluene, paraffin-wax. It evolves hydrochloric acid gas.Blasting gelatine contains 93 per cent nitroglycerine and 7 per cent nitrocotton. It is the most powerful explosive in common use.Crèsylite is a French explosive, and contains picric acid and nitrated cresol.Fumyl is a smoke-producing explosive, and contains trinitrotoluene and ammonium chloride. It was used to open poison-gas shells.Granatfülling (Shell Filling): a term used by the Germans.Granatfülling C/84 is picric acid.Granatfülling C/02 is trinitrotoluene.Other substances were used by them for shell filling, such as trinitroanisole, dinitrobenzene, hexanitrodiphenylamine, and hexanitrophenylsulphide.Lyddite: a term for picric acid formerly used in shells.T.N.T. is trinitrotoluene or trotyl.Toxol is a mixture of trinitrotoluene and trinitroxylene.Triplastite is a plastic high explosive containing 70 per cent nitrotoluenes, 8 per cent nitrocotton, 29 per cent lead nitrate. Used for shell filling.

Alumtol: ammonium nitrate, trinitrotoluene, aluminium powder. Used for trench mortars, bombs, &c.

Amatol: a mixture of ammonium nitrate and trinitrotoluene, used for shell-filling. Called by Germans Füllpulver. The Germans did not develop this explosive as much as the Entente Powers, who effected great economy of trinitrotoluene.

Blastine: ammonium perchlorate, sodium nitrate, dinitrotoluene, paraffin-wax. It evolves hydrochloric acid gas.

Blasting gelatine contains 93 per cent nitroglycerine and 7 per cent nitrocotton. It is the most powerful explosive in common use.

Crèsylite is a French explosive, and contains picric acid and nitrated cresol.

Fumyl is a smoke-producing explosive, and contains trinitrotoluene and ammonium chloride. It was used to open poison-gas shells.

Granatfülling (Shell Filling): a term used by the Germans.

Granatfülling C/84 is picric acid.

Granatfülling C/02 is trinitrotoluene.

Other substances were used by them for shell filling, such as trinitroanisole, dinitrobenzene, hexanitrodiphenylamine, and hexanitrophenylsulphide.

Lyddite: a term for picric acid formerly used in shells.

T.N.T. is trinitrotoluene or trotyl.

Toxol is a mixture of trinitrotoluene and trinitroxylene.

Triplastite is a plastic high explosive containing 70 per cent nitrotoluenes, 8 per cent nitrocotton, 29 per cent lead nitrate. Used for shell filling.

Some Miscellaneous Explosives

Anilite: Sprengel type. French liquid explosive used in aerial bombs.Centralite: not an explosive but a stabilizer and regulator. It is dimethyldiphenylurea.Collodion Cotton: low nitralion nitrocotton, soluble in a mixture of ether and alcohol. It dissolves in nitroglycerine and liquid nitro-body, preventing their exudation.Gelatine Dynamite: a mixture of blasting gelatine with potassium nitrate and wood-meal. It may also contain calcium and magnesium carbonate and mineral jelly.Gelignite is similar to Gelatine Dynamite, but contains less Blasting Gelatine.Halakite: contains potassium chlorate, ammonium nitrate, trinitrotoluene or other nitro-body; may contain nitrocotton, sodium nitrate, and wood-meal.Pyrocollodion: highly nitrated, soluble gun-cotton. Adopted by the United States.White Gunpowder: a mixture of potassium chlorate, potassium ferrocyanide, and sugar. Very sensitve, and only used in the laboratory.

Anilite: Sprengel type. French liquid explosive used in aerial bombs.

Centralite: not an explosive but a stabilizer and regulator. It is dimethyldiphenylurea.

Collodion Cotton: low nitralion nitrocotton, soluble in a mixture of ether and alcohol. It dissolves in nitroglycerine and liquid nitro-body, preventing their exudation.

Gelatine Dynamite: a mixture of blasting gelatine with potassium nitrate and wood-meal. It may also contain calcium and magnesium carbonate and mineral jelly.

Gelignite is similar to Gelatine Dynamite, but contains less Blasting Gelatine.

Halakite: contains potassium chlorate, ammonium nitrate, trinitrotoluene or other nitro-body; may contain nitrocotton, sodium nitrate, and wood-meal.

Pyrocollodion: highly nitrated, soluble gun-cotton. Adopted by the United States.

White Gunpowder: a mixture of potassium chlorate, potassium ferrocyanide, and sugar. Very sensitve, and only used in the laboratory.

Propellants for Shot-guns

Amberite: insoluble nitrocotton 18.6 per cent, nitrates 28 per cent, soluble nitrocotton 46 per cent, vaseline 6 per cent.Du Pont Smokeless Powder: nitroglycerine 10 per cent, ammonium nitrate 67.5 per cent, wood-pulp 8 per cent, salt 15 per cent (for coal-mines). Soluble nitrocotton 46 per cent, metallic nitrates 2.2 per cent (for shot-guns).E.C. Powder: insoluble nitrocotton 44 per cent to 48 per cent (Empire Powder), soluble nitrocotton 30 per cent to 34 per cent, metallic nitrates 14 per cent to 9 per cent, vaseline 6 per cent to 7 per cent, camphor 4.6 per cent.Ideal Powder: made by Nobels.Neonite. Similar to the above compositions, but containing 73 per cent of insoluble nitrocotton, 9 per cent soluble nitrocotton. It is also made for rifled small-arms especially for rim-fire rifles.New Explosives Company Smokeless Powder. Similar to above.Rifleite: insoluble nitrocotton 1.7 per cent, soluble nitrocotton 82.5 per cent, nitro-body 4.8 per cent. The nitrocellulose is made from curcuma.Ruby Powder: a cheap non-solvent powder, 46 per cent insoluble nitrocotton, 4 per cent soluble nitrocotton.Smokeless Diamond and Stoumarkel Smokeless are similar to above.

Amberite: insoluble nitrocotton 18.6 per cent, nitrates 28 per cent, soluble nitrocotton 46 per cent, vaseline 6 per cent.

Du Pont Smokeless Powder: nitroglycerine 10 per cent, ammonium nitrate 67.5 per cent, wood-pulp 8 per cent, salt 15 per cent (for coal-mines). Soluble nitrocotton 46 per cent, metallic nitrates 2.2 per cent (for shot-guns).

E.C. Powder: insoluble nitrocotton 44 per cent to 48 per cent (Empire Powder), soluble nitrocotton 30 per cent to 34 per cent, metallic nitrates 14 per cent to 9 per cent, vaseline 6 per cent to 7 per cent, camphor 4.6 per cent.

Ideal Powder: made by Nobels.

Neonite. Similar to the above compositions, but containing 73 per cent of insoluble nitrocotton, 9 per cent soluble nitrocotton. It is also made for rifled small-arms especially for rim-fire rifles.

New Explosives Company Smokeless Powder. Similar to above.

Rifleite: insoluble nitrocotton 1.7 per cent, soluble nitrocotton 82.5 per cent, nitro-body 4.8 per cent. The nitrocellulose is made from curcuma.

Ruby Powder: a cheap non-solvent powder, 46 per cent insoluble nitrocotton, 4 per cent soluble nitrocotton.

Smokeless Diamond and Stoumarkel Smokeless are similar to above.

Propellants for Rifled Fire-arms

Amide Powder: ammonium nitrate, potassium nitrate, charcoal. Has also been used in German artillery.Ammonpulver: ammonium nitrate and charcoal. Has been used by Austrian artillery, and lately reintroduced by the Germans.Ballistite: equal parts of nitroglycerine and soluble nitrocotton with some mineral jelly.Cordite: the principal smokeless powder of the British Empire.Indurite: gun-cotton and nitrobenzene. Abandoned by U.S. navy.Neonite: a gelatinized powder. Contains nitrocellulose insoluble and soluble, metallic nitrates, and vaseline.Noddite: a strip sporting-rifle powder containing nitroglycerine, nitrocellulose, mineral jelly.Rottweil Smokeless Powder: a gelatined powder containing camphor and diphenylamine.

Amide Powder: ammonium nitrate, potassium nitrate, charcoal. Has also been used in German artillery.

Ammonpulver: ammonium nitrate and charcoal. Has been used by Austrian artillery, and lately reintroduced by the Germans.

Ballistite: equal parts of nitroglycerine and soluble nitrocotton with some mineral jelly.

Cordite: the principal smokeless powder of the British Empire.

Indurite: gun-cotton and nitrobenzene. Abandoned by U.S. navy.

Neonite: a gelatinized powder. Contains nitrocellulose insoluble and soluble, metallic nitrates, and vaseline.

Noddite: a strip sporting-rifle powder containing nitroglycerine, nitrocellulose, mineral jelly.

Rottweil Smokeless Powder: a gelatined powder containing camphor and diphenylamine.

See alsoGrenade;Shell;Torpedo;Fireworks;Rockets.

Expo´nent.In algebraa3denotes threea's multiplied together;anmeans thatnof the letteraare to be multiplied. These numbers or letters placed immediately above and to the right of another number or letter are called exponents, and indicate the power to which the number or letter is raised. Exponents can be fractional or negative, in which case new interpretations can be found. On the assumption thatam×an=am+nfor all values ofmandn,a1/nis interpreted as thenth root ofa,a-nas the reciprocal ofan.

Exponential Theorem.Ifax= N,xis said to be the logarithm of N to the basea. There are two bases of logarithms in common use, the base 10 and the Napierian basee. The exponential theorem states that the value ofexis given by the infinite series 1 +x+x2/(1.2) +x3/(1.2.3) + ... +xn/(1.2.3..n) +, &c. Puttingxequal to 1,e= 1 + 1 + 1/(1.2) + 1/(1.2.3) + 1/(1.2.3.4) +, &c.ecan be expressed to any number of decimal places by working out the value of the terms on the right-hand side. It is an incommensurable number which to five decimal places is equal to 2.71828. SeeLogarithm.

Exports.SeeForeign Trade.

Ex Post Facto, in law, a term designating something as done after and bearing upon something previously done; thus a law is said to beex post facto, or retrospective, when it is enacted to punish an offence committed before the passing of the law.

Exposure, the situation of a building, &c., with respect to sun and wind; 'aspect' with regard to the quarter of the heavens. A house facing south-west or south-east will be found much healthier than one facing due north; and as it is also warmer, less fuel will be required for heating purposes.

Expressed Oils, in chemistry, are those which are obtainable from bodies only by pressing, to distinguish them from mineral and essential oils, which last are, for the most part, obtained by distillation.

Extension, (1) in physics and metaphysics, that property of a body in virtue of which it occupies a portion of space. (2) In logic,extensionis the extent of the application of a general term, that is, the objects collectively which are included under it; thus, the word figure is more extensive than triangle, circle, or parallelogram; European more extensive than French, Frenchman, German, &c. Matter and mind are the most extensive terms of which any definite conception can be formed. Extension is contrasted withcomprehensionorintension.—Cf. Titchner,Text-Book of Psychology.

Extincteur(eks-tan-teur), an apparatus for the extinction of fire, consisting of a metallic case containing water and materials for generating carbonic acid. When required, the materials are brought into contact by pushing a rod which breaks a bottle containing acid, the gas mixes with the water, and the pressure generated is sufficient to project the water charged with the gas to a distance of 40 or 50 feet.

Ex´tract, a term to denote all that can be dissolved out of a substance by a specified menstruum, such as water, alcohol, ether, &c. In modern pharmacy the term is applied to two kinds of preparation from vegetables. One is got by digesting the plant in water or other solvent, and evaporating or distilling away the excess of solvent until the extracted matter is sufficiently inspissated. The other is got by bruising the plant in a mortar, separating the juice, warming it until the green colouring-matter separates, and filtering it off. The juice is next heated until the albumen coagulates, and again filtered. The juice is now evaporated to asyrup, the green colouring-matter added and well mixed, and the evaporation is thereafter continued until the required concentration is attained. Extracts must be capable of being redissolved, so as to form a solution like that from which they were derived. Extracts are used in cookery, medicine, and the manufacture of perfumery.—Extract of Meat(extractum carnis) is a soft, yellowish-brown solid, or very thick syrup, which is employed as a portable soup. It is now manufactured on the large scale by processes proposed by Liebig.

Extradi´tion(Lat.ex, out, andtradere, to hand over), the act by which a person accused of a crime is given up by the Government in whose territories he has taken refuge to the Government of which he is a subject. Conventions have been entered into by Britain with almost all civilized countries for the apprehension and extradition of persons charged with particular offences, especially those of the most heinous stamp, such as murder, robbery, embezzlement, arson, rape, and piracy. The Extradition Act of 1870 makes special provision that no criminal shall be surrendered for a political offence, and that the criminal shall not be tried for any but the crime for which he was demanded. Other British Extradition Acts are those of 1873, 1895, and 1906. SeeInternational Law.—Cf. Sir E. Clarke,The Law of Extradition.

Extravagan´za, in music or the drama, a species of composition designed to produce effect by its wild irregularity and incoherence; differing from a burlesque in being an original composition and not a mere travesty.

Extravasa´tion(Lat.extra, beyond, andvas, vessel), an escape of some fluid, as blood or urine, from the vessel containing it.Blood extravasation, in contusions and other accidents, is when blood-vessels are ruptured by the injury, and the blood finds its way into the neighbouring tissues. In some accidents to the urethra and bladder extravasation of urine is a very serious occurrence.

Extreme Unctionhas been, since an early period, one of the seven sacraments of the Roman Catholic Church. It is performed in cases of mortal disease by anointing in the form of a cross, the eyes, ears, nose, mouth, hands, feet, and reins (in the case of males). It is administered after confession and the eucharist, and is believed to remove the last stains of sin. It can only be administered by a bishop or priest, and is not applied in the case of young children or excommunicated persons.

Exu´ma, GreatandLittle, two of the Bahama Islands. The former is 30 miles long and 3 miles wide, and has a good harbour. Pop. 3465.

Eyalet(ī´a-let), a former administrative division of the Turkish Empire, subdivided into sanjaks or provinces, and kazas or districts. It was ruled by a pasha, and gave place to the vilayet on the reorganization of the empire in 1871.

Eyck(īk), Hubert and Jan van, brothers, famous painters of the old Flemish school, born at Maaseyck, Hubert in 1366, Jan probably about 1385. They lived first at Bruges, whence the younger brother is called John of Bruges, and afterwards at Ghent, to which they removed about 1420. Here they executed the celebratedAdoration of the Lambfor the Cathedral of Ghent; a painting which, in its different parts, contains above three hundred figures, and is a masterpiece. It was in two horizontal divisions, comprising ten panels, of which only the two central ones remain at Ghent, the others being at Berlin. Hubert did not live to see it completed. He died at Ghent (1426), as did also his sister Margaret, who was likewise a painter (1431). Jan finished the work in 1432, and returned to Bruges, where he remained till his death, which took place in 1441, and executed several excellent pieces. His reputation became very great even during his lifetime, by his share in the introduction of oil-painting; the original invention of which has been incorrectly ascribed to him by many. Jan van Eyck also introduced improvements in linear and aerial perspective, and in painting upon glass. Three portraits by Jan van Eyck,The Scholar,The Man with a Turban, andGiovanni Arnolfini and his Wife, are in the National Gallery, London; theMadonna of the Chancellor Rollinis in the Louvre.—Cf. W. H. J. Weale,John and Hubert van Eyck.

Eye, the organ of vision, is an instrument presenting some analogy to a photographic camera. It is provided with a lens for focussing images upon a sensitive membrane called theretina. The walls of the globe of the eye are formed principally of two fibrous membranes: one white and opaque—thesclerotic(Gr.sklēros, hard)—which envelops two-thirds of the globe posteriorly; and the other transparent, and resembling a horny plate, whence its name,cornea(Lat.corneus, horny). The sclerotic is a tough fibrous coat, and is the part to which the phrase 'white of the eye' is applied. In the front of the globe the sclerotic is abruptly transformed into the transparent portion (the cornea), which is circular, and which forms a window through which one can see into the interior. A membrane, theconjunctiva, so named because it unites the eye to the lid, spreads over the anterior portion of the globe, and then folds back on itself and lines the internal surface of the eyelids. On the internal surface of the sclerotic is a vascular membrane called thechoroid. This is essentially the blood-vessel coat of the eyeball. About the place where the sclerotic passesinto the cornea the choroid becomes continuous with theiris, a round curtain, the structure seen through the cornea, differently coloured in different individuals. In its centre is a round hole, thepupil, which appears as if it were a black spot. Theirisforms a diaphragm suspended in the space behind the cornea which is filled with clear fluid, theaqueous humour. Theirisconsists of a framework of connective tissue, and its posterior surface is lined by cells containing pigment which gives the colour to the eye. In its substance are bundles of involuntary muscular fibres, arranged in a ring round the margin of the pupil. In a bright light the circular fibres contract and the pupil is made smaller; but in the dark these fibres relax and allow the pupil to dilate more or less widely, thus allowing more luminous rays to enter the eye. Just behind the pupil is thecrystalline lens, resembling a small, very strongly magnifying glass, convex on each side, though more so behind. Minute bands of muscle in the choroid can alter the convexity of the lens, and thus adapt its focus to the position of objects at different distances. The large space in the globe of the eye that intervenes between the retina lining its inner surface and the lens in front is occupied by a transparent jelly-like mass called thevitreous body. The internal surface of the choroid, or rather the pigmentary layer which covers it, is lined by the retina or nervous tunic upon which the images of the objects that we see are focussed. The retina is a very complex mechanism consisting of certain elements which are stimulated by light, and others that transmit the effects of such stimulation as a nervous current to the optic nerve which carries it to the brain. It is composed of cones and cylinders orrods, joined together like the stakes of a palisade, perpendicular to the plane of the membrane, and forming by their free extremities a mosaic, each microscopic division of which is about 0.0008 of a line in diameter according to Helmholtz, and represents a section of a rod. These rods and cones are believed to be the agents by whose aid the waves of light become transformed into the stimulus of a sensation. The ocular globe is put in motion in the orbit by six muscles, grouped two by two, which raise or lower the eye, turn it inward or outward, or on its antero-posterior axis. In these movements the centre of the globe is immovable, and the eye moves round its transverse and vertical diameters. These three orders of movements are independent of each other, and may be made singly or in combination, in such a manner as to direct the pupil towards all points of the circumference of the orbit. Each eye is furnished with two eyelids, moved by muscles, which shield it from too much light and keep it from being injured. They are fringed with short, fine hairs called eyelashes; and along the edge of the lids is a row of glands similar to the sebaceous glands of the skin. The eyebrows, ridges of thickened integument and muscle, situated on the upper circumference of the orbit and covered with short hairs, also regulate to some extent the admission of light by muscular contraction. In reptiles, some fishes (sharks, &c.), in birds, and in some mammals a third eyelid or nictitating membrane is present, and can be drawn over the surface of the eye so as to clear it of foreign matters, and also to modify the light. The lachrymal apparatus is composed of, firstly, thelachrymal gland, which lies in a depression of the orbital arch; secondly, thelachrymal canals, by which the tears are poured out upon the conjunctiva a little above the border of the upper lid; thirdly, thelachrymal ducts, which are destined to receive the tears after they have bathed the eye, and of which the orifices orlachrymal pointsare seen near the internal ends of the lids; fourthly, thelachrymal sac, in which the lachrymal ducts terminate, that empties the tears into thenasal canal. The tears, by running over the surface of the conjunctiva, render it supple and facilitate the movements of the globe and eyelids by lessening the friction. The influence of moral or physical causes increases their secretion, and when the lachrymal ducts do not suffice to carry them off they run over the lids.

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