DidunculusDidunculus strigirostris
Didun´culus, a genus of birds allied to the pigeons, and comprising only the one species,D. strigirostris, native to some of the Samoan Islands. This bird is of special interest as being the nearest living ally of the extinct dodo. It has a length of about 14 inches, with a glossy plumage verging from a velvety black on the back to greenish black on the head, breast, and abdomen. The large beak, which is nearly aslong as the head, is greatly arched on the upper half, while the lower is furnished with two or three tooth-like indentations.
Didym´ium, a rare metallic element, occurring along withlanthanumin the mineral cerite as discovered by Mosander in 1842. It has been resolved into two new elements:Praseodymium(Pr, 140.9) andNeodymium(Nd, 144.3).
Die, a metallic stamp for impressing a design or figure upon coins or other metallic objects. SeeDiesandDie-sinking.
Die(dē), an ancient town, France, department of Drôme, 26 miles south-east of Valence; with an ancient cathedral and Roman remains. Pop. 4000.
Dié(di-ā),St., a town, France, department of Vosges, on the Meurthe, 25 milesE.N.E.of Epinal. Both iron and copper are worked; there are marble quarries; and numerous manufactures are carried on. Pop. 19,029.
Diebitsch-Sabalkanski, Hans Karl, a Russian general, born at Grossleippe, in Silesia, in 1785, died 9th June, 1831. He was educated at the military school of Berlin, but in 1801 quitted the Prussian service for that of Russia. He was present at the battles of Austerlitz and Friedland, served with distinction in the campaign of 1812, took part in the battles of Dresden and Leipzig, and was made lieutenant-general at the age of twenty-eight. He had the chief command in the Turkish War of 1828-9, stormed Varna, and made the famous passage of the Balkans, for which the surname of Sabalkanski was conferred on him. In 1830 he commanded the army sent against the revolted Poles, but did not distinguish himself in this service.—Cf. Bantych-Kamenski,Biographies of Russian Field-marshals.
Dieffenbach(dē´fen-ba˙h), Johann Friedrich, German surgeon, born at Königsberg in 1792, died in 1847. After having studied at Bonn and Paris, he settled in Berlin, where his talent as an operator soon attracted notice. Surgery is particularly indebted to him for new methods of forming artificial noses, eyelids, and lips, and curing squinting and stammering.
Diego Garcia.SeeChagos.
Di´electric, in electricity, a name applied by Faraday to any medium through or across which electrostatic induction can take place. SeeElectricity(Electrostatics). Faraday first showed that electrostatic induction was not action at a distance, but took place by means of the insulating medium separating the two conductors. The medium he named adielectric, and measured its specific inductive capacity by taking that of common air as unity.
Diëly´tra, orDicentra, a genus of plants, of the nat. ord. Fumariaceæ or Fumitories. The best known isD. spectabilis, a native of Northern China and Siberia, now common in European and other gardens. It blossoms in April and May, and its long drooping racemes of purplish-red blossoms present a very graceful appearance. It grows freely in the open air. It is sometimes called bleeding heart or virgin's heart from the shape of the blossoms.
Diemen(dē´men), Anton van, Dutch administrator, was born in 1593, died in 1645. Having gone to India, he speedily rose to the highest dignities, and was at length, in 1636, made Governor-General. He administered the government with much ability, and contributed much to the establishment of the Dutch commerce in India. Abel Tasman, whom he sent with a vessel to the South Seas in 1642, gave the name ofVan Diemen's Landto the island now called Tasmania.
Dieppe(dē-ep´), a seaport town, France, department of Seine-Inférieure, on the English Channel, at the embouchure of the Arques, 93 milesN.N.W.of Paris. Almost the only public edifices worth special notice are the two Gothic churches, St. Jacques, begun in the thirteenth century, and St. Rémi, founded in 1522, and the old castle (1433), now a barracks. To the west of Dieppe proper is the suburb La Barre; and on the opposite side of the harbour Le Pollet, inhabited chiefly by sailors and fishermen. The old port is spacious, but a new channel with its own harbour system has been added, and vessels of 20-foot draft can now enter. Dieppe is one of the chief watering-places of France, and is much frequented by visitors in summer and autumn. The great bathing establishment forms a luxurious retreat for bathers and invalids, and includes a ballroom. The manufactures include works in ivory, horn, and bone, lace-making, sugar-refining, and shipbuilding. There is a busy fishery, and the foreign trade is still considerable. There is constant steam intercourse between this port and Newhaven. In early times Dieppe was the chief port of France, but its prosperity diminished after the revocation of the Edict of Nantes (1685). During the European War Dieppe was an important Allied base. Pop. 23,973.
Dierx, Léon, French poet, born in the Island of Réunion in 1838. Educated in Paris, he became one of the foremost of the Parnassians. His works include:Aspirations,Poèmes et Poésies,La rencontre, andLes Amants. His collected poems (1889-90) were crowned by the Académie. He died in Paris, 11th June, 1912.
Dies and Die-sinking.Die-sinking is the art of preparing dies, a die being a plate or block, usually of metal, so cut or shaped as to be capable, by means of stamping or pressure, of transferring a given design to some article which is to be manufactured in quantity. Thepressure may be applied by any sort of power, from hand to hydraulic.
The steel for the manufacture of steel dies is carefully selected, forged at a high heat into the rough die, softened by careful annealing, and then handed over to the engraver. After the engraver has worked out the design in intaglio, the die is put through the operation of hardening, after which, being cleaned and polished, it is called amatrix. This is not, however, generally employed in multiplying impressions, but is used for making apunchor steel impression for relief. For this purpose another block of steel of the same quality is selected, and, being carefully annealed or softened, is compressed by proper machinery upon the matrix till it receives the impression. When this process is complete, the impression is retouched by the engraver, and hardened and collared like the matrix. Any number of dies may now be made from this punch by impressing upon it plugs of soft steel.
There is hardly any article which does not in the course of its manufacture require the use of a die of some kind. For all sorts of metal-work, seals, rings, silverware, moulds and shapes of sheet steel or tin, dies are employed. For this class of work they are usually of steel. For embossing articles of leather, wood, celluloid, rubber, cloth, or clay, dies of brass and phosphor-bronze are commonly used, these being easier media to work in and yet sufficiently strong. The dies for letter headings and company seals are cut, in reverse to the design required, in steel; those for sealing-wax seals in steel or brass; the lettering being usually punched in by hand by separate letter punches, which themselves have been cut in relief on steel. Designs which are unusually ornate may be engraved by hand. Dies for embossing designs on leather, catalogue covers, cardboard articles, cards, and soft materials are usually modelled in brass. The design in reverse is cut out to a depth corresponding to the relief wanted. These dies are usually worked up by hand by the engraver. Dies for the reproduction of rubber stamps for printing on clay are cut in phosphor-bronze or hard brass in relief and reverse, and with an extreme bevel. The dies or blocks are then struck deeply into lead, and melted rubber is poured into the moulds so formed. When set, the rubber is removed and mounted as a hand-stamp ready to impress the clay in ink. Dies for wallpapers are cut on rollers. Steel dies for flower-shapes have a cutting edge, so that they can stamp out and emboss in one action. Of late years machinery has come much into use for relieving the engraver of some of his labour, but the designs are generally kept secret. One machine, called the pantograph or engraving machine, reproduces engravings in all metals and many shapes from patterns. Many of the stamp-duty steel dies made and issued by the Royal Mint are reproduced from this machine in reductions from brass patterns.—Bibliography: Lucas,Dies and Die-making; J. V. Woodworth,Dies: their Construction and Use.
Diesel, Rudolph, German inventor, born in Paris in 1858, died in 1913. Educated in England and at Munich, he proposed in 1893 to utilize directly the energy created by the combustion of fuel, a proposal which led to his invention of the Diesel engine. (SeeInternal Combustion Engines.) In 1913 he was called to England to consult with the Admiralty on the application of his motor, but was drowned in crossing the Channel. In 1894 he published a monograph entitledTheory and Construction of a Rational Heat Motor.
Dies Fasti et Nefasti, a Roman division of days, with reference to judicial business, into working-days and holidays. Adies fastuswas a day on which courts and assemblies could be held and judgments pronounced; adies nefastus, a day on which courts could not be held nor judgments pronounced.
Dies Iræ(dī'es ī'rē), one of the great Latin hymns of the Mediæval Church, generally used as part of the requiem or mass for the souls of the dead. It describes, as its name ('the day of wrath') denotes, the Last Judgment of the world, and seems to have been suggested by the description inZephaniah, i, 15 and 16. It is supposed to have been written by Thomas da Celano, a Franciscan friar of the thirteenth century. It was translated by Crashaw and Dryden in the seventeenth century, and by Macaulay and others in the nineteenth, but none of these translations conveys the solemn force of the original.
Diest(dēst), a town, Belgium, province of Brabant, 32 milesE.N.E.of Brussels. It has some manufactures, but the chief products of the place are beer and gin, the former being largely exported. The town was occupied by the Germans in 1914, and re-entered by the Belgians in 1918. Pop. 8800.
Diesterweg, Friedrich Adolf Wilhelm, German educator, born in 1790, died in 1866. In 1820 he became director of the new Teachers' Seminary at Mörs, and soon gained a reputation as teacher and educator. He was a follower of Pestalozzi, and aimed at making every subject of instruction a means of education. In 1827 he founded theRheinische Blätter für Erziehung und Unterricht, wherein he advocated his pedagogical views.
Di'et, a meeting of some body of men held for deliberation or other purposes; a term especially applied to the legislative or administrative assemblies of Austria, Germany, and Poland.
Dietet'ics(Gr.diaita, daily regimen), thatpart of medicine which relates to the regulation of diet. The ideal diet is clearly that which, without burdening the viscera uselessly, furnishes all necessary nutritive elements, with due consideration for special physiological conditions in any given case. Under the head ofAlimentthe physiological properties of various foods have already been considered theoretically in respect of their capacity to supply physical waste in nitrogenous and non-nitrogenous matter. (SeeAliment.) No single substance contains the elements needed to replace this waste in their requisite proportions, and a mixed diet is therefore necessary. For instance, to secure the required amount of carbon a man would need to eat about 4 lb. of lean beef, while 1 lb. would yield all the nitrogen required; thus, apart from the labour of digesting 4 lb. of beef, the body would be compelled to get rid of the excess of nitrogen. Bread, on the other hand, has carbon in abundance, but is deficient in nitrogen; so that by uniting 2 lb. of bread with ¾ lb. of lean meat, the due proportion of carbon and nitrogen is satisfactorily supplied. Milk and oatmeal taken together also contain nitrogenous and non-nitrogenous substances in nearly the required proportions. A certain proportion of saline matter is also necessary. The nature of the food most suitable for a healthy man is dependent in part upon general conditions, such as climate and season, and in part upon special conditions of individual habit. The inhabitants of the Arctic regions need large quantities of oleaginous food; those of the Tropics live chiefly on starchy products. With increased activity and exertion, as in training, an increase in the nitrogenous foods becomes necessary. In a state of health we need not draw hairbreadth distinctions as to the superior salubrity of the several sorts of diet, the quantity rather than the quality of food being the main consideration. Those persons who have been most remarkable for health and long life have generally been contented with two moderate meals a day, which are certainly quite sufficient during a state of health. In various countries the breakfast generally consists of tea, coffee, or cocoa, with a certain proportion of bread and butter; persons with delicate digestive powers, or who lead a sedentary life, cannot with safety or comfort eat animal foodconstantlyto breakfast. At dinner all made-dishes highly spiced, such as curries, turtle-soup, &c., as provoking appetite, are hurtful; and the custom of late dining is not to be commended. Stewed and boiled meats are more difficult to digest than meat cooked by fire alone. The flesh of young animals seems to be more difficult of digestion than that of old; and the flesh of tame than that of wild animals. All sorts of fat meat must be taken in smaller quantities. Hence, also, ham, bacon, and salted meats cannot be eaten in such quantities as the tender flesh of poultry. Fish has the advantage of being easily soluble. All boiled vegetables are in general easy of digestion; raw vegetables and salads are rather more difficult. Fruit should be taken in the forenoon rather than after a hearty meal. The moderate use of fermented liquors is far from being invariably an evil, but the smaller the quantity habitually used the better in the majority of cases.
In all diseases attended with much fever or quickness of pulse the stomach loathes animal food, and there is generally a great increase of thirst, to quench which water, either quite cold, or iced, or tepid, or rendered acid, may be freely indulged. Infusions, too, of barley, sage, balm, &c., may be taken. In chronic diseases attended with hectic fever, milk is the most proper diet. The best food for infants is, of course, their mother's milk; but whenever they begin to cut teeth a little animal food, such as soft-boiled eggs, beef-tea, and even chicken minced very fine, may be given. Many infants suffer from having too much sugar given them in their food.—Bibliography: R. H. Chittenden,Physiological Economy in Nutrition, andNutrition of Man; Hutchison,Food and Dietetics; Lusk,The Science of Nutrition.
Dietrich(dē´trih), Christian Wilhelm Ernst, a German painter and engraver, born in 1712, died in 1774. He studied under his father, and afterwards under Alexander Thiele at Dresden, where he became court-painter and professor in the academy. He adopted several different manners, successfully imitating Raphael and Mieris, Correggio, and Ostade.
Dietrich of Bern(dē´trih), the name under which Theodoric the Great, King of the Ostrogoths, appears in the old German legends. Bern stands for Verona, his capital.
Dieu, orD'Yeu(dyeu; ancientInsula Dei), an island off the west coast of France, department of Vendée. It is inaccessible on the west side, but on the east has a tolerable harbour defended by batteries. The chief industry is fishing. There are four lighthouses on the island. Pop. 3809.
Dieu et Mon Droit(dyeue mon˙drwä; 'God and my right'), the battle-cry of Richard I at the battle of Gisors (1198), signifying that he was not subject to France, but owed his power to God alone. The battle-cry was then adopted as the motto of the arms of England, and revived by Edward III in 1340, when he claimed the crown of France. Except during the reigns of Elizabeth and Anne, who used the mottoSemper eadem, and of William III, who personally usedJe maintiendray, it has ever since been the royal motto of England.
Diez(dēts), Friedrich Christian, German philologist of the Romance languages, born in 1794, died in 1876. Having qualified himself as a lecturer at Bonn, he was appointed professor of the Romance languages there in 1830. His work stands in much the same relation to the Romance dialects which the researches of Grimm occupy with respect to German dialects. In addition to various works on the poetry of the Troubadours, he published a very valuableGrammatik der Romanischen Sprachen(1836-42, translated into English by Cayley in 1863), and anEtymologisches Wörterbuch der Romanischen Sprachen(1853).
Difference, a stock-exchange term. When stock is bought or sold merely as a speculation for the rise or fall, with no intention of the buyer to 'take up' the stock, or of the seller to deliver it, the 'difference' is the movement in price which may take place between the date of the transaction and the following 'settling-day'. If the price falls, the buyer has to pay the difference upon 'carrying over' his purchase to the next account; if it rises, the seller is at the loss. Since the first weeks of the European War all stock-exchange transactions have been made, in theory at least, for cash, and speculative business of this nature has been consequently much reduced.
Differences, Finite, a calculus much used in actuarial work, which deals with a series of numbers by considering the differences of the successive terms.
Ifu1,u2,u3, ... are the terms of the series, thenu2-u1,u3-u2,u4-u3,... form another series called the series of first differences. The notation used isu2-u1=Δu1,u3-u2=Δu2,...
These first differences may themselves be differenced, giving the second differencesΔu2-Δu1,Δu3-Δu2, ..., which are writtenΔ2u1,Δ2u2,...
Similarly, we form the third differencesΔ3u1=Δ2u2-Δ2u1, and so on.
As an example, let the original series be the cubes of the natural numbers.
Here we begin by writing down the series of cubes as far, say, as 216; beneath these we write the first differences 8 - 1 = 7, 27 - 8 = 19, &c. We thus obtain the part of the table to the left of the diagonal line.
We observe that the third differences are constant, each being 6. (It is easy to prove generally that thenth differences of the series, 1n, 2n, 3n,..., are constant.) Knowing the third differences, we can now extend the table as far as we wish to the right of the diagonal line. We get first 6 + 30 = 36, 36 + 91 = 127, 127 + 216 = 343. We infer that 73= 343.
Sinceu1-u0=Δu0, we haveu1=u0+Δu0= (1 +Δ)u0.
Similarly,u2= (1 +Δ)u1= (1 +Δ)2u0; and, generally,
ux= (1 +Δ)xu0
ux= (1 +Δ)xu0
ux= (1 +Δ)xu0
a formula much used by calculators, and known as Newton's interpolation formula.
The above symbolic method of proof only applies whenxis a positive integer, but the result is used in practice even for fractional values ofx, as in most cases the high differences become negligible.
Ifnis a positive integer, it is easy to prove that
If thenth differences vanish, or are negligible, this gives
another useful interpolation formula, by which we can calculate any missing term of a series.—Bibliography: G. Boole,Finite Differences; Textbook of the Institute of Actuaries.
Differential Equation, an algebraical relation involving derivatives or differentials. Examples:
Anordinarydifferential equation involves only one independent variable, apartialdifferential equation involves more than one. Examples of ordinary equations:
Examples of partial differential equations:
Equations, whether ordinary or partial, canalso be classified aslinearornon-linear. A linear equation is a rational integral equation of the first degree in the dependent variable or variables and their derivatives. The equation
is linear, but
are non-linear. Theorderof an equation is the order of the highest derivative or differential which it contains. Of the three equations last written, the first islinear of the second order, the other two are of thefirst order and second degree. Tointegratea differential equation or system of equations is to find a relation or relations among the variables, equivalent to the given equation or equations. Thus the integral of
where A and B arearbitrary constants. An ordinary equation of thenth order with one dependent variable has exactlynarbitrary constants in its complete integral, or solution. In a practical problem the arbitrary constants are determined by theinitial, orboundary,conditions. The solution ofd2z/dt2=g, e.g. is completely determinate if the values ofzanddz/dtwhent= 0 are given. The solution ofpartialequations may involve arbitraryfunctions, which become definite when proper initial or boundary conditions are assigned. Thus the equationdu/dx=du/dthas for its complete solutionu=φ(x+t), whereφmay be a function of any form whatever; if now we are given that, whent= 0,u= a given functionf(x), we obtainf(x) =φ(x), so that the solution required isu=f(x+t). Certain ordinary linear equations of the second order are specially important, both from the beauty of their theory and from their usefulness in Mathematical Physics. Some of these equations are: Bessel's equation, Legendre's equation, the hypergeometric equation, Mathieu's equation, Lamé's equation. Linear partial equations of the second order are fundamental in Physics. Such are: Laplace's equation,
the wave equation,
the equation of conduction of heat,
These involve one dependent variable only. Equations with several dependent variables occur in Elasticity, Electrodynamics, and Hydrodynamics. A notable feature of the hydrodynamical equations is that they are not linear.
No general rules exist enabling us to deal with a differential equation taken at random, and only a few types have been completely solved. Of soluble equations, the most important are those which arelinear with constant coefficients.
Example 1.d2x/dt2- 7dx/dt+ 12 = 0. To solve this, tryx=emt. We findemt(m2- 7m+ 12) = 0. Thusm= 3 or 4. It is now easy to show thatx= Ae3t+ Be4tis a solution, where A and B are arbitrary constants. This is the general solution. We can determine A and B if the values ofxanddx/dtare given for a definite value oft, sayt= 0.
Example 2.d2y/dt2=c2d2y/dx2. Tryy=elx+mt. We findm2=c2l2, orm= ±cl. Hencey= Ael(x+ct)+ Bel(x-ct)is a solution for all values of A, B,l; so, also, is the sum of any number of terms of similar forms. We may infer that the general solution is
y=f(x+ct) + F(x-ct),
y=f(x+ct) + F(x-ct),
y=f(x+ct) + F(x-ct),
wherefand F are arbitrary functions. It is only in exceptional cases that an equation can be solved, as in these two examples, by an analytical formula; indeed, differential equations are the most fertile source of new functions in analysis. But, as in the analogous cases of algebraic equations and definite integrals, it may be quite possible to find, by methods of approximation, an arithmetical solution which is sufficient for the purpose in hand.—Bibliography: H. T. H. Piaggio,Differential Equations; J. M. Page,Ordinary Differential Equations; A. R. Forsyth,A Treatise on Differential Equations; E. T. Whittaker and G. N. Watson,Modern Analysis.
Diffrac´tion, a term applied to the bending that rays of light undergo in passing close to the edge of an opaque body. Thus when a beam of direct sunlight is admitted into a dark room through a narrow slit, and falls upon a screenplaced to receive it, there appears a line of white light bordered by coloured fringes; these fringes are produced by diffraction, and in the case given it may be seen that the red or long-wave rays are diffracted more than the blue rays. SeeInterference.
Diffu´sion, the gradual mixing of gases, liquids, or solids when brought into direct contact. When a block of lead is placed on a block of gold, with their smooth surfaces in close contact, it is found that, after several weeks, gold has diffused into the lead, and lead into the gold. In the case of gases, when a jar of oxygen and a jar of hydrogen are connected together by a tube or opening of any kind, they rapidly become mixed; and their mixture does not depend on gravity, but takes place in opposition to that force, as may be shown by placing the jar of hydrogen gas above the other. Oxygen is sixteen times heavier than hydrogen, bulk for bulk, but the heavier gas moves upwards and the lighter downwards, and the process of intermixture, ordiffusion, goes on till the two gases are apparently equably distributed throughout the whole space. After that they have no tendency whatever to separate. Similarly, if two vessels, one containing oxygen and the other hydrogen, be connected by a tube which is stuffed with a plug of porous material, such as plaster of Paris, the gases gradually diffuse one into the other through the porous plug. The two gases, however, do not pass through the porous separator at equal rates, but ininverse proportion to the square roots of the densities of the gases. Thus in the case of two vessels, one containing hydrogen and the other oxygen, which is sixteen times as heavy as hydrogen, the hydrogen will pass towards the oxygen jar four times as quickly as the oxygen will pass towards the hydrogen jar. Kindred phenomena occur when two liquids that are capable of mixing, such as alcohol and water, are put in contact, the two gradually diffusing one into the other in spite of the action of gravity. In some cases, however, as where ether and water are employed, the diffusion is only partial, this result arising from the fact that these two liquids are not miscible in all proportions. When solutions of various solid bodies are placed in contact, interdiffusion also takes place. On the results of his examination of the phenomena of diffusion of liquids and salts across porous membranes orsepta, Graham founded a method of separatingcolloidfromcrystalloidbodies, which he calleddialysis.
Digam´ma, a letter which once belonged to the Greek alphabet, and which remained longest in use among the Æolians. It resembled our letter F, and hence was calleddigamma, that is, doubleΓ. It appears to have had the force offorv. Its existence was first pointed out by Richard Bentley.
Digby, Sir Everard, an English gentleman, born of a Roman Catholic family in 1578. He enjoyed some consideration at the court of Elizabeth and James I, by whom he was knighted. Having contributed money to the Guy Fawkes conspiracy, he was tried and hanged in 1606.
Digby, Sir Kenelm, eldest son of the preceding, born in 1603, died in 1665. He studied at Oxford, was knighted in 1623, and on the accession of Charles I was created a gentleman of the bedchamber, a Commissioner of the Navy, and a governor of Trinity House. He soon after fitted out at his own expense a small but successful squadron against the French and Venetians. In 1636 he became a Roman Catholic, and was imprisoned as a Royalist during 1642-3, when he was allowed to retire to the Continent. At the Restoration he returned to England, became a member of the Royal Society, and was much visited by men of science. He wrote numerous works: aTreatise on the Nature of Bodies, aTreatise on the Nature and Operation of the Soul, andOf the Cure of Wounds by the Powder of Sympathy.
Di´gest, a name originally given to a collection or body of Roman laws, digested or arranged under proper titles by order of the Emperor Justinian. Hence applied to any somewhat similar collection.
Diges´ter, a strong vessel of copper or iron, on which is screwed an air-tight cover with a safety-valve, the object being to prevent loss of heat by evaporation, and to enable boiling to take place at a high pressure. Water may be thus heated to 400°F.; at which temperature its solvent power is so greatly increased that bones are converted into a jelly.
Diges´tionis that process in the animal body by which the aliments are so acted upon that the nutritive parts are prepared to enter the circulation, and separated from those which cannot afford nourishment to the body. The organs effecting this process are called thedigestiveorgans, and consist of the stomach, the great and small intestines, &c. (seeIntestine,Stomach), the liver, and pancreas. When the aliments, after being properly prepared and mixed with saliva by mastication, have reached the stomach, they are intimately united with a liquid substance called thegastric juice, by the motion of the stomach. By this motion the aliments are mechanically separated into their smallest parts, penetrated by the gastric juice, and transformed into a uniform pulpy or fluid mass. The gastric juice acts upon the albuminous parts of the food, converting them into peptones, which can pass through organic membranes and thus enter the blood. Thisaction is aided by the warmth of the stomach. The pulpy mass, calledchyme, proceeds from the stomach, through the pylorus, into that part of the intestinal canal called the small intestine, where it is mixed with the pancreatic juice, bile, and intestinal juice. The pancreatic juice converts starch into sugar, albumins into peptones, and emulsionizes fats, so that all these kinds of food are rendered capable of absorption. The process is aided by the intestinal juice. The bile also acts upon fats, and thus the food is formed into thechyle, which is absorbed into the system by the capillary vessels calledlacteals(seeChyle;Chyme), while the non-nutritious matters pass down the intestinal canal and are carried off.—Bibliography: F. Hare,Food Factor in Disease; Taylor,Digestion and Metabolism.
Digit(dij´it; Lat.digitus, a finger), in arithmetic, any one of the ten numerals, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0. Digit is also a measure of a finger's breadth, equal to ¾ inch.
Digit, in astronomy, is the measure by which we estimate the quantity of an eclipse. The diameter of the sun or moon's disk is conceived to be divided into twelve equal parts, calleddigits; and according to the number of those parts or digits which are obscured, so many digits are said to be eclipsed.
Digitalin(dij-i-tā´lin), a vegetable alkaloid, the active principle of theDigitālis purpurĕaor foxglove. It has a bitter taste, and is a strong poison, but is used medicinally, especially for the heart. See next article.
Digita´lis(dij-), a genus of plants, nat. ord. Scrophulariaceæ, containing about twenty species of tall herbs, natives of Europe and Western Asia. The purple foxglove (D. purpurĕa) is a common wild flower in Britain, and several species are grown in gardens. Various preparations from the foxglove receive this name, and are used in medicine, principally in cases of heart disease.
Digitigra´da(digitus, finger, toe, andgradi, to walk), a section of the Carnivora, so called from their walking on the ends of their toes; as the dog, cat, and their allies. SeePlantigrade.
Digito´rium, a small portable dumb instrument having a short keyboard with five keys like those of a piano, used by piano-players for practice, to give strength and flexibility to the fingers.
Digne(dēny), a town, France, capital of the department of Basses-Alpes, picturesquely situated on a mountain slope, 60 miles north-east of Marseilles. In 1629 a plague reduced the population from 20,000 to 1500. Pop. 7317.
Dijon(dē-zhōn; Lat.Castrum Divonense), a town in Eastern France, capital of the department of Côte-d'Or, in a fertile plain, at the foot of a range of vine-clad slopes, formerly surrounded by ramparts, which now furnish beautiful promenades. At some distance it is surrounded by a series of forts. Some of the buildings belong to the period when Dijon was capital of the dukedom of Burgundy, the chief being the cathedral of St. Bénigne, a building of vast extent with a lofty wooden spire above 300 feet high; the churches of Nôtre Dame and St. Michael; the ancient palace of the Dukes of Burgundy, now used as the hôtel de ville and museum; and thepalais de justice, formerly the Parliament House of Burgundy. Dijon is the birth-place of Bossuet. It has important educational institutions and a valuable library. Industries: woollens, hosiery, candles, mustard, vinegar, chemicals, paper-hangings, tanneries, foundries, machine factories, cotton- and oil-mills. The trade is considerable, particularly in the wines of Burgundy. Pop. 76,847.
Dike, orDyke(connected with the Gr.teichos, wall), a word variously used in different localities to represent a ditch or trench, and also an embankment, rampart, or wall. It is specially applied to an embankment raised to oppose the incursions of the sea or of a river, the dikes of Holland being notable examples of work of this kind. These are often raised 40 feet above the high-water mark, and are wide enough at the top for a common roadway or canal, sometimes for both. The Helder Dike, one of the largest, is about 6 miles in length and costly in upkeep. SeeEmbankment.
Dike, orDyke, in geology, a term applied to intrusive igneous masses, such as basalt, which fill up veins and fissures in the other rocks, and sometimes project on the surface like walls through their superior resistance to weathering.
Dilapidation, in English ecclesiastical law, is where an incumbent of a church living suffers the parsonage-house or outhouses to fall down, or be in decay for want of necessary repairs; or it is the pulling down or destroying any of the houses or buildings belonging to a spiritual living, or destroying of the woods, trees, &c., appertaining to the same. An outgoing incumbent (or his heirs) is liable for dilapidation to his successor. In general, the term is applied to the act of allowing or causing any lands, houses, &c., to become waste or to decay.
Dilem´ma(from Gr.di-, double, andlēmma, proposition, assumption), in logic, a form of argument used to prove the falsehood or absurdity of some assertion, as in the following instance: If he did so he must be either foolish or wicked; but we know he is neither foolish nor wicked; therefore he cannot have done so. The two suppositions, which are equally untenable, are called the 'horns' of the dilemma.
Dilettante(di-let-ta˙n´tā), an Italianexpression, signifying a lover of the arts and sciences, who devotes his leisure to them as a means of amusement and gratification, being thus nearly equivalent toamateur. It is also used in reference to the trifler and dabbler in art and science. In 1734 a number of gentlemen founded in London a Dilettanti Society, which published a splendid work onIonian Antiquities, 1769, 1881 (4 vols.);Specimens of Ancient Sculpture, 1809, 1835.
Dilke, Sir Charles Wentworth, English writer and politician, son and grandson of men well known in their day, was born in 1843, died in 1911. He graduated at Cambridge, and was called to the Bar. His first work,Greater Britain, the result of a tour round the world from 1866 to 1867, became very popular. In 1868 he was elected member of Parliament for Chelsea, and he remained so up to 1885. After a few years' retirement (due to a divorce case) he became member of Parliament for Forest of Dean. He was Under-Secretary for Foreign Affairs, President of the Local Government Board, &c. He succeeded his father as owner of theAthenæum, and became the proprietor ofNotes and Queries.The Present Position of European Politics, andProblems of Greater Britain, are among his works.
Dill, an umbelliferous plant,Anēthum graveŏlens, a native of the southern countries of Europe, the fruits, commonly but erroneously called seeds, of which are moderately warming, pungent, and aromatic, and are employed medicinally as a carminative.
Dillenia´ceæ, an order of plants, chiefly fine trees, inhabiting the East Indies, allied to Ranunculaceæ and Magnoliaceæ.
Dillingen(dil´ing-en), an old town, Bavaria, on the Danube, formerly the seat of a Jesuit university. Pop. 6291.
Dillon, John, Irish politician and agitator, born in Dublin in 1851, the son of John Blake Dillon (1816-66), a leader of the Young Ireland party. Educated at the Catholic University of Dublin and at the Royal College of Surgeons, he became a doctor of medicine. He identified himself with the Parnellite movement, and entered Parliament for Tipperary in 1880. An ardent Nationalist, not hesitating to incite his compatriots to lawlessness, he was sent to prison in 1888. Without a seat in Parliament from 1883 to 1885, he was returned in the latter year for East Mayo, which he represented thereafter. In 1918, after the death of John Redmond, he was elected chairman of the Irish Nationalist party, which, however, owing to the rise of the Sinn Fein party, was a nominal distinction only.
Dilman´, a town, Persia, province of Azerbijan, 75 miles west of Tabreez. Pop. estimated at 15,000.
Dilo´lo, a small lake in Angola, near the southern boundary of Belgian Congo, lat. 11° 22' S.; long. 22° 34' E.: regarded as the source of the Zambesi.
Dil´uents(Lat.diluere, to wash away), in medicine, are those substances which are taken to increase the proportion of fluid in the blood. They consist of water and watery liquors.
Dilu´vium, the name formerly given by geologists to certain gravels and comparatively recent deposits, which seemed to have been the result of a rush of water or deluge.
Dime(Fr.dîme, Lat.decimus, tenth), the term for the tenth part of a dollar or ten-cent piece in the United States of America, a silver coin whose English equivalent is about 5d.Hence the phrasesdime novels,dime museums, &c.
Dimensions, Algebraical.There are three dimensions in space: length, breadth, and height or depth. An area is said to be of two dimensions because it has length and breadth only; a volume is of three dimensions. In algebra terms likex2,xyare said to be of two dimensions because there are two letters multiplied together, and their product would measure an area if each letter denoted a length. Similarly,x3,xyzare said to be of three dimensions, and the meaning is extended to cover the product of any number of letters. An expression of more than one term is said to be of the same degree as its term of highest dimensions. For example, 3x2y2z2+ 5xyz+ 6x3+ 3x2y2is said to be of the sixth degree becausex2y2z2=x×x×y×y×z×zis of six dimensions.
Dimensions, Physical.One of the aims of physical science is to express all its measurements in terms of the three fundamental units of length, mass, and time. A velocity, for example, is specified by the number of units of length traversed in the unit of time, so that we may writev=l÷t, orv=lt-1. On this account velocity is said to have the dimensions LT-1. Similarly, acceleration, being velocity added per unit time, has the dimensions of velocity ÷ time, or LT-2; and force, being proportional to mass and acceleration jointly, has the dimensions MLT-2.
When a physical law is expressed as an equation connecting the numbers of units of the quantities involved, every term in this equation must be of the same dimensions in any one of the fundamental units. This is thePrinciple of Dimensions, first stated by Joseph Fourier, founder of the theory of the conduction of heat. In order to see its truth, we have only to observe that an equation containing terms of different dimensions would give inconsistent results if the unit of length were varied. Suppose it to be suggested, for example, that the period of vibrationtof a simplependulum of lengthlis given by the formulat= 2πl/g, wheregdenotes the acceleration of a falling body. The dimensions of the expression on the right are L ÷ (LT-2), or T2, whereas the termton the left has dimensions T1. Suppose the unit of length is the foot and the unit of time the second, so thatg= 32, and letl= 3. We find in this caset= 6π/32, so that the period is 3π/16 seconds. But if we change the unit of time to one minute,gbecomes 32 × 60 × 60, and the formula givest= 6π/(32 × 60 × 60), so that the period is 3π/(16 × 60 × 60) minutes.
The two results are obviously inconsistent. If, however, we take the correct formula, namelyt= 2π√(l/g), we find on trial that we obtain the same value for the period however we change the unit of time or the unit of length. Both sides are in this case of dimensions T1.
The principle of dimensions provides therefore a useful check on the accuracy of formulæ. But it does much more than this. It often gives very valuable information about the relations of physical phenomena in cases where these relations are far too complicated to be completely worked out by mathematical analysis. To mention but one example, it is by the use of this principle that modern naval architecture is able to predict the behaviour of ocean-going ships from experiments in ponds on small-scale models.
Dimin´utive, in grammar, a word having a special affix which conveys the idea of littleness, and all other ideas connected with this, as tenderness, affection, or contempt. The opposite ofdiminutiveisaugmentative. In Latin, diminutives almost always ended in-lus,-la, or-lum; asTulliola, meum corculum, little Tullia my dear, or little heart;homunculus, a manikin. The Italian is particularly rich in diminutives and augmentatives, such compound diminutives asfratellinucciettinetto(a diminutive offrate, brother) being sometimes employed. Among English diminutive affixes are-kin, as inmanikin, a little man;pipkin, a little pipe;-ling, as ingosling, a little goose; darling, that is,dearling, or little dear; and-et, as inpocket, frompoke, a bag or pouch;tablet, a little table. Diminutives are not confined to nouns, anddandle,scribble,tipple, are examples of diminutive verbs, andgreenish,whitish, are diminutives of adjectives. Diminutives are also formed, in colloquial and familiar language, by adding-yor-ieto the names, asCharley,Mousie, &c.
Dim´ity, a stout cotton fabric, ornamented in the loom either by raised stripes or fancy figures. It is usually employed white, as for bed and bedroom furniture.
Dimorph´ism, in crystallography, the crystallization of a body in forms belonging to two different systems, or in incompatible forms of the same system, a peculiarity exhibited by sulphur, carbon, &c.
Dimorphism, in botany. SeeHeterostyly.
Dinajpur´, a town, Hindustan, Bengal, capital of a district of same name, 205 miles north of Calcutta; pop. 12,500.—The district covers an area of about 4118 sq. miles; pop. 1,687,860.
Dinan(dē-nän), a town, France, department of Côtes-du-Nord (Brittany), on the Rance, 14 miles south of St. Malo. It was besieged and captured by the English under the Duke of Lancaster in 1359, but retaken by Du Guesclin. It stands on a steep hill nearly 200 feet above the river, is surrounded by high old walls pierced with four gates, and is a picturesque and interesting old place. In the cathedral of St. Sauveur the heart of Bertrand du Guesclin is buried. Pop. 11,410.
Dinant(dē-nän), a town, Belgium, in the province and 14 miles S. of Namur; picturesquely and strongly situated on the Meuse; a place of antique appearance. The town house was once the palace of the Princes of Liége. The town was destroyed by the Germans in 1914. It is one of the most popular Belgian summer resorts. Pop. 7690.
Dina´pur, a town, Hindustan, Patna district, Bengal, on the right bank of the Ganges, about 12 miles north-west of Patna, cantonment and military head-quarters of the district, with extensive barracks. The environs are studded with handsome bungalows. Pop. 31,025.
Dinar(Lat.denarius), formerly an Arab gold coin, also a Persian coin; at present the chief Serbian coin, value one franc.
Di´nas Bricks, an infusible kind of brick made of a peculiar rock, containing 98 per cent of silica, with a little alumina, which occurs at Dinas, in the Vale of Neath, in Glamorganshire, S. Wales. The rock is crushed, moistened with water, and moulded by a machine.
Dindigul, a town of India, Madura district, Madras, with a fort on a rocky height; manufactures cigars. Pop. 21,000.
Dindings, The, properly two small islands, also calledPangkor Islands, in the Straits of Malacca, belonging to the Straits Settlements, off the coast of Perak (British). The name now includes a strip of territory on the Malay Peninsula opposite; total area about 265 sq. miles, two-thirds of which is covered by dense forests. Coco-nuts, coffee, and pepper are grown with success. Lumut, on the mainland, has a fine natural harbour.
Din´dorf, Karl Wilhelm, German classical scholar, born 1802, lived most of his life atLeipzig, and died 1883. His chief publications were editions of the Greek dramatists (Poetæ Scenici Græci) and works elucidative of them and other Greek writers.