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diff --git a/40370-0.txt b/40370-0.txt new file mode 100644 index 0000000..b5978b4 --- /dev/null +++ b/40370-0.txt @@ -0,0 +1,21037 @@ +*** START OF THE PROJECT GUTENBERG EBOOK 40370 *** + +Transcriber's notes: + +(1) Numbers following letters (without space) like C2 were originally + printed in subscript. Letter subscripts are preceded by an + underscore, like C_n. + +(2) Characters following a carat (^) were printed in superscript. + +(3) Side-notes were relocated to function as titles of their respective + paragraphs. + +(4) Macrons and breves above letters and dots below letters were not + inserted. + +(5) [root] stands for the root symbol; [alpha], [beta], etc. for greek + letters. + +(6) The following typographical errors have been corrected: + + ARTICLE HYDROMECHANICS: "... and [omega] the angular velocity + about it generated by an impulse couple M, and M' is the couple + required to set the surrounding medium in motion ..." 'impulse' + amended from 'impluse'. + + ARTICLE HYMENOPTERA: "... see P. Cameron's British Phytophagous + Hymenoptera (4 vols., London, Roy. Soc., 1882-1893)." 'Roy' + amended from 'Ray'. + + ARTICLE HYRCANUS: "During its later years his reign was much + disturbed, however, by the contentions for ascendancy which arose + between the Pharisees and Sadducees, the two rival sects or + parties which then for the first time (under those names at least) + came into prominence." 'disturbed' amended from 'distrubed'. + + ARTICLE ICELAND: "Iceland is emphatically a land of proverbs, + while of folk-tales, those other keys to the people's heart, there + is plentiful store." 'people's' amended from 'poeple's'. + + + + + ENCYCLOPAEDIA BRITANNICA + + A DICTIONARY OF ARTS, SCIENCES, LITERATURE + AND GENERAL INFORMATION + + ELEVENTH EDITION + + + VOLUME XIV, SLICE II + + Hydromechanics to Ichnography + + + + +ARTICLES IN THIS SLICE: + + + HYDROMECHANICS HYTHE + HYDROMEDUSAE I + HYDROMETER IAMBIC + HYDROPATHY IAMBLICHUS (Greek philosopher) + HYDROPHOBIA IAMBLICHUS (Greek romance writer) + HYDROSPHERE IANNINA + HYDROSTATICS IAPETUS + HYDROXYLAMINE IAPYDES + HYDROZOA IATROCHEMISTRY + HYENA IAZYGES + HYÈRES IBADAN + HYGIEIA IBAGUÉ + HYGIENE IBARRA + HYGINUS (eighth pope) IBERIANS + HYGINUS (Latin writer) IBEX + HYGINUS, GAIUS JULIUS IBIS + HYGROMETER IBLIS + HYKSOS IBN 'ABD RABBIHI + HYLAS IBN 'ARABI + HYLOZOISM IBN ATHIR + HYMEN IBN BATUTA + HYMENOPTERA IBN DURAID + HYMETTUS IBN FARADI + HYMNS IBN FARID + HYPAETHROS IBN GABIROL + HYPALLAGE IBN HAUKAL + HYPATIA IBN HAZM + HYPERBATON IBN HISHAM + HYPERBOLA IBN ISHAQ + HYPERBOLE IBN JUBAIR + HYPERBOREANS IBN KHALDUN + HYPEREIDES IBN KHALLIKAN + HYPERION IBN QUTAIBA + HYPERSTHENE IBN SA'D + HYPERTROPHY IBN TIBBON + HYPNOTISM IBN TUFAIL + HYPOCAUST IBN USAIBI'A + HYPOCHONDRIASIS IBO + HYPOCRISY IBRAHIM AL-MAUSILI + HYPOSTASIS IBRAHIM PASHA + HYPOSTYLE IBSEN, HENRIK + HYPOSULPHITE OF SODA IBYCUS + HYPOTHEC ICA + HYPOTHESIS ICE + HYPOTRACHELIUM ICEBERG + HYPSOMETER ICELAND + HYRACOIDEA ICELAND MOSS + HYRCANIA ICE-PLANT + HYRCANUS ICE-YACHTING + HYSSOP I-CH'ANG + HYSTASPES ICHNEUMON + HYSTERESIS ICHNEUMON-FLY + HYSTERIA ICHNOGRAPHY + HYSTERON-PROTERON + + + + +HYDROMECHANICS ([Greek: hydromêchanika]), the science of the mechanics +of water and fluids in general, including _hydrostatics_ or the +mathematical theory of fluids in equilibrium, and _hydromechanics_, the +theory of fluids in motion. The practical application of hydromechanics +forms the province of hydraulics (q.v.). + + _Historical._--The fundamental principles of hydrostatics were first + given by Archimedes in his work [Greek: Peri tôn ochoumenôn], or _De + iis quae vehuntur in humido_, about 250 B.C., and were afterwards + applied to experiments by Marino Ghetaldi (1566-1627) in his _Promotus + Archimedes_ (1603). Archimedes maintained that each particle of a + fluid mass, when in equilibrium, is equally pressed in every + direction; and he inquired into the conditions according to which a + solid body floating in a fluid should assume and preserve a position + of equilibrium. + + In the Greek school at Alexandria, which flourished under the auspices + of the Ptolemies, the first attempts were made at the construction of + hydraulic machinery, and about 120 B.C. the fountain of compression, + the siphon, and the forcing-pump were invented by Ctesibius and Hero. + The siphon is a simple instrument; but the forcing-pump is a + complicated invention, which could scarcely have been expected in the + infancy of hydraulics. It was probably suggested to Ctesibius by the + _Egyptian Wheel_ or _Noria_, which was common at that time, and which + was a kind of chain pump, consisting of a number of earthen pots + carried round by a wheel. In some of these machines the pots have a + valve in the bottom which enables them to descend without much + resistance, and diminishes greatly the load upon the wheel; and, if we + suppose that this valve was introduced so early as the time of + Ctesibius, it is not difficult to perceive how such a machine might + have led to the invention of the forcing-pump. + + Notwithstanding these inventions of the Alexandrian school, its + attention does not seem to have been directed to the motion of fluids; + and the first attempt to investigate this subject was made by Sextus + Julius Frontinus, inspector of the public fountains at Rome in the + reigns of Nerva and Trajan. In his work _De aquaeductibus urbis Romae + commentarius_, he considers the methods which were at that time + employed for ascertaining the quantity of water discharged from + ajutages, and the mode of distributing the waters of an aqueduct or a + fountain. He remarked that the flow of water from an orifice depends + not only on the magnitude of the orifice itself, but also on the + height of the water in the reservoir; and that a pipe employed to + carry off a portion of water from an aqueduct should, as circumstances + required, have a position more or less inclined to the original + direction of the current. But as he was unacquainted with the law of + the velocities of running water as depending upon the depth of the + orifice, the want of precision which appears in his results is not + surprising. + + Benedetto Castelli (1577-1644), and Evangelista Torricelli + (1608-1647), two of the disciples of Galileo, applied the discoveries + of their master to the science of hydrodynamics. In 1628 Castelli + published a small work, _Della misura dell' acque correnti_, in which + he satisfactorily explained several phenomena in the motion of fluids + in rivers and canals; but he committed a great paralogism in supposing + the velocity of the water proportional to the depth of the orifice + below the surface of the vessel. Torricelli, observing that in a jet + where the water rushed through a small ajutage it rose to nearly the + same height with the reservoir from which it was supplied, imagined + that it ought to move with the same velocity as if it had fallen + through that height by the force of gravity, and hence he deduced the + proposition that the velocities of liquids are as the square root of + the head, apart from the resistance of the air and the friction of the + orifice. This theorem was published in 1643, at the end of his + treatise _De motu gravium projectorum_, and it was confirmed by the + experiments of Raffaello Magiotti on the quantities of water + discharged from different ajutages under different pressures (1648). + + In the hands of Blaise Pascal (1623-1662) hydrostatics assumed the + dignity of a science, and in a treatise on the equilibrium of liquids + (_Sur l'équilibre des liqueurs_), found among his manuscripts after + his death and published in 1663, the laws of the equilibrium of + liquids were demonstrated in the most simple manner, and amply + confirmed by experiments. + + The theorem of Torricelli was employed by many succeeding writers, but + particularly by Edmé Mariotte (1620-1684), whose _Traité du mouvement + des eaux_, published after his death in the year 1686, is founded on a + great variety of well-conducted experiments on the motion of fluids, + performed at Versailles and Chantilly. In the discussion of some + points he committed considerable mistakes. Others he treated very + superficially, and in none of his experiments apparently did he attend + to the diminution of efflux arising from the contraction of the liquid + vein, when the orifice is merely a perforation in a thin plate; but he + appears to have been the first who attempted to ascribe the + discrepancy between theory and experiment to the retardation of the + water's velocity through friction. His contemporary Domenico + Guglielmini (1655-1710), who was inspector of the rivers and canals at + Bologna, had ascribed this diminution of velocity in rivers to + transverse motions arising from inequalities in their bottom. But as + Mariotte observed similar obstructions even in glass pipes where no + transverse currents could exist, the cause assigned by Guglielmini + seemed destitute of foundation. The French philosopher, therefore, + regarded these obstructions as the effects of friction. He supposed + that the filaments of water which graze along the sides of the pipe + lose a portion of their velocity; that the contiguous filaments, + having on this account a greater velocity, rub upon the former, and + suffer a diminution of their celerity; and that the other filaments + are affected with similar retardations proportional to their distance + from the axis of the pipe. In this way the medium velocity of the + current may be diminished, and consequently the quantity of water + discharged in a given time must, from the effects of friction, be + considerably less than that which is computed from theory. + + The effects of friction and viscosity in diminishing the velocity of + running water were noticed in the _Principia_ of Sir Isaac Newton, who + threw much light upon several branches of hydromechanics. At a time + when the Cartesian system of vortices universally prevailed, he found + it necessary to investigate that hypothesis, and in the course of his + investigations he showed that the velocity of any stratum of the + vortex is an arithmetical mean between the velocities of the strata + which enclose it; and from this it evidently follows that the velocity + of a filament of water moving in a pipe is an arithmetical mean + between the velocities of the filaments which surround it. Taking + advantage of these results, Henri Pitot (1695-1771) afterwards showed + that the retardations arising from friction are inversely as the + diameters of the pipes in which the fluid moves. The attention of + Newton was also directed to the discharge of water from orifices in + the bottom of vessels. He supposed a cylindrical vessel full of water + to be perforated in its bottom with a small hole by which the water + escaped, and the vessel to be supplied with water in such a manner + that it always remained full at the same height. He then supposed this + cylindrical column of water to be divided into two parts,--the first, + which he called the "cataract," being an hyperboloid generated by the + revolution of an hyperbola of the fifth degree around the axis of the + cylinder which should pass through the orifice, and the second the + remainder of the water in the cylindrical vessel. He considered the + horizontal strata of this hyperboloid as always in motion, while the + remainder of the water was in a state of rest, and imagined that there + was a kind of cataract in the middle of the fluid. When the results of + this theory were compared with the quantity of water actually + discharged, Newton concluded that the velocity with which the water + issued from the orifice was equal to that which a falling body would + receive by descending through half the height of water in the + reservoir. This conclusion, however, is absolutely irreconcilable with + the known fact that jets of water rise nearly to the same height as + their reservoirs, and Newton seems to have been aware of this + objection. Accordingly, in the second edition of his _Principia_, + which appeared in 1713, he reconsidered his theory. He had discovered + a contraction in the vein of fluid (_vena contracta_) which issued + from the orifice, and found that, at the distance of about a diameter + of the aperture, the section of the vein was contracted in the + subduplicate ratio of two to one. He regarded, therefore, the section + of the contracted vein as the true orifice from which the discharge of + water ought to be deduced, and the velocity of the effluent water as + due to the whole height of water in the reservoir; and by this means + his theory became more conformable to the results of experience, + though still open to serious objections. Newton was also the first to + investigate the difficult subject of the motion of waves (q.v.). + + In 1738 Daniel Bernoulli (1700-1782) published his _Hydrodynamica seu + de viribus et motibus fluidorum commentarii_. His theory of the motion + of fluids, the germ of which was first published in his memoir + entitled _Theoria nova de motu aquarum per canales quocunque + fluentes_, communicated to the Academy of St Petersburg as early as + 1726, was founded on two suppositions, which appeared to him + conformable to experience. He supposed that the surface of the fluid, + contained in a vessel which is emptying itself by an orifice, remains + always horizontal; and, if the fluid mass is conceived to be divided + into an infinite number of horizontal strata of the same bulk, that + these strata remain contiguous to each other, and that all their + points descend vertically, with velocities inversely proportional to + their breadth, or to the horizontal sections of the reservoir. In + order to determine the motion of each stratum, he employed the + principle of the _conservatio virium vivarum_, and obtained very + elegant solutions. But in the absence of a general demonstration of + that principle, his results did not command the confidence which they + would otherwise have deserved, and it became desirable to have a + theory more certain, and depending solely on the fundamental laws of + mechanics. Colin Maclaurin (1698-1746) and John Bernoulli (1667-1748), + who were of this opinion, resolved the problem by more direct methods, + the one in his _Fluxions_, published in 1742, and the other in his + _Hydraulica nunc primum detecta, et demonstrata directe ex fundamentis + pure mechanicis_, which forms the fourth volume of his works. The + method employed by Maclaurin has been thought not sufficiently + rigorous; and that of John Bernoulli is, in the opinion of Lagrange, + defective in clearness and precision. The theory of Daniel Bernoulli + was opposed also by Jean le Rond d'Alembert. When generalizing the + theory of pendulums of Jacob Bernoulli (1654-1705) he discovered a + principle of dynamics so simple and general that it reduced the laws + of the motions of bodies to that of their equilibrium. He applied this + principle to the motion of fluids, and gave a specimen of its + application at the end of his _Dynamics_ in 1743. It was more fully + developed in his _Traité des fluides_, published in 1744, in which he + gave simple and elegant solutions of problems relating to the + equilibrium and motion of fluids. He made use of the same suppositions + as Daniel Bernoulli, though his calculus was established in a very + different manner. He considered, at every instant, the actual motion + of a stratum as composed of a motion which it had in the preceding + instant and of a motion which it had lost; and the laws of equilibrium + between the motions lost furnished him with equations representing the + motion of the fluid. It remained a desideratum to express by equations + the motion of a particle of the fluid in any assigned direction. These + equations were found by d'Alembert from two principles--that a + rectangular canal, taken in a mass of fluid in equilibrium, is itself + in equilibrium, and that a portion of the fluid, in passing from one + place to another, preserves the same volume when the fluid is + incompressible, or dilates itself according to a given law when the + fluid is elastic. His ingenious method, published in 1752, in his + _Essai sur la résistance des fluides_, was brought to perfection in + his _Opuscules mathématiques_, and was adopted by Leonhard Euler. + + The resolution of the questions concerning the motion of fluids was + effected by means of Euler's partial differential coefficients. This + calculus was first applied to the motion of water by d'Alembert, and + enabled both him and Euler to represent the theory of fluids in + formulae restricted by no particular hypothesis. + + One of the most successful labourers in the science of hydrodynamics + at this period was Pierre Louis Georges Dubuat (1734-1809). Following + in the steps of the Abbé Charles Bossut (_Nouvelles Experiences sur la + résistance des fluides_, 1777), he published, in 1786, a revised + edition of his _Principes d'hydraulique_, which contains a + satisfactory theory of the motion of fluids, founded solely upon + experiments. Dubuat considered that if water were a perfect fluid, and + the channels in which it flowed infinitely smooth, its motion would be + continually accelerated, like that of bodies descending in an inclined + plane. But as the motion of rivers is not continually accelerated, and + soon arrives at a state of uniformity, it is evident that the + viscosity of the water, and the friction of the channel in which it + descends, must equal the accelerating force. Dubuat, therefore, + assumed it as a proposition of fundamental importance that, when water + flows in any channel or bed, the accelerating force which obliges it + to move is equal to the sum of all the resistances which it meets + with, whether they arise from its own viscosity or from the friction + of its bed. This principle was employed by him in the first edition of + his work, which appeared in 1779. The theory contained in that edition + was founded on the experiments of others, but he soon saw that a + theory so new, and leading to results so different from the ordinary + theory, should be founded on new experiments more direct than the + former, and he was employed in the performance of these from 1780 to + 1783. The experiments of Bossut were made only on pipes of a moderate + declivity, but Dubuat used declivities of every kind, and made his + experiments upon channels of various sizes. + + The theory of running water was greatly advanced by the researches of + Gaspard Riche de Prony (1755-1839). From a collection of the best + experiments by previous workers he selected eighty-two (fifty-one on + the velocity of water in conduit pipes, and thirty-one on its velocity + in open canals); and, discussing these on physical and mechanical + principles, he succeeded in drawing up general formulae, which + afforded a simple expression for the velocity of running water. + + J. A. Eytelwein (1764-1848) of Berlin, who published in 1801 a + valuable compendium of hydraulics entitled _Handbuch der Mechanik und + der Hydraulik_, investigated the subject of the discharge of water by + compound pipes, the motions of jets and their impulses against plane + and oblique surfaces; and he showed theoretically that a water-wheel + will have its maximum effect when its circumference moves with half + the velocity of the stream. + + J. N. P. Hachette (1769-1834) in 1816-1817 published memoirs + containing the results of experiments on the spouting of fluids and + the discharge of vessels. His object was to measure the contracted + part of a fluid vein, to examine the phenomena attendant on additional + tubes, and to investigate the form of the fluid vein and the results + obtained when different forms of orifices are employed. Extensive + experiments on the discharge of water from orifices (_Expériences + hydrauliques_, Paris, 1832) were conducted under the direction of the + French government by J. V. Poncelet (1788-1867) and J. A. Lesbros + (1790-1860). P. P. Boileau (1811-1891) discussed their results and + added experiments of his own (_Traité de la mésure des eaux + courantes_, Paris, 1854). K. R. Bornemann re-examined all these + results with great care, and gave formulae expressing the variation of + the coefficients of discharge in different conditions (_Civil + Ingénieur_, 1880). Julius Weisbach (1806-1871) also made many + experimental investigations on the discharge of fluids. The + experiments of J. B. Francis (_Lowell Hydraulic Experiments_, Boston, + Mass., 1855) led him to propose variations in the accepted formulae + for the discharge over weirs, and a generation later a very complete + investigation of this subject was carried out by H. Bazin. An + elaborate inquiry on the flow of water in pipes and channels was + conducted by H. G. P. Darcy (1803-1858) and continued by H. Bazin, at + the expense of the French government (_Recherches hydrauliques_, + Paris, 1866). German engineers have also devoted special attention to + the measurement of the flow in rivers; the _Beiträge zur Hydrographie + des Königreiches Böhmen_ (Prague, 1872-1875) of A. R. Harlacher + (1842-1890) contained valuable measurements of this kind, together + with a comparison of the experimental results with the formulae of + flow that had been proposed up to the date of its publication, and + important data were yielded by the gaugings of the Mississippi made + for the United States government by A. A. Humphreys and H. L. Abbot, + by Robert Gordon's gaugings of the Irrawaddy, and by Allen J. C. + Cunningham's experiments on the Ganges canal. The friction of water, + investigated for slow speeds by Coulomb, was measured for higher + speeds by William Froude (1810-1879), whose work is of great value in + the theory of ship resistance (_Brit. Assoc. Report._, 1869), and + stream line motion was studied by Professor Osborne Reynolds and by + Professor H. S. Hele Shaw. (X.) + + +HYDROSTATICS + +Hydrostatics is a science which grew originally out of a number of +isolated practical problems; but it satisfies the requirement of perfect +accuracy in its application to phenomena, the largest and smallest, of +the behaviour of a fluid. At the same time, it delights the pure +theorist by the simplicity of the logic with which the fundamental +theorems may be established, and by the elegance of its mathematical +operations, insomuch that hydrostatics may be considered as the +Euclidean pure geometry of mechanical science. + +1. _The Different States of a Substance or Matter._--All substance in +nature falls into one of the two classes, solid and fluid; a solid +substance, the land, for instance, as contrasted with a fluid, like +water, being a substance which does not flow of itself. + +A _fluid_, as the name implies, is a substance which flows, or is +capable of flowing; water and air are the two fluids distributed most +universally over the surface of the earth. + +Fluids again are divided into two classes, termed a liquid and a gas, of +which water and air are the chief examples. + +A _liquid_ is a fluid which is incompressible or practically so, i.e. it +does not change in volume sensibly with change of pressure. + +A _gas_ is a compressible fluid, and the change in volume is +considerable with moderate variation of pressure. + +Liquids, again, can be poured from one open vessel into another, and can +be kept in an uncovered vessel, but a gas tends to diffuse itself +indefinitely and must be preserved in a closed reservoir. + +The distinguishing characteristics of the three kinds of substance or +states of matter, the solid, liquid and gas, are summarized thus in O. +Lodge's _Mechanics_:-- + + A solid has both size and shape. + A liquid has size but not shape. + A gas has neither size nor shape. + +2. _The Change of State of Matter._--By a change of temperature and +pressure combined, a substance can in general be made to pass from one +state into another; thus by gradually increasing the temperature a solid +piece of ice can be melted into the liquid state of water, and the water +again can be boiled off into the gaseous state as steam. Again, by +raising the temperature, a metal in the solid state can be melted and +liquefied, and poured into a mould to assume any form desired, which is +retained when the metal cools and solidifies again; the gaseous state of +a metal is revealed by the spectroscope. Conversely, a combination of +increased pressure and lowering of temperature will, if carried far +enough, reduce a gas to a liquid, and afterwards to the solid state; and +nearly every gaseous substance has now undergone this operation. + +A certain critical temperature is observed in a gas, above which the +liquefaction is impossible; so that the gaseous state has two +subdivisions into (i.) a true gas, which cannot be liquefied, because +its temperature is above the critical temperature, (ii.) a vapour, where +the temperature is below the critical, and which can ultimately be +liquefied by further lowering of temperature or increase of pressure. + +3. _Plasticity and Viscosity._--Every solid substance is found to be +plastic more or less, as exemplified by punching, shearing and cutting; +but the plastic solid is distinguished from the viscous fluid in that a +plastic solid requires a certain magnitude of stress to be exceeded to +make it flow, whereas the viscous liquid will yield to the slightest +stress, but requires a certain length of time for the effect to be +appreciable. + +According to Maxwell (_Theory of Heat_) "When a continuous alteration of +form is produced only by a stress exceeding a certain value, the +substance is called a solid, however soft and plastic it may be. But +when the smallest stress, if only continued long enough, will cause a +perceptible and increasing change of form, the substance must be +regarded as a viscous fluid, however hard it may be." Maxwell +illustrates the difference between a soft solid and a hard liquid by a +jelly and a block of pitch; also by the experiment of supporting a +candle and a stick of sealing-wax; after a considerable time the +sealing-wax will be found bent and so is a fluid, but the candle remains +straight as a solid. + +4. _Definition of a Fluid._--A fluid is a substance which yields +continually to the slightest tangential stress in its interior; that is, +it can be divided very easily along any plane (given plenty of time if +the fluid is viscous). It follows that when the fluid has come to rest, +the tangential stress in any plane in its interior must vanish, and the +stress must be entirely normal to the plane. This mechanical axiom of +the _normality of fluid pressure_ is the foundation of the mathematical +theory of hydrostatics. + +The theorems of hydrostatics are thus true for all stationary fluids, +however viscous they may be; it is only when we come to hydrodynamics, +the science of the motion of a fluid, that viscosity will make itself +felt and modify the theory; unless we begin by postulating the perfect +fluid, devoid of viscosity, so that the principle of the _normality of +fluid pressure_ is taken to hold when the fluid is in movement. + + 5. _The Measurement of Fluid Pressure._--The pressure at any point of + a plane in the interior of a fluid is the intensity of the normal + thrust estimated per unit area of the plane. + + Thus, if a thrust of P lb. is distributed uniformly over a plane area + of A sq. ft., as on the horizontal bottom of the sea or any reservoir, + the pressure at any point of the plane is P/A lb. per sq. ft., or + P/144A lb. per sq. in. (lb./ft.² and lb./in.², in the Hospitalier + notation, to be employed in the sequel). If the distribution of the + thrust is not uniform, as, for instance, on a vertical or inclined + face or wall of a reservoir, then P/A represents the average pressure + over the area; and the actual pressure at any point is the average + pressure over a small area enclosing the point. Thus, if a thrust + [Delta]P lb. acts on a small plane area [Delta]A ft.² enclosing a + point B, the pressure p at B is the limit of [Delta]P/[Delta]A; and + + p = lt([Delta]P/[Delta]A) = dP/dA, (1) + + in the notation of the differential calculus. + + 6. _The Equality of Fluid Pressure in all Directions._--This + fundamental principle of hydrostatics follows at once from the + principle of the normality of fluid pressure implied in the definition + of a fluid in § 4. Take any two arbitrary directions in the plane of + the paper, and draw a small isosceles triangle abc, whose sides are + perpendicular to the two directions, and consider the equilibrium of a + small triangular prism of fluid, of which the triangle is the cross + section. Let P, Q denote the normal thrust across the sides bc, ca, + and R the normal thrust across the base ab. Then, since these three + forces maintain equilibrium, and R makes equal angles with P and Q, + therefore P and Q must be equal. But the faces bc, ca, over which P + and Q act, are also equal, so that the pressure on each face is equal. + A scalene triangle abc might also be employed, or a tetrahedron. + + [Illustration: FIG. 1a.] + + It follows that the pressure of a fluid requires to be calculated in + one direction only, chosen as the simplest direction for convenience. + + 7. _The Transmissibility of Fluid Pressure._--Any additional pressure + applied to the fluid will be transmitted equally to every point in the + case of a liquid; this principle of the _transmissibility of pressure_ + was enunciated by Pascal, 1653, and applied by him to the invention of + the _hydraulic press_. + + This machine consists essentially of two communicating cylinders (fig. + 1a), filled with liquid and closed by pistons. If a thrust P lb. is + applied to one piston of area A ft.², it will be balanced by a thrust + W lb. applied to the other piston of area B ft.², where + + p = P/A = W/B, (1) + + the pressure p of the liquid being supposed uniform; and, by making + the ratio B/A sufficiently large, the mechanical advantage can be + increased to any desired amount, and in the simplest manner possible, + without the intervention of levers and machinery. + + Fig. 1b shows also a modern form of the hydraulic press, applied to + the operation of covering an electric cable with a lead coating. + + 8. _Theorem._--In a fluid at rest under gravity the pressure is the + same at any two points in the same horizontal plane; in other words, a + surface of equal pressure is a horizontal plane. + + This is proved by taking any two points A and B at the same level, and + considering the equilibrium of a thin prism of liquid AB, bounded by + planes at A and B perpendicular to AB. As gravity and the fluid + pressure on the sides of the prism act at right angles to AB, the + equilibrium requires the equality of thrust on the ends A and B; and + as the areas are equal, the pressure must be equal at A and B; and so + the pressure is the same at all points in the same horizontal plane. + If the fluid is a liquid, it can have a free surface without diffusing + itself, as a gas would; and this free surface, being a surface of zero + pressure, or more generally of uniform atmospheric pressure, will also + be a surface of equal pressure, and therefore a horizontal plane. + + [Illustration: FIG. 1b.] + + Hence the _theorem_.--The free surface of a liquid at rest under + gravity is a horizontal plane. This is the characteristic + distinguishing between a solid and a liquid; as, for instance, between + land and water. The land has hills and valleys, but the surface of + water at rest is a horizontal plane; and if disturbed the surface + moves in waves. + + 9. _Theorem._--In a homogeneous liquid at rest under gravity the + pressure increases uniformly with the depth. + + This is proved by taking the two points A and B in the same vertical + line, and considering the equilibrium of the prism by resolving + vertically. In this case the thrust at the lower end B must exceed the + thrust at A, the upper end, by the weight of the prism of liquid; so + that, denoting the cross section of the prism by [alpha] ft.², the + pressure at A and By by p0 and p lb./ft.², and by w the density of the + liquid estimated in lb./ft.³, + + p[alpha] - p0[alpha] = w[alpha]·AB, (1) + + p = w·AB + p0. (2) + + Thus in water, where w = 62.4lb./ft.³, the pressure increases 62.4 + lb./ft.², or 62.4 ÷ 144 = 0.433 lb./in.² for every additional foot of + depth. + + 10. _Theorem._--If two liquids of different density are resting in + vessels in communication, the height of the free surface of such + liquid above the surface of separation is inversely as the density. + + For if the liquid of density [sigma] rises to the height h and of + density [rho] to the height k, and p0 denotes the atmospheric + pressure, the pressure in the liquid at the level of the surface of + separation will be [sigma]h + p0 and [rho]k + p0, and these being + equal we have + + [sigma]h = [rho]k. (1) + + The principle is illustrated in the article BAROMETER, where a column + of mercury of density [sigma] and height h, rising in the tube to the + Torricellian vacuum, is balanced by a column of air of density [rho], + which may be supposed to rise as a homogeneous fluid to a height k, + called the height of the homogeneous atmosphere. Thus water being + about 800 times denser than air and mercury 13.6 times denser than + water, + + k/h = [sigma]/[rho] = 800 × 13.6 = 10,880; (2) + + and with an average barometer height of 30 in. this makes k 27,200 + ft., about 8300 metres. + + 11. _The Head of Water or a Liquid._--The pressure [sigma]h at a depth + h ft. in liquid of density [sigma] is called the pressure due to a + _head_ of h ft. of the liquid. The atmospheric pressure is thus due to + an average head of 30 in. of mercury, or 30 × 13.6 ÷ 12 = 34 ft. of + water, or 27,200 ft. of air. The pressure of the air is a convenient + unit to employ in practical work, where it is called an "atmosphere"; + it is made the equivalent of a pressure of one kg/cm²; and one + ton/inch², employed as the unit with high pressure as in artillery, + may be taken as 150 atmospheres. + + 12. _Theorem._--A body immersed in a fluid is buoyed up by a force + equal to the weight of the liquid displaced, acting vertically upward + through the centre of gravity of the displaced liquid. + + For if the body is removed, and replaced by the fluid as at first, + this fluid is in equilibrium under its own weight and the thrust of + the surrounding fluid, which must be equal and opposite, and the + surrounding fluid acts in the same manner when the body replaces the + displaced fluid again; so that the resultant thrust of the fluid acts + vertically upward through the centre of gravity of the fluid + displaced, and is equal to the weight. + + When the body is floating freely like a ship, the equilibrium of this + liquid thrust with the weight of the ship requires that the weight of + water displaced is equal to the weight of the ship and the two centres + of gravity are in the same vertical line. So also a balloon begins to + rise when the weight of air displaced is greater than the weight of + the balloon, and it is in equilibrium when the weights are equal. This + theorem is called generally the _principle of Archimedes_. + + It is used to determine the density of a body experimentally; for if W + is the weight of a body weighed in a balance in air (strictly _in + vacuo_), and if W´ is the weight required to balance when the body is + suspended in water, then the upward thrust of the liquid or weight of + liquid displaced is W - W´, so that the _specific gravity_ (S.G.), + defined as the ratio of the weight of a body to the weight of an equal + volume of water, is W/(W - W´). + + As stated first by Archimedes, the principle asserts the obvious fact + that a body displaces its own volume of water; and he utilized it in + the problem of the determination of the adulteration of the crown of + Hiero. He weighed out a lump of gold and of silver of the same weight + as the crown; and, immersing the three in succession in water, he + found they spilt over measures of water in the ratio 1/14 : 4/77 : + 2/21 or 33 : 24 : 44; thence it follows that the gold : silver alloy + of the crown was as 11 : 9 by weight. + + 13. _Theorem._--The resultant vertical thrust on any portion of a + curved surface exposed to the pressure of a fluid at rest under + gravity is the weight of fluid cut out by vertical lines drawn round + the boundary of the curved surface. + + _Theorem._--The resultant horizontal thrust in any direction is + obtained by drawing parallel horizontal lines round the boundary, and + intersecting a plane perpendicular to their direction in a plane + curve; and then investigating the thrust on this plane area, which + will be the same as on the curved surface. + + The proof of these theorems proceeds as before, employing the + normality principle; they are required, for instance, in the + determination of the liquid thrust on any portion of the bottom of a + ship. + + In casting a thin hollow object like a bell, it will be seen that the + resultant upward thrust on the mould may be many times greater than + the weight of metal; many a curious experiment has been devised to + illustrate this property and classed as a hydrostatic paradox (Boyle, + _Hydrostatical Paradoxes_, 1666). + + [Illustration: FIG. 2.] + + Consider, for instance, the operation of casting a hemispherical bell, + in fig. 2. As the molten metal is run in, the upward thrust on the + outside mould, when the level has reached PP´, is the weight of metal + in the volume generated by the revolution of APQ; and this, by a + theorem of Archimedes, has the same volume as the cone ORR´, or 1/3 + [pi]y³, where y is the depth of metal, the horizontal sections being + equal so long as y is less than the radius of the outside hemisphere. + Afterwards, when the metal has risen above B, to the level KK´, the + additional thrust is the weight of the cylinder of diameter KK´ and + height BH. The upward thrust is the same, however thin the metal may + be in the interspace between the outer mould and the core inside; and + this was formerly considered paradoxical. + + _Analytical Equations of Equilibrium of a Fluid at rest under any + System of Force._ + + 14. Referred to three fixed coordinate axes, a fluid, in which the + pressure is p, the density [rho], and X, Y, Z the components of + impressed force per unit mass, requires for the equilibrium of the + part filling a fixed surface S, on resolving parallel to Ox, + _ _ _ _ _ + / / / / / + | | lp dS = | | | [rho]X dx dy dz, (1) + _/ _/ _/ _/ _/ + + where l, m, n denote the direction cosines of the normal drawn outward + of the surface S. + + But by Green's transformation + _ _ _ _ _ + / / / / / dp + | | lp dS = | | | -- dx dy dz, (2) + _/ _/ _/ _/ _/ dx + + thus leading to the differential relation at every point + + dp dp dp + -- = [rho]X, -- = [rho]Y, -- = [rho]Z. (3) + dx dy dz + + The three equations of equilibrium obtained by taking moments round + the axes are then found to be satisfied identically. + + Hence the space variation of the pressure in any direction, or the + _pressure-gradient_, is the resolved force per unit volume in that + direction. The resultant force is therefore in the direction of the + steepest pressure-gradient, and this is normal to the surface of equal + pressure; for equilibrium to exist in a fluid the lines of force must + therefore be capable of being cut orthogonally by a system of + surfaces, which will be surfaces of equal pressure. + + Ignoring temperature effect, and taking the density as a function of + the pressure, surfaces of equal pressure are also of equal density, + and the fluid is stratified by surfaces orthogonal to the lines of + force; + + 1 dp 1 dp 1 dp + ----- --, ----- --, ----- --, or X, Y, Z (4) + [rho] dx [rho] dy [rho] dz + + are the partial differential coefficients of some function P, = + [int]dp/[rho], of x, y, z; so that X, Y, Z must be the partial + differential coefficients of a potential -V, such that the force in + any direction is the downward gradient of V; and then + + dP dV + -- + -- = 0, or P + V = constant, (5) + dx dx + + in which P may be called the hydrostatic head and V the head of + potential. + + With variation of temperature, the surfaces of equal pressure and + density need not coincide; but, taking the pressure, density and + temperature as connected by some relation, such as the gas-equation, + the surfaces of equal density and temperature must intersect in lines + lying on a surface of equal pressure. + + 15. As an example of the general equations, take the simplest case of + a uniform field of gravity, with Oz directed vertically downward; + employing the gravitation unit of force, + + 1 dp 1 dp 1 dp + ----- -- = 0, ----- -- = 0, ----- -- = 1, (1) + [rho] dx [rho] dy [rho] dz + _ + / + P = | dp/[rho] = z + a constant. (2) + _/ + + When the density [rho] is uniform, this becomes, as before in (2) § 9 + + p = [rho]z + p0. (3) + + Suppose the density [rho] varies as some nth power of the depth below + O, then + + dp/dz = [rho] = [mu]z^n (4) + + z^(n+1) [rho]z [rho] /[rho]\^1/n + p = [mu]------- = ------ = ----- ( ----- ) , (5) + n + 1 n + 1 n + 1 \[mu] / + + supposing p and [rho] to vanish together. + + These equations can be made to represent the state of convective + equilibrium of the atmosphere, depending on the gas-equation + + p = [rho]k = R[rho][theta], (6) + + where [theta] denotes the absolute temperature; and then + + d[theta] d / p \ 1 + R-------- = -- ( ----- ) = -------, (7) + dz dz \[rho]/ (n + 1) + + so that the temperature-gradient d[theta]/dz is constant, as in + convective equilibrium in (11). + + From the gas-equation in general, in the atmosphere + + 1 dp 1 dp 1 d[theta] [rho] 1 d[theta] 1 1 d[theta] + ----- -- = --- -- - ------- -------- = ----- - ------- -------- = --- - ------- --------, (8) + [rho] dz p dz [theta] dz p [theta] dz k [theta] dz + + which is positive, and the density [rho] diminishes with the ascent, + provided the temperature-gradient d[theta]/dz does not exceed + [theta]/k. + + With uniform temperature, taking k constant in the gas-equation, + + dp/dz = [rho] = p/k, p = p0e^(z/k), (9) + + so that in ascending in the atmosphere of thermal equilibrium the + pressure and density diminish at compound discount, and for pressures + p1 and p2 at heights z1 and z2 + + (z1 - z2)/k = log e (p2/p1) = 2.3 log10 (p2/p1). (10) + + In the convective equilibrium of the atmosphere, the air is supposed + to change in density and pressure without exchange of heat by + conduction; and then + + [rho]/[rho]0 = ([theta]/[theta]0)^n, p/p0 = + ([theta]/[theta]0)^(n+1), (11) + + dz 1 dp p 1 + -------- = ----- -------- = (n + 1)------------R, [gamma] = 1 + ---, + d[theta] [rho] d[theta] [rho][theta] n + + where [gamma] is the ratio of the specific heat at constant pressure + and constant volume. + + In the more general case of the convective equilibrium of a spherical + atmosphere surrounding the earth, of radius a, + + dp p0 d[theta] a² + ----- = (n + 1)------ -------- = - --- dr, (12) + [rho] [rho]0 [theta]0 r² + + gravity varying inversely as the square of the distance r from the + centre; so that, k = p0/[rho]0, denoting the height of the homogeneous + atmosphere at the surface, [theta] is given by + + (n + 1) k (1 - [theta]/[theta]0) = a(1 - a/r), (13) + + or if c denotes the distance where [theta] = 0, + + [theta] a c - r + -------- = --- · -----. (14) + [theta]0 r c - a + + When the compressibility of water is taken into account in a deep + ocean, an experimental law must be employed, such as + + p - p0 = k([rho] - [rho]0), or [rho]/[rho]0 = 1 + + (p - p0)/[lambda], [lambda] = k[rho]0, (15) + + so that [lambda] is the pressure due to a head k of the liquid at + density [rho]0 under atmospheric pressure p0; and it is the gauge + pressure required on this law to double the density. Then + + dp/dz = kd[rho]/dz = [rho], [rho] = [rho]0e^(z/k), + p - p0 = k[rho]0(e^(z/k) - 1); (16) + + and if the liquid was incompressible, the depth at pressure p would be + (p - p0)/p0, so that the lowering of the surface due to compression is + + ke^(z/k) - k - z = ½z²/k, when k is large. (17) + + For sea water, [lambda] is about 25,000 atmospheres, and k is then + 25,000 times the height of the water barometer, about 250,000 metres, + so that in an ocean 10 kilometres deep the level is lowered about 200 + metres by the compressibility of the water; and the density at the + bottom is increased 4%. + + On another physical assumption of constant cubical elasticity + [lambda], + + dp = [lambda]d[rho]/[rho], (p - p0)/[lambda] = log([rho]/[rho]0), (18) + + dp [lambda] d[rho] / 1 1 \ [rho]0 z + -- = -------- ------ = [rho], [lambda]( ------ - ----- ) = z, 1 - ------ = ---, [lambda] = k[rho]0, (19) + zd [rho] dz \[rho]0 [rho]/ [rho] k + + and the lowering of the surface is + + p - p0 [rho] / z \ z² + ------ - z = k log ------ - z = k log ( 1 - --- ) - z [approx] --- (20) + [rho]0 [rho]0 \ k / 2k + + as before in (17). + + 16. _Centre of Pressure._--A plane area exposed to fluid pressure on + one side experiences a single resultant thrust, the integrated + pressure over the area, acting through a definite point called the + centre of pressure (C.P.) of the area. + + Thus if the plane is normal to Oz, the resultant thrust + _ _ + / / + R = | |pdxdy, (1) + _/_/ + + and the coordinates [=x], [=y] of the C.P. are given by + _ _ _ _ + / / / / + [=x]R = | | xp dx dy, [=y]R = | | yp dx dy. (2) + _/_/ _/_/ + + The C·P. is thus the C·G. of a plane lamina bounded by the area, in + which the surface density is p. + + If p is uniform, the C·P. and C·G. of the area coincide. + + For a homogeneous liquid at rest under gravity, p is proportional to + the depth below the surface, i.e. to the perpendicular distance from + the line of intersection of the plane of the area with the free + surface of the liquid. + + If the equation of this line, referred to new coordinate axes in the + plane area, is written + + x cos [alpha] + y sin [alpha] - h = 0, (3) + _ _ + / / + R = | | [rho](h - x cos [alpha] - y sin [alpha]) dx dy, (4) + _/_/ + _ _ + / / + [=x]R = | | [rho]x(h - x cos [alpha] - y sin [alpha]) dx dy, (5) + _/_/ + _ _ + / / + [=y]R = | | [rho]y(h - x cos [alpha] - y sin [alpha]) dx dy. + _/_/ + + Placing the new origin at the C.G. of the area A, + _ _ _ _ + / / / / + | | xd x dy = 0, | | y dx dy = 0, (6) + _/_/ _/_/ + + R = [rho]hA, (7) + _ _ _ _ + / / / / + [=x]hA = -cos [alpha] | | x² dA - sin [alpha] | | xy dA, (8) + _/_/ _/_/ + _ _ _ _ + / / / / + [=y]hA = -cos [alpha] | | xy dA - sin [alpha] | | y² dA. (9) + _/_/ _/_/ + + Turning the axes to make them coincide with the principal axes of the + area A, thus making [int][int] xy dA = 0, + + [=x]h = -a² cos [alpha], [=y]h = -b² sin [alpha], (10) + + where + _ _ _ _ + / / / / + | | x² dA = Aa², | | y² dA = Ab², (11) + _/_/ _/_/ + + a and b denoting the semi-axes of the momental ellipse of the area. + + This shows that the C.P. is the antipole of the line of intersection + of its plane with the free surface with respect to the momental + ellipse at the C.G. of the area. + + Thus the C.P. of a rectangle or parallelogram with a side in the + surface is at 2/3 of the depth of the lower side; of a triangle with a + vertex in the surface and base horizontal is ¾ of the depth of the + base; but if the base is in the surface, the C·P. is at half the depth + of the vertex; as on the faces of a tetrahedron, with one edge in the + surface. + + The _core_ of an area is the name given to the limited area round its + C.G. within which the C·P. must lie when the area is immersed + completely; the boundary of the core is therefore the locus of the + antipodes with respect to the momental ellipse of water lines which + touch the boundary of the area. Thus the core of a circle or an + ellipse is a concentric circle or ellipse of one quarter the size. + + The C.P. of water lines passing through a fixed point lies on a + straight line, the antipolar of the point; and thus the core of a + triangle is a similar triangle of one quarter the size, and the core + of a parallelogram is another parallelogram, the diagonals of which + are the middle third of the median lines. + + In the design of a structure such as a tall reservoir dam it is + important that the line of thrust in the material should pass inside + the core of a section, so that the material should not be in a state + of tension anywhere and so liable to open and admit the water. + +[Illustration: FIG. 3.] + +17. _Equilibrium and Stability of a Ship or Floating Body. The +Metacentre._--The principle of Archimedes in § 12 leads immediately to +the conditions of equilibrium of a body supported freely in fluid, like +a fish in water or a balloon in the air, or like a ship (fig. 3) +floating partly immersed in water and the rest in air. The body is in +equilibrium under two forces:--(i.) its weight W acting vertically +downward through G, the C.G. of the body, and (ii.) the buoyancy of the +fluid, equal to the weight of the displaced fluid, and acting vertically +upward through B, the C.G. of the displaced fluid; for equilibrium these +two forces must be equal and opposite in the same line. + +The conditions of equilibrium of a body, floating like a ship on the +surface of a liquid, are therefore:-- + +(i.) the weight of the body must be less than the weight of the total +volume of liquid it can displace; or else the body will sink to the +bottom of the liquid; the difference of the weights is called the +"reserve of buoyancy." + +(ii.) the weight of liquid which the body displaces in the position of +equilibrium is equal to the weight W of the body; and + +(iii.) the C.G., B, of the liquid displaced and G of the body, must lie +in the same vertical line GB. + +18. In addition to satisfying these conditions of equilibrium, a ship +must fulfil the further condition of stability, so as to keep upright; +if displaced slightly from this position, the forces called into play +must be such as to restore the ship to the upright again. The stability +of a ship is investigated practically by inclining it; a weight is moved +across the deck and the angle is observed of the heel produced. + + Suppose P tons is moved c ft. across the deck of a ship of W tons + displacement; the C.G. will move from G to G1 the reduced distance + G1G2 = c(P/W); and if B, called the centre of buoyancy, moves to B1, + along the curve of buoyancy BB1, the normal of this curve at B1 will + be the new vertical B1G1, meeting the old vertical in a point M, the + centre of curvature of BB1, called the _metacentre_. + + If the ship heels through an angle [theta] or a slope of 1 in m, + + GM = GG1cot[theta] = mc(P/W), (1) + + and GM is called the metacentric height; and the ship must be + ballasted, so that G lies below M. If G was above M, the tangent drawn + from G to the evolute of B, and normal to the curve of buoyancy, would + give the vertical in a new position of equilibrium. Thus in H.M.S. + "Achilles" of 9000 tons displacement it was found that moving 20 tons + across the deck, a distance of 42 ft., caused the bob of a pendulum 20 + ft. long to move through 10 in., so that + + 240 20 + GM = --- × 42 × ---- = 2.24 ft.; (2) + 10 9000 + + also + + cot [theta] = 24, [theta] = 2°24´. (3) + + In a diagram it is conducive to clearness to draw the ship in one + position, and to incline the water-line; and the page can be turned if + it is desired to bring the new water-line horizontal. + + Suppose the ship turns about an axis through F in the water-line area, + perpendicular to the plane of the paper; denoting by y the distance of + an element dA if the water-line area from the axis of rotation, the + change of displacement is [sum]ydA tan[theta], so that there is no + change of displacement if [sum]ydA = 0, that is, if the axis passes + through the C.G. of the water-line area, which we denote by F and call + the centre of flotation. + + The righting couple of the wedges of immersion and emersion will be + + [Sigma]wy dA tan [theta]·y = w tan [theta] [Sigma] y² dA + = w tan [theta]·Ak² ft. tons, (4) + + w denoting the density of water in tons/ft.³, and W = wV, for a + displacement of V ft.³ + + This couple, combined with the original buoyancy W through B, is + equivalent to the new buoyancy through B, so that + + W.BB1 = wAk² tan [theta], (5) + + BM = BB1 cot [theta] = Ak²/V, (6) + + giving the radius of curvature BM of the curve of buoyancy B, in terms + of the displacement V, and Ak² the moment of inertia of the water-line + area about an axis through F, perpendicular to the plane of + displacement. + + An inclining couple due to moving a weight about in a ship will heel + the ship about an axis perpendicular to the plane of the couple, only + when this axis is a principal axis at F of the momental ellipse of the + water-line area A. For if the ship turns through a small angle [theta] + about the line FF´, then b1, b2, the C·G. of the wedge of immersion + and emersion, will be the C·P. with respect to FF´ of the two parts of + the water-line area, so that b1b2 will be conjugate to FF´ with + respect to the momental ellipse at F. + + The naval architect distinguishes between the _stability of form_, + represented by the righting couple W.BM, and the _stability of + ballasting_, represented by W.BG. Ballasted with G at B, the righting + couple when the ship is heeled through [theta] is given by W.BM. + tan[theta]; but if weights inside the ship are raised to bring G above + B, the righting couple is diminished by W.BG.tan[theta], so that the + resultant righting couple is W·GM·tan[theta]. Provided the ship is + designed to float upright at the smallest draft with no load on board, + the stability at any other draft of water can be arranged by the + stowage of the weight, high or low. + + 19. Proceeding as in § 16 for the determination of the C.P. of an + area, the same argument will show that an inclining couple due to the + movement of a weight P through a distance c will cause the ship to + heel through an angle [theta] about an axis FF´ through F, which is + conjugate to the direction of the movement of P with respect to an + ellipse, not the momental ellipse of the water-line area A, but a + confocal to it, of squared semi-axes + + a² - hV/A, b² - hV/A, (1) + + h denoting the vertical height BG between C.G. and centre of buoyancy. + The varying direction of the inclining couple Pc may be realized by + swinging the weight P from a crane on the ship, in a circle of radius + c. But if the weight P was lowered on the ship from a crane on shore, + the vessel would sink bodily a distance P/wA if P was deposited over + F; but deposited anywhere else, say over Q on the water-line area, the + ship would turn about a line the antipolar of Q with respect to the + confocal ellipse, parallel to FF´, at a distance FK from F + + FK = (k² - hV/A)/FQ sin QFF´ (2) + + through an angle [theta] or a slope of one in m, given by + + 1 P P V + sin [theta] = --- = ----- = --- · -------- FQ sin QFF´, (3) + m wA·FK W Ak² - hV + + where k denotes the radius of gyration about FF´ of the water-line + area. Burning the coal on a voyage has the reverse effect on a + steamer. + + +HYDRODYNAMICS + +20. In considering the motion of a fluid we shall suppose it +non-viscous, so that whatever the state of motion the stress across any +section is normal, and the principle of the normality and thence of the +equality of fluid pressure can be employed, as in hydrostatics. The +practical problems of fluid motion, which are amenable to mathematical +analysis when viscosity is taken into account, are excluded from +treatment here, as constituting a separate branch called "hydraulics" +(q.v.). Two methods are employed in hydrodynamics, called the Eulerian +and Lagrangian, although both are due originally to Leonhard Euler. In +the Eulerian method the attention is fixed on a particular point of +space, and the change is observed there of pressure, density and +velocity, which takes place during the motion; but in the Lagrangian +method we follow up a particle of fluid and observe how it changes. The +first may be called the statistical method, and the second the +historical, according to J. C. Maxwell. The Lagrangian method being +employed rarely, we shall confine ourselves to the Eulerian treatment. + + +_The Eulerian Form of the Equations of Motion._ + +21. The first equation to be established is the _equation of +continuity_, which expresses the fact that the increase of matter within +a fixed surface is due to the flow of fluid across the surface into its +interior. + + In a straight uniform current of fluid of density [rho], flowing with + velocity q, the flow in units of mass per second across a plane area + A, placed in the current with the normal of the plane making an angle + [theta] with the velocity, is [rho]Aq cos [theta], the product of the + density [rho], the area A, and q cos [theta] the component velocity + normal to the plane. + + Generally if S denotes any closed surface, fixed in the fluid, M the + mass of the fluid inside it at any time t, and [theta] the angle which + the outward-drawn normal makes with the velocity q at that point, + + dM/dt = rate of increase of fluid inside the surface, (1) + + = flux across the surface into the interior + _ _ + / / + = - | | [rho]q cos [theta] dS, + _/_/ + + the integral equation of continuity. + + In the Eulerian notation u, v, w denote the components of the velocity + q parallel to the coordinate axes at any point (x, y, z) at the time + t; u, v, w are functions of x, y, z, t, the independent variables; and + d is used here to denote partial differentiation with respect to any + one of these four independent variables, all capable of varying one at + a time. + + To transfer the integral equation into the differential equation of + continuity, Green's transformation is required again, namely, + _ _ _ _ _ + / / / /d[xi] d[eta] d[zeta] \ / / + | | | ( ----- + ------ + ------- )dx dy dz = | | (l[xi] + m[eta] + n[zeta]) dS, (2) + _/_/_/ \ dx dy dz / _/_/ + + or individually + _ _ _ _ _ + / / / d[xi] / / + | | | ----- dx dy dz = | | l[xi] dS,..., (3) + _/_/_/ dx _/_/ + + where the integrations extend throughout the volume and over the + surface of a closed space S; l, m, n denoting the direction cosines of + the outward-drawn normal at the surface element dS, and [xi], [eta], + [zeta] any continuous functions of x, y, z. + + The integral equation of continuity (1) may now be written + _ _ _ _ _ + / / / d[rho] / / + | | | ----- dx dy dz = | | (l[rho]u + m[rho]v + n[rho]w) dS = 0, (4) + _/_/_/ dt _/_/ + + which becomes by Green's transformation + _ _ _ + / / / /d[rho] d([rho]u) d([rho]v) d([rho]w)\ + | | | ( ------ + --------- + --------- + -------- ) dx dy dz = 0, (5) + _/_/_/ \ dt dx dy dz / + + leading to the differential equation of continuity when the + integration is removed. + +22. The equations of motion can be established in a similar way by +considering the rate of increase of momentum in a fixed direction of the +fluid inside the surface, and equating it to the momentum generated by +the force acting throughout the space S, and by the pressure acting over +the surface S. + + Taking the fixed direction parallel to the axis of x, the time-rate of + increase of momentum, due to the fluid which crosses the surface, is + _ _ _ _ + / / / / + - | | [rho]uq cos [theta] dS = - | | (l[rho]u² + m[rho]uv + n[rho]uw) dS, (1) + _/_/ _/_/ + + which by Green's transformation is + _ _ _ + / / / /d([rho]u²) d([rho]uv) d([rho]uw)\ + - | | | (---------- + ---------- + ---------- ) dx dy dz. (2) + _/_/_/ \ dx dy dz / + + The rate of generation of momentum in the interior of S by the + component of force, X per unit mass, is + _ _ _ + / / / + | | | [rho]X dx dy dz, (3) + _/_/_/ + + and by the pressure at the surface S is + _ _ _ _ _ + / / / / / dp + - | | lp dS = - | | | -- dx dy dz, (4) + _/_/ _/_/_/ dx + + by Green's transformation. + + The time rate of increase of momentum of the fluid inside S is + _ _ _ + / / / d([rho]u) + | | | --------- dx dy dz; (5) + _/_/_/ dt + + and (5) is the sum of (1), (2), (3), (4), so that + _ _ _ + / / / /d[rho]u d[rho]u² d[rho]uv d[rho]uw dp \ + | | | ( ------- + -------- + -------- + -------- - [rho]X + -- ) dx dy dz = 0, (6) + _/_/_/ \ dt dx dy dz dx / + + leading to the differential equation of motion + + d[rho]u d[rho]u² d[rho]uv, d[rho]uw dp + ------- + -------- + -------- + -------- = [rho]X - --, (7) + dt dx dy dz dx + + with two similar equations. + + The absolute unit of force is employed here, and not the gravitation + unit of hydrostatics; in a numerical application it is assumed that + C.G.S. units are intended. + + These equations may be simplified slightly, using the equation of + continuity (5) § 21; for + + d[rho]u d[rho]u² d[rho]uv d[rho]uw + ------- + -------- + -------- + -------- + dt dx dy dz + + /du du du du \ + = [rho] ( -- + u-- + v-- + w-- ) + \dt dx dy dz / + + /d[rho] d[rho]u d[rho]v d[rho]w \ + + u ( ------ + ------- + ------- + ------- ), (8) + \ dt dx dy dz / + + reducing to the first line, the second line vanishing in consequence + of the equation of continuity; and so the equation of motion may be + written in the more usual form + + du du du du 1 dp + -- + u-- + v-- + w-- = X - ----- --, (9) + dt dx dy dz [rho] dx + + with the two others + + dv dv dv dv 1 dp + -- + u-- + v-- + w-- = Y - ----- --, (10) + dt dx dy dz [rho] dy + + dw dw dw dw 1 dp + -- + u-- + v-- + w-- = Z - ----- --. (11) + dt dx dy dz [rho] dz + + + +23. As a rule these equations are established immediately by determining +the component acceleration of the fluid particle which is passing +through (x, y, z) at the instant t of time considered, and saying that +the reversed acceleration or kinetic reaction, combined with the +impressed force per unit of mass and pressure-gradient, will according +to d'Alembert's principle form a system in equilibrium. + + To determine the component acceleration of a particle, suppose F to + denote any function of x, y, z, t, and investigate the time rate of F + for a moving particle; denoting the change by DF/dt, + + DF F(x + u[delta]t, y + v[delta]t, z + w[delta]t, t + [delta]t) - F(x, y, z, t) + -- = lt·---------------------------------------------------------------------------- + dt [delta]t + + dF dF dF dF + = -- + u-- + v-- + w--; (1) + dt dx dy dz + + and D/dt is called particle differentiation, because it follows the + rate of change of a particle as it leaves the point x, y, z; but + + dF/dt, dF/dx, dF/dy, dF/dz (2) + + represent the rate of change of F at the time t, at the point, x, y, + z, fixed in space. + + The components of acceleration of a particle of fluid are consequently + + Du du du du du + -- = -- + u-- + v-- + w--, (3) + dt dt dx dy dz + + Dv dv dv dv dv + -- = -- + u-- + v-- + w--, (4) + dt dt dx dy dz + + Dw dw dw dw dw + -- = -- + u-- + v-- + w--, (5) + dt dt dx dy dz + + leading to the equations of motion above. + + If F (x, y, z, t) = 0 represents the equation of a surface containing + always the same particles of fluid, + + DF dF dF dF dF + -- = 0, or -- + u-- + v-- + w-- = 0, (6) + dt dt dx dy dz + + which is called the differential equation of the _bounding surface_. A + bounding surface is such that there is no flow of fluid across it, as + expressed by equation (6). The surface always contains the same fluid + inside it, and condition (6) is satisfied over the complete surface, + as well as any part of it. + + But turbulence in the motion will vitiate the principle that a + bounding surface will always consist of the same fluid particles, as + we see on the surface of turbulent water. + + 24. To integrate the equations of motion, suppose the impressed force + is due to a potential V, such that the force in any direction is the + rate of diminution of V, or its downward gradient; and then + + X = -dV/dx, Y = -dV/dy, Z = -dV/dz; (1) + + and putting + + dw dv du dw dv du + -- - -- = 2[xi], -- - -- = 2[eta], -- - -- = 2[zeta], (2) + dy dz dz dx dx dy + + d[xi] d[eta] d[zeta] + ----- + ------ + ------- = 0, (3) + dx dy dz + + the equations of motion may be written + + du dH + -- - 2v[zeta] + 2w[eta] + -- = 0, (4) + dt dx + + dv dH + -- - 2w[xi] + 2u[zeta] + -- = 0, (5) + dt dy + + dw dH + -- - 2u[eta] + 2w[xi] + -- = 0, (6) + dt dz + + where + _ + / + H = | dp/[rho] + V + ½q², (7) + _/ + + q² = u² + v² + w², (8) + + and the three terms in H may be called the pressure head, potential + head, and head of velocity, when the gravitation unit is employed and + ½q² is replaced by ½q²/g. + + Eliminating H between (5) and (6) + + D[xi] du dv dw / du dv dw \ + ----- - [xi]-- - [eta]-- - [zeta]-- + [xi]( -- + -- + -- ) = 0, (9) + dt dx dx dx \ dx dy dz / + + and combining this with the equation of continuity + + 1 D[rho] du dv dw + ----- ------ + -- + -- + -- = 0, (10) + [rho] dt dx dy dz + + we have + + D /[xi] \ [xi] du [eta] dv [zeta] dw + -- ( ----- ) - ----- -- - ----- -- - ------ -- = 0, (11) + dt \[rho]/ [rho] dx [rho] dx [rho] dx + + with two similar equations. + + Putting + + [omega]² = [xi]² + [eta]² + [zeta]², (12) + + a _vortex line_ is defined to be such that the tangent is in the + direction of [omega], the resultant of [xi], [eta], [zeta], called the + components of molecular rotation. A small sphere of the fluid, if + frozen suddenly, would retain this angular velocity. + + If [omega] vanishes throughout the fluid at any instant, equation (11) + shows that it will always be zero, and the fluid motion is then called + _irrotational_; and a function [phi] exists, called the _velocity + function_, such that + + udx + vdy + wdz = -d[phi], (13) + + and then the velocity in any direction is the space-decrease or + downward gradient of [phi]. + + 25. But in the most general case it is possible to have three + functions [phi], [psi], m of x, y, z, such that + + udx + vdy + wdz = -d[phi] - md[psi], (1) + + as A. Clebsch has shown, from purely analytical considerations + (_Crelle_, lvi.); and then + + d([psi], m) d([psi], m) d([psi], m) + [xi] = ½ -----------, [eta] = ½ -----------, [zeta] = ½ -----------, (2) + d(y, z) d(z, x) d(x, y) + + and + + d[psi] d[psi] d[psi] dm dm dm + [xi]------ + [eta]------ + [zeta]------ = 0, [xi]-- + [eta]-- + [zeta]-- = 0, (3) + dx dy dz dx dy dz + + so that, at any instant, the surfaces over which [psi] and m are + constant intersect in the vortex lines. + + Putting + + d[phi] d[psi] + H - ------ - m ------ = K, (4) + dt dt + the equations of motion (4), (5), (6) § 24 can be written + + dK d([psi],m) + -- - 2u[zeta] + 2w[eta] - ---------- = 0, ..., ...; (5) + dx d(x,t) + + and therefore + + dK dK dK + [xi]-- + [eta]-- + [zeta]-- = 0. (6) + dx dy dz + + Equation (5) becomes, by a rearrangement, + + dK d[psi] /dm dm dm dm \ + -- - ------ ( -- + u-- + v-- + w-- ) + dx dx \dt dx dy dz / + + dm / d[psi] d[psi] d[psi] d[psi] \ + + -- ( ------ + u------ + v------ + w------ ) = 0, ..., ..., (7) + dx \ dt dx dy dz / + + dK d[psi] Dm dm D[psi] + -- - ------ -- + -- ------ = 0, ..., ..., (8) + dx dx dt dx dt + + and as we prove subsequently (§ 37) that the vortex lines are composed + of the same fluid particles throughout the motion, the surface m and + [psi] satisfies the condition of (6) § 23; so that K is uniform + throughout the fluid at any instant, and changes with the time only, + and so may be replaced by F(t). + + 26. When the motion is _steady_, that is, when the velocity at any + point of space does not change with the time, + + dK + -- - 2v[zeta] + 2w[eta] = 0, ..., ... (1) + dx + + dK dK dK dK dK dK + [xi]-- + [eta]-- + [zeta]-- = 0, u-- + v-- + w-- = 0, (2) + dx dy dz dx dy dz + and + _ + / + K = | dp/[rho] + V + ½q² = H (3) + _/ + + is constant along a vortex line, and a _stream line_, the path of a + fluid particle, so that the fluid is traversed by a series of H + surfaces, each covered by a network of stream lines and vortex lines; + and if the motion is irrotational H is a constant throughout the + fluid. + + Taking the axis of x for an instant in the normal through a point on + the surface H = constant, this makes u = 0, [xi] = 0; and in steady + motion the equations reduce to + + dH/d[nu] = 2v[zeta] - 2w[eta] = 2q[omega] sin [theta], (4) + + where [theta] is the angle between the stream line and vortex line; + and this holds for their projection on any plane to which d[nu] is + drawn perpendicular. + + In plane motion (4) reduces to + + dH / dQ q \ + ----- = 2q[zeta] = q ( -- + --- ), (5) + d[nu] \ dv r / + + if r denotes the radius of curvature of the stream line, so that + + 1 dp dV dH d½q² q² + ----- ----- + ----- = ----- - ----- = ---, (6) + [rho] d[nu] d[nu] d[nu] d[nu] r + + the normal acceleration. + + The osculating plane of a stream line in steady motion contains the + resultant acceleration, the direction ratios of which are + + du du du d½q² d½q² dH + u-- + v-- + w-- = ---- - 2v[zeta] + 2w[eta] = ---- - --, ..., (7) + dx dy dz dx dx dx + + and when q is stationary, the acceleration is normal to the surface H + = constant, and the stream line is a geodesic. + + Calling the sum of the pressure and potential head the statical head, + surfaces of constant statical and dynamical head intersect in lines on + H, and the three surfaces touch where the velocity is stationary. + + Equation (3) is called Bernoulli's equation, and may be interpreted as + the balance-sheet of the energy which enters and leaves a given tube + of flow. + + If homogeneous liquid is drawn off from a vessel so large that the + motion at the free surface at a distance may be neglected, then + Bernoulli's equation may be written + + H = p/[rho] + z + q²/2g = P/[rho] + h, (8) + + where P denotes the atmospheric pressure and h the height of the free + surface, a fundamental equation in hydraulics; a return has been made + here to the gravitation unit of hydrostatics, and Oz is taken + vertically upward. + + In particular, for a jet issuing into the atmosphere, where p = P, + + q²/2g = h - z, (9) + + or the velocity of the jet is due to the head k - z of the still free + surface above the orifice; this is Torricelli's theorem (1643), the + foundation of the science of hydrodynamics. + + 27. _Uniplanar Motion._--In the uniplanar motion of a homogeneous + liquid the equation of continuity reduces to + + du dv + -- + -- = 0, (1) + dx dy + + so that we can put + + u = -d[psi]/dy, v = d[psi]/dx, (2) + + where [psi] is a function of x, y, called the stream- or + current-function; interpreted physically, [psi] - [psi]0, the + difference of the value of [psi] at a fixed point A and a variable + point P is the flow, in ft.³/second, across any curved line AP from A + to P, this being the same for all lines in accordance with the + continuity. + + Thus if d[psi] is the increase of [psi] due to a displacement from P + to P´, and k is the component of velocity normal to PP´, the flow + across PP´ is d[psi] = k·PP´; and taking PP´ parallel to Ox, d[psi] = + vdx; and similarly d[psi]= -udy with PP´ parallel to Oy; and generally + d[psi]/ds is the velocity across ds, in a direction turned through a + right angle forward, against the clock. + + In the equations of uniplanar motion + + dv du d²[psi] d²[psi] + 2[zeta] = -- - -- = ------ + ------ = -[Nabla]²[psi], suppose, (3) + dx dy dx² dy² + + so that in steady motion + + dH d[psi] dH d[psi] dH + -- + [Nabla]²[psi]------ = 0, -- + [Nabla]²[psi]------ = 0, ------ + [Nabla]²[psi] = 0, (4) + dx dx dy dy d[psi] + + and [Nabla]²[psi] must be a function of [psi]. + + If the motion ia irrotational, + + d[phi] d[psi] d[phi] d[psi] + u = - ------ = - ------, v = - ----- = ------, (5) + dx dy dy dx´ + + so that [psi] and [phi] are conjugate functions of x and y, + + [phi] + [psi]i = [f](x + yi), [Nabla]²[psi] = 0, [Nabla]²[phi] = 0; (6) + + or putting + + [phi] + [psi]i = w, x + yi = z, w = [f](z). + + The curves [phi] = constant and [psi] = constant form an orthogonal + system; and the interchange of [phi] and [psi] will give a new state + of uniplanar motion, in which the velocity at every point is turned + through a right angle without alteration of magnitude. + + For instance, in a uniplanar flow, radially inward towards O, the flow + across any circle of radius r being the same and denoted by 2[pi]m, + the velocity must be m/r, and + + [phi] = m log r, [psi] = m[theta], + [phi] + [psi]i = m log re^(i[theta]), w = m log z. (7) + + Interchanging these values + + [psi] = m log r, [phi] = m[theta], + [psi] + [phi]i = m log re^(i[theta]) (8) + + gives a state of vortex motion, circulating round Oz, called a + straight or columnar vortex. + + A single vortex will remain at rest, and cause a velocity at any point + inversely as the distance from the axis and perpendicular to its + direction; analogous to the magnetic field of a straight electric + current. + + If other vortices are present, any one may be supposed to move with + the velocity due to the others, the resultant stream-function being + + [psi] = [Sigma]m log r = log [Pi]r^m; (9) + + the path of a vortex is obtained by equating the value of [psi] at the + vortex to a constant, omitting the r^m of the vortex itself. + + When the liquid is bounded by a cylindrical surface, the motion of a + vortex inside may be determined as due to a series of vortex-images, + so arranged as to make the flow zero across the boundary. + + For a plane boundary the image is the optical reflection of the + vortex. For example, a pair of equal opposite vortices, moving on a + line parallel to a plane boundary, will have a corresponding pair of + images, forming a rectangle of vortices, and the path of a vortex will + be the Cotes' spiral + + r sin 2[theta] = 2a, or x^(-2) + y^(-2) = a^(-2); (10) + + this is therefore the path of a single vortex in a right-angled + corner; and generally, if the angle of the corner is [pi]/n, the path + is the Cotes' spiral + + r sin n[theta] = na. (11) + + A single vortex in a circular cylinder of radius a at a distance c + from the centre will move with the velocity due to an equal opposite + image at a distance a²/c, and so describe a circle with velocity + + mc/(a² - c²) in the periodic time 2[pi](a² - c²)/m. (12) + + Conjugate functions can be employed also for the motion of liquid in a + thin sheet between two concentric spherical surfaces; the components + of velocity along the meridian and parallel in colatitude [theta] and + longitude [lambda] can be written + + d[phi] 1 d[psi] 1 d[psi] d[psi] + -------- = ----------- ---------, ----------- --------- = - --------, (13) + d[theta] sin [theta] d[lambda] sin [theta] d[lambda] d[theta] + + and then + + [phi] + [psi]i = F(tan ½[theta]·e^([lambda]i)). (14) + + 28. _Uniplanar Motion of a Liquid due to the Passage of a Cylinder + through it._--A stream-function [psi] must be determined to satisfy + the conditions + + [Nabla]²[psi] = 0, throughout the liquid; (1) + + [psi] = constant, over any fixed boundary; (2) + + d[psi]/ds = normal velocity reversed over a solid boundary, (3) + + so that, if the solid is moving with velocity U in the direction Ox, + d[psi]/ds = -Udy/ds, or [psi] + Uy = constant over the moving + cylinder; and [psi] + Uy = [psi]´ is the stream function of the + relative motion of the liquid past the cylinder, and similarly [psi] - + Vx for the component velocity V along Oy; and generally + + [psi]´ = [psi] + Uy - Vx (4) + + is the relative stream-function, constant over a solid boundary moving + with components U and V of velocity. + + If the liquid is stirred up by the rotation R of a cylindrical body, + + d[psi]/ds = normal velocity reversed + + dx dy + = -Rx-- - Ry--, (5) + ds ds + + [psi] + ½R(x² + y²) = [psi]´, (6) + + a constant over the boundary; and [psi]´ is the current-function of + the relative motion past the cylinder, but now + + V²[psi]´ + 2R = 0, (7) + + throughout the liquid. + + Inside an equilateral triangle, for instance, of height h, + + [psi]´ = -2R[alpha][beta][gamma]/h, (8) + + where [alpha], [beta], [gamma] are the perpendiculars on the sides of + the triangle. + + In the general case [psi]´ = [psi] + Uy - Vx + ½R(x² + y²) is the + relative stream function for velocity components, U, V, R. + + 29. _Example 1._--Liquid motion past a circular cylinder. + + Consider the motion given by + + [omega] = U(z + a²/z), (1) + + so that + + / a²\ / a² \ + [phi] = U ( r + -- ) cos [theta] = U ( 1 + -- )x, (2) + \ r / \ r² / + + / a²\ / a² \ + [psi] = U ( r - -- ) sin [theta] = U ( 1 - -- )y. + \ r / \ r² / + + Then [psi] = 0 over the cylinder r = a, which may be considered a + fixed post; and a stream line past it along which [psi] = Uc, a + constant, is the curve + + / a²\ + ( r - -- ) sin [theta] = c, (x² + y²)(y - c) - a²y = 0 (3) + \ r / + + a cubic curve (C3). + + Over a concentric cylinder, external or internal, of radius r = b, + + / a²\ + [psi]´ = [psi] + U1y = [U ( 1 - --- ) + U1] y, (4) + \ b²/ + + and [psi]´ is zero if + + U1/U = (a² - b²)/b²; (5) + + so that the cylinder may swim for an instant in the liquid without + distortion, with this velocity U1, and [omega] in (1) will give the + liquid motion in the interspace between the fixed cylinder r = a and + the concentric cylinder r = b, moving with velocity U1. + + When b = 0, U1 = [oo]; and when b = [oo], U1 = -U, so that at infinity + the liquid is streaming in the direction xO with velocity U. + + If the liquid is reduced to rest at infinity by the superposition of + an opposite stream given by [omega] = -Uz, we are left with + + [omega] = Ua²/z, (6) + + [phi] = U(a²/r) cos [theta] = Ua²x/(x² + y²), (7) + + [psi] = -U(a²/r) sin [theta] = -Ua²y/(x² + y²), (8) + + giving the motion due to the passage of the Cylinder r = a with + velocity U through the origin O in the direction Ox. + + If the direction of motion makes an angle [theta]´ with Ox, + + d[phi] / d[phi] 2xy + tan[theta]´ = ----- / ----- = ------ = tan 2[theta], [theta] = ½[theta]´, (9) + dy / dx x² - y² + + and the velocity is Ua²/r². + + Along the path of a particle, defined by the C3 of (3), + + y² y(y - c) + sin² ½[theta]´ = ------- = -------, (10) + x² + y² a² + + d[theta]´ 2y - c dy + ½ sin [theta]´ --------- = ------ --, (11) + ds a² ds + + on the radius of curvature is ¼a²/(y - ½c), which shows that the curve + is an Elastica or Lintearia. (J. C. Maxwell, _Collected Works_, ii. + 208.) + + If [phi]1 denotes the velocity function of the liquid filling the + cylinder r = b, and moving bodily with it with velocity U1, + + [phi]1 = -U1x, (12) + + and over the separating surface r = b + + [phi] U / a²\ a² + b² + --------- = - -- ( 1 + -- ) = -------, (13) + [phi]1 U1 \ b²/ a² - b² + + and this, by § 36, is also the ratio of the kinetic energy in the + annular interspace between the two cylinders to the kinetic energy of + the liquid moving bodily inside r = b. + + Consequently the inertia to overcome in moving the cylinder r = b, + solid or liquid, is its own inertia, increased by the inertia of + liquid (a² + b²)/(a² - b²) times the volume of the cylinder r = b; + this total inertia is called the effective inertia of the cylinder r = + b, at the instant the two cylinders are concentric. + + With liquid of density [rho], this gives rise to a kinetic reaction to + acceleration dU/dt, given by + + a² + b² dU a² + b² dU + [pi][rho]b² ------- -- = ------- M´--, (14) + a² - b² dt a² - b² dt + + if M´ denotes the mass of liquid displaced by unit length of the + cylinder r = b. In particular, when a = [oo], the extra inertia is M´. + + When the cylinder r = a is moved with velocity U and r = b with + velocity U1 along Ox, + + a² / b² \ b² / a²\ + [phi] = U ------- ( --- + r ) cos [theta] - U1------- ( r + --- ) cos [theta], (15) + b² - a² \ r / b² - a² \ r / + + a² / b² \ b² / a²\ + [psi] = -U ------- ( --- - r ) sin [theta] - U1------- ( r - --- ) sin [theta]; (16) + b² - a² \ r / b² - a² \ r / + + and similarly, with velocity components V and V1 along Oy + + a² / b² \ b² / a²\ + [phi] = V ------- ( --- + r ) sin [theta] - V1------- ( r + --- ) sin [theta], (17) + b² - a² \ r / b² - a² \ r / + + a² / b² \ b² / a²\ + [psi] = V ------- ( --- - r ) cos [theta] + V1------- ( r - --- ) cos [theta], (18) + b² - a² \ r / b² - a² \ r / + + and then for the resultant motion + a² z a²b² U + Vi + w = (U² + V²) ------- ------ + ------- ------ + b² - a² U + Vi b² - a² z + + a² z a²b² U1 + V1i + -(U1² + V1²) ------- -------- + ------- --------. (19) + b² - a² U1 + V1i b² - a² z + + The resultant impulse of the liquid on the cylinder is given by the + component, over r = a (§ 36), + _ + / / b² + a² 2b² \ + X = | [rho][phi] cos [theta]·ad[theta] = [pi][rho]a² ( U ------- - U1 ------- ); (20) + _/ \ b² - a² b² - a²/ + + and over r = b + _ + / / 2a² b² + a² \ + X1 = | [rho][phi] cos [theta]·bd[theta] = [pi][rho]b² ( U ------ - U1------- ), (21) + _/ \ b² - a² b² - a² / + + and the difference X - X1 is the component momentum of the liquid in + the interspace; with similar expressions for Y and Y1. + + Then, if the outside cylinder is free to move + + V1 2a² b² - a² + X1 = 0, -- = -------, X = [pi][rho]a²U -------. (22) + U b² + a² b² + a² + + But if the outside cylinder is moved with velocity U1, and the inside + cylinder is solid or filled with liquid of density [sigma], + + U1 2[rho]b² + X = -[pi][rho]a²U, -- = --------------------------------, + U [rho](b² + a²) + [sigma](b² - a²) + + U - U1 ([rho] - [sigma])(b² - a²) + ------ = ---------------------------------, (23) + U1 [rho](b² + a²) + [sigma](b² - a²) + + and the inside cylinder starts forward or backward with respect to the + outside cylinder, according as [rho] > or < [sigma]. + + 30. The expression for [omega] in (1) § 29 may be increased by the + addition of the term + + im log z = -m[theta] + im log r, (1) + + representing vortex motion circulating round the annulus of liquid. + + Considered by itself, with the cylinders held fixed, the vortex sets + up a circumferential velocity m/r on a radius r, so that the angular + momentum of a circular filament of annular cross section dA is + [rho]mdA, and of the whole vortex is [rho]m[pi](b² - a²). + + Any circular filament can be started from rest by the application of a + circumferential impulse [pi][rho]mdr at each end of a diameter; so + that a mechanism attached to the cylinders, which can set up a uniform + distributed impulse [pi][rho]m across the two parts of a diameter in + the liquid, will generate the vortex motion, and react on the cylinder + with an impulse couple -[rho]m[pi]a² and [rho]m[pi]b², having + resultant [rho]m[pi](b² - a²), and this couple is infinite when b = + [oo], as the angular momentum of the vortex is infinite. Round the + cylinder r = a held fixed in the U current the liquid streams past + with velocity + + q´ = 2U sin [theta] + m/a; (2) + + and the loss of head due to this increase of velocity from U to q´ is + + q´² - U² (2U sin [theta] + m/a)² - U² + -------- = ----------------------------, (3) + 2g 2g + + so that cavitation will take place, unless the head at a great + distance exceeds this loss. + + The resultant hydrostatic thrust across any diametral plane of the + cylinder will be modified, but the only term in the loss of head which + exerts a resultant thrust on the whole cylinder is 2mU sin[theta]/ga, + and its thrust is 2[pi][rho]mU absolute units in the direction Cy, to + be counteracted by a support at the centre C; the liquid is streaming + past r = a with velocity U reversed, and the cylinder is surrounded by + a vortex. Similarly, the streaming velocity V reversed will give rise + to a thrust 2[pi][rho]mV in the direction xC. + + Now if the cylinder is released, and the components U and V are + reversed so as to become the velocity of the cylinder with respect to + space filled with liquid, and at rest at infinity, the cylinder will + experience components of force per unit length + + (i.) - 2[pi][rho]mV, 2[pi][rho]mU, due to the vortex motion; + + (ii.) - [pi][rho]a² dU/dt, -[pi][rho]a² dV/dt, due to the kinetic + reaction of the liquid; + + (iii.) 0, -[pi]([sigma] - [rho])a²g, due to gravity, + + taking Oy vertically upward, and denoting the density of the cylinder + by [sigma]; so that the equations of motion are + + dU dU + [pi][rho]a²-- = - [pi][rho]a²-- - 2[pi][rho]mV, (4) + dt dt + + dV dV + [pi][rho]a²-- = - [pi][rho]a²-- + 2[pi][rho]mV - [pi]([sigma] - [rho])a²g, (5) + dt dt + + or, putting m = a²[omega], so that the vortex velocity is due to an + angular velocity [omega] at a radius a, + + ([sigma] + [rho])dU/dt + 2[rho][omega]V = 0, (6) + + ([sigma] + [rho])dV/dt - 2[rho][omega]U + ([sigma] - [rho])g = 0. (7) + + Thus with g = 0, the cylinder will describe a circle with angular + velocity 2[rho][omega]/([sigma] + [rho]), so that the radius is + ([sigma] + [rho])v/2[rho][omega], if the velocity is v. With [sigma] = + 0, the angular velocity of the cylinder is 2[omega]; in this way the + velocity may be calculated of the propagation of ripples and waves on + the surface of a vertical whirlpool in a sink. + + Restoring [sigma] will make the path of the cylinder a trochoid; and + so the swerve can be explained of the ball in tennis, cricket, + baseball, or golf. + + Another explanation may be given of the sidelong force, arising from + the velocity of liquid past a cylinder, which is encircled by a + vortex. Taking two planes x = ± b, and considering the increase of + momentum in the liquid between them, due to the entry and exit of + liquid momentum, the increase across dy in the direction Oy, due to + elements at P and P´ at opposite ends of the diameter PP´, is + + [rho]dy (U - Ua²r^(-2) cos 2[theta] + mr^(-1) sin [theta])(Ua²r^(-2) sin 2[theta] + mr^(-1) cos [theta]) + + [rho]dy (- U + Ua²r^(-2) cos 2[theta] + mr^(-1) sin [theta])(Ua²r^(-2) sin 2[theta] - mr^(-1) cos [theta]) + = 2[rho]dymUr^(-1)(cos [theta] - a^2r^(-2)cos 3[theta]), (8) + + and with y = b tan [theta], r = b sec [theta], this is + + 2[rho]mUd[theta] (1 - a²b^(-2) cos 3[theta] cos [theta]), (9) + + and integrating between the limits [theta] = ±½[pi], the resultant, as + before, is 2[pi][rho]mU. + + 31. _Example 2.--Confocal Elliptic Cylinders._--Employ the elliptic + coordinates [eta], [xi], and [zeta] = [eta] + [xi]i, such that + + z = c ch[zeta], x = c ch [eta] cos [xi], y = c sh [eta] sin [zeta]; (1) + + then the curves for which [eta] and [xi] are constant are confocal + ellipses and hyperbolas, and + + d(x, y) + J = -------, [xi]) = c²(ch²[eta] - cos² [xi]) + d([eta] + + = ½c²(ch 2[eta] - cos 2[xi]) = r1r2 = OD², (2) + + if OD is the semi-diameter conjugate to OP, and r1, r2 the focal + distances, + + r1, r2 = c(ch[eta] ± cos [xi]); (3) + + r² = x² + y² = c²(ch²[eta] - sin² [xi]) + + = ½c²(ch 2[eta] + cos 2[xi]). (4) + + Consider the streaming motion given by + + w = m ch([zeta] - [gamma]), [gamma] = [alpha] + [beta]i, (5) + + [phi] = m ch([eta] - [alpha]) cos ([xi] - [beta]), + [psi] = m sh([eta] - [alpha]) sin ([xi] - [beta]). (6) + + Then [psi] = 0 over the ellipse [eta] = [alpha], and the hyperbola + [xi] = [beta], so that these may be taken as fixed boundaries; and + [psi] is a constant on a C4. + + Over any ellipse [eta], moving with components U and V of velocity, + + [psi]´ = [psi] + Uy - Vx = [m sh([eta] - [alpha]) cos [beta] + Uc sh[eta]] sin [xi] + + -[m sh ([eta] - [alpha]) sin [beta] + Vc ch [eta] cos [xi]; (7) + + so that [psi]´ = 0, if + + m sh([eta] - [alpha]) m sh([eta] - [alpha]) + U = - --- ------------------- cos [beta], V = - --- - ------------------- sin [beta], (8) + c sh[eta] c ch[eta] + + having a resultant in the direction PO, where P is the intersection of + an ellipse [eta] with the hyperbola [beta]; and with this velocity the + ellipse [eta] can be swimming in the liquid, without distortion for an + instant. + + At infinity + + m m + U = - --- e^(-a) cos [beta] = - ----- cos [beta], + c a - b + + m m + V = - --- e^(-a) sin [beta] = - ----- sin [beta], (9) + c a + b + + a and b denoting the semi-axes of the ellipse [alpha]; so that the + liquid is streaming at infinity with velocity Q = m/(a + b) in the + direction of the asymptote of the hyperbola [beta]. + + An ellipse interior to [eta] = [alpha] will move in a direction + opposite to the exterior current; and when [eta] = 0, U = [oo], but V + = (m/c) sh [alpha] sin [beta]. + + Negative values of [eta] must be interpreted by a streaming motion on + a parallel plane at a level slightly different, as on a double Riemann + sheet, the stream passing from one sheet to the other across a cut SS´ + joining the foci S, S´. A diagram has been drawn by Col. R. L. + Hippisley. + + The components of the liquid velocity q, in the direction of the + normal of the ellipse [eta] and hyperbola [xi], are + + -mJ^(-1)sh([eta] - [alpha]) cos([xi] - [beta]), + mJ^(-1)ch([eta] - [alpha]) sin ([xi] - [beta]). (10) + + The velocity q is zero in a corner where the hyperbola [beta] cuts the + ellipse [alpha]; and round the ellipse [alpha] the velocity q reaches + a maximum when the tangent has turned through a right angle, and then + + [root](ch 2[alpha] - cos 2[beta]) + q = Qe^a ---------------------------------; (11) + sh 2[alpha] + + and the condition can be inferred when cavitation begins. + + With [beta] = 0, the stream is parallel to x0, and + + [phi] = m ch([eta] - [alpha])cos [xi] + + = -Uc ch([eta] - [alpha])sh [eta] cos [xi]/sh([eta] - [alpha]) (12) + + over the cylinder [eta], and as in (12) § 29, + + [phi]1 = -Ux = -Uc ch [eta] cos [xi], (13) + + for liquid filling the cylinder; and + + [phi] th [eta] + ------ = --------------------, (14) + [phi]1 th ([eta] - [alpha]) + + over the surface of [eta]; so that parallel to Ox, the effective + inertia of the cylinder [eta], displacing M´ liquid, is increased by + M´th [eta]/th([eta]- [alpha]), reducing when [alpha] = [oo] to M´th + [eta] = M´(b/a). + + Similarly, parallel to Oy, the increase of effective inertia is M´/th + [eta] th([eta] - [alpha]), reducing to M´/th [eta] = M´(a/b), when + [alpha] = [oo], and the liquid extends to infinity. + + 32. Next consider the motion given by + + [phi] = m ch 2([eta] - [alpha]) sin 2[xi], + [psi] = -m sh 2([eta] - [alpha]) cos 2[xi]; (1) + + in which [psi] = 0 over the ellipse [alpha], and + + [psi]´ = [psi] + ½R(x² + y²) + = [-m sh 2([eta] - [alpha]) + ¼Rc²] cos 2[xi] + ¼Rc² ch 2[eta], (2) + + which is constant over the ellipse [eta] if + + ¼Rc² = m sh 2([eta] - [alpha]); (3) + + so that this ellipse can be rotating with this angular velocity R for + an instant without distortion, the ellipse [alpha] being fixed. + + For the liquid filling the interior of a rotating elliptic cylinder of + cross section + + x²/a² + y²/b² = 1, (4) + + [psi]1´ = m1(x²/a² + y²/b²) (5) + + with + + [nabla]²[psi]1´ = -2R = -2m1(1/a² + 1/b²), + + [psi]1 = m1(x²/a² + y²/b²) - ½R(x² + y²) + = -½R(x² - y²)(a² - b²)/(a² + b²), (6) + + [phi]1 = Rxy(a² - b²)/(a² + b²), + + w1 = [phi]1 + [psi]1i = -½iR(x + yi)²(a² - b²)/(a² + b²). + + The velocity of a liquid particle is thus (a² - b²)/(a² + b²) of what + it would be if the liquid was frozen and rotating bodily with the + ellipse; and so the effective angular inertia of the liquid is (a² - + b²)²/(a² + b²)² of the solid; and the effective radius of gyration, + solid and liquid, is given by + + k² = ¼(a² + b²), and ¼(a² - b²)²/(a² + b²). (7) + + For the liquid in the interspace between [alpha] and [eta], + + [phi] m ch 2([eta] - [alpha]) sin 2[xi] + ------ = ------------------------------------------- + [phi]1 ¼Rc² sh 2[eta] sin 2[xi](a² - b²)/(a² + b²) + + = 1/th 2([eta] - [alpha])th 2[eta]; (8) + + and the effective k² of the liquid is reduced to + + ¼c²/th 2([eta] - [alpha]) sh 2[eta], (9) + + which becomes ¼c²/sh 2[eta] = 1/8 (a² - b²)/ab, when [alpha] = [oo], + and the liquid surrounds the ellipse [eta] to infinity. + + An angular velocity R, which gives components -Ry, Rx of velocity to a + body, can be resolved into two shearing velocities, -R parallel to Ox, + and R parallel to Oy; and then [psi] is resolved into [psi]1 + [psi]2, + such that [psi]1 + ½Rx² and [psi]2 + ½Ry² is constant over the + boundary. + + Inside a cylinder + + [phi]1 + [psi]1i = -½iR(x + yi)²a²/(a² + b²), (10) + + [phi]2 + [psi]2i = ½iR(x + yi)²b²/(a² + b²), (11) + + and for the interspace, the ellipse [alpha] being fixed, and [alpha]1 + revolving with angular velocity R + + [phi]1 + [psi]1i = -1/8 iRc²sh 2([eta] - [alpha] + + [xi]i)(ch 2[alpha] + 1)/sh 2([alpha]1 - [alpha]), (12) + + [phi]2 + [psi]2i = 1/8 iRc²sh 2([eta] - [alpha] + + [xi]i)(ch 2[alpha] - 1)/sh 2([alpha]1 - [alpha]), (13) + + satisfying the condition that [psi]1 and [psi]2 are zero over [eta] = + [alpha], and over [eta] = [alpha]1 + + [psi]1 + ½Rx² = 1/8 Rc²(ch 2[alpha]1 + 1), (14) + + [psi]2 + ½Ry² = 1/8 Rc²(ch 2[alpha]1 - 1), (15) + + constant values. + + In a similar way the more general state of motion may be analysed, + given by + + w = m ch 2([zeta] - [gamma]), [gamma] = [alpha] + [beta]i, (16) + + as giving a homogeneous strain velocity to the confocal system; to + which may be added a circulation, represented by an additional term + m[zeta] in w. + + Similarly, with + + x + yi = c[root][sin ([xi] + [eta]i)] (17) + + the function + + [psi] = Qc sh ½([eta] - [alpha]) sin ½([xi] - [beta]) (18) + + will give motion streaming past the fixed cylinder [eta] = [alpha], + and dividing along [xi] = [beta]; and then + + x² - y² = c² sin [xi] ch [eta], 2xy = c² cos [xi] sh [eta]. (19) + + In particular, with sh [alpha] = 1, the cross-section of [eta] = + [alpha] is + + x^4 + 6x²y² + y^4 = 2c^4, or x^4 + y^4 = c^4 (20) + + when the axes are turned through 45°. + + 33. _Example 3._--Analysing in this way the rotation of a rectangle + filled with liquid into the two components of shear, the stream + function [psi]1 is to be made to satisfy the conditions + + (i.) [nabla]²[psi]1 = 0, + + (ii.) [psi]1 + ½Rx² = ½Ra², or [psi]1 = 0 when x = ±a, + + (iii.) [psi]1 + ½Rx² = ½Ra², [psi]1 = ½R(a² - x²), when y = ± b. + + Expanded in a Fourier series, + + 32 __ cos (2n + 1) ½[pi]x/a + a² - x² = ----- a² \ ---------------------, (1) + [pi]³ /__ (2n + 1)³ + + so that + + 16 __ cos (2n + 1) ½[pi]x/a · ch(2n + 1) ½[pi]y/a) + [psi]1 = ----- a² \ ---------------------------------------------, + [pi]³ /__ (2n + 1)^3 · ch(2n + 1) ½[pi]b/a + + + 16 __ cos (2n + 1) ½[pi]z/a + w1 = [phi]1 + [psi]1i = iR ----- \ ------------------------------, (2) + [pi]³ /__ (2n + 1)^3 ch(2n + 1) ½[pi]b/a + + an elliptic-function Fourier series; with a similar expression for + [psi]2 with x and y, a and b interchanged; and thence [psi] = [psi]1 + + [psi]2. + + _Example 4._--Parabolic cylinder, axial advance, and liquid streaming + past. + + The polar equation of the cross-section being + + r^½ cos ½[theta] = a^½, or r + x = 2a, (3) + + the conditions are satisfied by + + [psi]´ = Ur sin [theta] - 2Ua^½ r^½ sin ½[theta] + = 2Ur^½ sin ½[theta](r^½ cos ½[theta] - a^½), (4) + + [psi] = 2Ua^½ r^½ sin ½[theta] = -U[root][2a(r-x)], (5) + + w = -2Ua^½ z^½, (6) + + and the resistance of the liquid is 2[pi][rho]aV²/2g. + + A relative stream line, along which [psi]´ = Uc, is the quartic curve + + (4a²y² - (y - c)^4 4a²y² + (y-c)^4 + y - c = [root][2a(r - x)], x = -------------------, r = ---------------, (7) + (4a(y - c)² 4a(y - c)² + + and in the absolute space curve given by [psi], + + dy (y - c)² 2ac + -- = - --------, x = - ----- 2a log (y - c). (8) + dx 2ay y - c + + 34. _Motion symmetrical about an Axis._--When the motion of a liquid + is the same for any plane passing through Ox, and lies in the plane, a + function [psi] can be found analogous to that employed in plane + motion, such that the flux across the surface generated by the + revolution of any curve AP from A to P is the same, and represented by + 2[pi]([psi] - [psi]0); and, as before, if d[psi] is the increase in + [psi] due to a displacement of P to P´, then k the component of + velocity normal to the surface swept out by PP´ is such that + 2[pi]d[psi] = 2[pi]yk.PP´; and taking PP´ parallel to Oy and Ox, + + u = -d[psi]/ydy, v = d[psi]/ydx, (1) + + and [psi] is called after the inventor, "Stokes's stream or current + function," as it is constant along a stream line (_Trans. Camb. Phil. + Soc._, 1842; "Stokes's Current Function," R. A. Sampson, _Phil. + Trans._, 1892); and d[psi]/yds is the component velocity across ds in + a direction turned through a right angle forward. + + In this symmetrical motion + + d / 1 d[psi] \ d / 1 d[psi]\ + [xi] = 0, [eta] = 0, 2[zeta] = -- ( --- ------ ) + -- ( --- ------ ) + dx \ y dx / dy \ y dy / + + 1 /d²[psi] d²[psi] 1 d[psi]\ 1 + = --- ( ------- + ------- - --- ------ ) = - ---[nabla]²[psi], (2) + y \ dx² dy² y dy / y + + suppose; and in steady motion, + + dH 1 d[psi] dH 1 d[psi] + -- + --- ----- [nabla]²[psi] = 0, -- + --- ------ [nabla]²[psi] = 0, (3) + dx y² dx dy y² dy + + so that + + 2[zeta]/y = -y^(-2)[nabla]²[psi] = dH/d[psi] (4) + + is a function of [psi], say [f]´([psi]), and constant along a stream line; + + dH/dv = 2q[zeta], H - [f]([psi]) = constant, (5) + + throughout the liquid. + + When the motion is irrotational, + + d[phi] 1 d[psi] d[phi] 1 d[psi] + [zeta] = 0, u = - ------ = - --- ------, v = - ------ = --- ------, (6) + dx y dy dy y dx + + d²[psi] d²[psi] 1 d[psi] + [nabla]²[psi] = 0, or ------- + ------- - --- ------ = 0. (7) + dx² dy² y dy + + Changing to polar coordinates, x = r cos[theta], y = r sin[theta], the + equation (2) becomes, with cos[theta] = [mu], + + d²[psi] d²[psi] + r²------- + (1 - [mu]²) ------- = 2[zeta]r³ sin [theta], (8) + dr² d[mu]² + + of which a solution, when [zeta] = 0, is + + / B \ dPn / B \ dPn + [psi] = ( Ar^(n+1) + --- ) (1 - [mu]²) ----- = ( Ar^(n-1) + ------- ) y²-----, (9) + \ r^n / d[mu] \ r^(n+2) / d[mu] + + [phi] = {(n + 1)Ar^n - nBr^(-n-1)} Pn, (10) + + where Pn denotes the zonal harmonic of the nth order; also, in the + exceptional case of + + [psi] = A0 cos[theta], [phi] = A0/r; + + [psi] = B0r, [phi] = -B0 log tan ½[theta] + = -½B0 sh(-1) x/y. (11) + + Thus cos[theta] is the Stokes' function of a point source at O, and PA + - PB of a line source AB. + + The stream function [psi] of the liquid motion set up by the passage + of a solid of revolution, moving with axial velocity U, is such that + + 1 d[psi] dy + --- ------ = -U --, [psi] + ½Uy² = constant, (12) + y ds ds + + over the surface of the solid; and [psi] must be replaced by [psi]´ = + [psi] + ½Uy² in the general equations of steady motion above to obtain + the steady relative motion of the liquid past the solid. + + For instance, with n = 1 in equation (9), the relative stream function + is obtained for a sphere of radius a, by making it + + [psi]´ = [psi] + ½Uy² = ½U(r² - a³/r) sin² [theta], + [psi] = -½Ua³ sin² [theta]/r; (13) + + and then + + [phi]´ = Ux(1 + ½a³/r²), [phi] = ½Ua³ cos [theta]/r², (14) + + d[phi] a³ d[phi] a³ + - ------ = U -- cos [theta], - --------- = ½U -- sin [theta], (15) + dr r³ rd[theta] r³ + + so that, if the direction of motion makes an angle [psi] with Ox, + + tan ([psi] - [theta]) = ½ tan [theta], + tan [psi] = 3 tan [theta]/(2 - tan² [theta]), (16) + + Along the path of a liquid particle [psi]´ is constant, and putting it + equal to ½Uc², + + (r² - a³/r) sin² [theta] = c², sin² [theta] = c²r/(r³ - a³), (17) + + the polar equation; or + + y² = c²r³/(r³ - a³), r³ = a³y²/(y² - c²), (18) + + a curve of the 10th degree (C10). + + In the absolute path in space + + cos [psi] = (2 - 3 sin² [theta])/[root](4 - sin² [theta]), + and sin³ [theta] = (y³ - c²y)/a³, (19) + + which leads to no simple relation. + + The velocity past the surface of the sphere is + + 1 d[psi]´ / a³ \ sin² [theta] + ------------ ------- = ½U ( 2r + -- ) ------------- = 3/2 U sin [theta], when r = a; (20) + r sin[theta] dr \ r² / r sin [theta] + + so that the loss of head is + + (9/4 sin² [theta] - 1) U²/2g, having a maximum 5/4 U²/2g, (21) + + which must be less than the head at infinite distance to avoid + cavitation at the surface of the sphere. + + With n = 2, a state of motion is given by + + [psi] = -½Uy²a^4[mu]/r^4, [psi]´ = ½Uy²(1 - a^4[mu]/r^4), (22) + + [phi]´ = Ux + [phi], [phi] = -1/3 U(a^4/r³)P2, P2 = 3/2 [mu]² - ½, (23) + + representing a stream past the surface r^4 = a^4[mu]. + +35. A circular vortex, such as a smoke ring, will set up motion +symmetrical about an axis, and provide an illustration; a half vortex +ring can be generated in water by drawing a semicircular blade a short +distance forward, the tip of a spoon for instance. The vortex advances +with a certain velocity; and if an equal circular vortex is generated +coaxially with the first, the mutual influence can be observed. The +first vortex dilates and moves slower, while the second contracts and +shoots through the first; after which the motion is reversed +periodically, as if in a game of leap-frog. Projected perpendicularly +against a plane boundary, the motion is determined by an equal opposite +vortex ring, the optical image; the vortex ring spreads out and moves +more slowly as it approaches the wall; at the same time the molecular +rotation, inversely as the cross-section of the vortex, is seen to +increase. The analytical treatment of such vortex rings is the same as +for the electro-magnetic effect of a current circulating in each ring. + + 36. _Irrotational Motion in General._--Liquid originally at rest in a + singly-connected space cannot be set in motion by a field of force due + to a single-valued potential function; any motion set up in the liquid + must be due to a movement of the boundary, and the motion will be + irrotational; for any small spherical element of the liquid may be + considered a smooth solid sphere for a moment, and the normal pressure + of the surrounding liquid cannot impart to it any rotation. + + The kinetic energy of the liquid inside a surface S due to the + velocity function [phi] is given by + _ _ _ _ _ + / / / | /d[phi]\² /d[phi]\² /d[phi]\² | + T = ½[rho] | | | | ( ------ ) + ( ------ ) + ( ------ ) | dx dy dz, + _/_/_/ |_ \ dx / \ dy / \ dz / _| + _ _ + / / d[phi] + = ½[rho] | | [phi] ------ dS (1) + _/_/ d[nu] + + by Green's transformation, d[nu] denoting an elementary step along the + normal to the exterior of the surface; so that d[phi]/d[nu] = 0 over + the surface makes T = 0, and then + + /d[phi]\² /d[phi]\² /d[phi]\² d[phi] d[phi] d[phi] + ( ------ ) + ( ------ ) + ( ------ ) = 0, ------ = 0, ------ = 0, ------ = 0 (2) + \ dx / \ dy / \ dz / dx dy dz + + If the actual motion at any instant is supposed to be generated + instantaneously from rest by the application of pressure impulse over + the surface, or suddenly reduced to rest again, then, since no natural + forces can act impulsively throughout the liquid, the pressure impulse + [~[omega]] satisfies the equations + + 1 d[~omega] 1 d[~omega] 1 d[~omega] + ----- --------- = -u, ----- --------- = -v, ----- --------- = -[~omega], (3) + [rho] dx [rho] dy [rho] dz + + [~omega] = [rho][phi] + a constant, (4) + + and the constant may be ignored; and Green's transformation of the + energy T amounts to the theorem that the work done by an impulse is + the product of the impulse and average velocity, or half the velocity + from rest. + + In a multiply connected space, like a ring, with a multiply valued + velocity function [phi], the liquid can circulate in the circuits + independently of any motion of the surface; thus, for example, + + [phi] = m[theta] = m tan^(-1) y/x (5) + + will give motion to the liquid, circulating in any ring-shaped figure + of revolution round Oz. + + To find the kinetic energy of such motion in a multiply connected + space, the channels must be supposed barred, and the space made + acyclic by a membrane, moving with the velocity of the liquid; and + then if k denotes the cyclic constant of [phi] in any circuit, or the + value by which [phi] has increased in completing the circuit, the + values of [phi] on the two sides of the membrane are taken as + differing by k, so that the integral over the membrane + _ _ _ _ + / / d[phi] / / d[phi] + | | [phi] ------ dS = k | | ------ dS, (6) + _/_/ d[nu] _/_/ d[nu] + + and this term is to be added to the terms in (1) to obtain the + additional part in the kinetic energy; the continuity shows that the + integral is independent of the shape of the barrier membrane, and its + position. Thus, in (5), the cyclic constant k = 2[pi]m. + + In plane motion the kinetic energy per unit length parallel to Oz + _ _ _ _ _ _ _ _ + / / | /d[phi]\² /d[phi]\² | / / | /d[psi]\² /d[psi]\² | + T = ½[rho] | | | ( ------ ) + ( ------ ) | dx dy = ½[rho] | | | ( ------ ) + ( ------ ) | dx dy + _/_/ |_ \ dx / \ dy / _| _/_/ |_ \ dx / \ dy / _| + _ _ + / d[phi] / d[phi] + = ½[rho] | [phi] ------ ds = ½[rho] | [psi] ------ ds. (7) + _/ d[nu] _/ d[nu] + + For example, in the equilateral triangle of (8) § 28, referred to + coordinate axes made by the base and height, + + [psi]´ = -2R[alpha][beta][gamma]/h = -½Ry[(h - y)² - 3x²]/h (8) + + [psi] = [psi]´ - ½R [(1/3h - y)² + x²] + + = -½R [½h³ + 1/3 h²y + h) (x² - y²) - 3x²y + y³] /h (9) + + and over the base y = 0, + + dx/d[nu] = -dx/dy = + ½R(1/3 h² - 3x²)/h, [psi] = -½R(1/9 h² + x²). (10) + + Integrating over the base, to obtain one-third of the kinetic energy + T, + _ + / h/[root]3 + 1/3 T = ½[rho] | ¼R²(3x^4 - 1/27 h^4) dx/h + _/ -h/[root]3 + + = [rho]R²h^4/135[root]3 (11) + + so that the effective k² of the liquid filling the triangle is given + by + + k² = T/½[rho]R²A = 2h²/45 + + = 2/5 (radius of the inscribed circle)², (12) + + or two-fifths of the k² for the solid triangle. + + Again, since + + d[phi]/d[nu] = d[psi]/ds, d[phi]/ds = -d[psi]/d[nu], (13) + _ _ + / / + T = ½[rho] | [phi] d[psi] = -½[rho] | [psi] d[phi]. (14) + _/ _/ + + With the Stokes' function [psi] for motion symmetrical about an + axis. + _ _ + / d[psi] / + T = ½[rho] | [phi] ------ 2[pi]y ds = [pi][rho] | [phi] d[psi]. (15) + _/ yds _/ + + 37. _Flow, Circulation, and Vortex Motion._--The line integral of the + tangential velocity along a curve from one point to another, defined + by + _ _ + / / dx dy dz \ / + | ( u-- + v-- + w-- ) ds = | (u dx + v dy + z dz), (1) + _/ \ ds ds ds / _/ + + is called the "flux" along the curve from the first to the second + point; and if the curve closes in on itself the line integral round + the curve is called the "circulation" in the curve. + + With a velocity function [phi], the flow + _ + / + - | d[phi] = [phi]1 - [phi]2, (2) + _/ + + so that the flow is independent of the curve for all curves mutually + reconcilable; and the circulation round a closed curve is zero, if the + curve can be reduced to a point without leaving a region for which + [phi] is single valued. + + If through every point of a small closed curve the vortex lines are + drawn, a tube is obtained, and the fluid contained is called a _vortex + filament_. + + By analogy with the spin of a rigid body, the component spin of the + fluid in any plane at a point is defined as the circulation round a + small area in the plane enclosing the point, divided by twice the + area. For in a rigid body, rotating about Oz with angular velocity + [zeta], the circulation round a curve in the plane xy is + _ + / / dy dx \ + | [zeta] ( x -- - y -- ) ds = [zeta] times twice the area. (3) + _/ \ ds ds / + + In a fluid, the circulation round an elementary area dxdy is equal to + + / dv \ / du \ / dv du \ + udx + ( v + --dx )dy - ( u + --dy )dx - vdy = ( -- - -- )dx dy, (4) + \ dx / \ dy / \ dx dy / + + so that the component spin is + + / dv du \ + ½ ( -- - -- ) = [zeta], (5) + \ dx dy / + + in the previous notation of § 24; so also for the other two components + [xi] and [eta]. + + Since the circulation round any triangular area of given aspect is the + sum of the circulation round the projections of the area on the + coordinate planes, the composition of the components of spin, [xi], + [eta], [zeta], is according to the vector law. Hence in any + infinitesimal part of the fluid the circulation is zero round every + small plane curve passing through the vortex line; and consequently + the circulation round any curve drawn on the surface of a vortex + filament is zero. + + If at any two points of a vortex line the cross-section ABC, A´B´C´ is + drawn of the vortex filament, joined by the vortex line AA´, then, + since the flow in AA´ is taken in opposite directions in the complete + circuit ABC AA´B´C´ A´A, the resultant flow in AA´ cancels, and the + circulation in ABC, A´B´C´ is the same; this is expressed by saying + that at all points of a vortex filament [omega][alpha] is constant + where [alpha] is the cross-section of the filament and [omega] the + resultant spin (W. K. Clifford, _Kinematic_, book iii.). + + So far these theorems on vortex motion are kinematical; but + introducing the equations of motion of § 22, + + Du dQ Dv dQ Dw dQ + -- + -- = 0, -- + -- = 0, -- + -- = 0, (6) + dt dx dt dy dt dz + _ + / + Q = | dp/[rho] + V, (7) + _/ + + and taking dx, dy, dz in the direction of u, v, w, and + + dx : dy : dz = u : v : w, + + D / \ Du D dx + -- (u dx + v dy + w dz ) = -- dx + u ---- + ... = -dQ + ½dq², (8) + dt \ / dt dt + + and integrating round a closed curve + _ + D / + -- | (u dx + v dy + w dz) = 0, (9) + dt _/ + + and the circulation in any circuit composed of the same fluid + particles is constant; and if the motion is differential irrotational + and due to a velocity function, the circulation is zero round all + reconcilable paths. Interpreted dynamically the normal pressure of the + surrounding fluid on a tube cannot create any circulation in the tube. + + The circulation being always zero round a small plane curve passing + through the axis of spin in vortical motion, it follows conversely + that a vortex filament is composed always of the same fluid particles; + and since the circulation round a cross-section of a vortex filament + is constant, not changing with the time, it follows from the previous + kinematical theorem that [alpha][omega] is constant for all time, and + the same for every cross-section of the vortex filament. + + A vortex filament must close on itself, or end on a bounding surface, + as seen when the tip of a spoon is drawn through the surface of water. + + Denoting the cross-section [alpha] of a filament by dS and its mass by + dm, the quantity [omega]dS/dm is called the _vorticity_; this is the + same at all points of a filament, and it does not change during the + motion; and the vorticity is given by [omega] cos[epsilon]dS/dm, if dS + is the oblique section of which the normal makes an angle [epsilon] + with the filament, while the aggregate vorticity of a mass M inside a + surface S is + _ + / + M^(-1) | [omega] cos [epsilon] dS. + _/ + + Employing the equation of continuity when the liquid is homogeneous, + + / d[zeta] d[eta]\ d² d² d² + 2( ------ - ------ ) = [nabla]²u, ... , [nabla]² = - --- - --- - ---, (10) + \ dy dz / dx² dy² dz² + + which is expressed by + + [nabla]²(u,v,w) = 2 curl ([xi], [eta], [zeta]), + ([xi], [eta], [zeta]) = ½ curl (u, v, w). (11) + + 38. _Moving Axes in Hydrodynamics._--In many problems, such as the + motion of a solid in liquid, it is convenient to take coordinate axes + fixed to the solid and moving with it as the movable trihedron frame + of reference. The components of velocity of the moving origin are + denoted by U, V, W, and the components of angular velocity of the + frame of reference by P, Q, R; and then if u, v, w denote the + components of fluid velocity in space, and u´, v´, w´ the components + relative to the axes at a point (x, y, z) fixed to the frame of + reference, we have + + u = U + u´ - yR + zQ, (1) + v = V + v´- zP + xR, + w = W + w´ - xQ + yP. + + Now if k denotes the component of absolute velocity in a direction + fixed in space whose direction cosines are l, m, n, + + k = lu + mv + nw; (2) + + and in the infinitesimal element of time dt, the coordinates of the + fluid particle at (x, y, z) will have changed by (u´, v´, w´)dt; so + that + + Dk dl dm dn + -- = --u + --v + --w + dt dt dt dt + + / du du du du \ + + l( -- + u´-- + v´-- + w´-- ) + \ dt dx dy dz / + + / dv dv dv dv \ + + m( -- + u´-- + v´-- + w´-- ) + \ dt dx dy dz / + + / dw dw dw dw \ + + n( -- + u´-- + v´-- + w´-- ). (3) + \ dt dx dy dz / + + But as l, m, n are the direction cosines of a line fixed in space, + + dl dm dn + -- = mR - nQ, -- = nP - lR, -- = lQ - mP; (4) + dt dt dt + + so that + + Dk / du du du du \ + -- = l( -- - vR + wQ + u´-- + v´-- + w´-- ) + m(...) + n(...) + dt \ dt dx dy dz / + + / 1 dp \ / 1 dp \ / 1 dp \ + = l( X- --- -- ) + m( Y - --- -- ) + n( Z - --- -- ), (5) + \ p dx / \ p dy / \ p dz / + + for all values of l, m, n, leading to the equations of motion with + moving axes. + + When the motion is such that + + d[phi] d[psi] d[phi] d[psi] d[phi] d[psi] + u = - ------ - m------, v = - ------ - m------, w = - ------ - m------, (6) + dx dx dy dy dz dz + + as in §25 (1), a first integral of the equations in (5) may be written + _ + / dp d[phi] d[psi] / d[phi] d[psi] \ + | ----- + V + ½q² - ------ - m------ + (u - u´) ( ------ + m------ ) + _/ [rho] dt dt \ dx dx / + + / d[phi] d[psi] \ / d[phi] d[psi] \ + + (v - v´)( ------ + m------ ) + (w - w´)( ------ + m------ ) = F(t), (7) + \ dy dy / \ dz dz / + in which + + d[phi] d[phi] d[phi] d[phi] + ------ - (u - u´)------ - (v -v´)------ - (w - w´)------ + dt dx dy dz + + d[phi] d[phi] d[phi] d[phi] + = ------ - (U - yR + zQ)------ - (V - zP + xR)------ - (W - xQ + yP)------ (8) + dt dx dy dz + + is the time-rate of change of [phi] at a point fixed in space, which + is left behind with velocity components u - u´, v - v´, w - w´. + + In the case of a steady motion of homogeneous liquid symmetrical about + Ox, where O is advancing with velocity U, the equation (5) of § 34 + + p/[rho] + V + ½q´² - [f]([psi]´) = constant (9) + + becomes transformed into + + p U d[psi] + ----- + V + ½q² - --- ------ + ½U² - [f]([psi] + ½Uy²) = constant, (10) + [rho] y dy + + [psi]´ = [psi] + ¼U², (11) + + subject to the condition, from (4) §34, + + y^(-2)[nabla]²[psi]´ = -[f]´([psi]´), + y^(-2)[nabla]²[psi] = -[f]´([psi] + ½Uy²). (12) + + Thus, for example, with + + [psi]´ = ¾Uy²(r²a^(-2) - 1), r² = x² + y², (13) + + for the space inside the sphere r = a, compared with the value of + [psi]´ in §34 (13) for the space outside, there is no discontinuity of + the velocity in crossing the surface. + + Inside the sphere + + d / 1 d[psi]´\ d / 1 d[psi]´\ 15 y + 2[zeta] = --- ( --- ------- ) + --- ( --- ------- ) = ---U ---, (14) + dx \ y dx / dy \ y dy / 2 a² + + so that §34 (4) is satisfied, with + + 15 15 + [f]´([psi]´)= ---Ua^(-2), [f]([psi]´) = ---U[psi]´a^(-2); (15) + 2 2 + + and (10) reduces to + _ _ + p 9 | / x² \² / y² \² | + ----- + V - ---U | ( --- -1 ) - ( --- - ½ ) | = constant; (16) + [rho] 8 |_ \ a² / \ a² / _| + + this gives the state of motion in M. J. M. Hill's spherical vortex, + advancing through the surrounding liquid with uniform velocity. + + 39. As an application of moving axes, consider the motion of liquid + filling the ellipsoidal case + + x² y² z² + --- + --- + --- = 1; (1) + a² b² c² + + and first suppose the liquid to be frozen, and the ellipsoid to be + rotating about the centre with components of angular velocity [xi], + [eta], [zeta]; then + + u = - y[zeta] + z[eta], v = - z[xi] + x[zeta], + w = - x[eta] + y[xi]. (2) + + Now suppose the liquid to be melted, and additional components of + angular velocity [Omega]1, [Omega]2, [Omega]3 communicated to the + ellipsoidal case; the additional velocity communicated to the liquid + will be due to a velocity-function + + b² - c² c² - a² a² - b² + [phi] = - [Omega]1 ------- yz - [Omega]2 -------zx - [Omega]3 -------xy, (3) + b² + c² c² + a² a² + b² + + as may be verified by considering one term at a time. + + If u´, v´, w´ denote the components of the velocity of the liquid + relative to the axes, + + 2a² 2a² + u´ = u + yR - zQ = ------- [Omega]3 y - ------- [Omega]2 z, (4) + a² + b² c² + a² + + 2b² 2b² + v´ = v + zP - xR = ------- [Omega]1 z - ------- [Omega]3 x, (5) + b² + c² a² + b² + + 2c² 2c² + w´ = w + xQ - yP = ------- [Omega]2 x - ------- [Omega]1 y, (6) + c² + a² b² + c² + + P = [Omega]1 + [xi], Q = [Omega]2 + [eta], R = [Omega]3 + [zeta]. (7) + + Thus + + x y z + u´ --- + v´ --- + w´ --- = 0, (8) + a2 b2 c2 + + so that a liquid particle remains always on a similar ellipsoid. + + The hydrodynamical equations with moving axes, taking into account the + mutual gravitation of the liquid, become + + 1 dp du du du du + ----- -- + 4[pi][rho]Ax + -- - vR + wQ + u´-- + v´-- + w´-- = 0, ... , ... , (9) + [rho] dx dt dx dy dz + + where + _ + / [oo] abcd[lambda] + A, B, C = | ---------------------------------------------- + _/ 0 (a² + [lambda], b² + [lambda], c² + [lambda])P + + P² = 4(a² + [lambda]) (b² + [lambda]) (c² + [lambda]). (10) + + With the values above of u, v, w, u´, v´, w´, the equations become of + the form + + 1 dp + ----- -- + 4[pi][rho]Ax + [alpha]x + hy + gz = 0, (11) + [rho] dx + + 1 dp + ----- -- + 4[pi][rho]By + hx + [beta]y + fz = 0, (12) + [rho] dy + + 1 dp + ----- -- + 4[pi][rho]Cz + gx + fy + [gamma]z = 0, (13) + [rho] dz + + and integrating + + p[rho]^(-1) + 2[pi][rho](Ax² + By² + Cz²) + + + ½([alpha]x² + [beta]y² + [gamma]z² + 2fyz + 2gzx + 2hxy) = const., (14) + + so that the surfaces of equal pressure are similar quadric surfaces, + which, symmetry and dynamical considerations show, must be coaxial + surfaces; and f, g, h vanish, as follows also by algebraical + reduction; and + + 4c²(c² - a²) / c² - a² \² + [alpha] = ------------[Omega]2² - ( -------[Omega]2 - [eta] ) + (c² + a²)² \ c² + a² / + + 4b²(a² - b²) / a² - b² \² + - ------------[Omega]3² - ( -------[Omega]3 - [zeta] ), (15) + (a² + b²)² \ a² + b² / + + with similar equations for [beta] and [gamma]. + + If we can make + + (4[pi][rho]A + [alpha])x² = (4[pi][rho]B + [beta])b² + = (4[pi][rho]C + [gamma])c², (16) + + the surfaces of equal pressure are similar to the external case, which + can then be removed without affecting the motion, provided [alpha], + [beta], [gamma] remain constant. + + This is so when the axis of revolution is a principal axis, say Oz; + when + + [Omega]1 = 0, [Omega]2 = 0, [xi] = 0, [eta] = 0. (17) + + If [Omega]3 = 0 or [theta]3 = [zeta] in addition, we obtain the + solution of Jacobi's ellipsoid of liquid of three unequal axes, + rotating bodily about the least axis; and putting a = b, Maclaurin's + solution is obtained of the rotating spheroid. + + In the general motion again of the liquid filling a case, when a = b, + [Omega]3 may be replaced by zero, and the equations, hydrodynamical + and dynamical, reduce to + + d[xi] 2c² d[eta] 2a² + ----- = - -------[Omega]2 [zeta], ------ = -------[Omega]1 [zeta], + dt a² + c² dt a² + c² + + d[zeta] 2c² + ------- = -------([Omega]2 [xi] - [Omega]2 [eta]) (18) + dt a² + c² + + d[Omega]1 a² + c² + --------- = [Omega]2 [zeta] + -------[eta][zeta], + dt a² - c² + + d[Omega]2 a² + c² + --------- = [Omega]1 [zeta] + -------[xi][zeta]; (19) + dt a² - c² + + of which three integrals are + + a² + [xi]² + [eta]² = L - --[zeta]², (20) + c² + + (a² + c²)² + [Omega]1² + [Omega]2² = M + ------------ [zeta]², (21) + 2c²(a² - c²) + + a² + c² + [Omega]1 [xi] + [Omega]2 [eta]N = + ------- [zeta]²; (22) + 4c² + and then + + / d[zeta]\² 4c^4 + ( ------- ) = --------- ([Omega]2[xi] - [Omega]1²[eta])² + \ dt / (a² + c²) + + 4c^4 + = ---------- [([xi]² + [eta]²)([Omega)1² + [Omega]2²) -([Omega]1[xi] + [Omega]2[eta])²] + (a² + c²)² + _ + 4c^4 | / (a² + c²)² a² (a² + c²)\ + = ---------- | LM - N² + ( L------------ - M --- - N --------- ) [zeta]² + (a² + c²)² |_ \ 2c²(a² + c²) c² 2c² / + _ + (a² + c²)(9a² - c²) | + - ------------------- [zeta]^4 | = Z, (23) + 16c^4(a² - c²) _| + + where Z is a quadratic in [zeta]², so that [zeta] is an elliptic + function of t, except when c = a, or 3a. + + Put [Omega]1 = [Omega] cos [phi], [Omega]2 = -[Omega] sin [phi], + + d[phi] d[Omega]1 d[Omega]2 (a² + c²) + [Omega]2 ------ = -----------[Omega]2 - [Omega]1 --------- = [Omega]²[zeta] - ---------([Omega]1 [xi] + [Omega]2 [eta])[zeta], (24) + dt dt dt (a² - c²) + + a² + c² + N + ------- + d[phi] (a² + c²) 4c² + ------ = [zeta] - --------- · -------------------------, (25) + dt (a² - c²) (a² + c²)² + M + ------------[zeta]² + 2c²(a² - c²) + + a² + c² + _ _ N + -------[zeta]² + / [zeta]d a² + c² / 4c² [zeta] d[zeta] + [phi] = | ------- - ------- | ------------------------ · --------------, (26) + _/ [root]Z a² - c² _/ (a² + c²)² [root]Z + M + ------------[zeta]² + 2c²(a² - c²) + + which, as Z is a quadratic function of [zeta]², are non-elliptic + integrals; so also for [psi], where [xi] = [omega] cos [psi], [eta] = + -[omega] sin [psi]. + + In a state of steady motion + + d[zeta] [Omega]1 [Omega]2 + ------- = 0, -------- = --------, (27) + dt [xi] [eta] + + [phi] = [psi] = nt, suppose, (28) + + [Omega]1[xi] + [Omega]2 [eta] = [Omega][omega], (29) + + d[phi] a² + c² [omega] + ------ = [zeta]- ------- -------[zeta], (30) + dt a² - c² [Omega] + + d[psi] 2a² [Omega] + ------ = - ------- -------[zeta], (31) + dt a² + c² [omega] + + a² + c² [omega] 2a² [Omega] + 1 - ------- ------- = - ------- -------, (32) + a² - c² [Omega] a² + c² [omega] + + / [omega] a² + c² \² (a² - c²)(9a² - c²) + ( ------- - ½ ------- ) = -------------------, (33) + \ [Omega] a² - c² / 4(a² + c²) + + and a state of steady motion is impossible when 3a > c > a. + +An experiment was devised by Lord Kelvin for demonstrating this, in +which the difference of steadiness was shown of a copper shell filled +with liquid and spun gyroscopically, according as the shell was slightly +oblate or prolate. According to the theory above the stability is +regained when the length is more than three diameters, so that a modern +projectile with a cavity more than three diameters long should fly +steadily when filled with water; while the old-fashioned type, not so +elongated, would be highly unsteady; and for the same reason the gas +bags of a dirigible balloon should be over rather than under three +diameters long. + +40. _A Liquid Jet._--By the use of the complex variable and its +conjugate functions, an attempt can be made to give a mathematical +interpretation of problems such as the efflux of water in a jet or of +smoke from a chimney, the discharge through a weir, the flow of water +through the piers of a bridge, or past the side of a ship, the wind +blowing on a sail or aeroplane, or against a wall, or impinging jets of +gas or water; cases where a surface of discontinuity is observable, more +or less distinct, which separates the running stream from the dead water +or air. + + Uniplanar motion alone is so far amenable to analysis; the velocity + function [phi] and stream function [psi] are given as conjugate + functions of the coordinates x, y by + + w = [f](z) where z = x + yi, w = [phi] + [psi]i, (1) + + and then + + dw d[phi] d[psi] + -- = ------ + i------ = -u + vi; (2) + dz dx dx + + so that, with u = q cos [theta], v = q sin [theta], the function + + dz Q Q Q + [zeta] = -Q -- = -------- = ---(u + vi) = --- (cos [theta] + i sin [theta]), (3) + dw (u - vi) q² q + + gives [zeta] as a vector representing the reciprocal of the velocity q + in direction and magnitude, in terms of some standard velocity Q. + + To determine the motion of a jet which issues from a vessel with plane + walls, the vector [zeta] must be Constructed so as to have a constant + direction [theta] along a plane boundary, and to give a constant skin + velocity over the surface of a jet, where the pressure is constant. + + It is convenient to introduce the function + + [Omega] = log [zeta] = log(Q/q) + [theta]i (4) + + so that the polygon representing [Omega] conformally has a boundary + given by straight lines parallel to the coordinate axes; and then to + determine [Omega] and w as functions of a variable u (not to be + confused with the velocity component of q), such that in the conformal + representation the boundary of the [Omega] and w polygon is made to + coincide with the real axis of u. + + [Illustration: FIG. 4.] + + It will be sufficient to give a few illustrations. + + Consider the motion where the liquid is coming from an infinite + distance between two parallel walls at a distance xx´ (fig. 4), and + issues in a jet between two edges A and A´; the wall xA being bent at + a corner B, with the external angle [beta] = ½[pi]/n. + + The theory of conformal representation shows that the motion is given + by + _ _ + | [root](b - a´·u - a) + [root](b - a·u - a´) |^1/n + [zeta] = | ------------------------------------------- | , u = ae^(-[pi]w/m); (5) + |_ [root](a - a´·u - b) _| + + where u = a, a´ at the edge A, A¹; u = b at a corner B; u = 0 across + xx´ where [phi] = [oo]; and u = [oo], [phi] = [oo] across the end JJ´ + of the jet, bounded by the curved lines APJ, A´P´J´, over which the + skin velocity is Q. The stream lines xBAJ, xA´J´ are given by [psi] = + 0, m; so that if c denotes the ultimate breadth JJ´ of the jet, where + the velocity may be supposed uniform and equal to the skin velocity Q, + + m = Qc, c = m/Q. + + If there are more B corners than one, either on xA or x´A´, the + expression for [zeta] is the product of corresponding factors, such as + in (5). + + Restricting the attention to a single corner B, + + / Q \^n [root](b - a´·u - a) + [root](b - a·u - a´) + [zeta]^n = ( --- ) (cos n[theta] + i sin n[theta] = -------------------------------------------, (6) + \ q / [root](a - a´.u - b) + + / Q \^n / Q \^n + ch n[omega] = ch log( --- ) cos n[theta] + i sh log ( --- ) sin n[theta] + \ q / \ q / + + /b - a´ /u - a´ + = ½([zeta]^n + [zeta]^(-n)) = / ------ / ------ (7) + \/ a - a´ \/ u - b´ + + / Q \ / Q \^n + sh n[Omega] = sh log ( --- ) cos n[theta] + i ch log ( --- ) sin n[theta] + \ q / \ q / + + /b - a´ /u - a´ + = ½([zeta]^n - [zeta]^(-n)) = / ------ / ------ (8) + \/ a - a´ \/ u - b´ + + [oo] > a > b > 0 > a´ > -[oo] (9) + + and then + + d[Omega] 1 [root](b - a´·b - a´) dw m + -------- = - -- ---------------------------, -- = - ------ (10) + du 2n (u - b)[root](a - a·u - a´) du [pi]u´ + + the formulas by which the conformal representation is obtained. + + For the [Omega] polygon has a right angle at u = a, a´, and a zero + angle at u = b, where [theta] changes from 0 to ½[pi]/n and [Omega] + increases by ½i[pi]/n; so that + + d[Omega] A [root](b - a·b - a´) + -------- = ---------------------------, where A = --------------------. (11) + du (u - b)[root](u - a·u - a´) 2n + + And the w polygon has a zero angle at u = 0, [oo], where [psi] changes + from 0 to m and back again, so that w changes by im, and + + dw B m + -- = ---, where B = - ----. (12) + du u [pi] + + Along the stream line xBAPJ, + + [psi] = 0, u = ae^(-[pi][phi]/m); (13) + + and over the jet surface JPA, where the skin velocity is Q, + + d[phi] + ------ = -q = -Q, u = ae^([pi]sQ/m) = ae^([pi]s/c), (14) + ds + + denoting the arc AP by s, starting at u = a; + + /b - a´ /u - a´ + ch n[Omega] = cos n[theta] = / ----- / ------ (15) + \/ a - a´ \/ u - b´ + + /a - b /u - a´ + sh n[Omega] = i sin n[theta] = i / ------ / ------ (16) + \/ a - a´ \/ u - b´ + + [oo] > u = ae^([pi]s/c) > a, (17) + + and this gives the intrinsic equation of the jet, and then the radius + of curvature + + ds 1 d[phi] i dw i dw / d[Omega] + [rho] = - -------- = --- -------- = --- ------- = --- -- / ------- + d[theta] Q d[theta] Q d[Omega] Q du / du + + c u - b [root](u - a·u - a´) + = ----·2n----- --------------------, (18) + [pi] u [root](a - b·b - a´) + + not requiring the integration of (11) and (12) + + If [theta] = [alpha] across the end JJ´ of the jet, where u = [oo], q + = Q, + + /b - a´ /a - b + ch n[Omega] = cos n[alpha] = /-------, sh n[Omega] = i sin n[alpha]= / ------, (19) + \/ a - a´ \/ a - a´ + + Then + + a - b·b - a´ a - a´ + cos 2n[alpha] - cos 2n[theta] = 2------------ = ½ sin² 2n[alpha]------ + a - a´·u - b u - b + + [root](a - b.b - a´)[root](u - a·u - b´) + sin 2n[theta] = 2---------------------------------------- (20) + a - a´·u - b + + [root](a - a·b - a´) + = sin 2n[alpha]--------------------; + u - b + + 2n c / b \ [root](a - b·b - a´) + ----- ----- = ( 1 + ----- ) -------------------- (21) + [phi] [rho] \ u - b/ [root](u - a·u - a´) + + a - a´ + (a + a´) cos 2n[alpha] - [a + a´ + (a - a´) cos 2n[alpha] cos 2n[theta] + = -------------------------------------------------------------------------------- + (a - a´) sin² 2n[alpha] + + cos 2n[alpha] - cos 2n[theta] + × ----------------------------- + sin 2n[theta] + + Along the wall AB, cos n[theta] = 0, sin n[theta] = 1, + + a > u > b, (22) + + / Q \^n /b - a´ /a - u + ch n[Omega] = i sh log ( --- ) = i / ------ / ------ (23) + \ q / \/ a - a´ \/ u - b´ + + / Q \^n /a - b /u - a´ + sh n[Omega] = i ch log ( --- ) = i / ------ / ------ (24) + \ q / \/ a - a´ \/ u - b´ + + ds ds d[phi] m c Q + -- = ------ ------ = ------ = --- -- (25) + du d[phi] dt [pi]qu [pi] qu + _ + AB / a Q du + [pi]-- = | --- -- + c _/ b q u + _ _ _ + / | [root](a - b)[root](u - a´) + [root](b - a´)[root](a - u) |^1/n du + = | | --------------------------------------------------------- | --. (26) + _/ |_ [root](a - a´)[root](u - b´) _| u + + Along the wall Bx, cos n[theta] = 1, sin n[theta] = 0, + + b > u > 0 (27) + + / Q \^n /b - a´ /a - u + ch n[Omega] = ch log ( --- ) = / ------ / ------ (28) + \ q / \/ a - a´ \/ b - u´ + + / Q \^n /a - b /u - a´ + sh n[Omega] = sh log ( --- ) = / ------ / ------. (29) + \ q / \/ a - a´ \/ b - u + + At x where [phi] = [oo], u = 0, and q = q0, + + / Q \^n /b - a´ / a /a - b / -a´ + ( --- ) = / ------ / --- + / ------ / ---. (30) + \ q0 / \/ a - a´ \/ b \/ a - a´ \/ q + + In crossing to the line of flow x´A´P´J´, [psi] changes from 0 to m, + so that with q = Q across JJ´, while across xx´ the velocity is q0, so + that + + m = q0.xx´ = Q.JJ´ (31) + _ _ + JJ´ q0 | /b - a´ / a /a - b / -a´ |^1/n + -- = --- = | / ------ / --- - / ------ / --- | , (32) + xx´ Q |_ \/ a - a´ \/ b \/ a - a´ \/ q _| + + giving the contraction of the jet compared with the initial breadth of + the stream. + + Along the line of flow x´A´P´J´, [psi] = m, u = a´e^(-[pi][phi]/m), + and from x´ to A´, cos n[theta] = 1, sin n[theta] = 0, + + / Q \^n /b - a´ /a - u + ch n[Omega] = ch log ( --- ) = / ------ / ------, (33) + \ q / \/ a - a´ \/ b - u´ + + / Q \^n /a - b /u - a´ + sh n[Omega] = sh log ( --- ) = / ------ / ------. (34) + \ q / \/ a - a´ \/ b - u´ + + 0 > u > a´. (35) + + Along the jet surface A´J´, q = Q, + + /b - a´ /a - u + ch n[Omega] = cos n[theta] = / ------ / ------, (36) + \/ a - a´ \/ b - u´ + + /a - b /a´ - u + sh n[Omega] = i sin n[theta] = i / ------ / ------, (37) + \/ a - a´ \/ b - u´ + + a´ > u = a´e^([pi]/sc) > -[oo], (38) + + giving the intrinsic equation. + + 41. The first problem of this kind, worked out by H. v. Helmholtz, of + the efflux of a jet between two edges A and A1 in an infinite wall, is + obtained by the symmetrical duplication of the above, with n = 1, b = + 0, a´ = -[oo], as in fig. 5, + + /u - a / -a + ch [Omega] = / -----, sh [Omega] = / ---; (1) + \/ u \/ u + + and along the jet APJ, [oo] > u = ae^([pi]s/c) > a, + + sh [Omega] = i sin [theta] - i[root](a/u) = ie^(-½[pi]s/c), (2) + _ _ + / [oo] / c c + PM = | sin [theta] ds = | e^(-½[pi]s/c) ds = ----- e^(-½[pi]s/c) = ----- sin [theta], (3) + _/ s _/ ½[pi] ½[pi] + + so that PT = c/½[pi], and the curve AP is the tractrix; and the + coefficient of contraction, or + + breadth of the jet [pi] + ---------------------- = --------. (4) + breadth of the orifice [pi] + 2 + + A change of [Omega] and [theta] into n[Omega] and n[theta] will give + the solution for two walls converging symmetrically to the orifice AA1 + at an angle [pi]/n. With n = ½, the reentrant walls are given of + Borda's mouthpiece, and the coefficient of contraction becomes ½. + Generally, by making a´ = - [oo], the line x´A´ may be taken as a + straight stream line of infinite length, forming an axis of symmetry; + and then by duplication the result can be obtained, with assigned n, + a, and b, of the efflux from a symmetrical converging mouthpiece, or + of the flow of water through the arches of a bridge, with wedge-shaped + piers to divide the stream. + + [Illustration: FIG. 5.] + + [Illustration: FIG. 6.] + + 42. Other arrangements of the constants n, a, b, a´ will give the + results of special problems considered by J. M. Michell, _Phil. + Trans._ 1890. + + Thus with a´ = 0, a stream is split symmetrically by a wedge of angle + [pi]/n as in Bobyleff's problem; and, by making a = [oo], the wedge + extends to infinity; then + + / b / n + ch n[Omega] = / -----, sh n[Omega] = / -----. (1) + \/ b - u \/ b - u + + Over the jet surface [psi] = m, q = Q, + + u = - e^([pi][phi]/m) = - be^([pi]²/c), + + / 1 / e^([pi]²/c) + ch [Omega] = cos n[theta] = / ---------------, sh [Omega] = i sin n[theta] = i / ---------------, (2) + \/ e^([pi]²/c) + 1 \/ e^([pi]²/c) + 1 + + ½[pi] ds 2n + e^(½[pi]²/c) = tan n[theta], ----- -------- = -------------. (3) + c d[theta] sin 2n[theta] + + For a jet impinging normally on an infinite plane, as in fig. 6, n = 1, + + e^(½[pi]²/c) = tan [theta], ch (½[pi]s/c) sin 2[theta] = 1, (4) + + sh ½[pi]x/c = cot [theta], sh ½[pi]y/c = tan [theta], + + sh ½[pi]x/c sh ½[pi]y/c = 1, e^(½[pi](x + y)/c) = e^(½[pi]x/c) + e^(½[pi]y/c) + 1. (5) + + With n = ½, the jet is reversed in direction, and the profile is the + catenary of equal strength. + + In Bobyleff's problem of the wedge of finite breadth, + + / b /u - a /b - a / u + ch n[Omega] = / --- / -----, sh n[Omega] = / ----- / -----, (6) + \/ a \/ u - b \/ a \/ u - b + + / b /a - b + cos n[alpha] = / ---, sin n[alpha] = / -----, (7) + \/ a \/ a + + and along the free surface APJ, q = Q, [psi] = 0, u = e^(-[pi][phi]/m) = ae^([pi]s/c), + + / e^([pi]²/c) - 1 + cos n[theta] = cos n[alpha] / ---------------------------, + \/ e^([pi]²/c) - cos² n[alpha] + + cos² n[alpha] sin² n[theta] + e^([pi]²/c) = -----------------------------, (8) + sin² n[theta] - sin² n[alpha] + + the intrinsic equation, the other free surface A´P´J´ being given by + + cos² n[alpha] sin² n[theta] + e^([pi]²/c) = -----------------------------. (9) + sin² n[alpha] - sin² n[theta] + + Putting n = 1 gives the case of a stream of finite breadth disturbed + by a transverse plane, a particular case of Fig. 7. + + When a = b, [alpha] = 0, and the stream is very broad compared with + the wedge or lamina; so, putting w = w´(a - b)/a in the penultimate + case, and + + u = ae^(-w) [asympt] a - (a - b)w´, (10) + + /w´ + 1 / 1 + ch n[Omega] = / ------, sh n[Omega] = / --------, (11) + \/ w´ \/ [root]w´ + + in which we may write + + w´ = [phi] + [psi]i. (12) + + Along the stream line xABPJ, [psi] = 0; and along the jet surface APJ, + -1 > [phi] > -[oo]; and putting [phi] = -[pi]s/c - 1, the intrinsic + equation is + + [pi]s/c = cot² n[theta], (13) + + which for n = 1 is the evolute of a catenary. + + [Illustration: FIG. 7.] + + 43. When the barrier AA´ is held oblique to the current, the stream + line xB is curved to the branch point B on AA´ (fig. 7), and so must + be excluded from the boundary of u; the conformal representation is + made now with + + d[Omega] [root](b - a·b - a´) + -------- = - ---------------------------- (1) + du (u - b) [root](u - a·u - a´) + + dw m 1 m´ 1 m + m´ u - b + -- = - ---- ----- - ---- -----, = - ------ · -------------, + du [pi] u - j [pi] u - j [pi] u - j·u - j´ + + mj´ + m´j + b = ---------, (2) + m + m´ + + taking u = [oo] at the source where [phi] = [oo], u = b at the branch + point B, u = j, j´ at the end of the two diverging streams where [phi] + = -[oo]; while [psi] = 0 along the stream line which divides at B and + passes through A, A´; and [psi] = m, -m´ along the outside boundaries, + so that m/Q, m´/Q is the final breadth of the jets, and (m + m´)/Q is + the initial breadth, c1 of the impinging stream. Then + + /b - a´ /u - a /b - a /u - a´ + ch ½[Omega] = / ------ / -----, sh ½[Omega] = / ------ / ------, (3) + \/ a - a´ \/ u - b \/ a - a´ \/ u - b + + 2b - a - a´ N + ch [Omega] = ----------- - -----, + a - a´ u - b + + / [root](2·a - u·u - a´) + sh [Omega] = / N----------------------, + \/ u - b + + a - b·b - a´ + N = 2------------. (4) + a - a´ + + Along a jet surface, q = Q, and + + ch[Omega] = cos [theta] = cos [alpha] - ½sin² [alpha](a - a´)/(u - b), (5) + + if [theta] = [alpha] at the source x of the jet xB, where u = [oo]; + and supposing [theta] = [beta], [beta]´ at the end of the streams + where u = j, j´, + + u - b ½ sin² [alpha] u - j cos[theta] - cos[beta] + ----- = -------------------------, ------ = ½ sin² [alpha]-----------------------------------------------------, + a - a´ cos [alpha] - cos [theta] a - a´ (cos [alpha] - cos [beta])(cos [alpha] - cos [theta]) + + u - j´ cos [theta] - cos [beta]´ + ----- = ½ sin² [alpha]------------------------------------------------------; (6) + a - a´ (cos [alpha] - cos [beta]´)(cos [alpha] - cos [theta]) + + and [psi] being constant along a stream line + + d[phi] dw ds d[phi] dw du + ------ = --, Q -------- = -------- = -- --------, + du du d[theta] d[theta] du d[theta] + + [pi]Q ds [pi] ds (cos [alpha] - cos [beta])(cos [alpha] - cos [beta]´)sin[theta] + ------ -------- = ---- -------- = ---------------------------------------------------------------------------------, + m + m´ d[theta] c d[theta] (cos [alpha] - cos [theta])(cos [theta] - cos [beta])(cos [theta] - cos [alpha]´) + + sin [theta] cos [alpha] - cos [beta]´ sin [theta] + = ------------------------- + ------------------------- · ------------------------ + cos [alpha] - cos [theta] cos [beta] - cos [beta]´ cos [theta] - cos [beta] + + cos [alpha] - cos [beta] sin [theta] + ------------------------ · -------------------------, (7) + cos [beta] - cos [beta]´ cos [theta] - cos [beta]´ + + giving the intrinsic, equation of the surface of a jet, with proper + attention to the sign. + + From A to B, a > u > b, [theta] = 0, + + Q a - a´ + ch [Omega] = ch log --- = cos [alpha] - ½ sin² [alpha] ------ + q a - b + + Q [root](a - u·u - a´) + sh [Omega] = sh log --- = -------------------- sin [alpha] + q u - b + + Q (u - b) cos [alpha] - ½(a - a´) sin² [alpha] + [root](a - u·u - a´)sin[alpha] + --- = ----------------------------------------------------------------------------- (8) + q u - b + + ds ds d[phi] Q dw + Q -- = Q ------ ------ = - --- -- + du d[phi] du q du + + m + m´ (u - b) cos [alpha] - ½(a - a´) sin² [alpha] + [root](a - u·u - a´) sin [alpha] + = ------ · ------------------------------------------------------------------------------- (9) + [pi] j - u·u - j´ + _ + AB / a (2b - a - a´)(u - b) - 2(a - b)(b - a´) + 2[root](a - b·b -a´·a - u·u -a´) + [pi]-- = | -------------------------------------------------------------------------- du, (10) + c _/ b a - a´·j - u·u - j´ + + with a similar expression for BA´. + + The motion of a jet impinging on an infinite barrier is obtained by + putting j = a, j´ = a´; duplicated on the other side of the barrier, + the motion reversed will represent the direct collision of two jets of + unequal breadth and equal velocity. When the barrier is small compared + with the jet, [alpha] = [beta] = [beta]´, and G. Kirchhoff's solution + is obtained of a barrier placed obliquely in an infinite stream. + + Two corners B1 and B2 in the wall xA, with a´ = -[oo], and n = 1, will + give the solution, by duplication, of a jet issuing by a reentrant + mouthpiece placed symmetrically in the end wall of the channel; or + else of the channel blocked partially by a diaphragm across the + middle, with edges turned back symmetrically, problems discussed by J. + H. Michell, A. E. H. Love and M. Réthy. + + When the polygon is closed by the walls joining, instead of reaching + back to infinity at xx´, the liquid motion must be due to a source, + and this modification has been worked out by B. Hopkinson in the + _Proc. Lond. Math. Soc._, 1898. + + Michell has discussed also the hollow vortex stationary inside a + polygon (_Phil. Trans._, 1890); the solution is given by + + ch n[Omega] = sn w, sh n[Omega] = i cn w (11) + + so that, round the boundary of the polygon, [psi] = K´, sin n[theta] = + 0; and on the surface of the vortex [psi] = 0, q = Q, and + + cos n[theta] = sn [phi], n[theta] = ½[pi] - am s/c, (12) + + the intrinsic equation of the curve. + + This is a closed Sumner line for n = 1, when the boundary consists of + two parallel walls; and n = ½ gives an Elastica. + + 44. _The Motion of a Solid through a Liquid._--An important problem in + the motion of a liquid is the determination of the state of velocity + set up by the passage of a solid through it; and thence of the + pressure and reaction of the liquid on the surface of the solid, by + which its motion is influenced when it is free. + + Beginning with a single body in liquid extending to infinity, and + denoting by U, V, W, P, Q, R the components of linear and angular + velocity with respect to axes fixed in the body, the velocity function + takes the form + + [phi] = U_[phi]1 + V_[phi]2 + W_[phi]3 + P_[chi]1 + Q_[chi]2 + R_[chi]3, (1) + + where the [phi]'s and [chi]'s are functions of x, y, z, depending on + the shape of the body; interpreted dynamically, C - [rho][phi] + represents the impulsive pressure required to stop the motion, or C + + [rho][phi] to start it again from rest. + + The terms of [phi] may be determined one at a time, and this problem + is purely kinematical; thus to determine [phi]1, the component U alone + is taken to exist, and then l, m, n, denoting the direction cosines of + the normal of the surface drawn into the exterior liquid, the function + [phi]1 must be determined to satisfy the conditions + + (i.) [nabla]²[phi]1 = 0. throughout the liquid; + + (ii.) d[ph]1/d[upsilon] = -l, the gradient of [phi] down the normal at + the surface of the moving solid; + + (iii.) d[ph]1/d[upsilon] = 0, over a fixed boundary, or at infinity; + + similarly for [phi]2 and [phi]3. + + To determine [chi]1 the angular velocity P alone is introduced, and + the conditions to be satisfied are + + (i.) [nabla]²[chi]1 = 0, throughout the liquid; + + (ii.) d[chi]1/d[upsilon] = mz - ny, at the surface of the moving body, + but zero over a fixed surface, and at infinity; the same for [chi]2 + and [chi]3. + + For a cavity filled with liquid in the interior of the body, since the + liquid inside moves bodily for a motion of translation only, + + [phi]1 = -x, [phi]2 = -y, [phi]3 = -z; (2) + + but a rotation will stir up the liquid in the cavity, so that the + [chi]'s depend on the shape of the surface. + + The ellipsoid was the shape first worked out, by George Green, in his + _Research on the Vibration of a Pendulum in a Fluid Medium_ (1833); + the extension to any other surface will form an important step in this + subject. + + A system of confocal ellipsoids is taken + + x² y² z² + ------------- + ------------- + ------------- = 1 (3) + a² + [lambda] b² + [lambda] c² + [lambda] + + and a velocity function of the form + + [phi] = x[psi], (4) + + where [psi] is a function of [lambda] only, so that [psi] is constant + over an ellipsoid; and we seek to determine the motion set up, and the + form of [psi] which will satisfy the equation of continuity. + + Over the ellipsoid, p denoting the length of the perpendicular from + the centre on a tangent plane, + + px py pz + l = -------------, m = -------------, n = ------------- (5) + a² + [lambda] b² + [lambda] c² + [lambda] + + p²x² p²y² p²z² + 1 = ---------------- + ---------------- + ----------------, (6) + (a² + [lambda])² (b² + [lambda])² (c² + [lambda])² + + p² = (a² + [lambda])l² + (b² + [lambda])m² + (c² + [lambda])n², (7) + = a²l² + b²m² + c²n² + [lambda], + + dp d[lambda] + 2p-- = ---------; (8) + ds ds + + Thence + + d[phi] dx d[psi] + ------ = --[psi] + x------ + ds ds ds + + dx d[psi] dp + = --[psi] + 2(a² + [lambda])--------- l--, (9) + ds d[lambda] ds + + so that the velocity of the liquid may be resolved into a component + -[psi] parallel to Ox, and -2(a² + [lambda])l d[psi]/d[lambda] along + the normal of the ellipsoid; and the liquid flows over an ellipsoid + along a line of slope with respect to Ox, treated as the vertical. + + Along the normal itself + + d[phi] / d[psi] \ + ----- = ( [psi] + 2(a² + [lambda])-------- )l, (10) + ds \ d[lambda] / + + so that over the surface of an ellipsoid where [lambda] and [psi] are + constant, the normal velocity is the same as that of the ellipsoid + itself, moving as a solid with velocity parallel to Ox + + d[psi] + U = -[psi] - 2(a² + [lambda])---------, (11) + d[lambda] + + and so the boundary condition is satisfied; moreover, any ellipsoidal + surface [lambda] may be supposed moving as if rigid with the velocity + in (11), without disturbing the liquid motion for the moment. + + The continuity is secured if the liquid between two ellipsoids + [lambda] and [lambda]1, moving with the velocity U and U1 of equation + (11), is squeezed out or sucked in across the plane x = 0 at a rate + equal to the integral flow of the velocity [psi] across the annular + area [alpha]1 - [alpha] of the two ellipsoids made by x = 0; or if + _ + / [lambda]1 d[alpha] + [alpha]U - [alpha]1U1 = | [psi]-------- d[lambda], (12) + _/ [lambda] d[lambda] + + [alpha] = [pi][root](b² + [lambda]·c² + [lambda]). (13) + + Expressed as a differential relation, with the value of U from (11), + _ _ + d | d[psi] | d[alpha] + --------- | [alpha][psi] + 2(a² + [lambda])[alpha]--------- | - [psi]--------- = 0, (14) + d[lambda] |_ d[lambda] _| d[lambda] + + d[psi] d / d[psi] \ + 3[alpha]--------- + 2(a² + [lambda])-------- ( [alpha]-------- ) = 0, (15) + d[lambda] d[lambda] \ d[lambda]/ + + and integrating + + d[psi] + (a² + [lambda])^3/2 [alpha]-------- = a constant, (16) + d[lambda] + + so that we may put + _ + / Md[lambda] + [psi] = | ----------------, (17) + _/ (a² + [lambda])P + + P² = 4(a² + [lambda])(b² + [lambda])(c² + [lambda]), (18) + + where M denotes a constant; so that [psi] is an elliptic integral of + the second kind. + + The quiescent ellipsoidal surface, over which the motion is entirely + tangential, is the one for which + + d[psi] + 2(a² + [lambda])--------- + [psi] = 0, (19) + d[lambda] + + and this is the infinite boundary ellipsoid if we make the upper limit + [lambda]1 = [oo]. + + The velocity of the ellipsoid defined by [lambda] = 0 is then + + d[psi]0 + U = -2a²--------- - [psi]0 + d[lambda] + _ + M / [oo] Md[lambda] + = --- - | ---------------- + abc _/ 0 (a² + [lambda])P + + M + = --- (1 - A0), (20) + abc + + with the notation + _ + / [oo] abc d[lambda] + A or A_[lambda] = | ---------------- + _/[lambda] (a² + [lambda])P + _ + d / [oo] d[lambda] + = -2abc--- | ---------, (21) + da²_/ [lambda] P + + so that in (4) + + M UxA xA_[lambda] + [phi] = ---xA = ------, [phi]1 = -----------, (22) + abc 1 - A0 1 - A0 + + in (1) for an ellipsoid. + + The impulse required to set up the motion in liquid of density [rho] + is the resultant of an impulsive pressure [rho][phi] over the surface + S of the ellipsoid, and is therefore + _ _ _ _ + / / / / + | | [rho][phi]l dS = [rho][psi]0 | | xl dS + _/_/ _/_/ + + = [rho][psi]0 (volume of the ellipsoid) = [psi]0 W´, (23) + + where W´ denotes the weight of liquid displaced. + + Denoting the effective inertia of the liquid parallel to Ox by + [alpha]W´. the momentum + + [alpha]W´U = [psi]0W´ (24) + + [psi]0 A0 + [alpha] = ------ = ------; (25) + U 1 - A0 + + in this way the air drag was calculated by Green for an ellipsoidal + pendulum. + + Similarly, the inertia parallel to Oy and Oz is + + B0 C0 + [beta]W´ = ------ W´, [gamma]W´ = ------ W´, (26) + 1 - B0 1 - C0 + _ + / [oo] abc d[lambda] + B_[lambda], C_[lambda] = | -------------------------------; (27) + _/[lambda] (b² + [lambda], c² + [lambda])P + + and + + A + B + C = abc/½P, A0 + B0 + C0 = 1. (28) + + For a sphere + + a = b = c, A0 = B0 = C0 = 1/3, [alpha] = [beta] = [gamma] = ½, (29) + + so that the effective inertia of a sphere is increased by half the + weight of liquid displaced; and in frictionless air or liquid the + sphere, of weight W, will describe a parabola with vertical + acceleration + + W - W´ + ------- g. (30) + W + ½W´ + + Thus a spherical air bubble, in which W/W´ is insensible, will begin + to rise in water with acceleration 2g. + + 45. When the liquid is bounded externally by the fixed ellipsoid + [lambda] = [lambda]1, a slight extension will give the velocity + function [phi] of the liquid in the interspace as the ellipsoid + [lambda] = 0 is passing with velocity U through the confocal position; + [phi] must now take the form x([psi] + N), and will satisfy the + conditions in the shape + _ + abc /[lambda]1 abcd[lambda] + ------ + | ---------------- + A + B1 + C1 a1b1c1 _/ [lambda] (a² + [lambda])P + [phi] = Ux ----------------- = Ux ------------------------------------------, (1) + B0 + C0 - B1 - C1 abc /[lambda]1 abcd[lambda] + 1 - ------ - | ---------------- + a1b1c1 _/0 (a² + [lambda])P + + and any confocal ellipsoid defined by [lambda], internal or external + to [lambda] = [lambda]1, may be supposed to swim with the liquid for + an instant, without distortion or rotation, with velocity along Ox + + B_[lambda] + C_[lambda] - B1 - C1 + U ---------------------------------- + B0 + C0 - B1 - C1 + + Since - Ux is the velocity function for the liquid W´ filling the + ellipsoid [lambda] = 0, and moving bodily with it, the effective + inertia of the liquid in the interspace is + + A0 + B1 + C1 + ----------------- W´. (2) + B0 + C0 - B1 - C1 + + If the ellipsoid is of revolution, with b = c, + + A + 2B1 + [phi] = ½Ux -------, (3) + B0 - B1 + + and the Stokes' current function [psi] can be written down + + B - B1 + [psi] = - ½Uy² -------; (4) + B0 - B1 + + reducing, when the liquid extends to infinity and B1 = 0, to + A B + [phi] = ½Ux --, [psi] = - ½Uy² --; (5) + B0 B0 + + so that in the relative motion past the body, as when fixed in the + current U parallel to xO, + + / A \ / B \ + [phi]´ = ½Ux ( 1 + -- ), [psi]´ = ½Uy² ( 1 - -- ). (6) + \ B0 / \ B0 / + + Changing the origin from the centre to the focus of a prolate + spheroid, then putting b² = pa, [lambda] = [lambda]´a, and proceeding + to the limit where a = [oo], we find for a paraboloid of revolution + + p B p + B = ½ -------------, -- = -------------, (7) + p + [lambda]´ B0 p + [lambda]´ + + y² + ------------- = p + [lambda]´ - 2x, (8) + p + [lambda]´ + + with [lambda]´ = 0 over the surface of the paraboloid; and then + + [psi]´ = ½U [y² - p[root](x² + y²) + px]; (9) + + [psi] = -½Up [[root](x² + y²) - x]; (10) + + [phi] = -½Up log [ [root](x² + y²) + x]. (11) + + The relative path of a liquid particle is along a stream line + + [psi]´ = ½Uc², a constant, (12) + + p²y² - (y² - c²)² p²y² - (y² - c²)² + x = -----------------, [root](x² + y²) = ----------------- (13) + 2p(y² - c²) 2p(y² - c²) + + a C4; while the absolute path of a particle in space will be given by + + dy r - x y² - c² + -- = - ----- = -------, (14) + dx y 2py + + y² - c² = a²e^(-x/p). (15) + + 46. Between two concentric spheres, with + + a² + [lambda] = r², a² + [lambda]1 = a1², (1) + + A = B = C = a³/3r³, + + a³ a³ a³ a³ + -- + 2 --- -- + 2 --- + r³ a1³ r³ a1³ + [phi] = ½Ux -----------, [psi] = ½Uy² ----------; (2) + 1 - a^4/a1² 1 - a³/a1³ + + and the effective inertia of the liquid in the interspace is + + A0 + 2A1 a1³ + 2a³ + --------- W´ = ½ --------- W´. (3) + 2A0 - 2A1 a1³ - a³ + + When the spheres are not concentric, an expression for the effective + inertia can be found by the method of images (W. M. Hicks, _Phil. + Trans._, 1880). + + The image of a source of strength [mu] at S outside a sphere of radius + a is a source of strength [mu]a/[f] at H, where OS = [f], OH = a²/f, + and a line sink reaching from the image H to the centre O of line + strength - [mu]/a; this combination will be found to produce no flow + across the surface of the sphere. + + Taking Ox along OS, the Stokes' function at P for the source S is [mu] + cos PSx, and of the source H and line sink OH is [mu](a/[f]) cos PHx + and -([mu]/a)(PO - PH); so that + + / a PO - PH \ + [psi] = [mu] (cos PSx + --- cos PHx - ------- ), (4) + \ [f] a / + + and [psi] = -[mu], a constant, over the surface of the sphere, so that + there is no flow across. + + When the source S is inside the sphere and H outside, the line sink + must extend from H to infinity in the image system; to realize + physically the condition of zero flow across the sphere, an equal sink + must be introduced at some other internal point S´. + + When S and S´ lie on the same radius, taken along Ox, the Stokes' + function can be written down; and when S and S´ coalesce a doublet is + produced, with a doublet image at H. + + For a doublet at S, of moment m, the Stokes' function is + + d y² + m-- cos PSx = -m---; (5) + df PS³ + + and for its image at H the Stokes' function is + + d a³ y² + m-- cos PHx = -m-- ---; (6) + df f³ PH³ + + so that for the combination + + /a³ 1 1 \ y² / a³ f³\ + [psi] = my² ( -- --- - --- ) = m-- ( --- - --- ), (7) + \f³ PH³ PS³/ f³ \PH³ PS³/ + + and this vanishes over the surface of the sphere. + + There is ao Stokes' function when the axis of the doublet at S does + not pass through O; the image system will consist of an inclined + doublet at H, making an equal angle with OS as the doublet S, and of a + parallel negative line doublet, extending from H to O, of moment + varying as the distance from O. + + A distribution of sources and doublets over a moving surface will + enable an expression to be obtained for the velocity function of a + body moving in the presence of a fixed sphere, or inside it. + + The method of electrical images will enable the stream function [psi]´ + to be inferred from a distribution of doublets, finite in number when + the surface is composed of two spheres intersecting at an angle + [pi]/m, where m is an integer (R. A. Herman, _Quart. Jour. of Math._ + xxii.). + + Thus for m = 2, the spheres are orthogonal, and it can be verified + that + + / a1³ a2³ a³ \ + [psi]´ = ½Uy² ( 1 - --- - --- + -- ), (8) + \ r1³ r2³ r³ / + + where a1, a2, a = a1a2/[root](a1² + a2²) is the radius of the spheres + and their circle of intersection, and r1, r2, r the distances of a + point from their centres. + + The corresponding expression for two orthogonal cylinders will be + + / a1² a2² a² \ + [psi]´ = Uy ( 1 - --- - --- + -- ). (9) + \ r1² r2² r² / + + With a2 = [oo], these reduce to + + / a^5 \ x / a^4 \ x + [psi]´ = ½Uy² ( 1 - --- ) ---, or Uy ( 1 - --- ) ---, (10) + \ r^5 / a \ r^4 / a + + for a sphere or cylinder, and a diametral plane. + + Two equal spheres, intersecting at 120°, will require + _ _ + | x a³ a^4(a - 2x) a³ a^4(a + 2x) | + [psi]´ = ½Uy² | --- - ---- + ----------- + ---- - ----------- |, (11) + |_ a 2r1³ 2r1^5 2r2³ 2r2^5 _| + + with a similar expression for cylinders; so that the plane x = 0 may + be introduced as a boundary, cutting the surface at 60°. The motion of + these cylinders across the line of centres is the equivalent of a line + doublet along each axis. + + 47. The extension of Green's solution to a rotation of the ellipsoid + was made by A. Clebsch, by taking a velocity function + + [phi] = xy[chi] (1) + + for a rotation R about Oz; and a similar procedure shows that an + ellipsoidal surface [lambda] may be in rotation about Oz without + disturbing the motion if + + / 1 1 \ dx + ( ------------ + ------------ ) [chi] + 2--------- + \ a² + [lambda] b² + [lambda] / d[lambda] + R = - -----------------------------------------------------, (2) + 1/(b² + [lambda] - 1/(a² = [lambda]) + + and that the continuity of the liquid is secured if + + d[chi] + (a² + [lambda])^3/2 (b² + [lambda])^3/2 (c² + [lambda]) ½--------- = constant, (3) + d[lambda] + _ + / [oo] Nd[lambda] N B_[lambda] - A_[lambda] + [chi] = | ------------------------------- = --- . -----------------------; (4) + _/[lambda] (a² + [lambda])(b² + [lambda])P abc a² - b² + + and at the surface [lambda] = 0, + + / 1 1\ N B0 - A0 N 1 + ( -- + -- ) --- ------- - --- ---- + \a² b²/ abc a² - b² abc a²b² + R = - ----------------------------------, (5) + 1/b² - 1/a² + + N 1/b² - 1/a² + --- = R --------------------------, (6) + abc 1 / 1 1\ B0 - A0 + ---- - ( -- + -- ) ------- + a²b² \a² b²/ a² - b² + + (a² - b²)²/(a² + b²) + = R -------------------------------. + (a² - b²)/(a² + b²) - (B0 - A0) + + The velocity function of the liquid inside the ellipsoid [lambda] = 0 + due to the same angular velocity will be + + [phi]1 = Rxy(a² - b²)/(a² + b²), (7) + + and on the surface outside + + N B0 - A0 + [phi]0 = xy[chi]0 = xy--- -------, (8) + abc a² - b² + + so that the ratio of the exterior and interior value of [phi] at the + surface is + + [phi]0 B0 - A0 + ------ = -------------------------------, (9) + [phi]1 (a² - b²)/(a² + b²) - (B0 - A0) + + and this is the ratio of the effective angular inertia of the liquid, + outside and inside the ellipsoid [lambda] = 0. + + The extension to the case where the liquid is bounded externally by a + fixed ellipsoid [lambda] = [lambda]1 is made in a similar manner, by + putting + + [phi] = xy([chi] + M), (10) + + and the ratio of the effective angular inertia in (9) is changed to + + a1² - b1² abc + (B0 - A0) - (B1 - A1) + --------- ------ + a1² + b1² a1b1c1 + --------------------------------------------------. (11) + a² - b² a1² - b1² abc + ------- - --------- ------ - (B0 - A0) + (B1 - A1) + a² + b² a1² + b1² a1b1c1 + + Make c = [oo] for confocal elliptic cylinders; and then + _ + /[oo] ab ab / /b² + [lambda] \ + A[lambda] = | ----------------------------------------------------- = ------- ( 1 - / ------------- ), (12) + _/[lambda] (a² + [lambda])[root]([4·a² + [lambda]·b² + [lambda]) a² - b² \ \/ a² + [lambda] / + + ab / /a² + [lambda] \ + B[lambda] = ------- ( / ------------- - 1 ), C[lambda]= 0; + a² - b² \ \/ b² + [lambda] / + + and then as above in § 31, with + + a = c ch [alpha], b = c sh [alpha], + a1 = [root](a² + [lambda]) = c ch [alpha]1, b1 = c sh [alpha]1 (13) + + the ratio in (11) agrees with § 31 (6). + + As before in § 31, the rotation may be resolved into a shear-pair, in + planes perpendicular to Ox and Oy. + + A torsion of the ellipsoidal surface will give rise to a velocity + function of the form [phi] = xyz[Omega], where [Omega] can be + expressed by the elliptic integrals A_[lambda], B_[lambda], + C_[lambda], in a similar manner, since + _ + / [oo] + [Omega] = L | d[lambda]/P³ + _/ [lambda] + + 48. The determination of the [phi]'s and [chi]'s is a kinematical + problem, solved as yet only for a few cases, such as those discussed + above. + + But supposing them determined for the motion of a body through a + liquid, the kinetic energy T of the system, liquid and body, is + expressible as a quadratic function of the components U, V, W, P, Q, + R. The partial differential coefficient of T with respect to a + component of velocity, linear or angular, will be the component of + momentum, linear or angular, which corresponds. + + Conversely, if the kinetic energy T is expressed as a quadratic + function of x1, x2, x3, y1, y2, y3, the components of momentum, the + partial differential coefficient with respect to a momentum component + will give the component of velocity to correspond. + + These theorems, which hold for the motion of a single rigid body, are + true generally for a flexible system, such as considered here for a + liquid, with one or more rigid bodies swimming in it; and they express + the statement that the work done by an impulse is the product of the + impulse and the arithmetic mean of the initial and final velocity; so + that the kinetic energy is the work done by the impulse in starting + the motion from rest. + + Thus if T is expressed as a quadratic function of U, V, W, P, Q, R, + the components of momentum corresponding are + + dT dT dT + x1 = --, x2 = --, x3 = --, (1) + dU dV dW + + dT dT dT + y1 = --, y2 = --, y3 = --; + dP dQ dR + + but when it is expressed as a quadratic function of x1, x2, x3, y1, + y2, y3, + + dT dT dT + U = ---, V = ---, W = ---, (2) + dx1 dx2 dx3 + + dT dT dT + P = ---, Q = ---, R = ---. + dy1 dy2 dy3 + + The second system of expression was chosen by Clebsch and adopted by + Halphen in his _Fonctions elliptiques_; and thence the dynamical + equations follow + + dx1 dT dT + X = --- - x2--- + x3---, Y = ..., Z = ..., (3) + dt dy3 dy2 + + dy1 dT dT dT dT + L = --- - y2--- + y3--- - x2--- + x2---, M = ..., N = ..., (4) + dt dy3 dy2 dx3 dx2 + + where X, Y, Z, L, M, N denote components of external applied force on + the body. + + These equations are proved by taking a line fixed in space, whose + direction cosines are l, m, n, then + + dl dm dn + -- = mR - nQ, -- = nP - lR, -- = lQ - mP. (5) + dt dt dt + + If P denotes the resultant linear impulse or momentum in this + direction + + P = lx1 + mx2 + nx3, (6) + + dP dl dm dn + -- = --x1 + --x2 + --x3 + dt dt dt dt + + dx1 dx2 dx3 + + l--- + m--- + n---, + dt dt dt + + / dx1 \ + = l ( --- - x2R + x3Q ) + \ dt / + + / dx2 \ + + m ( --- - x3P + x1R ) + \ dt / + + / dx3 \ + + n ( --- - x1Q + x2P ) + \ dt / + + = lX + mY + nZ, (7) + + for all values of l, m, n. + + Next, taking a fixed origin [Omega] and axes parallel to Ox, Oy, Oz + through O, and denoting by x, y, z the coordinates of O, and by G the + component angular momentum about [Omega] in the direction (l, m, n) + + G = l(y1 - x2z + x3y) + + m(y2 - x3x + x1z) + + n(y3 - x1y + x2x). (8) + + Differentiating with respect to t, and afterwards moving the fixed + origin up to the moving origin O, so that + + dx dy dz + x = y = z = 0, but -- = U, -- = V, -- = W, + dt dt dt + + dG / dy1 \ + -- = l ( --- - y2R + y3Q - x2W + x3V ) + dt \ dt / + + / dy2 \ + + m ( --- - y3P + y1R - x3U + x1W ) + \ dt / + + / dy3 \ + + n ( --- - y1Q + y2P - x1V + x2U ) + \ dt / + + = lL + mM + nN, (9) + + for all values of l, m, n. + + When no external force acts, the case which we shall consider, there + are three integrals of the equations of motion + + (i.) T = constant, + + (ii.) x1² + x2² + x3² = F², a constant, + + (iii.) x1y1 + x2y2 + x3y3 = n = GF, a constant; + + and the dynamical equations in (3) express the fact that x1, x2, x3 + are the components of a constant vector having a fixed direction; + while (4) shows that the vector resultant of y1, y2, y3 moves as if + subject to a couple of components + + x2W - x3V, x3U - x1W, x1V - x2U, (10) + + and the resultant couple is therefore perpendicular to F, the + resultant of x1, x2, x3, so that the component along OF is constant, + as expressed by (iii). + + If a fourth integral is obtainable, the solution is reducible to a + quadrature, but this is not possible except in a limited series of + cases, investigated by H. Weber, F. Kötter, R. Liouville, Caspary, + Jukovsky, Liapounoff, Kolosoff and others, chiefly Russian + mathematicians; and the general solution requires the double-theta + hyperelliptic function. + + 49. In the motion which can be solved by the elliptic function, the + most general expression of the kinetic energy was shown by A. Clebsch + to take the form + + T = ½p(x1² + x2²) + ½p´x3² + + q(x1y1 + x2y2) + q´x3y3 + + ½r(y1² + y2²) + ½r´y3² (1) + + so that a fourth integral is given by + + dy3/dt = 0, y3 = constant; (2) + + dx3 + --- = x1(qx2 + ry2) - x2(qx1 + ry1) = r(x1y2 - x2y1), (3) + dt + + 1 / dx3 \² + -- ( --- ) = (x1² + x2²)(y1² + y2²) - (x1y1 + x2y2)² + r² \ dt / + + = (x1² + x2²)(y1² + y2²) - (FG - x3y3)² + = (x1² + x2²)(y1² + y2² + y3² - G²) - (Gx3 - Fy3)², (4) + + in which + + x1² + x2² = F² - x3², x1y1 + x2y2 = FG - x3y3, (5) + + r(y1² + y2²) = 2T - p(x1² + x2²) - p´x3² + - 2q(x1y1 + x2y2) - 2q´x3y3 - r´y3² + = (p - p´)x3² + 2(q - q´)x3y3 + m1, (6) + + m1 - 2T - pF² - 2qFG - r1y3² (7) + + so that + + 1 / dx3 \² + -- ( --- ) = X3 (8) + r² \ dt / + + where X3 is a quartic function of x3, and thus t is given by an + elliptic integral of the first kind; and by inversion x3 is in + elliptic function of the time t. Now + + (x1 - x2i)(y1 + y2i) = x1y1 + x2y2 + i(x1y2 - x2y1) + = FG - xy3y3 + i[V-]X3, (9) + + y1 + y2i FG - x3y3 + i[root]X3 + -------- = --------------------- , (10) + x1 + x2i x1² + x2² + + d + -- (x1 + x2i) = -i[(q´ - q)x3 + r´y3] + irx3(y1 + y2i), (11) + dt + + d FG - x3y3 + i[root]X3 + --- log (x1 + x2i) = dti -(q´ - q)x - r´y + rx ---------------------, (12) + dti F² - x3² + + d /x1 + x2i Fy3 - Gx3 + --- log \ / -------- = -(q´ - q)x3 - (r´ - r)y3 - Fr---------, (13) + dti \/ x1 - x2i F² - x3² + + requiring the elliptic integral of the third kind; thence the + expression of x1 + x2i and y1 + y2i. + + Introducing Euler's angles [theta], [phi], [psi], + + x1 = F sin [theta] sin [phi], x2 = F sin [theta] cos [phi], + + x1 + x2i = iF sin [theta][epsilon]^(-[psi]i), x3 = F cos [theta]; (14) + + d[psi] + sin [theta] ------ = P sin [phi] + Q cos[phi], (15) + dt + + d[psi] dT dT + F sin²[theta] ------ = --- x1 + --- x2 + dt dy1 dy2 + + = (qx1 + ry1)x1 + (qx2 + ry2)x2 + + = qx1² + x2²) + r (x1y1 + x2y2) + + = gF² sin² [theta] + r(FG - x3y3), (16) + _ + / FG - x3y3 Fr dx3 + [psi] - qFt = | --------- --------, (17) + _/ F² - x3² [root]X3 + + elliptic integrals of the third kind. + + Employing G. Kirchhoff's expressions for X, Y, Z, the coordinates of + the centre of the body, + __ __ __ + FX = y1 cos xY + y2 cos yY + y3 cos zY, (18) + __ __ __ + FY = -y1 cos xX + y2 cos yX + y3 cos zX, (19) + __ __ __ + G = y1 cos xZ + y2 cos yZ + y3 cos zZ, (20) + + F²(X² + Y²) = y1² + y2² + y3² - G², (21) + + Fy3 - Gx3 + i[root]X3 + F(X + Yi) = --------------------- [epsilon]^[psi]_i. (22) + [root](F² - x3²) + + Suppose x3 - F is a repeated factor of X3, then y3 = G, and + _ _ + | p´ - p q´ - q | + X3 = (x3 - F)² | ------(x3 + F)² + 2------G(x3 + F) - G² |, (23) + |_ r r _| + + and putting x3 - F = y, + _ + / dy \² | p´ - p q´ - q + ( -- ) = r²y² | 4 ------ F² + 4 ------ FG - G² + \ dt / |_ r r + _ + / p´ - p q´ - q \ p´ - p | + + 2 ( 2 ------ F + ------ G ) y + ------ y² |, (24) + \ r r / r _| + + so that the stability of this axial movement is secured if + + p´ - p q´ - q + A = 4 ------F² + 4 ------FG - G² (25) + r r + + is negative, and then the axis makes r[V-](-A)/[pi] nutations per + second. Otherwise, if A is positive + _ + / dy + rt = | ---------------------- + _/ y[root](A + 2By + Cy²) + + 1 sh^(-1) [root]A[root](A + 2By + Cy²) 1 ch^(-1) A + By + = ------- ---------------------------- = ------- ---------------, (26) + [root]A ch^(-1) y[root](B² ~ AC) [root]A sh^(-1) y[root](B² ~ AC) + + and the axis falls away ultimately from its original direction. + + A number of cases are worked out in the American Journal of + Mathematics (1907), in which the motion is made algebraical by the use + of the pseudo-elliptic integral. To give a simple instance, changing + to the stereographic projection by putting tan ½[theta] = x, + + (Nxe[psi]i)^3/2 = (x + 1)[root]X1 + i(x - 1)[root]X2, (27) + + X1 + -- = ±ax^4 + 2ax³ ± 3(a + b)x² + 2bx ± b, (28) + X2 + + N³ = -8(a + b), (29) + + will give a possible state of motion of the axis of the body; and the + motion of the centre may then be inferred from (22). + +50. The theory preceding is of practical application in the +investigation of the stability of the axial motion of a submarine boat, +of the elongated gas bag of an airship, or of a spinning rifled +projectile. In the steady motion under no force of such a body in a +medium, the centre of gravity describes a helix, while the axis +describes a cone round the direction of motion of the centre of gravity, +and the couple causing precession is due to the displacement of the +medium. + +In the absence of a medium the inertia of the body to translation is the +same in all directions, and is measured by the weight W, and under no +force the C.G. proceeds in a straight line, and the axis of rotation +through the C.G. preserves its original direction, if a principal axis +of the body; otherwise the axis describes a cone, right circular if the +body has uniaxial symmetry, and a Poinsot cone in the general case. + +But the presence of the medium makes the effective inertia depend on the +direction of motion with respect to the external shape of the body, and +on W´ the weight of fluid medium displaced. + + Consider, for example, a submarine boat under water; the inertia is + different for axial and broadside motion, and may be represented by + + c1 = W + W´[alpha], c2 = W + W´[beta], (1) + + where [alpha], [beta] are numerical factors depending on the external + shape; and if the C.G. is moving with velocity V at an angle [phi] + with the axis, so that the axial and broadside component of velocity + is u = V cos [phi], v = V sin [phi], the total momentum F of the + medium, represented by the vector OF at an angle [theta] with the + axis, will have components, expressed in sec. lb., + + u V v V + F cos [theta] = c1 --- = (W + W´[alpha]) --- cos [phi], F sin [theta] = c2 --- = (W + W´[beta]) --- sin [phi]. (2) + g g g g + + Suppose the body is kept from turning as it advances; after t seconds + the C.G. will have moved from O to O´, where OO´ = Vt; and at O´ the + momentum is the same in magnitude as before, but its vector is + displaced from OF to O´F´. + + For the body alone the resultant of the components of momentum + + V V V + W --- cos [phi] and W --- sin [phi] is W --- sec. lb., (3) + g g g + + acting along OO´, and so is unaltered. + + But the change of the resultant momentum F of the medium as well as of + the body from the vector OF to O´F´ requires an impulse couple, + tending to increase the angle FOO´, of magnitude, in sec. foot-pounds + + F·OO´·sin FOO´ = FVt sin ([theta] - [phi]), (4) + + equivalent to an incessant couple + + N = FV sin ([theta] - [phi]) + = (F sin [theta] cos [phi] - F cos [theta] sin [phi])V + = (c2 - c1)(V²/g) sin [phi] cos [phi] + = W´([beta] - [alpha]uv/g). (5) + + This N is the couple in foot-pounds changing the momentum of the + medium, the momentum of the body alone remaining the same; the medium + reacts on the body with the same couple N in the opposite direction, + tending when c2-c1 is positive to set the body broadside to the + advance. + + An oblate flattened body, like a disk or plate, has c2 - c1 negative, + so that the medium steers the body axially; this may be verified by a + plate dropped in water, and a leaf or disk or rocket-stick or piece of + paper falling in air. A card will show the influence of the couple N + if projected with a spin in its plane, when it will be found to change + its aspect in the air. + + An elongated body like a ship has c2-c1 positive, and the couple N + tends to disturb the axial movement and makes it unstable, so that a + steamer requires to be steered by constant attention at the helm. + + Consider a submarine boat or airship moving freely with the direction + of the resultant momentum horizontal, and the axis at a slight + inclination [theta]. With no reserve of buoyancy W = W´, and the + couple N, tending to increase [theta], has the effect of diminishing + the metacentric height by h ft. vertical, where + + c1 u² + Wh tan[theta] = N = (c2 - c1) -- --- tan [theta], (6) + c2 g + + c2 - c1 c1 u² 1 + [alpha] u² + h = ------- -- --- = ([beta] - [alpha] ----------- ---. (7) + W c2 g 1 + [beta] g + +51. An elongated shot is made to preserve its axial flight through the +air by giving it the spin sufficient for stability, without which it +would turn broadside to its advance; a top in the same way is made to +stand upright on the point in the position of equilibrium, unstable +statically but dynamically stable if the spin is sufficient; and the +investigation proceeds in the same way for the two problems (see +GYROSCOPE). + + The effective angular inertia of the body in the medium is now + required; denote it by C1 about the axis of the figure, and by C2 + about a diameter of the mean section. A rotation about the axis of a + figure of revolution does not set the medium in motion, so that C1 is + the moment of inertia of the body about the axis, denoted by Wk1². But + if Wk2² is the moment of inertia of the body about a mean diameter, + and [omega] the angular velocity about it generated by an impulse + couple M, and M´ is the couple required to set the surrounding medium + in motion, supposed of effective radius of gyration k´, + + Wk2²[omega] = M - M´, W´k´²[omega] = M´, (1) + + Wk2² + W´k´²[omega] = M, (2) + + C2 = Wk2² + W´k´² = (W + W´[epsilon])k2², (3) + + in which we have put k´² = [epsilon]k², where [epsilon] is a numerical + factor depending on the shape. + + If the shot is spinning about its axis with angular velocity p, and is + preceding steadily at a rate [mu] about a line parallel to the + resultant momentum F at an angle [theta], the velocity of the vector + of angular momentum, as in the case of a top, is + + C1p[mu] sin [theta] - C2[mu]² sin [theta] cos [theta]; (4) + + and equating this to the impressed couple (multiplied by g), that is, + to + + c1 + gN = (c1 - c2)-- u² tan [theta], (5) + c2 + + and dividing out sin[theta], which equated to zero would imply perfect + centring, we obtain + + c1 + C2[mu]² cos [theta] - C1p[mu] + (c2 - c1)-- u² sec [theta] = 0. (6) + c2 + + The least admissible value of p is that which makes the roots equal of + this quadratic in [mu], and then + + C1 + [mu] = ½ --p sec [theta], (7) + C2 + + the roots would be imaginary for a value of p smaller than given by + + c1 + C1²p² - 4(c2 - c1)-- C2u² = 0, (8) + c2 + + p² c1 C2 + -- = 4 (c2 - c1) -- ---. (9) + u² c2 C1² + + _Table of Rifling for Stability of an Elongated Projectile, x Calibres + long, giving [delta] the Angle of Rifling, and n the Pitch of Rifling + in Calibres._ + + +-----------------------+-----------------+-----------------+-----------------+-----------------+ + | | Cast-iron Common| Palliser Shell | Solid Steel | Solid Lead | + | | Shell [f] = 2/3,| [f] = ½, S.G. 8.| Bullet | Bullet [f] = 0, | + | | S.G. 7.2. | | [f] = 0, S.G. 8.| S.G. 10.9. | + +--------+--------------+--------+--------+--------+--------+--------+--------+--------+--------+ + | x |[beta]-[alpha]|[delta] | n |[delta] | n |[delta] | n |[delta] | n | + +--------+--------------+--------+--------+--------+--------+--------+--------+--------+--------+ + | 1.0 | 0.0000 | 0° 0´|Infinity| 0° 0´|Infinity| 0° 0´|Infinity| 0° 0´|Infinity| + | 2.0 | 0.4942 | 2 49 | 63.87 | 2 32 | 71.08 | 2 29 | 72.21 | 2 08 | 84.29 | + | 2.5 | 0.6056 | 3 46 | 47.91 | 3 23 | 53.32 | 3 19 | 54.17 | 2 51 | 63.24 | + | 3.0 | 0.6819 | 4 41 | 38.45 | 4 13 | 42.79 | 4 09 | 43.47 | 3 38 | 50.74 | + | 3.5 | 0.7370 | 5 35 | 32.13 | 5 02 | 35.75 | 4 58 | 36.33 | 4 15 | 42.40 | + | 4.0 | 0.7782 | 6 30 | 27.60 | 5 51 | 30.72 | 5 45 | 31.21 | 4 56 | 36.43 | + | 4.5 | 0.8100 | 7 24 | 24.20 | 6 40 | 26.93 | 6 32 | 27.36 | 5 37 | 31.94 | + | 5.0 | 0.8351 | 8 16 | 21.56 | 7 28 | 23.98 | 7 21 | 24.36 | 6 18 | 28.44 | + | 6.0 | 0.8721 | 10 05 | 17.67 | 9 04 | 19.67 | 8 56 | 19.98 | 7 40 | 23.33 | + | 10.0 | 0.9395 | 16 57 | 10.31 | 15 19 | 11.47 | 15 05 | 11.65 | 13 00 | 13.60 | + |Infinity| 1.0000 | 90 00 | 0.00 | 90 00 | 0.00 | 90 00 | 0.00 | 90 00 | 0.00 | + +--------+--------------+--------+--------+--------+--------+--------+--------+--------+--------+ + + If the shot is moving as if fired from a gun of calibre d inches, in + which the rifling makes one turn in a pitch of n calibres or nd + inches, so that the angle [delta] of the rifling is given by + + tan [delta] = [pi]d/nd = ½ dp/u, (10) + + which is the ratio of the linear velocity of rotation ½dp to u, the + velocity of advance, + + c1 C2d² + tan² [delta] = [pi]²/n² = d²p²/4u² = (c2 - c1) -- ---- + c2 C1² + + W´ / W´ \ / k2 \² + 1 + --- [alpha] ( 1 + ---[epsilon] ) ( -- ) + W´ W \ W / \ d / + = --- ([beta] - [alpha]) --------------- · -----------------------------. (11) + W W´ / k1 \^4 + 1 + ---[beta] ( -- ) + W \ d / + + For a shot in air the ratio W´/W is so small that the square may be + neglected, and formula (11) can be replaced for practical purpose in + artillery by + + [pi]² W´ / k2 \² / / k1 \^4 + tan²[delta] = ----- = --- ([beta] - [alpha]) ( -- ) / ( -- ), (12) + n² W \ d / / \ d / + + if then we can calculate [beta], [alpha], or [beta] - [alpha] for the + external shape of the shot, this equation will give the value of + [delta] and n required for stability of flight in the air. + + The ellipsoid is the only shape for which [alpha] and [beta] have so + far been determined analytically, as shown already in § 44, so we must + restrict our calculation to an egg-shaped bullet, bounded by a prolate + ellipsoid of revolution, in which, with b = c, + _ _ + / [oo] ab² d[lambda] / [oo] ab² d[lambda] + A0 = | ------------------------------------------------------- = | -----------------------------------, (13) + _/ 0 (a² + [lambda])[root][4(a² + [lambda])(b² + [lambda])²] _/ 0 2(a² + [lambda])^3/2 (b² + [lambda]) + + A0 + 2B0 = 1, (14) + + A0 B0 1 - A0 1 + [alpha] = ------, [beta] = ------ = ------ = ------------. (15) + 1 - A0 1 - B0 1 + A0 1 + 2[alpha] + + The length of the shot being denoted by l and the calibre by d, and + the length in calibres by x + + l/d = 2a/2b = x, (16) + + x 1 + A0 = ----------- ch^(-1)x - ------, (17) + (x²- 1)^3/2 x² - 1 + + -x x² + 2B0 = ----------- ch^(-1)x + ------, (18) + x² - 1)^3/2 x² + 1 + + x sh^(-1) [root](x²-1) x + x²A0 + 2B0 = ---------------------- = ------------ log [x + [root](x² - 1)]. (19) + [root](x²-1) [root](x²-1) + + If [sigma] denotes the density of the metal, and if the shell has a + cavity homothetic with the external ellipsoidal shape, a fraction f of + the linear scale; then the volume of a round shot being 1/6 [pi] d^3, + and 1/6 [pi] d^3 x of a shot x calibres long + + W = 1/6 [pi] d^3 x (i - f^3) [sigma], (20) + + d² + Wk1² = 1/6 [pi] d^3 x -- (1 - f^5) [sigma], (21) + 10 + + l² + d² + Wk2² = 1/6 [pi] d^3 x ------- (1 - f^5) [sigma]. (22) + 20 + + If [rho] denotes the density of the air or medium + + W´ = 1/6 [pi] d^3 x [rho], (23) + + W´ 1 [rho] + --- = ------ -------, (24) + W 1 - f³ [sigma] + + k1² 1 1 - f^5 k2² x² + 1 + --- = --- -------, ---- = ------, (25) + d² 10 1 - f³ k1² 2 + + [rho] x² + 1 + tan² [delta] = ------- ([beta] - [alpha])-------------, (26) + [sigma] 1/5 (1 - f^5) + + in which [sigma]/[rho] may be replaced by 800 times the S.G. of the + metal, taking water as 800 times denser than air on the average, in + round numbers, and formula (10) may be written n tan [delta] = [pi], + or n[delta] = 180, when [delta] is a small angle, and given in + degrees. + + From this formula (26) the table following has been calculated by A. + G. Hadcock, and the results are in agreement with practical + experience. + + 52. In the steady motion the centre of the shot describes a helix, + with axial velocity + + / c1 \ + u cos [theta]= v sin [theta] = ( l + -- tan² [theta] ) u cos [theta] [asympt] u sec [theta], (1) + \ c2 / + + and transverse velocity + + / c1 \ + u sin [theta] - v cos [theta] = ( l - -- ) u sin [theta] [asympt] ([beta] - [alpha]) u sin [theta]; (2) + \ c2 / + + and the time of completing a turn of the spiral is 2[pi]/[mu]. + + When [mu] has the critical value in (7), + + 2[pi] 4[pi] C2 2[pi] + ----- = ----- -- cos [theta] = ----- (x² + 1) cos [theta], (3) + [mu] p C1 p + + which makes the circumference of the cylinder on which the helix + is wrapped + + 2[pi] 2[pi]u + -----(u sin [theta] - v cos [theta] = ------ ([beta] - [alpha]) (x² + 1) sin² [theta] cos [theta] + [mu] p + + = nd ([beta] - [alpha]) (x² + 1) sin [theta] cos [theta], (4) + + and the length of one turn of the helix + + 2[pi] + ----- (u cos [theta] + v sin [theta] ) = nd(x² + 1); (5) + [mu] + + thus for x = 3, the length is 10 times the pitch of the rifling. + + 53. _The Motion of a Perforated Solid in Liquid._--In the preceding + investigation, the liquid stops dead when the body is brought to rest; + and when the body is in motion the surrounding liquid moves in a + uniform manner with respect to axes fixed in the body, and the force + experienced by the body from the pressure of the liquid on its surface + is the opposite of that required to change the motion of the liquid; + this has been expressed by the dynamical equations given above. But if + the body is perforated, the liquid can circulate through a hole, in + reentrant stream lines linked with the body, even while the body is at + rest; and no reaction from the surface can influence this circulation, + which may be supposed started in the ideal manner described in § 29, + by the application of impulsive pressure across an ideal membrane + closing the hole, by means of ideal mechanism connected with the body. + The body is held fixed, and the reaction of the mechanism and the + resultant of the impulsive pressure on the surface are a measure of + the impulse, linear [xi], [eta], [zeta], and angular [lambda], [mu], + [nu], required to start the circulation. + + This impulse will remain of constant magnitude, and fixed relatively + to the body, which thus experiences an additional reaction from the + circulation which is the opposite of the force required to change the + position in space of the circulation impulse; and these extra forces + must be taken into account in the dynamical equations. + + An article may be consulted in the _Phil. Mag._, April 1893, by G. H. + Bryan, in which the analytical equations of motion are deduced of a + perforated solid in liquid, from considerations purely hydrodynamical. + + The effect of an external circulation of vortex motion on the motion + of a cylinder has been investigated in § 29; a similar procedure will + show the influence of circulation through a hole in a solid, taking as + the simplest illustration a ring-shaped figure, with uniplanar motion, + and denoting by [xi] the resultant axial linear momentum of the + circulation. + + As the ring is moved from O to O´ in time t, with velocity Q, and + angular velocity R, the components of liquid momentum change from + + [alpha]M´U + [xi] and [beta]M´V along Ox and Oy + + to + + [alpha]M´U´ + [xi] and [beta]M´V´ along O´x´ and O´y´, (1) + + the axis of the ring changing from Ox to O´x´; and + + U = Q cos [theta], V = Q sin [theta], + + U´ = Q cos ([theta] - Rt), V´ = Q sin ([theta] - Rt), (2) + + so that the increase of the components of momentum, X1, Y1, and N1, + linear and angular, are + + X1 = ([alpha]M´U´ + [xi])[cos] Rt - [alpha]M´U - [xi] - [beta]M´V´ sin Rt + = ([alpha] - [beta])M´Q sin ([theta] - Rt) sin Rt - [xi] ver Rt (3) + + Y1 = ([alpha]M´U´ + [xi]) sin Rt + [beta]M´V´ cos Rt - [beta]M´V + = ([alpha] - [beta])M´Q cos ([theta] - Rt) sin Rt + [xi] sin RT, (4) + + N1 = [ -([alpha]M´U´ + [xi]) sin ([theta] - Rt) + [beta]M´V´ cos ([theta] - Rt)OO´ + = [ -([alpha] - [beta])´Q cos ([theta] - Rt) sin ([theta] - Rt) - [xi] sin ([theta] - Rt)]Qt. (5) + + The components of force, X, Y, and N, acting on the liquid at O, and + reacting on the body, are then + + X = lt. X1/t = ([alpha] - [beta])M´QR sin [theta] = ([alpha] - [beta])M´VR, (6) + + Y = lt. Y1/t = ([alpha] - [beta])M´QR cos [theta] + [xi]R = ([alpha] - [beta])M´UR + [xi]R, (7) + + Z = lt. Z1/t = -([alpha] - [beta])M´Q² sin [theta]cos[theta] - [xi]Q sin [theta] + = [-([alpha] - [beta])M´U + [xi]]V. (8) + + Now suppose the cylinder is free; the additional forces acting on the + body are the components of kinetic reaction of the liquid + + / dU \ / dV \ dR + -[alpha]M´ ( -- - VR ), -[beta]M´ ( -- + UR ), [epsilon]C´--, (9) + \ dt / \ dt / dt + + so that its equations of motion are + + / dU \ / dU \ + M ( -- -VR ) = -[alpha]M´ ( -- - VR ) - ([alpha] - [beta])M´VR, (10) + \ dt / \ dt / + + / dV \ / dV \ + M ( -- + UR ) = -[beta]M´ ( -- + UR ) - ([alpha] - [beta])M´UR - [xi]R, (11) + \ dt / \ dt / + + dR dR + C-- = -[epsilon]C´-- + ([alpha] - [beta])M´UV + [xi]V; (12) + dt dt + + and putting as before + + M + [alpha]M´ = c1, M + [beta]M´ = c2, C + [epsilon]C´ = C3, (13) + + dU + c1-- - c2 VR = 0, (14) + dt + + dV + c2-- + (c1 U + [xi])R = 0, (15) + dt + + dR + c3-- - (c1U + [xi] - c2 U)V = 0; (16) + dt + + showing the modification of the equations of plane motion, due to the + component [xi] of the circulation. + + The integral of (14) and (15) may be written + + c1U + [xi] = F cos [theta], c2V = - F sin [theta], (17) + + dx F cos² [theta] F sin² [theta] [xi] + -- = U cos [theta] - V sin [theta] = -------------- + -------------- - ---- cos [theta], (18) + dt c1 c2 c1 + + d[mu] / F F \ [xi] + ----- = U sin [theta] + V cos [theta] = ( -- - -- ) sin [theta] cos [theta] - ---- sin [theta], (19) + dt \ c1 c2 / c1 + + d²[theta] / F² F² \ F[xi] d[mu] + C3--------- = ( -- - -- ) sin [theta] cos [theta] - ----- sin [theta] = F-----, (20) + dt² \ c1 c2 / c1 dt + _ _ + d[theta] / | F² cos² [theta] F² sin² [theta] F[xi] | + C3-------- = Fy = / | - --------------- - --------------- + 2----- cos [theta] + H |; (21) + dt \/ |_ c1 c2 c1 _| + + so that cos [theta] and y is an elliptic function of the time. + + When [xi] is absent, dx/dt is always positive, and the centre of the + body cannot describe loops; but with [xi], the influence may be great + enough to make dx/dt change sign, and so loops occur, as shown in A. + B. Basset's _Hydrodynamics_, i. 192, resembling the trochoidal curves, + which can be looped, investigated in § 29 for the motion of a cylinder + under gravity, when surrounded by a vortex. + + The branch of hydrodynamics which discusses wave motion in a liquid or + gas is given now in the articles SOUND and WAVE; while the influence + of viscosity is considered under HYDRAULICS. + + REFERENCES.--For the history and references to the original memoirs + see _Report to the British Association_, by G. G. Stokes (1846), and + W. M. Hicks (1882). See also the _Fortschritte der Mathematik_, and A. + E. H. Love, "Hydrodynamik" in the _Encyklöpadie der mathematischen + Wissenschaften_ (1901). (A. G. G.) + + + + +HYDROMEDUSAE, a group of marine animals, recognized as belonging to the +Hydrozoa (q.v.) by the following characters. (1) The polyp (hydropolyp) +is of simple structure, typically much longer than broad, without +ectodermal oesophagus or mesenteries, such as are seen in the anthopolyp +(see article ANTHOZOA); the mouth is usually raised above the peristome +on a short conical elevation or hypostome; the ectoderm is without cilia. +(2) With very few exceptions, the polyp is not the only type of +individual that occurs, but alternates in the life-cycle of a given +species, with a distinct type, the medusa (q.v.), while in other cases +the polyp-stage may be absent altogether, so that only medusa-individuals +occur in the life-cycle. + +The Hydromedusae represent, therefore, a sub-class of the Hydrozoa. The +only other sub-class is the Scyphomedusae (q.v.). The Hydromedusae +contrast with the Scyphomedusae in the following points. (1) The polyp, +when present, is without the strongly developed longitudinal retractor +muscles, forming ridges (_taeniolae_) projecting into the digestive +cavity, seen in the scyphistoma or scyphopolyp. (2) The medusa, when +present, has a velum and is hence said to be _craspedote_; the nervous +system forms two continuous rings running above and below the velum; the +margin of the umbrella is not lobed (except in Narcomedusae) but entire; +there are characteristic differences in the sense-organs (see below, and +SCYPHOMEDUSAE); and gastral filaments (phacellae), subgenital pits, &c., +are absent. (3) The gonads, whether formed in the polyp or the medusa, +are developed in the ectoderm. + +The Hydromedusae form a widespread, dominant and highly differentiated +group of animals, typically marine, and found in all seas and in all +zones of marine life. Fresh-water forms, however, are also known, very +few as regards species or genera, but often extremely abundant as +individuals. In the British fresh-water fauna only two genera, _Hydra_ +and _Cordylophora_, are found; in America occurs an additional genus, +_Microhydra_. The paucity of fresh-water forms contrasts sharply, with +the great abundance of marine genera common in all seas and on every +shore. The species of _Hydra_, however, are extremely common and +familiar inhabitants of ponds and ditches. + +In fresh-water Hydromedusae the life-cycle is usually secondarily +simplified, but in marine forms the life-cycle may be extremely +complicated, and a given species often passes in the course of its +history through widely different forms adapted to different habitats and +modes of life. Apart from larval or embryonic forms there are found +typically two types of person, as already stated, the polyp and the +medusa, each of which may vary independently of the other, since their +environment and life-conditions are usually quite different. Hence both +polyp and medusa present characters for classification, and a given +species, genus or other taxonomic category may be defined by +polyp-characters or medusa-characters or by both combined. If our +knowledge of the life-histories of these organisms were perfect, their +polymorphism would present no difficulties to classification; but +unfortunately this is far from being the case. In the majority of cases +we do not know the polyp corresponding to a given medusa, or the medusa +that arises from a given polyp.[1] Even when a medusa is seen to be +budded, from a polyp under observation in an aquarium, the difficulty is +not always solved, since the freshly-liberated, immature medusa may +differ greatly from the full-grown, sexually-mature medusa after several +months of life on the high seas (see figs. 11, B, C, and 59, a, b, c). +To establish the exact relationship it is necessary not only to breed +but to rear the medusa, which cannot always be done in confinement. The +alternative is to fish all stages of the medusa in its growth in the +open sea, a slow and laborious method in which the chance of error is +very great, unless the series of stages is very complete. + +At present, therefore, classifications of the Hydromedusae have a more +or less tentative character, and are liable to revision with increased +knowledge of the life-histories of these organisms. Many groups bear at +present two names, the one representing the group as defined by +polyp-characters, the other as defined by medusa-characters. It is not +even possible in all cases to be certain that the polyp-group +corresponds exactly to the medusa-group, especially in minor systematic +categories, such as families. + +The following is the main outline of the classification that is Adopted +in the present article. Groups founded on polyp-characters are printed +in ordinary type, those founded on medusa-characters in italics. For +definitions of the groups see below. + + Sub-class Hydromedusae (_Hydrozoa Craspedota_). + + Order I. Eleutheroblastea. + " II. Hydroidea (_Leptolinae_). + Sub-order 1. Gymnoblastea (_Anthomedusae_). + " 2. Calyptoblastea (_Leptomedusae_). + Order III. Hydrocorallinae. + " IV. Graptolitoidea. + " V. Trachylinae. + Sub-order 1. _Trachomedusae_. + " 2. _Narcomedusae_. + Order VI. Siphonophora. + Sub-order 1. Chondrophorida. + " 2. Calycophorida. + " 3. Physophorida. + " 4. Cystophorida. + + + _Organization and Morphology of the Hydromedusae._ + +As already stated, there occur in the Hydromedusae two distinct types of +person, the polyp and the medusa; and either of them is capable of +non-sexual reproduction by budding, a process which may lead to the +formation of colonies, composed of more or fewer individuals combined +and connected together. The morphology of the group thus falls naturally +into four sections--(1) the hydropolyp, (2) the polyp-colony, (3) the +hydromedusa, (4) the medusa-colonies. Since, however, medusa-colonies +occur only in one group, the Siphonophora, and divergent views are held +with regard to the morphological interpretation of the members of a +siphonophore, only the first three of the above subdivisions of +hydromedusa morphology will be dealt with here in a general way, and the +morphology of the Siphonophora will be considered under the heading of +the group itself. + + [Illustration: FIG. 1.--Diagram of a typical Hydropolyp. + + a, Hydranth; + b, Hydrocaulus; + c, Hydrorhiza; + t, Tentacle; + ps, Perisarc, forming in the region of the hydranth a cup or + hydrotheca (h, t),--which, however, is only found in polyps of the + order Calyptoblastea.] + + 1. _The Hydropolyp_ (fig. 1)--The general characters of this organism + are described above and in the articles HYDROZOA and POLYP. It is + rarely free, but usually fixed and incapable of locomotion. The foot + by which it is attached often sends out root-like processes--the + _hydrorhiza_ (c). The column (b) is generally long, slender and + stalk-like (_hydrocaulus_). Just below the crown of tentacles, + however, the body widens out to form a "head," termed, the _hydranth_ + (a), containing a stomach-like dilatation of the digestive cavity. On + the upper face of the hydranth the crown of tentacles (t) surrounds + the peristome, from which rises the conical hypostome, bearing the + mouth at its extremity. The general ectoderm covering the surface of + the body has entirely lost the cilia present in the earlier larval + stages (planula), and may be naked, or clothed in a cuticle or + exoskeleton, the perisarc (ps), which in its simplest condition is a + chitinous membrane secreted by the ectoderm. The perisarc when present + invests the hydrorhiza and hydrocaulus; it may stop short below the + hydranth, or it may extend farther. In general there are two types of + exoskeleton, characteristic of the two principal divisions of the + Hydroidea. In the Gymnoblastea the perisarc either stops below the + hydranth, or, if continued on to it, forms a closely-fitting + investment extending as a thin cuticle as far as the bases of the + tentacles (e.g. _Bimeria_, see G. J. Allman [1],[2] pl. xii. figs, 1 + and 3). In the Calyptoblastea the perisarc is always continued above + the hydrocaulus, and forms a cup, the hydrangium or hydrotheca (h, t), + standing off from the body, into which the hydranth can be retracted + for shelter and protection. + + [Illustration: From Allman's _Gymnoblastic Hydroids_, by permission of + the Council of the Ray Society. + + FIG. 2.--_Stauridium productum_, portion of the colony magnified; p, + polyp; rh, hydrorhiza.] + + [Illustration: FIG. 3.--Diagram of _Corymorpha_. A, A hydriform person + giving rise to medusiform persons by budding from the margin of the + disk; B, free swimming medusa (_Steenstrupia_ of Forbes) detached from + the same, with manubrial genitalia, (_Anthomedusae_) and only one + tentacle. (After Allman).] + + The architecture of the hydropolyp, simple though it be, furnishes a + long series of variations affecting each part of the body. The + greatest variation, however, is seen in the tentacles. As regards + number, we find in the aberrant forms _Protohydra_ and _Microhydra_ + tentacles entirely absent. In the curious hydroid _Monobrachium_ a + single tentacle is present, and the same is the case in _Clathrozoon_; + in _Amphibrachium_ and in _Lar_ (fig. 11, A) the polyp bears two + tentacles only. The reduction of the tentacles in all these forms may + be correlated with their mode of life, and especially with living in a + constant current of water, which brings food-particles always from one + direction and renders a complete whorl or circle of tentacles + unnecessary. Thus _Microhydra_ lives amongst Bryozoa, and appears to + utilize the currents produced by these animals. _Protohydra_ occurs in + oyster-banks and _Monobrachium_ also grows on the shells of bivalves, + and both these hydroids probably fish in the currents produced by the + lamellibranchs. _Amphibrachium_ grows in the tissues of a sponge, + _Euplectella_, and protrudes its hydranth into the canal-system of the + sponge; and _Lar_ grows on the tubes of the worm _Sabella_. With the + exception of these forms, reduced for the most part in correlation + with a semi-parasitic mode of life, the tentacles are usually + numerous. It is rare to find in the polyp a regular, symmetrical + disposition of the tentacles as in the medusa. The primitive number of + four in a whorl is seen, however, in _Stauridium_ (fig. 2) and + _Cladonema_ (Allman [1], pl. xvii.), and in _Clavatella_ each whorl + consists regularly of eight (Allman, _loc. cit._ pl. xviii.). As a + rule, however, the number in a whorl is irregular. The tentacles may + form a single whorl, or more than one; thus in _Corymorpha_ (fig. 3) + and _Tubularia_ (fig. 4) there are two circlets; in _Stauridium_ (fig. + 2) several; in _Coryne_ and _Cordylophora_ the tentacles are scattered + irregularly over the elongated hydranth. + + As regards form, the tentacles show a number of types, of which the + most important are (1) filiform, _i.e._ cylindrical or tapering from + base to extremity, as in _Clava_ (fig. 5); (2) capitate, i.e. knobbed + at the extremity, as in _Coryne_ (see Allman, loc. cit. pl. iv.); (3) + branched, a rare form in the polyp, but seen in _Cladocoryne_ (see + Allman, loc. cit. p. 380, fig. 82). Sometimes more than one type of + form is found in the same polyp; in _Pennaria_ and _Stauridium_ (fig. + 2) the upper whorls are capitate, the lower filiform. Finally, as + regards structure, the tentacles may retain their primitive hollow + nature, or become solid by obliteration of the axial cavity. + + The hypostome of the hydropolyp may be small, or, on the other hand, + as in _Eudendrium_ (Allman, loc. cit. pls. xiii., xiv.), large and + trumpet-shaped. In the curious polyp _Myriothela_ the body of the + polyp is differentiated into nutritive and reproductive portions. + + [Illustration: FIG. 4.--Diagram of _Tubularia indivisa_. A single + hydriform person a bearing a stalk carrying numerous degenerate + medusiform persons or sporosacs b. (After Allman.)] + + _Histology._--The ectoderm of the hydropolyp is chiefly sensory, + contractile and protective in function. It may also be glandular in + places. It consists of two regions, an external epithelial layer and a + more internal sub-epithelial layer. + + The epithelial layer consists of (1) so-called "indifferent" cells + secreting the perisarc or cuticle and modified to form glandular cells + in places; for example, the adhesive cells in the foot. (2) Sensory + cells, which may be fairly numerous in places, especially on the + tentacles, but which occur always scattered and isolated, never + aggregated to form sense-organs as in the medusa. (3) Contractile or + myo-epithelial cells, with the cell prolonged at the base into a + contractile muscle-fibre (fig. 6, B). In the hydropolyp the ectodermal + muscle-fibres are always directed longitudinally. Belonging primarily + to the epithelial layer, the muscular cells may become secondarily + sub-epithelial. + + [Illustration: From Allman's _Gymnoblastic Hydroids_, by permission of + the Council of the Ray Society. + + FIG. 5.--Colonies of _Clava_. A, _Clava squamata_, magnified. B, _C. + multicornis_, natural size; p, _polyp_; _gon_, gonophores; rh, + hydrorhiza.] + + The sub-epithelial layer consists primarily of the so-called + interstitial cells, lodged between the narrowed basal portions of the + epithelial cells. From them are developed two distinct types of + histological elements; the genital cells and the cnidoblasts or + mother-cells of the nematocysts. The sub-epithelial layer thus + primarily constituted may be recruited by immigration from without of + other elements, more especially by nervous (ganglion) cells and + muscle-cells derived from the epithelial layer. In its fullest + development, therefore, the sub-epithelial layer consists of four + classes of cell-elements. + + [Illustration: FIG. 6 A.--Portion of the body-wall of _Hydra_, showing + ectoderm cells above, separated by "structureless lamella" from three + flagellate endoderm cells below. The latter are vacuolated, and + contain each a nucleus and several dark granules. In the middle + ectoderm cell are seen a nucleus and three nematocysts, with trigger + hairs projecting beyond the cuticle. A large nematocyst, with everted + thread, is seen in the right-hand ectodermal cell. (After F. E. + Schulze.)] + + The genital cells are simple wandering cells (archaeocytes), at first + minute and without any specially distinctive features, until they + begin to develop into germ-cells. According to Wulfert [60] the + primitive germ-cells of _Gonothyraea_ can be distinguished soon after + the fixation of the planula, appearing amongst the interstitial cells + of the ectoderm. The germ-cells are capable of extensive migrations, + not only in the body of the same polyp, but also from parent to bud + through many non-sexual generations of polyps in a colony (A. Weismann + [58]). + + [Illustration: FIG. 6 B.--Epidermo-muscular cells of _Hydra_. m, + muscular-fibre processes. (After Kleinenberg, from Gegenbaur.)] + + The cnidoblasts are the mother-cells of the nematocysts, each cell + producing one nematocyst in its interior. The complete nematocyst + (fig. 7) is a spherical or oval capsule containing a hollow thread, + usually barbed, coiled in its interior. The capsule has a double wall, + an outer one (o.c.), tough and rigid in nature, and an inner one + (i.c.) of more flexible consistence. The outer wall of the capsule is + incomplete at one pole, leaving an aperture through which the thread + is discharged. The inner membrane is continuous with the wall of the + hollow thread at a spot immediately below the aperture in the outer + wall, so that the thread itself (f) is simply a hollow prolongation of + the wall of the inner capsule inverted and pushed into its cavity. The + entire nematocyst is enclosed in the cnidoblast which formed it. When + the nematocyst is completely developed, the cnidoblast passes outwards + so as to occupy a superficial position in the ectoderm, and a delicate + protoplasmic process of sensory nature, termed the _cnidocil_ (cn) + projects from the cnidoblast like a fine hair or cilium. Many points + in the development and mechanism of the nematocyst are disputed, but + it is tolerably certain (1) that the cnidocil is of sensory nature, + and that stimulation, by contact with prey or in other ways, causes a + reflex discharge of the nematocyst; (2) that the discharge is an + explosive change whereby the in-turned thread is suddenly everted and + turned inside out, being thus shot through the opening in the outer + wall of the capsule, and forced violently into the tissues of the + prey, or, it may be, of an enemy; (3) that the thread inflicts not + merely a mechanical wound, but instils an irritant poison, numbing and + paralysing in its action. The points most in dispute are, first, how + the explosive discharge is brought about, whether by pressure exerted + external to the capsule (i.e. by contraction of the cnidoblast) or by + internal pressure. N. Iwanzov [27] has brought forward strong grounds + for the latter view, pointing out that the cnidoblast has no + contractile mechanism and that measurements show discharged capsules + to be on the average slightly larger than undischarged ones. He + believes that the capsule contains a substance which swells very + rapidly when brought into contact with water, and that in the + undischarged condition the capsule has its opening closed by a plug of + protoplasm (x, fig. 7) which prevents access of water to the contents; + when the cnidocil is stimulated it sets in action a mechanism or + perhaps a series of chemical changes by which the plug is dissolved or + removed; as a result water penetrates into the capsule and causes its + contents to swell, with the result that the thread is everted + violently. A second point of dispute concerns the spot at which the + poison is lodged. Iwanzov believes it to be contained within the + thread itself before discharge, and to be introduced into the tissues + of the prey by the eversion of the thread. A third point of dispute is + whether the nematocysts are formed _in situ_, or whether the + cnidoblasts migrate with them to the region where they are most + needed; the fact that in _Hydra_, for example, there are no + interstitial cells in the tentacles, where nematocysts are very + abundant, is certainly in favour of the view that the cnidoblasts + migrate on to the tentacles from the body, and that like the genital + cells the cnidoblasts are wandering cells. + + [Illustration: FIG. 7.--Diagrams to show the structure of Nematocysts + and their mode of working. (After Iwanzov.) + + a, Undischarged nematocyst. + b, Commencing discharge. + c, Discharge complete. + cn, Cnidocil. + N, Nucleus of cnidoblast. + o.c, Outer capsule. + x, Plug closing the opening of the outer capsule. + i.c., Inner capsule, continuous with the wall of the filament, f. + b, Barbs.] + + The muscular tissue consists primarily of processes from the bases of + the epithelial cells, processes which are contractile in nature and + may be distinctly striated. A further stage in evolution is that the + muscle-cells lose their connexion with the epithelium and come to lie + entirely beneath it, forming a sub-epithelial contractile layer, + developed chiefly in the tentacles of the polyp. The evolution of the + ganglion-cells, is probably similar; an epithelial cell develops + processes of nervous nature from the base, which come into connexion + with the bases of the sensory cells, with the muscular cells, and with + the similar processes of other nerve-cells; next the nerve-cell loses + its connexion with the outer epithelium and becomes a sub-epithelial + ganglion-cell which is closely connected with the muscular layer, + conveying stimuli from the sensory cells to the contractile elements. + The ganglion-cells of Hydromedusae are generally very small. In the + polyp the nervous tissue is always in the form of a scattered plexus, + never concentrated to form a definite nervous system as in the medusa. + + [Illustration: From Gegenbaur's _Elements of Comparative Anatomy_. + + FIG. 8.--Vacuolated Endoderm Cells of cartilaginous consistence from + the axis of the tentacle of a Medusa (_Cunina_).] + + The endoderm of the polyp is typically a flagellated epithelium of + large cells (fig. 6), from the bases of which arise contractile + muscular processes lying in the plane of the transverse section of the + body. In different parts of the coelenteron the endoderm may be of + three principal types--(1) digestive endoderm, the primitive type, + with cells of large size and considerably vacuolated, found in the + hydranth; some of these cells may become special glandular cells, + without flagella or contractile processes; (2) circulatory endoderm, + without vacuoles and without basal contractile processes, found in the + hydrorhiza and hydrocaulus; (3) supporting endoderm (fig. 8), seen in + solid tentacles as a row of cubical vacuolated cells, occupying the + axis of the tentacle, greatly resembling notochordal tissue, + particularly that of _Amphioxus_ at a certain stage of development; as + a fourth variety of endodermal cells excretory cells should perhaps be + reckoned, as seen in the pores in the foot of _Hydra_ and elsewhere + (cf. C. Chun, HYDROZOA [1], pp. 314, 315). + + The mesogloea in the hydropolyp is a thin elastic layer, in which may + be lodged the muscular fibres and ganglion cells mentioned above, but + which never contains any connective tissue or skeletogenous cells or + any other kind of special mesogloeal corpuscles. + + [Illustration: From Allman's _Gymnoblastic Hydroids_, by permission of + the Council of the Ray Society. + + FIG. 9.--Colony of _Hydractinia echinata_, growing on the Shell of a + Whelk. Natural size.] + + [Illustration: From Allman's _Gymnoblastic Hydroids_, by permission of + the Council of the Ray Society. + + FIG. 10.--Polyps from a Colony of _Hydractinia_, magnified. dz, + dactylozoid; gz, gastrozoid: b, blastostyle; gon, gonophores; rh, + hydrorhiza.] + + 2. _The Polyp-colony._--All known hydropolyps possess the power of + reproduction by budding, and the buds produced may become either + polyps or medusae. The buds may all become detached after a time and + give rise to separate and independent individuals, as in the common + _Hydra_, in which only polyp-individuals are produced and sexual + elements are developed upon the polyps themselves; or, on the other + hand, the polyp-individuals produced by budding may remain permanently + in connexion with the parent polyp, in which case sexual elements are + never developed on polyp-individuals but only on medusa-individuals, + and a true colony is formed. Thus the typical hydroid colony starts + from a "founder" polyp, which in the vast majority of cases is fixed, + but which may be floating, as in _Nemopsis_, _Pelagohydra_, &c. The + founder-polyp usually produces by budding polyp-individuals, and these + in their turn produce other buds. The polyps are all non-sexual + individuals whose function is purely nutritive. After a time the + polyps, or certain of them, produce by budding medusa-individuals, + which sooner or later develop sexual elements; in some cases, however, + the founder-polyp remains solitary, that is to say, does not produce + polyp-buds, but only medusa-buds, from the first (_Corymorpha_, fig. + 3, _Myriothela_, &c.). In primitive forms the medusa-individuals are + set free before reaching sexual maturity and do not contribute + anything to the colony. In other cases, however, the + medusa-individuals become sexually mature while still attached to the + parent polyp, and are then not set free at all, but become appanages + of the hydroid colony and undergo degenerative changes leading to + reduction and even to complete obliteration of their original medusan + structure. In this way the hydroid colony becomes composed of two + portions of different function, the nutritive "trophosome," composed + of non-sexual polyps, and the reproductive "gonosome," composed of + sexual medusa-individuals, which never exercise a nutritive function + while attached to the colony. As a general rule polyp-buds are + produced from the hydrorhiza and hydrocaulus, while medusa-buds are + formed on the hydranth. In some cases, however, medusa-buds are formed + on the hydrorhiza, as in Hydrocorallines. + + In such a colony of connected individuals, the exact limits of the + separate "persons" are not always clearly marked out. Hence it is + necessary to distinguish between, first, the "zooids," indicated in + the case of the polyps by the hydranths, each with mouth and + tentacles; and, secondly, the "coenosarc," or common flesh, which + cannot be assigned more to one individual than another, but consists + of a more or less complicated network of tubes, corresponding to the + hydrocaulus and hydrorhiza of the primitive independent + polyp-individual. The coenosarc constitutes a system by which the + digestive cavity of any one polyp is put into communication with that + of any other individual either of the trophosome or gonosome. In this + manner the food absorbed by one individual contributes to the welfare + of the whole colony, and the coenosarc has the function of circulating + and distributing nutriment through the colony. + + The hydroid colony shows many variations in form and architecture + which depend simply upon differences in the methods in which polyps + are budded. + + [Illustration: After Hincks, Forbes, and Browne. A and B modified from + Hincks; C modified from Forbes's _Brit. Naked-eyed Medusae_. + + FIG. 11.--_Lar sabellarum_ and two stages of its Medusa, _Willia + stellata_. A, colony of _Lar_; B and C, young and adult medusae.] + + In the first place, buds may be produced only from the hydrorhiza, + which grows out and branches to form a basal _stolon_, typically + net-like, spreading over the substratum to which the founder-polyp + attached itself. From the stolon the daughter-polyps grow up + vertically. The result is a spreading or creeping colony, with the + coenosarc in the form of a root-like horizontal network (fig. 5, B; + 11, A). Such a colony may undergo two principal modifications. The + meshes of the basal network may become very small or virtually + obliterated, so that the coenosarc becomes a crust of tubes tending to + fuse together, and covered over by a common perisarc. Encrusting + colonies of this kind are seen in _Clava squamata_ (fig. 5, A) and + _Hydractinia_ (figs. 9, 10), the latter having the perisarc calcified. + A further very important modification is seen when the tubes of the + basal perisarc do not remain spread out in one plane, but grow in all + planes forming a felt-work; the result is a massive colony, such as is + seen in the so-called Hydrocorallines (fig. 60), where the interspaces + between the coenosarcal tubes are filled up with calcareous matter, or + _coenosteum_, replacing the chitinous perisarc. The result is a stony, + solid mass, which contributes to the building up of coral reefs. In + massive colonies of this kind no sharp distinction can be drawn + between hydrorhiza and hydrocaulus in the coenosarc; it is practically + all hydrorhiza. Massive colonies may assume various forms and are + often branching or tree-like. A further peculiarity of this type of + colony is that the entire coenosarcal complex is covered externally by + a common layer of ectoderm; it is not clear how this covering layer is + developed. + + [Illustration: FIG. 12.--Colony of _Bougainvillea fruticosa_, natural + size, attached to the underside of a piece of floating timber. (After + Allman.)] + + In the second place, the buds may be produced from the hydrocaulus, + growing out laterally from it; the result is an arborescent, tree-like + colony (figs. 12, 13). Budding from the hydrocaulus may be combined + with budding from the hydrorhiza, so that numerous branching colonies + arise from a common basal stolon. In the formation of arborescent + colonies, two sharply distinct types of budding are found, which are + best described in botanical terminology as the monopodial or racemose, + and the sympodial or cymose types respectively; each is characteristic + of one of the two sub-orders of the Hydroidea, the Gymnoblastea and + Calyptoblastea. + + In the monopodial method (figs. 12, 14) the founder-polyp is, + theoretically, of unlimited growth in a vertical direction, and as it + grows up it throws out buds right and left alternately, so that the + first bud produced by it is the lowest down, the second bud is above + the first, the third above this again, and so on. Each bud produced by + the founder proceeds to grow and to bud in the same way as the founder + did, producing a side branch of the main stem. Hence, in a colony of + gymnoblastic hydroids, the oldest polyp of each system, that is to + say, of the main stem or of a branch, is the topmost polyp; the + youngest polyp of the system is the one nearest to the topmost polyp; + and the axis of the system is a true axis. + + [Illustration: FIG. 13.--Portion of colony of _Bougainvillea + fruticosa_ (_Anthomedusae-Gymnoblastea_) more magnified. (From + Lubbock, after Allman.)] + + [Illustration: FIG. 14.--Diagrams of the monopodial method of budding, + shown in five stages (1-5). F, the founder-polyp; 1, 2, 3, 4, the + succession of polyps budded from the founder-polyp; a´, b´, c´, the + succession of polyps budded from 1; a², b², polyps budded from 2; a³, + polyp budded from 3.] + + In the sympodial method of budding, on the other hand, the + founder-polyp is of limited growth, and forms a bud from its side, + which is also of limited growth, and forms a bud in its turn, and so + on (figs. 15, 16). Hence, in a colony of calyptoblastic hydroids, the + oldest polyp of a system is the lowest; the youngest polyp is the + topmost one; and the axis of the system is a false axis composed of + portions of each of the consecutive polyps. In this method of budding + there are two types. In one, the biserial type (fig. 15), the polyps + produce buds right and left alternately, so that the hydranths are + arranged in a zigzag fashion, forming a "scorpioid cyme," as in + _Obelia_ and _Sertularia_. In the other, the uniserial type (fig. 16), + the buds are formed always on the same side, forming a "helicoid + cyme," as in _Hydrallmania_, according to H. Driesch, in which, + however, the primitively uniserial arrangement becomes masked later by + secondary torsions of the hydranths. + + [Illustration: FIG. 15.--Diagram of sympodial budding, biserial type, + shown in five stages (1-5). F, founder-polyp; 1, 2, 3, 4, 5, 6, + succession of polyps budded from the founder; a, b, c, second series + of polyps budded from the founder; a³, b³, series budded from 3.] + + [Illustration: FIG. 16.--Diagram of sympodial budding, uniserial type, + shown in four stages (1-4). F, founder-polyp; 1, 2, 3, succession of + polyps budded from the founder.] + + In a colony formed by sympodial budding, a polyp always produces first + a bud, which contributes to the system to which it belongs, i.e. + continues the stem or branch of which its parent forms a part. The + polyp may then form a second bud, which becomes the starting point of + a new system, the beginning, that is, of a new branch; and even a + third bud, starting yet another system, may be produced from the same + polyp. Hence the colonies of Calyptoblastea may be complexly branched, + and the budding may be biserial throughout, uniserial throughout, or + partly one, partly the other. Thus in _Plumularidae_ (figs. 17, 18) + there is formed a main stem by biserial budding; each polyp on the + main stem forms a second bud, which usually forms a side branch or + _pinnule_ by uniserial budding. In this way are formed the familiar + feathery colonies of _Plumularia_, in which the pinnules are all in + one plane, while in the allied _Antennularia_ the pinnules are + arranged in whorls round the main biserial stem. The pinnules never + branch again, since in the uniserial mode of budding a polyp never + forms a second polyp-bud. On the other hand, a polyp on the main stem + may form a second bud which, instead of forming a pinnule by uniserial + budding, produces by biserial budding a branch, from which pinnules + arise as from the main stem (fig. 18--3, 6). Or a polyp on the main + stem, after having budded a second time to form a pinnule, may give + rise to a third bud, which starts a new biserial system, from which + uniserial pinnules arise as from the main stem--type of _Aglaophenia_ + (fig. 19). The laws of budding in hydroids have been worked out in an + interesting manner by H. Driesch [13], to whose memoirs the reader + must be referred for further details. + + [Illustration: FIG. 17.--Diagram of sympodial budding, simple + unbranched _Plumularia_-type. F, founder; 1-8, main axis formed by + biserial budding from founder; a-e, pinnule formed by uniserial + budding from founder; a¹-d¹, branch formed by similar budding from 1; + a²-d² from 2, and so forth.] + + _Individualization of Polyp-Colonies._--As in other cases where animal + colonies are formed by organic union of separate individuals, there is + ever a tendency for the polyp-colony as a whole to act as a single + individual, and for the members to become subordinated to the needs of + the colony and to undergo specialization for particular functions, + with the result that they simulate organs and their individuality + becomes masked to a greater or less degree. Perhaps the earliest of + such specializations is connected with the reproductive function. + Whereas primitively any polyp in a colony may produce medusa-buds, in + many hydroid colonies medusae are budded only by certain polyps termed + _blastostyles_ (fig. 10, b). At first not differing in any way from + other polyps (fig. 5), the blastostyles gradually lose their nutritive + function and the organs connected with it; the mouth and tentacles + disappear, and the blastostyle obtains the nutriment necessary for its + activity by way of the coenosarc. In the Calyptoblastea, where the + polyps are protected by special capsules of the perisarc, the + _gonothecae_ enclosing the blastostyles differ from the hydrothecae + protecting the hydranths (fig. 54). + + [Illustration: FIG. 18.--Diagram showing method of branching in the + _Plumularia_-type; compare with fig. 17. Polyps 3 and 6, instead of + producing uniserial pinnules, have produced biserial branches (3¹, 3², + 3³, 3^4; 6¹-6³), which give off uniserial branches in their turn.] + + In other colonies the two functions of the nutritive polyp, namely, + capture and digestion of food, may be shared between different polyps + (fig. 10). One class of polyps, the _dactylozoids_ (dz), lose their + mouth and stomach, and become elongated and tentacle-like, showing + great activity of movement. Another class, the _gastrozoids_ (gz), + have the tentacles reduced or absent, but have the mouth and stomach + enlarged. The dactylozoids capture food, and pass it on to the + gastrozoids, which swallow and digest it. + + [Illustration: FIG. 19.--Diagram showing method of branching in the + _Aglaophenia_-type. Polyp 7 has produced as its first bud, 8; as its + second bud, a^7, which starts a uniserial pinnule; and as a third bud + I^7, which starts a biserial branch (II^7-VI^7) that repeats the + structure of the main stem and gives off pinnules. The main stem is + indicated by-·-·-·, the new stem by ······.] + + Besides the three types of individual above mentioned, there are other + appendages of hydroid colonies, of which the individuality is + doubtful. Such are the "guard-polyps" (machopolyps) of _Plumularidae_, + which are often regarded as individuals of the nature of dactylozoids, + but from a study of the mode of budding in this hydroid family Driesch + concluded that the guard-polyps were not true polyp-individuals, + although each is enclosed in a small protecting cup of the perisarc, + known as a nematophore. Again, the spines arising from the basal crust + of _Podocoryne_ have been interpreted by some authors as reduced + polyps. + + 3. _The Medusa._--In the Hydromedusae the medusa-individual occurs, as + already stated, in one of two conditions, either as an independent + organism leading a true life in the open seas, or as a subordinate + individuality in the hydroid colony, from which it is never set free; + it then becomes a mere reproductive appendage or _gonophore_, losing + successively its organs of sense, locomotion and nutrition, until its + medusoid nature and organization become scarcely recognizable. Hence + it is convenient to consider the morphology of the medusa from these + two aspects. + + (a) _The Medusa as an Independent Organism._--The general structure + and characteristics of the medusa are described elsewhere (see + articles HYDROZOA and MEDUSA), and it is only necessary here to deal + with the peculiarities of the Hydromedusa. + + [Illustration: From Allman's _Gymnoblastic Hydroids_, by permission of + the Council of the Ray Society. + + FIG. 20.--_Cladonema radiatum_, the medusa walking on the basal + branches of its tentacles (t), which are turned up over the body.] + + [Illustration: From Allman's _Gymnoblastic Hydroids_, by permission of + the Council of the Ray Society. + + FIG. 21.--_Clavatella prolifera_, ambulatory medusa. t, tentacles; oc, + ocelli.] + + As regards habit of life the vast majority of Hydromedusae are pelagic + organisms, floating on the surface of the open sea, propelling + themselves feebly by the pumping movements of the umbrella produced by + contraction of the sub-umbral musculature, and capturing their prey + with their tentacles. The genera _Cladonema_ (fig. 20) and + _Clavatella_ (fig. 21), however, are ambulatory, creeping forms, + living in rock-pools and walking, as it were, on the tips of the + proximal branches of each of the tentacles, while the remaining + branches serve for capture of food. _Cladonema_ still has the typical + medusan structure, and is able to swim about, but in _Clavatella_ the + umbrella is so much reduced, that swimming is no longer possible. The + remarkable medusa _Mnestra parasites_ is ecto-parasitic throughout + life on the pelagic mollusc _Phyllirrhoe_, attached to it by the + sub-umbral surface, and its tentacles have become rudimentary or + absent. It is interesting to note that _Mnestra_ has been shown by J. + W. Fewkes [15] and R. T. Günther [19] to belong to the same family + (_Cladonemidae_) as _Cladonema_ and _Clavatella_, and it is reasonable + to suppose that the non-parasitic ancestor of _Mnestra_ was, like the + other two genera, an ambulatory medusa which acquired louse-like + habits. In some species of the genus _Cunina_ (Narcomedusae) the + youngest individuals (actinulae) are parasitic on other medusae (see + below), but in later life the parasitic habit is abandoned. No other + instances are known of sessile habit in Hydromedusae. + + [Illustration: After E. T. Browne, from _Proc. Zool. Soc. of London_. + + FIG. 22.--_Corymorpha nutans_, adult female Medusa. Magnified 10 + diameters.] + + The external form of the Hydromedusae varies from that of a deep bell + or thimble, characteristic of the Anthomedusae, to the shallow + saucer-like form characteristic of the Leptomedusae. It is usual for + the umbrella to have an even, circular, uninterrupted margin; but in + the order Narcomedusae secondary down-growths between the tentacles + produce a lobed, indented margin to the umbrella. The marginal + tentacles are rarely absent in non-parasitic forms, and are typically + four in number, corresponding to the four perradii marked by the + radial canals. Interradial tentacles may be also developed, so that + the total number present may be increased to eight or to an + indefinitely large number. In _Willia_, _Geryonia_, &c., however, the + tentacles and radial canals are on the plan of six instead of four + (figs. 11 and 26). On the other hand, in some cases the tentacles are + less in number than the perradii; in _Corymorpha_ (figs. 3 and 22) + there is but a single tentacle, while two are found in _Amphinema_ and + _Gemmaria_ (Anthomedusae), and in _Solmundella bitentaculata_ (fig. + 67) and _Aeginopsis hensenii_ (fig. 23) (Narcomedusae). The tentacles + also vary considerably in other ways than in number: first, in form, + being usually simple, with a basal bulb, but in _Cladonemidae_ they + are branched, often in complicated fashion; secondly, in grouping, + being usually given off singly, and at regular intervals from the + margin of the umbrella, but in _Margelidae_ and in some Trachomedusae + they are given off in tufts or bunches (fig. 24); thirdly, in position + and origin, being usually implanted on the extreme edge of the + umbrella, but in Narcomedusae they become secondarily shifted and are + given off high up on the ex-umbrella (figs. 23 and 25); and, fourthly, + in structure, being hollow or solid, as in the polyp. In some medusae, + for instance, the remarkable deep-sea family _Pectyllidae_, the + tentacles may bear suckers, by which the animal may attach itself + temporarily. It should be mentioned finally that the tentacles are + very contractile and extensible, and may therefore present themselves, + in one and the same individual, as long, drawn-out threads, or in the + form of short corkscrew-like ringlets; they may stream downwards from + the sub-umbrella, or be held out horizontally, or be directed upwards + over the ex-umbrella (fig. 23). Each species of medusa usually has a + characteristic method of carrying its tentacles. + + [Illustration: After O. Maas, _Die craspedoten Medusen der Plankton + Expedition_, by permission of Lipsius and Tischer. + + FIG. 23.--_Aeginopsis hensenii_, slightly magnified, showing the + manner in which the tentacles are carried in life.] + + [Illustration: After O. Maas, _Craspedoten Medusen der + Siboga-Expedition_, by permission of E. S. Brill & Co. + + FIG. 24.--_Rathkea octonemalis._] + + The sub-umbrella invariably shows a velum as an inwardly projecting + ridge or rim at its margin, within the circle of tentacles; hence the + medusae of this sub-class are termed craspedote. The manubrium is + absent altogether in the fresh-water medusa _Limnocnida_, in which the + diameter of the mouth exceeds half that of the umbrella; on the other + hand, the manubrium may attain a great length, owing to the centre of + the sub-umbrella with the stomach being drawn into it, as it were, to + form a long proboscis, as in _Geryonia_. The mouth may be a simple, + circular pore at the extremity of the manubrium, or by folding of the + edges it may become square or shaped like a Maltese cross, with four + corners and four lips. The corners of the mouth may then be drawn out + into lobes or lappets, which may have a branched or fringed outline + (fig. 27), and in _Margelidae_ the subdivisions of the fringe simulate + tentacles (fig. 24). + + [Illustration: After O. Maas, _Medusae_, in Prince of Monaco's series. + + FIG. 25.--_Aeginura grimaldii._] + + The internal anatomy of the Hydromedusae shows numerous variations. + The stomach may be altogether lodged in the manubrium, from which the + radial canals then take origin directly as in _Geryonia_ + (Trachomedusae); it may be with or without gastric pouches. The radial + canals may be simple or branched, primarily four, rarely six in + number. The ring-canal is drawn out in Narcomedusae into festoons + corresponding with the lobes of the margin, and may be obliterated + altogether (_Solmaris_). In this order the radial canals are + represented only by wide gastric pouches, and in the family Solmaridae + are suppressed altogether, so that the tentacles and the festoons of + the ring-canal arise directly from the stomach. In _Geryonia_, + centripetal canals, ending blindly, arise from the ring-canal and run + in a radial direction towards the centre of the umbrella (fig. 26). + + _Histology of the Hydromedusa._--The histology described above for the + polyp may be taken as the primitive type, from which that of the + medusa differs only in greater elaboration and differentiation of the + cell-elements, which are also more concentrated to form distinct + tissues. + + [Illustration: FIG. 26.--_Carmarina (Geryonia) hastata_, one of the + _Trachomedusae_. (After Haeckel.) + + a, Nerve ring, + a´, Radial nerve. + b, Tentaculocyst. + c, Circular canal. + e, Radiating canal, + g´´. Ovary. + h, Peronia or cartilaginous process ascending from the cartilaginous + margin of the disk centripetally in the outer surface of the + jelly-like disk; six of these are perradial, six interradial, + corresponding to the twelve solid larval tentacles, resembling those + of _Cunina_. + k, Dilatation (stomach) of the manubrium. + l, Jelly of the disk. + p, Manubrium. + t, Tentacle (hollow and tertiary, i.e. preceded by six perradial and + six interradial solid larval tentacles). + u, Cartilaginous margin of the disk covered by thread-cells. + v. Velum.] + + The ectoderm furnishes the general epithelial covering of the body, + and the muscular tissue, nervous system and sense-organs. The external + epithelium is flat on the ex-umbral surface, more columnar on the + sub-umbral surface, where it forms the muscular tissue of the + sub-umbrella and the velum. The nematocysts of the ectoderm may be + grouped to form batteries on the tentacles, umbrellar margin and oral + lappets. In places the nematocysts may be crowded so thickly as to + form a tough, supporting, "chondral" tissue, resembling cartilage, + chiefly developed at the margin of the umbrella and forming streaks or + bars supporting the tentacles ("Tentakelspangen," _peronia_) or the + tentaculocysts ("Gehörspangen," _otoporpae_). + + [Illustration: After O. Maas in _Results of the "Albatross" + Expedition_, Museum of Comparative Zoology, Cambridge, Mass., U.S.A. + + FIG. 27.--_Stomotoca divisa_, one of the _Tiaridae_ (Anthomedusae).] + + The muscular tissue of the Hydromedusae is entirely ectodermal. The + muscle-fibres arise as processes from the bases of the epithelial + cells; such cells may individually become sub-epithelial in position, + as in the polyp; or, in places where muscular tissue is greatly + developed, as in the velum or sub-umbrella, the entire muscular + epithelium may be thrown into folds in order to increase its surface, + so that a deeper sub-epithelial muscular layer becomes separated + completely from a more superficial body-epithelium. + + In its arrangement the muscular tissue forms two systems: the one + composed of striated fibres arranged circularly, that is to say, + concentrically round the central axis of the umbrella; the other of + non-striated fibres running longitudinally, that is to say, in a + radial direction from, or (in the manubrium) parallel to, the same + ideal axis. The circular system is developed continuously over the + entire sub-umbral surface, and the velum represents a special local + development of this system, at a region where it is able to act at the + greatest mechanical advantage in producing the contractions of the + umbrella by which the animal progresses. The longitudinal system is + discontinuous, and is subdivided into proximal, medial and distal + portions. The proximal portion forms the retractor muscles of the + manubrium, or proboscis, well developed, for example, in _Geryonia_. + The medial portion forms radiating tracts of fibres, the so-called + "bell-muscles" running underneath, and parallel to, the radial canals; + when greatly developed, as in _Tiaridae_, they form ridges, so-called + mesenteries, projecting into the sub-umbral cavity. The distal + portions form the muscles of the tentacles. In contrast with the + polyp, the longitudinal muscle-system is entirely ectodermal, there + being no endodermal muscles in craspedote medusae. + + [Illustration: FIG. 28.--Muscular Cells of Medusae (_Lizzia_). The + uppermost is a purely muscular cell from the sub-umbrella; the two + lower are epidermo-muscular cells from the base of a tentacle; the + upstanding nucleated portion forms part of the epidermal mosaic on the + free surface of the body. (After Hertwig.)] + + The nervous system of the medusa consists of sub-epithelial + ganglion-cells, which form, in the first place, a diffuse plexus of + nervous tissue, as in the polyp, but developed chiefly on the + sub-umbral surface; and which are concentrated, in the second place, + to form a definite central nervous system, never found in the polyp. + In Hydromedusae the central nervous system forms two concentric + nerve-rings at the margin of the umbrella, near the base of the velum. + One, the "upper" or ex-umbral nerve-ring, is derived from the ectoderm + on the ex-umbral side of the velum; it is the larger of the two rings, + containing more numerous but smaller ganglion-cells, and innervates + the tentacles. The other, the "lower" or sub-umbral nerve-ring, is + derived from the ectoderm on the sub-umbral side of the velum; it + contains fewer but larger ganglion-cells and innervates the muscles of + the velum (see diagram in article MEDUSAE). The two nerve-rings are + connected by fibres passing from one to the other. + + [Illustration: After O. Maas, _Craspedoten Medusen der Siboga + Expedition_, by permission of E. S. Brill & Co. + + FIG. 29.--_Tiaropsis rosea_ (Ag. and Mayer) showing the eight adradial + Statocysts, each close to an Ocellus. Cf. fig. 30.] + + The sensory cells are slender epithelial cells, often with a cilium or + stiff protoplasmic process, and should perhaps be regarded as the only + ectoderm-cells which retain the primitive ciliation of the larval + ectoderm, otherwise lost in all Hydrozoa. The sense-cells form, in the + first place, a diffuse system of scattered sensory cells, as in the + polyp, developed chiefly on the manubrium, the tentacles and the + margin of the umbrella, where they form a sensory ciliated epithelium + covering the nerve-centres; in the second place, the sense-cells are + concentrated to form definite sense-organs, situated always at the + margin of the umbrella, hence often termed "marginal bodies." The + possession of definite sense-organs at once distinguishes the medusa + from the polyp, in which they are never found. + + The sense-organs of medusae are of two kinds--first, organs sensitive + to light, usually termed _ocelli_ (fig. 29); secondly, organs commonly + termed _otocysts_, on account of their resemblance to the auditory + vesicles of higher animals, but serving for the sense of balance and + orientation, and therefore given the special name of _statocysts_ + (fig. 30). The sense-organs may be _tentaculocysts_, i.e. + modifications of a tentacle, as in Trachylinae, or developed from the + margin of the umbrella, in no connexion with a tentacle (or, if so + connected, not producing any modification in the tentacle), as in + Leptolinae. In Hydromedusae the sense-organs are always exposed at the + umbrellar margin (hence _Gymnophthalmata_), while in Scyphomedusae + they are covered over by flaps of the umbrellar margin (hence + _Steganophthalmata_). + + [Illustration: Modified after Linko, _Traveaux Soc. Imp. Nat._, St. + Petersbourg, xxix. + + FIG. 30.--Section of a Statocyst and Ocellus of _Tiaropsis diademata_; + cf. fig. 29. + + ex, Ex-umbral ectoderm. + sub, Sub-umbral ectoderm. + c.c, Circular canal. + v, Velum. + st.e, Cavity of statocyst. + con, Concrement-cell with otolith.] + + The _statocysts_ present in general the structure of either a knob or + a closed vesicle, composed of (1) indifferent supporting epithelium: + (2) sensory, so-called auditory epithelium of slender cells, each + bearing at its free upper end a stiff bristle and running out at its + base into a nerve-fibre; (3) concrement-cells, which produce + intercellular concretions, so-called otoliths. By means of vibrations + or shocks transmitted through the water, or by displacements in the + balance or position of the animal, the otoliths are caused to impinge + against the bristles of the sensory cells, now on one side, now on the + other, causing shocks or stimuli which are transmitted by the basal + nerve-fibre to the central nervous system. Two stages in the + development of the otocyst can be recognized, the first that of an + open pit on a freely-projecting knob, in which the otoliths are + exposed, the second that of a closed vesicle, in which the otoliths + are covered over. Further, two distinct types of otocyst can be + recognized in the Hydromedusae: that of the Leptolinae, in which the + entire organ is ectodermal, concrement-cells and all, and the organ is + not a tentaculocyst; and that of the Trachylinae, in which the organ + is a tentaculocyst, and the concrement-cells are endodermal, derived + from the endoderm of the modified tentacle, while the rest of the + organ is ectodermal. + + [Illustration: Modified after O. and R, Hertwig, _Nervensystem und + Sinnesorgane der Medusen_, by permission of F. C. W. Vogel. + + FIG. 31.--Section of a Statocyst of _Mitrocoma annae_. + + sub, Sub-umbral ectoderm. + c.c, Circular canal. + v, Velum. + st.c,. Cavity of statocyst. + con, Concrement-cell with otolith.] + + [Illustration: Modified after O. and R, Hertwig, _Nervensystem und + Sinnesorgane der Medusen_, by permission of F. C. W. Vogel. + + FIG. 32.--Section of a Statocyst of _Phialidium_. + + ex, Ex-umbral ectoderm. + sub, Sub-umbral ectoderm. + v, Velum. + st.c, Cavity of statocyst. + con, Concrement-cell with otolith.] + + [Illustration: Modified after O. and R, Hertwig, _Nervensystem und + Sinnesorgane der Medusen_, by permission of F. C. W. Vogel. + + FIG. 33.--Optical Section of a Statocyst of _Octorchis_. + + con, Concrement-cell with otolith. + st.c, Cavity of statocyst.] + + In the Leptolinae the otocysts are seen in their first stage in + _Mitrocoma annae_ (fig. 31) and _Tiaropsis_ (figs. 29, 30) as an open + pit at the base of the velum, on its sub-umbral side. The pit has its + opening turned towards the sub-umbral cavity, while its base or fundus + forms a bulge, more or less pronounced, on the ex-umbral side of the + velum. At the _fundus_ are placed the concrement-cells with their + conspicuous otoliths (_con_) and the inconspicuous auditory cells, + which are connected with. the sub-umbral nerve-ring. From the open + condition arises the closed condition very simply by closing up of the + aperture of the pit. We then find the typical otocyst of the + Leptomedusae, a vesicle bulging on the ex-umbral side of the velum + (figs. 32, 33). The otocysts are placed on the outer wall of the + vesicle (the fundus of the original pit) or on its sides; their + arrangement and number vary greatly and furnish useful characters for + distinguishing genera. The sense-cells are innervated, as before, from + the sub-umbral nerve-ring. The inner wall of the vesicle (region of + closure) is frequently thickened to form a so-called "sense-cushion," + apparently a ganglionic offshoot from the sub-umbral nerve-ring. In + many Leptomedusae the otocysts are very small, inconspicuous and + embedded completely in the tissues; hence they may be easily + overlooked in badly-preserved material, and perhaps are present in + many cases where they have been said to have been wanting. + + [Illustration: After O. and R, Hertwig, _Nervensystem und Sinnesorgane + der Medusen_, by permission of F. C. W. Vogel. + + FIG. 34.--Tentaculocyst (statorhabd) of _Cunina solmaris_. n.c, + Nerve-cushion; end, endodermal concrement-cells; con, otolith.] + + [Illustration: After O. and R, Hertwig, _Nervensystem und Sinnesorgane + der Medusen_, by permission of F. C. W. Vogel. + + FIG. 35.--Tentaculocyst of _Cunina lativentris_. + + ect, Ectoderm. + n.c, Nerve-cushion. + end, Endodermal concrement-cells. + con, Otolith.] + + In the Trachylinae the simplest condition of the otocyst is a freely + projecting club, a so-called _statorhabd_ (figs. 34, 35), representing + a tentacle greatly reduced in size, covered with sensory ectodermal + epithelium (_ect._), and containing an endodermal core (_end._), which + is at first continuous with the endoderm of the ring-canal, but later + becomes separated from it. In the endoderm large concretions are + formed (_con._). Other sensory cells with long cilia cover a sort of + cushion (_n.c._) at the base of the club; the club may be long and the + cushion small, or the cushion large and the club small. The whole + structure is innervated, like the tentacles, from the ex-umbral + nerve-ring. An advance towards the second stage is seen in such a form + as _Rhopalonema_ (fig. 36), where the ectoderm of the cushion rises up + in a double fold to enclose the club in a protective covering forming + a cup or vesicle, at first open distally; finally the opening closes + and the closed vesicle may sink inwards and be found far removed from + the surface, as in _Geryonia_ (fig. 37). + + [Illustration: FIG. 36.--Simple tentaculocyst of _Rhopalonema + velatum_. The process carrying the otolith or concretion hk, formed by + endoderm cells, is enclosed by an upgrowth forming the "vesicle," + which is not yet quite closed in at the top. (After Hertwig.)] + + The _ocelli_ are seen in their simplest form as a pigmented patch of + ectoderm, which consists of two kinds of cells--(1) pigment-cells, + which are ordinary indifferent cells of the epithelium containing + pigment-granules, and (2) visual cells, slender sensory epithelial + cells of the usual type, which may develop visual cones or rods at + their free extremity. The ocelli occur usually either on the inner or + outer sides of the tentacles; if on the inner side, the tentacle is + turned upwards and carried over the ex-umbrella, so as to expose the + ocellus to the light; if the ocellus be on the outer side of a + tentacle, two nerves run round the base of the tentacle to it. In + other cases ocelli may occur between tentacles, as in _Tiaropsis_ + (fig. 29). + + The simple form of ocellus described in the foregoing paragraph may + become folded into a pit or cup, the interior of which becomes filled + with a clear gelatinous secretion forming a sort of vitreous body. The + distal portion of the vitreous body may project from the cavity of the + cup, forming a non-cellular lens as in _Lizzia_ (fig. 28). Beyond this + simple condition the visual organs of the Hydromedusae do not advance, + and are far from reaching the wonderful development of the eyes of + Scyphomedusae (_Charybdaea_). + + [Illustration: After O. and R, Hertwig, _Nervensystem und Sinnesorgane + der Medusen_, by permission of F. C. W. Vogel. + + FIG. 37.--Section of statocyst of _Geryonia_ (_Carmarina hastata_). + + st.c, Statocyst containing the minute tentaculocyst. + nr1, Ex-umbral nerve-ring. + nr2, Sub-umbral nerve-ring. + ex, Ex-umbral ectoderm. + sub, Sub-umbral ectoderm. + c.c, Circular canal. + v, Velum.] + + Besides the ordinary type of ocellus just described, there is found in + one genus (_Tiaropsis_) a type of ocellus in which the visual elements + are inverted, and have their cones turned away from the light, as in + the human retina (fig. 30). In this case the pigment-cells are + endodermal, forming a cup of pigment in which the visual cones are + embedded. A similar ocellus is formed in _Aurelia_ among the + Scyphomedusae (q.v.). + + Other sense organs of Hydromedusae are the so-called _sense-clubs_ or + _cordyli_ found in a few Leptomedusae, especially in those genera in + which otocysts are inconspicuous or absent (fig. 39). Each cordylus is + a tentacle-like structure with an endodermal axis containing an axial + cavity which may be continuous with the ring-canal, or may be + partially occluded. Externally the cordylus is covered, by very + flattened ectoderm, and bears no otoliths or sense-cells, but the base + of the club rests upon the ex-umbral nerve-ring. Brooks regards these + organs as sensory, serving for the sense of balance, and representing + a primitive stage of the tentaculocysts of Trachylinae; Linko, on the + other hand, finding no nerve-elements connected with them, regards + them as digestive (?) in function. + + The sense-organs of the two fresh-water medusae _Limnocodium_ and + _Limnocnida_ are peculiar and of rather doubtful nature (see E. T. + Browne [10]). + + FIG. 38.--Ocellus of _Lizzia koellikeri_. oc, Pigmented ectodermal + cells; l, lens. (After Hertwig.) + + The endoderm of the medusa shows the same general types of structure + as in the polyp, described above. We can distinguish (1) digestive + endoderm, in the stomach, often with special glandular elements; (2) + circulatory endoderm, in the radial and ring-canals; (3) supporting + endoderm in the axes of the tentacles and in the endoderm-lamella; the + latter is primitively a double layer of cells, produced by + concrescence of the ex-umbral and sub-umbral layers of the + coelenteron, but it is usually found as a single layer of flattened + cells (fig. 40); in _Geryonia_, however, it remains double, and the + centripetal canals arise by parting of the two layers; (4) excretory + endoderm, lining pores at the margin of the umbrella, occurring in + certain Leptomedusae as so-called "marginal tubercles," opening, on + the one hand, into the ring-canal and, on the other hand, to the + exterior by "marginal funnels," which debouch into the sub-umbral + cavity above the velum. As has been described above, the endoderm may + also contribute to the sense-organs, but such contributions are always + of an accessory nature, for instance, concrement-cells in the + otocysts, pigment in the ocelli, and never of sensory nature, + sense-cells being in all cases ectodermal. + + The reproductive cells may be regarded as belonging primarily to + neither ectoderm nor endoderm, though lodged in the ectoderm in all + Hydromedusae. As described for the polyp, they are wandering cells + capable of extensive migrations before reaching the particular spot at + which they ripen. In the Hydromedusae they usually, if not invariably, + ripen in the ectoderm, but in the neighbourhood of the main sources of + nutriment, that is to say, not far from the stomach. Hence the gonads + are found on the manubrium in Anthomedusae generally; on the base of + the manubrium, or under the gastral pouches, or in both these + situations (_Octorchidae_), or under the radial canals, in + Trachomedusae; under the gastral pouches or radial canals, in + Narcomedusae. When ripe, the germ-cells are dehisced directly to the + exterior. + + [Illustration: After W. K. Brooks, _Journal of Morphology_, x., by + permission of Ginn & Co. + + FIG. 39.--Section of a Cordylus of _Laodice_. + + c.c, Circular canal. + v, Velum. + t, Tentacle. + c, Cordylus, composed of flattened ectoderm ec covering a large-celled + endodermal axis en.] + + Hydromedusae are of separate sexes, the only known exception being + _Amphogona apsteini_, one of the Trachomedusae (Browne [9]). Moreover, + all the medusae budded from a given hydroid colony are either male or + female, so that even the non-sexual polyp must be considered to have a + latent sex. (In _Hydra_, on the other hand, the individual is usually + hermaphrodite.) The medusa always reproduces itself sexually, and in + some cases non-sexually also. The non-sexual reproduction takes the + form of fission, budding or sporogony, the details of which are + described below. Buds may be produced from the manubrium, radial + canals, ring-canal, or tentacle-bases, or from an aboral stolon + (Narcomedusae). In all cases only medusa-buds are produced, never + polyp-buds. + + The mesogloea of the medusa is largely developed and of great + thickness in the umbrella. The sub-epithelial tissues, i.e. the + nervous and muscular cells, are lodged in the mesogloea, but in + Hydromedusae it never contains tissue-cells or mesogloeal corpuscles. + + (b) _The Medusae as a Subordinate Individuality._--It has been shown + above that polyps are budded only from polyps and that the medusae may + be budded either from polyps or from medusae. In any case the + daughter-individuals produced from the buds may be imagined as + remaining attached to the parent and forming a colony of individuals + in organic connexion with one another, and thus three possible cases + arise. The first case gives a colony entirely composed of polyps, as + in many Hydroidea. The second case gives a colony partly composed of + polyp-individuals, partly of medusa-individuals, a possibility also + realized in many colonies of Hydroidea. The third case gives a colony + entirely composed of medusa-individuals, a possibility perhaps + realized in the Siphonophora, which will be discussed in dealing with + this group. + + [Illustration: FIG. 40.--Portions of Sections through the Disk of + Medusae--the upper one of _Lizzia_, the lower of _Aurelia_. (After + Hertwig.) + + el, Endoderm lamella. + m, Muscular processes of the ectoderm-cells in cross section. + d, Ectoderm. + en, Endoderm lining the enteric cavity. + e, Wandering endoderm cells of the gelatinous substance.] + + The first step towards the formation of a mixed hydroid colony is + undoubtedly a hastening of the sexual maturity of the + medusa-individual. Normally the medusae are liberated in quite an + immature state; they swim away, feed, grow and become adult mature + individuals. From the bionomical point of view, the medusa is to be + considered as a means of spreading the species, supplementing the + deficiencies of the sessile polyp. It may be, however, that increased + reproductiveness becomes of greater importance to the species than + wide diffusion; such a condition will be brought about if the medusae + mature quickly and are either set free in a mature condition or remain + in the shelter of the polyp-colony, protected from risks of a free + life in the open sea. In this way the medusa sinks from an independent + personality to an organ of the polyp-colony, becoming a so-called + _medusoid gonophore_, or bearer of the reproductive organs, and losing + gradually all organs necessary for an independent existence, namely + those of sense, locomotion and nutrition. + + In some cases both free medusae and gonophores may be produced from + the same hydroid colony. This is the case in _Syncoryne mirabilis_ + (Allman [1], p. 278) and in _Campanularia volubilis_; in the latter, + free medusae are produced in summer, gonophores in winter (Duplessis + [14]). Again in _Pennaria_, the male medusae are set free in a state + of maturity, and have ocelli; the female medusae remain attached and + have no sense organs. + + [Illustration: Modified from Weismann, _Entstehung der Sexualzellen + bei den Hydromedusen_. + + FIG. 41.--Diagrams of the Structure of the Gonophores of various + Hydromedusae, based on the figures of G. J. Allman and A. Weismann. + + A, "Meconidium" of _Gonothyraea_. + B, Type of _Tubularia_. + C, Type of _Garveia_, &c. + D, Type of _Plumularia_, _Agalma_, &c. + E, Type of _Coryne_, _Forskalia_, &c. + F, G, H, Sporosacs. + F, With simple spadix. + G, With spadix prolonged (_Eudendrium_). + H, With spadix branched (_Cordylophora_). + s.c, Sub-umbral cavity. + t, Tentacles. + c.c, Circular canal, + g, Gonads. + sp, Spadix. + e.l, Endoderm-lamella. + ex, Ex-umbral ectoderm. + ect, Ectotheca.] + + The gonophores of different hydroids differ greatly in structure from + one another, and form a series showing degeneration of the + medusa-individual, which is gradually stripped, as it were, of its + characteristic features of medusan organization and finally reduced to + the simplest structure. A very early stage in the degeneration is well + exemplified by the so-called "meconidium" of _Gonothyraea_ (fig. 41, + A). Here the medusoid, attached by the centre of its ex-umbral + surface, has lost its velum and sub-umbral muscles, its sense organs + and mouth, though still retaining rudimentary tentacles. The gonads + (g) are produced on the manubrium, which has a hollow endodermal axis, + termed the spadix (sp.), in open communication with the coenosarc of + the polyp-colony and serving for the nutrition of the generative + cells. A very similar condition is seen in _Tubularia_ (fig. 41, B), + where, however, the tentacles have quite disappeared, and the circular + rim formed by the margin of the umbrella has nearly closed over the + manubrium leaving only a small aperture through which the embryos + emerge. The next step is illustrated by the female gonophores of + _Cladocoryne_, where the radial and ring-canals have become + obliterated by coalescence of their walls, so that the entire endoderm + of the umbrella is in the condition of the endoderm-lamella. Next the + opening of the umbrella closes up completely and disappears, so that + the sub-umbral cavity forms a closed space surrounding the manubrium, + on which the gonads are developed; such a condition is seen in the + male gonophore of _Cladocoryne_ and in _Garveia_ (fig. 41, C), where, + however, there is a further complication in the form of an + adventitious envelope or ectotheca (ect.) split off from the gonophore + as a protective covering, and not present in _Cladocoryne_. The + sub-umbral cavity (s.c.) functions as a brood-space for the developing + embryos, which are set free by rupture of the wall. It is evident that + the outer envelope of the gonophore represents the ex-umbral ectoderm + (ex.), and that the inner ectoderm lining the cavity represents the + sub-umbral ectoderm of the free medusa. The next step is the gradual + obliteration of the sub-umbral cavity (s.c.) by disappearance of which + the sub-umbral ectoderm comes into contact with the ectoderm of the + manubrium. Such a type is found in _Plumularia_ and also in _Agalma_ + (fig. 41, D); centrally is seen the spadix (sp.), bearing the + generative cells (g), and external to these (1) a layer of ectoderm + representing the epithelium of the manubrium; (2) the layer of + sub-umbral ectoderm; (3) the endoderm-lamella (e.l.); (4) the + ex-umbral ectoderm (ex.); and (5) there may or may not be present also + an ectotheca. Thus the gonads are covered over by at least four layers + of epithelium, and since these are unnecessary, presenting merely + obstacles to the dehiscence of the gonads, they gradually undergo + reduction. The sub-umbral ectoderm and that covering the manubrium + undergo concrescence to form a single layer (fig. 41, E), which + finally disappears altogether, and the endoderm-lamella disappears. + The gonophore is now reduced to its simplest condition, known as the + _sporosac_ (fig. 41, F, G, H), and consists of the spadix bearing the + gonads covered by a single layer of ectoderm (ex.), with or without + the addition of an ectotheca. It cannot be too strongly emphasized, + however, that the sporosac should not be compared simply with the + manubrium of the medusa, as is sometimes done. The endodermal spadix + (sp) of the sporosac represents the endoderm of the manubrium; the + ectodermal lining of the sporosac (ex.) represents the ex-umbral + ectoderm of the medusa; and the intervening layers, together with the + sub-umbral cavity, have disappeared. The spadix, as the organ of + nutrition for the gonads, may be developed in various ways, being + simple (fig. 41, F) or branched (fig. 41, H); in _Eudendrium_ (fig. + 41, G) it curls round the single large ovum. + + [Illustration: After Allman, _Gymnoblastic Hydroids_, by permission of + the Council of the Ray Society. + + FIG. 42.--Gonophores of _Dicoryne conferta_. + + A, A male gonophore still enclosed in its ectotheca. + B and C, Two views of a female gonophore after liberation. + t, Tentacles. + ov, Ova, two carried on each female gonophore. + sp, Testis.] + + The hydroid _Dicoryne_ is remarkable for the possession of gonophores, + which are ciliate and become detached and swim away by means of their + cilia. Each such sporosac has two long tentacle-like processes thickly + ciliated. + + It has been maintained that the gonads of _Hydra_ represent sporosacs + or gonophores greatly reduced, with the last traces of medusoid + structure completely obliterated. There is, however, no evidence + whatever for this, the gonads of _Hydra_ being purely ectodermal + structures, while all medusoid gonophores have an endodermal portion. + _Hydra_ is, moreover, bisexual, in contrast with what is known of + hydroid colonies. + + In some Leptomedusae the gonads are formed on the radial canals and + form protruding masses resembling sporosacs superficially, but not in + structure. Allman, however, regarded this type of gonad as equivalent + to a sporosac, and considered the medusa bearing them as a non-sexual + organism, a "blastocheme" as he termed it, producing by budding + medusoid gonophores. As medusae are known to bud medusae from the + radial canals there is nothing impossible in Allman's theory, but it + cannot be said to have received satisfactory proof. + + +_Reproduction and Ontogeny of the Hydromedusae._ + +Nearly every possible method of reproduction occurs amongst the +Hydromedusae. In classifying methods of generation it is usual to make +use of the sexual or non-sexual nature of the reproduction as a primary +difference, but a more scientific classification is afforded by the +distinction between tissue-cells (histocytes) and germinal cells, actual +or potential (archaeocytes), amongst the constituent cells of the animal +body. In this way we may distinguish, first, _vegetative_ reproduction, +the result of discontinuous growth of the tissues and cell-layers of the +body as a whole, leading to (1) _fission_, (2) _autotomy_, or (3) +_vegetative budding_; secondly, _germinal_ reproduction, the result of +the reproductive activity of the archaeocytes or germinal tissue. In +germinal reproduction the proliferating cells may be _undifferentiated_, +so-called primitive germ-cells, or they may be _differentiated_ as +sexual cells, male or female, i.e. spermatozoa and ova. If the +germ-cells are _undifferentiated_, the offspring may arise from many +cells or from a single cell; the first type is (4) _germinal budding_, +the second is (5) _sporogony_. If the germ-cells are _differentiated_, +the offspring arises by _syngamy_ or sexual union of the ordinary type +between an ovum and spermatozoon, so-called fertilization, of the ovum, +or by _parthenogenesis_, i.e. development of an ovum without +fertilization. The only one of these possible modes of reproduction not +known to occur in Hydromedusae is parthenogenesis. + +(1) True _fission_ or longitudinal division of an individual into two +equal and similar daughter-individuals is not common but occurs in +_Gastroblasta_, where it has been described in detail by Arnold Lang +[30]. + +(2) _Autotomy_, sometimes termed transverse fission, is the name given +to a process of unequal fission in which a portion of the body separates +off with subsequent regeneration. In _Tubularia_ by a process of +decapitation the hydranths may separate off and give rise to a separate +individual, while the remainder of the body grows a new hydranth. +Similarly in _Schizocladium_ portions of the hydrocaulus are cut off to +form so-called "spores," which grow into new individuals (see Allman +[1]). + +[Illustration: Much modified from C. Chun, "Coelenterata," in Bronn's +_Tierreich_. + +FIG. 43.--Direct Budding of _Cunina_. + + A, B, C, E, F, In vertical section. + D, Sketch of external view. + st, Stomach. + m, Manubrium. + t. Tentacle. + s.o, Sense organ. + v, Velum. + s.c, Sub-umbral cavity. + n.s, Nervous system.] + +(3) _Vegetative budding_ is almost universal in the Hydromedusae. By +budding is understood the formation of a new individual from a fresh +growth of undifferentiated material. It is convenient to distinguish +buds that give rise to polyps from those that form medusae. + + (a) _The Polyp._--The buds that form polyps are very simple in mode of + formation. Four stages may be distinguished; the first is a simple + outgrowth of both layers, ectoderm and endoderm, containing a + prolongation of the coelenteric cavity; in the second stage the + tentacles grow out as secondary diverticula from the side of the first + outgrowth; in the third stage the mouth is formed as a perforation of + the two layers; and, lastly, if the bud is to be separated, it becomes + nipped off from the parent polyp and begins a free existence. + + (b) _The Medusae._--Two types of budding must be distinguished--the + direct, so-called, palingenetic type, and the _indirect_, so-called + coenogenetic type. + + The direct type of budding is rare, but is seen in _Cunina_ and + _Millepora_. In _Cunina_ there arises, first, a simple outgrowth of + both layers, as in a polyp-bud (fig. 43, A); in this the mouth is + formed distally as a perforation (B); next the sides of the tube so + formed bulge out laterally near the attachment to form the umbrella, + while the distal undilated portion of the tube represents the + manubrium (C); the umbrella now grows out into a number of lobes or + lappets, and the tentacles and tentaculocysts grow out, the former in + a notch between two lappets, the latter on the apex of each lappet (D, + E); finally, the velum arises as a growth of the ectoderm alone, the + whole bud shapes itself, so to speak, and the little medusa is + separated off by rupture of the thin stalk connecting it with the + parent (F). The direct method of medusa-budding only differs from the + polyp-bud by its greater complexity of parts and organs. + + [Illustration: FIG. 44.--Diagrams of Medusa budding with the formation + of an entocodon. The endoderm is shaded, the ectoderm left clear. + + A, B, C, D, F, Successive stages in vertical section. + E, Transverse section of a stage similar to D. + Gc, Entocodon. + s.c, Cavity of entocodon, forming the future sub-umbral cavity. + st, Stomach. + r.c, Radial canal. + c.c, Circular canal. + e.l, Endoderm lamella. + m, Manubrium. + v, Velum. + t, Tentacle.] + + The indirect mode of budding (figs. 44, 45) is the commonest method by + which medusa-buds are formed. It is marked by the formation in the bud + of a characteristic structure termed the _entocodon_ (_Knospenkern_, + _Glockenkern_). + + [Illustration: FIG. 45.--Modifications of the method of budding shown + in fig. 44, with solid Entocodon (Gc.) and formation of an ectotheca + (ect.).] + + The first stage is a simple hollow outgrowth of both body-layers (fig. + 44, A); at the tip of this is formed a thickening of the ectoderm, + arising primitively as a hollow ingrowth (fig. 44, B), but more + usually as a solid mass of ectoderm-cells (fig. 45, A). The ectodermal + ingrowth is the entocodon (Gc.); it bulges into, and pushes down, the + endoderm at the apex of the bud, and if solid it soon acquires a + cavity (fig. 44, C, s.c.). The cavity of the entocodon increases + continually in size, while the endoderm pushes up at the sides of it + to form a cup with hollow walls, enclosing but not quite surrounding + the entocodon, which remains in contact at its outer side with the + ectoderm covering the bud (fig. 44, D, v). The next changes that take + place are chiefly in the endoderm-cup (fig. 44, D, E); the cavity + between the two walls of the cup becomes reduced by concrescence to + form the radial canals (r.c.), ring-canal (c.c.), and endoderm-lamella + (e.l., fig. 44, E), and at the same time the base of the cup is thrust + upwards to form the manubrium (m), converting the cavity of the + entocodon into a space which is crescentic or horse-shoe-like in + section. Next tentacles (t, fig. 44, F) grow out from the ring-canal, + and the double plate of ectoderm on the distal side of the entocodon + becomes perforated, leaving a circular rim composed of two layers of + ectoderm, the velum (v) of the medusa. Finally, a mouth is formed by + breaking through at the apex of the manubrium, and the now + fully-formed medusa becomes separated by rupture of the stalk of the + bud and swims away. + + [Illustration: Fig. 46.--Diagrams to show the significance of the + Entocodon in Medusa-buds. (Modified from a diagram given by A. + Weismann.) + + I, Ideally primitive method of budding, in which the mouth is formed + first (Ia), next the tentacles (Ib), and lastly the umbrella. + II, Method. of _Cunina_; (a) the mouth arises, next the umbrella + (b), and lastly the tentacles (c). + III, Hypothetical transition from II to the indirect method with an + entocodon; the formation of the manubrium is retarded, that of the + umbrella hastened (IIIa, b). + IV, a, b, c, budding with an entocodon (cf. fig. 44). + V, Budding with a solid entocodon (cf. fig. 45).] + + If the bud, however, is destined to give rise not to a free medusa, + but to a gonophore, the development is similar but becomes arrested at + various points, according to the degree to which the gonophore is + degenerate. The entocodon is usually formed, proving the medusoid + nature of the bud, but in sporosacs the entocodon may be rudimentary + or absent altogether. The process of budding as above described may be + varied or complicated in various ways; thus a secondary, amnion-like, + ectodermal covering or ectotheca (fig. 45, C, ect.) may be formed over + all, as in _Garveia_, &c.; or the entocodon may remain solid and + without cavity until after the formation of the manubrium, or may + never acquire a cavity at all, as described above for the gonophores. + + _Phylogenetic Significance of the Entocodon._--It is seen from the + foregoing account of medusa-budding that the entocodon is a very + important constituent of the bud, furnishing some of the most + essential portions of the medusa; its cavity becomes the sub-umbral + cavity, and its lining furnishes the ectodermal epithelium of the + manubrium and of the sub-umbral cavity as far as the edge of the + velum. Hence the entocodon represents a precocious formation of the + sub-umbral surface, equivalent to the peristome of the polyp, + differentiated in the bud prior to other portions of the organism + which must be regarded as antecedent to it in phylogeny. + + If the three principal organ-systems of the medusa, namely mouth, + tentacles and umbrella, be considered in the light of phylogeny, it is + evident that the manubrium bearing the mouth must be the oldest, as + representing a common property of all the Coelentera, even of the + gastrula embryo of all Enterozoa. Next in order come the tentacles, + common to all Cnidaria. The special property of the medusa is the + umbrella, distinguishing the medusa at once from other morphological + types among the Coelentera. If, therefore, the formation of these + three systems of organs took place according to a strictly + phylogenetic sequence, we should expect them to appear in the order + set forth above (fig. 46, Ia, b, c). The nearest approach to the + phylogenetic sequence is seen in the budding of _Cunina_, where the + manubrium and mouth appear first, but the umbrella is formed before + the tentacles (fig. 46, IIa, b, c). In the indirect or coenogenetic + method of budding, the first two members of the sequence exhibited by + Cunina change places, and the umbrella is formed first, the manubrium + next, and then the tentacles; the actual mouth-perforation being + delayed to the very last (fig. 46, IVa, b, c). Hence the budding of + medusae exemplifies very clearly a common phenomenon in development, a + phylogenetic series of events completely dislocated in the ontogenetic + time-sequence. + + The entocodon is to be regarded, therefore, not as primarily an + ingrowth of ectoderm, but rather as an upgrowth of both body-layers, + in the form of a circular rim (IVa), representing the umbrellar + margin; it is comparable to the bulging that forms the umbrella in the + direct method of budding, but takes place before a manubrium is + formed, and is greatly reduced in size, so as to become a little pit. + By a simple modification, the open pit becomes a solid ectodermal + ingrowth, just as in Teleostean fishes the hollow medullary tube, or + the auditory pit of other vertebrate embryos, is formed at first as a + solid cord of cells, which acquires a cavity secondarily. Moreover, + the entocodon, however developed, gives rise at first to a closed + cavity, representing a closing over of the umbrella, temporary in the + bud destined to be a free medusa, but usually permanent in the sessile + gonophore. As has been shown above, the closing up of the sub-umbral + cavity is one of the earliest degenerative changes in the evolution of + the gonophore, and we may regard it as the umbrellar fold taking on a + protective function, either temporarily for the bud or permanently for + the gonophore. + + To sum up, the entocodon is a precocious formation of the umbrella, + closing over to protect the organs in the umbrellar cavity. The + possession of an entocodon proves the medusa-nature of the bud, and + can only be explained on the theory that gonophores are degenerate + medusae, and is inexplicable on the opposed view that medusae are + derived from gonophores secondarily set free. In the sporosac, + however, the medusa-individual has become so degenerate that even the + documentary proof, so to speak, of its medusoid nature may have been + destroyed, and only circumstantial evidence of its nature can be + produced. + +4. _Germinal Budding._--This method of budding is commonly described as +budding from a single body-layer, instead of from both layers. The layer +that produces the bud is invariably the ectoderm, i.e. the layer in +which, in Hydromedusae, the generative cells are lodged; and in some +cases the buds are produced in the exact spot in which later the gonads +appear. From these facts, and from those of the sporogony, to be +described below, we may regard budding to this type as taking place from +the germinal epithelium rather than from ordinary ectoderm. + + (a) _The Polyp._--Budding from the ectoderm alone has been described + by A. Lang [29] in _Hydra_ and other polyps. The tissues of the bud + become differentiated into ectoderm and endoderm, and the endoderm of + the bud becomes secondarily continuous with that of the parent, but no + part of the parental endoderm contributes to the building up of the + daughter-polyp. Lang regarded this method of budding as universal in + polyps, a notion disproved by O. Seeliger [52] who went to the + opposite extreme and regarded the type of budding described by Lang as + non-existent. In view, however, both of the statements and figures of + Lang and of the facts to be described presently for medusae + (_Margellium_), it is at least theoretically possible that both + germinal and vegetative budding may occur in polyps as well as in + medusae. + + (b) _The Medusa._--The clearest instance of germinal budding is + furnished by _Margellium (Rathkea) octopunctatum_, one of the + _Margelidae_. The budding of this medusa has been worked out in detail + by Chun (HYDROZOA, [1]), to whom the reader must be referred for the + interesting laws of budding regulating the sequence and order of + formation of the buds. + + The buds of _Margellium_ are produced on the manubrium in each of the + four interradii, and they arise from the ectoderm, that is to say, the + germinal epithelium, which later gives rise to the gonads. The buds do + not appear simultaneously but successively on each of the four sides + of the manubrium, thus: + + 1 + 3 4 + 2 + + and secondary buds may be produced on the medusa-buds before the + latter are set free as medusae. Each bud arises as a thickening of the + epithelium, which first forms two or three layers (fig. 47, A), and + becomes separated into a superficial layer, future ectoderm, + surrounding a central mass, future endoderm (fig. 47, B). The + ectodermal epithelium on the distal side of the bud becomes thickened, + grows inwards, and forms a typical entocodon (fig. 37, D, E, F). The + remaining development of the bud is just as described above for the + indirect method of medusa-budding (fig. 47, G, H). When the bud is + nearly complete, the body-wall of the parent immediately below it + becomes perforated, placing the coelenteric cavity of the parent in + secondary communication with that of the bud (H), doubtless for the + better nutrition of the latter. + + Especially noteworthy in the germinal budding of _Margellium_ is the + formation of the entocodon, as in the vegetative budding of the + indirect type. + +5. _Sporogony._--This method of reproduction has been described by E. +Metchnikoff in _Cunina_ and allied genera. In individuals either of the +male or female sex, germ-cells which are quite undifferentiated and +neutral in character, become amoeboid, and wander into the endoderm. +They divide each into two sister-cells, one of which--the spore--becomes +enveloped by the other. The spore-cell multiplies by division, while the +enveloping cell is nutrient and protective. The spore cell gives rise to +a "spore-larva," which is set free in the coelenteron and grows into a +medusa. Whether sporogony occurs also in the polyp or not remains to be +proved. + +6. _Sexual Reproduction and Embryology._--The ovum of Hydromedusae is +usually one of a large number of oögonia, and grows at the expense of +its sister-cells. No regular follicle is formed, but the oöcyte absorbs +nutriment from the remaining oögonia. In _Hydra_ the oöcyte is a large +amoeboid cell, which sends out pseudopodia amongst the oögonia and +absorbs nutriment from them. When the oöcyte is full grown, the residual +oögonia die off and disintegrate. + +[Illustration: FIG. 47.--Budding from the Ectoderm (germinal epithelium) +in _Margellium_. (After C. Chun.) + + A, The epithelium becomes two-layered. + B, The lower layer forms a solid mass of cells, which (C) becomes a + vesicle, the future endoderm, containing the coelenteric cavity + (coel), while the outer layer furnishes the future ectoderm. + D, E, F, a thickening of the ectoderm on the distal side of the bud + forms an entocodon (Gc). + G,H, Formation of the medusae. + s.c, Sub-umbral cavity. + r.c, Radial canal. + st, Stomach, which in H acquires a secondary communication with the + digestive cavity of the mother. + cc, Circular canal. + v, Velum. + t, Tentacle.] + +The spermatogenesis and maturation and fertilization of the germ-cells +present nothing out of the common and need not be described here. These +processes have been studied in detail by A. Brauer [2] for _Hydra_. + + The general course of the development is described in the article + HYDROZOA. We may distinguish the following series of stages: (1) ovum; + (2) cleavage, leading to formation of a blastula; (3) formation of an + inner mass or parenchyma, the future endoderm, by immigration or + delamination, leading to the so-called parenchymula-stage; (4) + formation of an archenteric cavity, the future coelenteron, by a + splitting of the internal parenchyma, and of a blastopore, the future + mouth, by perforation at one pole, leading to the gastrula-stage; (5) + the outgrowth of tentacles round the mouth (blastopore), leading to + the actinula-stage; and (6) the actinula becomes the polyp or medusa + in the manner described elsewhere (see articles HYDROZOA, POLYP and + MEDUSA). This is the full, ideal development, which is always + contracted or shortened to a greater or less extent. If the embryo is + set free as a free-swimming, so-called planula-larva, in the blastula, + parenchymula, or gastrula stage, then a free actinula stage is not + found; if, on the other hand, a free actinula occurs, then there is no + free planula stage. + + The cleavage of the ovum follows two types, both seen in _Tubularia_ + (Brauer [3]). In the first, a cleavage follows each nuclear division; + in the second, the nuclei multiply by division a number of times, and + then the ovum divides into as many blastomeres as there are nuclei + present. The result of cleavage in all cases is a typical blastula, + which when set free becomes oval and develops a flagellum to each + cell, but when not set free, it remains spherical in form and has no + flagella. + + The germ-layer formation is always by immigration or delamination, + never by invagination. When the blastula is oval and free-swimming the + inner mass is formed by unipolar immigration from the hinder pole. + When the blastula is spherical and not set free, the germ-layer + formation is always multipolar, either by immigration or by + delamination, i.e. by tangential division of the cells of the + blastoderm, as in _Geryonia_, or by a mixture of immigration and + delamination, as in _Hydra_, _Tubularia_, &c. The blastopore is formed + as a secondary perforation at one spot, in free-swimming forms at the + hinder pole. Formation of archenteron and blastopore may, however, be + deferred till a later stage (actinula or after). + + The actinula stage is usually suppressed or not set free, but it is + seen in _Tubularia_ (fig. 48), where it is ambulatory, in _Gonionemus_ + (Trachomedusae), and in _Cunina_ (Narcomedusae), where it is + parasitic. + + [Illustration: Modified from a plate by L. Agassiz, _Contributions to + Nat. Hist. U.S._, iv. + + FIG. 48.--Free Actinula of _Tubularia_.] + + In Leptolinae the embryonic development culminates in a polyp, which + is usually formed by fixation of a planula (parenchymula), rarely by + fixation of an actinula. The planula may fix itself (1) by one end, + and then becomes the hydrocaulus and hydranth, while the hydrorhiza + grows out from the base; or (2) partly by one side and then gives rise + to the hydrorhiza as well as to the other parts of the polyp; or (3) + entirely by its side, and then forms a recumbent hydrorhiza from which + a polyp appears to be budded as an upgrowth. + + In Trachylinae the development produces always a medusa, and there is + no polyp-stage. The medusa arises direct from the actinula-stage and + there is no entocodon formed, as in the budding described above. + + _Life-cycles of the Hydromedusae._--The life-cycle of the Leptolinae + consists of an alternation of generations in which non-sexual + individuals, polyps, produce by budding sexual individuals, medusae, + which give rise by the sexual process to the non-sexual polyps again, + so completing the cycle. Hence the alternation is of the type termed + metagenesis. The Leptolinae are chiefly forms belonging to the inshore + fauna. The Trachylinae, on the other hand, are above all oceanic + forms, and have no polyp-stage, and hence there is typically no + alternation in their life-cycle. It is commonly assumed that the + Trachylinae are forms which have lost the alternation of generations + possessed by them ancestrally, through secondary simplification of the + life-cycle. Hence the Trachylinae are termed "hypogenetic" medusae to + contrast them with the metagenetic Leptolinae. The whole question has, + however, been argued at length by W. K. Brooks [4], who adduces strong + evidence for a contrary view, that is to say, for regarding the direct + type of development seen in Trachylinae as more primitive, and the + metagenesis seen in Leptolinae as a secondary complication introduced + into the life-cycle by the acquisition of _larval budding_. The polyp + is regarded, on this view, as a form phylogenetically older than the + medusa, in short, as nothing more than a sessile actinula. In + Trachylinae the polyp-stage is passed over, and is represented only by + the actinula as a transitory embryonic stage. In Leptolinae the + actinula becomes the sessile polyp which has acquired the power of + budding and producing individuals either of its own or of a higher + rank; it represents a persistent larval stage and remains in a + sexually immature condition as a neutral individual, sex being an + attribute only of the final stage in the development, namely the + medusa. The polyp of the Leptolinae has reached the limit of its + individual development and is incapable of becoming itself a medusa, + but only produces medusa-buds; hence a true alternation of generations + is produced. In Trachylinae also the beginnings of a similar + metagenesis can be found. Thus in _Cunina octonaria_, the ovum + develops into an actinula which buds daughter-actinulae; all of them, + both parent and offspring, develop into medusae, so that there is no + alternation of generations, but only larval multiplication. In _Cunina + parasitica_, however, the ovum develops into an actinula, which buds + actinulae as before, but only the daughter-actinulae develop into + medusae, while the original, parent-actinula dies off; here, + therefore, larval budding has led to a true alternation of + generations. In _Gonionemus_ the actinula becomes fixed and + polyp-like, and reproduces by budding, so that here also an + alternation of generations may occur. In the Leptolinae we must first + substitute polyp for actinula, and then a condition is found which can + be compared to the case of _Cunina parasitica_ or Gonionemus, if we + suppose that neither the parent-actinula (i.e. founder-polyp) nor its + offspring by budding (polyps of the colony) have the power of becoming + medusae, but only of producing medusae by budding. For further + arguments and illustrations the reader must be referred to Brooks's + most interesting memoir. The whole theory is one most intimately + connected with the question of the relation between polyp and medusa, + to be discussed presently. It will be seen elsewhere, however, that + whatever view may be held as to the origin of metagenesis in + Hydromedusae, in the case of Scyphomedusae (q.v.) no other view is + possible than that the alternation of generations is the direct result + of larval proliferation. + + To complete our survey of life-cycles in the Hydromedusae it is + necessary to add a few words about the position of _Hydra_ and its + allies. If we accept the view that _Hydra_ is a true sexual polyp, and + that its gonads are not gonophores (i.e. medusa-buds) in the extreme + of degeneration, then it follows from Brooks's theory that _Hydra_ + must be descended from an archaic form in which the medusan type of + organization had not yet been evolved. _Hydra_ must, in short, be a + living representative of the ancestor of which the actinula-stage is a + transient reminiscence in the development of higher forms. It may be + pointed out in this connexion that the fixation of _Hydra_ is only + temporary, and that the animal is able at all times to detach itself, + to move to a new situation, and to fix itself again. There is no + difficulty whatever in regarding _Hydra_ as bearing the same relation + to the actinula-stage of other Hydromedusae that a Rotifer bears to a + trochophore-larva or a fish to a tadpole. + +_The Relation of Polyp and Medusa._--Many views have been put forward as +to the morphological relationship between the two types of person in the +Hydromedusae. For the most part, polyp and medusa have been regarded as +modifications of a common type, a view supported by the existence, among +Scyphomedusae (q.v.), of sessile polyp-like medusae (_Lucernaria_, &c.). +R. Leuckart in 1848 compared medusae in general terms to flattened +polyps. G. J. Allman [1] put forward a more detailed view, which was as +follows. In some polyps the tentacles are webbed at the base, and it was +supposed that a medusa was a polyp of this kind set free, the umbrella +being a greatly developed web or membrane extending between the +tentacles. A very different theory was enunciated by E. Metchnikoff. In +some hydroids the founder-polyp, developed from a planula after +fixation, throws out numerous outgrowths from the base to form the +hydrorhiza; these outgrowths may be radially arranged so as to form by +contact or coalescence a flat plate. Mechnikov considered the plate thus +formed at the base of the polyp as equivalent to the umbrella, and the +body of the polyp as equivalent to the manubrium, of the medusa; on this +view the marginal tentacles almost invariably present in medusae are new +formations, and the tentacles of the polyp are represented in the medusa +by the oral arms which may occur round the mouth, and which sometimes, +e.g. in _Margelidae_, have the appearance and structure of tentacles. +Apart from the weighty arguments which the development furnishes against +the theories of Allman and Mechnikov, it may be pointed out that neither +hypothesis gives a satisfactory explanation of a structure universally +present in medusae of whatever class, namely the endoderm-lamella, +discovered by the brothers O. and R. Hertwig. It would be necessary to +regard this structure as a secondary extension of the endoderm in the +tentacle-web, on Allman's theory, or between the outgrowths of the +hydrorhiza, on Mechnikov's hypothesis. The development, on the contrary, +shows unequivocally that the endoderm-lamella arises as a local +coalescence of the endodermal linings of a primitively extensive gastral +space. + +The question is one intimately connected with the view taken as to the +nature and individuality of polyp, medusa and gonophore respectively. On +this point the following theories have been put forward. + + 1. The theory that the medusa is simply an organ, which has become + detached and has acquired a certain degree of independence, like the + well-known instance of the hectocotyle of the cuttle-fish. On this + view, put forward by E. van Beneden and T. H. Huxley, the sporosac is + the starting-point of an evolution leading up through the various + types of gonophores to the free medusa as the culminating point of a + phyletic series. The evidence against this view may be classed under + two heads: first, comparative evidence; hydroids very different in + their structural characters and widely separate in the systematic + classification of these organisms may produce medusae very similar, at + least so far as the essential features of medusan organization are + concerned; on the other hydroids closely allied, perhaps almost + indistinguishable, may produce gonophores in the one case, medusae in + the other; for example, _Hydractinia_ (gonophores) and _Podocoryne_ + (medusae), _Tubularia_ (gonophores) and _Ectopleura_ (medusae), + _Coryne_ (gonophores) and _Syncoryne_ (medusae), and so on. If it is + assumed that all these genera bore gonophores ancestrally, then medusa + of similar type must have been evolved quite independently in a great + number of cases. Secondly, there is the evidence from the development, + namely, the presence of the entocodon in the medusa-bud, a structure + which, as explained above, can only be accounted for satisfactorily by + derivation from a medusan type of organization. Hence it may be + concluded that the gonophores are degenerate medusae, and not that the + medusae are highly elaborated gonophores, as the organ-theory + requires. + + 2. The theory that the medusa is an independent individual, fully + equivalent to the polyp in this respect, is now universally accepted + as being supported by all the facts of comparative morphology and + development. The question still remains open, however, which of the + two types of person may be regarded as the most primitive, the most + ancient in the race-history of the Hydromedusae. F. M. Balfour put + forward the view that the polyp was the more primitive type, and that + the medusa is a special modification of the polyp for reproductive + purposes, the result of division of labour in a polyp-colony, whereby + special reproductive persons become detached and acquire organs of + locomotion for spreading the species. W. K. Brooks, on the other hand, + as stated above, regards the medusa as the older type and looks upon + both polyp and medusa, in the Hydromedusae, as derived from a + free-swimming or floating actinula, the polyp being thus merely a + fixed nutritive stage, possessing secondarily acquired powers of + multiplication by budding. + + The Hertwigs when they discovered the endoderm-lamella showed on + morphological grounds that polyp and medusa are independent types, + each produced by modification in different directions of a more + primitive type represented in development by the actinula-stage. If a + polyp, such as _Hydra_, be regarded simply as a sessile actinula, we + must certainly consider the polyp to be the older type, and it may be + pointed out that in the Anthozoa only polyp-individuals occur. This + must not be taken to mean, however, that the medusa is derived from a + sessile polyp; it must be regarded as a direct modification of the + more ancient free actinula form, without primitively any intervening + polyp-stage, such as has been introduced secondarily into the + development of the Leptolinae and represents a revival, so to speak, + of an ancestral form or larval stage, which has taken on a special + role in the economy of the species. + + +SYSTEMATIC REVIEW OF THE HYDROMEDUSAE + +ORDER I. Eleutheroblastea.--Simple polyps which become sexually mature +and which also reproduce non-sexually, but without any medusoid stage in +the life-cycle. + +The sub-order includes the family _Hydridae_, containing the common +fresh-water polyps of the genus _Hydra_. Certain other forms of doubtful +affinities have also been referred provisionally to this section. + + _Hydra._--This genus comprises fresh-water polyps of simple structure. + The body bears tentacles, but shows no division into hydrorhiza, + hydrocaulus or hydranth; it is temporarily fixed and has no perisarc. + The polyp is usually hermaphrodite, developing both ovaries and testes + in the same individual. There is no free-swimming planula larva, but + the stage corresponding to it is passed over in an enveloping cyst, + which is secreted round the embryo by its own ectodermal layer, + shortly after the germ-layer formation is complete, i.e. in the + parenchymula-stage. The envelope is double, consisting of an external + chitinous stratified shell, and an internal thin elastic membrane. + Protected by the double envelope, the embryo is set free as a + so-called "egg," and in Europe it passes the winter in this condition. + In the spring the embryo bursts its shell and is set free as a minute + actinula which becomes a _Hydra_. + + Many species are known, of which three are common in European waters. + It has been shown by C. F. Jickeli (28) that the species are + distinguishable by the characters of their nematocysts. They also show + characteristic differences in the egg (Brauer [2]). In _Hydra viridis_ + the polyp is of a green colour and produces a spherical egg with a + smooth shell which is dropped into the mud. _H. grisea_ is greyish in + tint and produces a spherical egg with a spiky shell, which also is + dropped into the mud. _H. fusca_ (= _H. vulgaris_) is brown in colour, + and produces a bun-shaped egg, spiky on the convex surface, and + attached to a water-weed or some object by its flattened side. Brauer + found a fourth species, similar in appearance to _H. fusca_, but + differing from the three other species in being of separate sexes, and + in producing a spherical egg with a knobby shell, which is attached + like that of _H. fusca_. + + The fact already noted that the species of _Hydra_ can be + distinguished by the characters of their nematocysts is a point of + great interest. In each species, two or three kinds of nematocysts + occur, some large, some small, and for specific identification the + nematocysts must be studied collectively in each species. It is very + remarkable that this method of characterizing and diagnozing species + has never been extended to the marine hydroids. It is quite possible + that the characters of the nematocysts might afford data as useful to + the systematist in this group as do the spicules of sponges, for + instance. It would be particularly interesting to ascertain how the + nematocysts of a polyp are related to those possessed by the medusa + budded from it, and it is possible that in this manner obscure + questions of relationship might be cleared up. + + _Protohydra_ is a marine genus characterized by the absence of + tentacles, by a great similarity to _Hydra_ in histological structure, + and by reproduction by transverse fission. It was found originally in + an oyster-farm at Ostend. The sexual reproduction is unknown. For + further information see C. Chun (HYDROZOA [1]. Pl. I.). + + [Illustration: FIG. 49.--Diagram showing possible modifications of + persons of a gymnoblastic _Hydromedusa_. (After Allman.) + + a, Hydrocaulus (stem). + b, Hydrorhiza (root). + c, Enteric cavity. + d, Endoderm. + e, Ectoderm. + f, Perisarc, (horny case). + g, Hydranth (hydriform person) expanded. + g', Hydranth (hydriform person) contracted. + h, Hypostome, bearing mouth at its extremity. + k, Sporosac springing from the hydrocaulus. + k', Sporosac springing from m, a modified hydriform person + (blastostyle): the genitalia are seen surrounding the spadix or + manubrium. + l, Medusiform person or medusa. + m, Blastostyle.] + + _Polypodium hydriforme_ Ussow is a fresh-water form parasitic on the + eggs of the sterlet. A "stolon" of unknown origin produces thirty-two + buds, which become as many _Polypodia_; each has twenty-four tentacles + and divides by fission repeated twice into four individuals, each with + six tentacles. The daughter-individuals grow, form the full number of + twenty-four tentacles and divide again. The polyps are free and walk + on their tentacles. See Ussow [54]. + + _Tetraplatia volitans_ Viguier is a remarkable floating marine form. + See C. Viguier [56] and Delage and Hérouard (Hydrozoa [2]). + + _Haleremita_ Schaudinn. See F. Schaudinn [50] and Delage and Hérouard + (HYDROZOA [2]). + + In all the above-mentioned genera, with the exception of _Hydra_, the + life-cycle is so imperfectly known that their true position cannot be + determined in the present state of our knowledge. They may prove + eventually to belong to other orders. Hence only the genus _Hydra_ can + be considered as truly representing the order Eleutheroblastea. The + phylogenetic position of this genus has been discussed above. + +ORDER II. Hydroidea seu Leptolinae.--Hydromedusae with alternation of +generations (metagenesis) in which a non-sexual polyp-generation +(trophosome) produces by budding a sexual medusa-generation (gonosome). +The polyp may be solitary, but more usually produces polyps by budding +and forms a polyp-colony. The polyp usually has the body distinctly +divisible into hydranth, hydrocaulus and hydrorhiza, and is usually +clothed in a perisarc. The medusae may be set free or may remain +attached to the polyp-colony and degenerate into a gonophore. When fully +developed the medusa is characterized by the sense organs being composed +entirely of ectoderm, developed independently of the tentacles, and +innervated from the sub-umbral nerve-ring. + + The two kinds of persons present in the typical Hydroidea make the + classification of the group extremely difficult, for reasons explained + above. Hence the systematic arrangement that follows must be + considered purely provisional. A natural classification of the + Hydroidea has yet to be put forward. Many genera and families are + separated by purely artificial characters, mere shelf-and-bottle + groupings devised, for the convenience of the museum curator and the + collector. Thus many subdivisions are diagnosed by setting free + medusae in one case, or producing gonophores in another, although it + is very obvious, as pointed out above, that a genus producing medusae + may be far more closely allied to one producing gonophores than to + another producing medusae, or vice versa, and that in some cases the + production of medusae or gonophores varies with the season or the sex. + Moreover, P. Hallez [22] has recently shown that hydroids hitherto + regarded as distinct species are only forms of the same species grown + under different conditions. + +SUB-ORDER 1. HYDROIDEA GYMNOBLASTEA (ANTHOMEDUSAE).--Trophosome without +hydrothecae or gonothecae, with monopodial type of budding. Gonosome +with free medusae or gonophores; medusae usually with ocelli, never with +otocysts. The gymnoblastic polyp usually has a distinct perisarc +investing the hydrorhiza and the hydrocaulus, sometimes also the +hydranth as far as the bases of the tentacles (_Bimeria_); but in such +cases the perisarc forms a closely-fitting investment or cuticule on the +hydranth, never a hydrotheca standing off from it, as in the next +sub-order. The polyps may be solitary, or form colonies, which may be of +the spreading or encrusting type, or arborescent, and then always of +monopodial growth and budding. In some cases, any polyp of the colony +may bud medusae; in other cases, only certain polyps, the blastostyles, +have this power. When blastostyles are present, however, they are never +enclosed in special gonothecae as in the next sub-order. In this +sub-order the characters of the hydranth are very variable, probably +owing to the fact that it is exposed and not protected by a hydrotheca, +as in Calyptoblastea. + +[Illustration: FIG. 50.--_Sarsia (Dipurena) gemnifera._ b, The long +manubrium, bearing medusiform buds; a, mouth.] + +[Illustration: FIG. 51.--_Sarsia prolifera._ Ocelli are seen at the base +of the tentacles, and also (as an exception) groups of medusiform buds.] + + Speaking generally, three principal types of hydranth can be + distinguished, each with subordinate varieties of form. + + 1. Club-shaped hydranths with numerous tentacles, generally scattered + irregularly, sometimes with a spiral arrangement, or in whorls + ("verticillate"). + + (a) Tentacles filiform; type of _Clava_ (fig. 5), _Cordylophora_, + &c. + + (b) Tentacles capitate, simple; type of _Coryne_ and _Syncoryne_; + _Myriothela_ is an aberrant form with some of the tentacles modified + as "claspers" to hold the ova. + + (c) Tentacles capitate, branched, wholly or in part; type of + _Cladocoryne_. + + (d) Tentacles filiform or capitate, tending to be arranged in + definite whorls; type of _Stauridium_ (fig. 2), _Cladonema_ and + _Pennaria_. + + 2. Hydranth more shortened, daisy-like in form, with two whorls of + tentacles, oral and aboral. + + (a) Tentacles filiform, simple, radially arranged or scattered + irregularly; type of _Tubularia_ (fig. 4), _Corymorpha_ (fig. 3), + _Nemopsis_, _Pelagohydra_, &c. + + (b) Tentacles with a bilateral arrangement, branched tentacles in + addition to simple filiform ones; type of _Branchiocerianthus_. + + 3. Hydranth with a single circlet of tentacles. + + (a) With filiform tentacles; the commonest type, seen in + _Bougainvillea_ (fig. 13), _Eudendrium_, &c. + + (b) With capitate tentacles; type of _Clavatella_. + + 4. Hydranth with tentacles reduced below four; type of _Lar_ (fig. + 11), _Monobrachium_, &c. + +The _Anthomedusa_ in form is generally deep, bell-shaped. The sense +organs are typically ocelli, never otocysts. The gonads are borne on the +manubrium, either forming a continuous ring (Codonid type), or four +masses or pairs of masses (Oceanid type). The tentacles may be scattered +singly round the margin of the umbrella ("monerenematous") or arranged +in tufts ("lophonematous"); in form they may be simple or branched +(Cladonemid type); in structure they may be hollow ("coelomerinthous"); +or solid ("pycnomerinthous"). When sessile gonophores are produced, they +may show all stages of degeneration. + + _Classification._--Until quite recently the hydroids (Gymnoblastea) + and the medusae (Anthomedusae) have been classified separately, since + the connexion between them was insufficiently known. Delage and + Hérouard (HYDROZOA [2]) were the first to make an heroic attempt to + unite the two classifications into one, to which Hickson (HYDROZOA + [4]) has made some additions and slight modifications. The + classification given here is for the most part that of Delage and + Hérouard. It is certain, however, that no such classification can be + considered final at present, but must undergo continual revision in + the future. With this reservation we may recognize fifteen + well-characterized families and others of more doubtful nature. + Certain discrepancies must also be noted. + + 1. _Margelidae_ (= medusa-family _Margelidae_ + hydroid families + _Bougainvillidae_, _Dicorynidae_, _Bimeridae_ and _Eudendridae_). + Trophosome arborescent, with hydranths of _Bougainvillea_-type; + gonosome free medusae or gonophores, the medusae with solid tentacles + in tufts (lophonematous). Common genera are the hydroid + _Bougainvillea_ (figs. 12, 13), and the medusae _Hippocrene_ (budded + from _Bougainvillea_), _Margelis_, _Rathkea_ (fig. 24), and + _Margellium_. Other hydroids are _Garveia_, _Bimeria_, _Eudendrium_ + and _Heterocordyle_, with gonophores, and _Dicoryne_ with peculiar + sporosacs. + + [Illustration: After Haeckel, _System der Medusen_, by permission of + Gustav Fischer. + + FIG. 52.--_Tiara pileata_, L. Agassiz.] + + 2. _Podocorynidae_ (= medusa-families _Thamnostomidae_ and _Cytaeidae_ + + hydroid families _Podocorynidae_ and _Hydractiniidae_). Trophosome + encrusting with hydranths of _Bougainvillea_-type, polyps + differentiated into blastostyles, gastrozoids and dactylozoids; + gonosome free medusae or gonophores. The typical genus is the + well-known hydroid _Podocoryne_, budding the medusa known as + _Dysmorphosa_; _Thamnostylus_, _Cytaeis_, &c., are other medusae with + unknown hydroids. _Hydractinia_ (figs. 9, 10) is a familiar hydroid + genus, bearing gonophores. + + 3. _Cladonemidae_.--Trophosome, polyps with two whorls of tentacles, + the lower filiform, the upper capitate; gonosome, free medusae, with + tentacles solid and branched. The type-genus _Cladonema_ (fig. 20) is + a common British form. + + 4. _Clavatellidae._--Trophosome, polyps with a single whorl of + capitate tentacles; gonosome, free medusae, with tentacles branched, + solid. _Clavatella_ (fig. 21), with a peculiar ambulatory medusa is a + British form. + + 5. _Pennariidae_.--Trophosome, polyps with an upper circlet of + numerous capitate tentacles, and a lower circlet of filiform + tentacles. _Pennaria_, with a free medusa known as _Globiceps_, is a + common Mediterranean form. _Stauridium_ (fig. 2) is a British hydroid. + + 6. _Tubulariidae._--Trophosome, polyps with two whorls of tentacles, + both filiform. _Tubularia_ (fig. 4), a well-known British hydroid, + bears gonophores. + + 7. _Corymorphidae_ (including the medusa-family + _Hybocodonidae_).--Trophosome solitary polyps, with two whorls of + tentacles; gonosome, free medusae or gonophores. _Corymorpha_ (fig. + 3), a well-known British genus, sets free a medusa known as + _Steenstrupia_ (fig. 22). Here belong the deep-sea genera _Monocaulus_ + and _Branchiocerianthus_, including the largest hydroid polyps known, + both genera producing sessile gonophores. + + [Illustration: After Haeckel, _System der Medusen_, by permission of + Gustav Fischer. + + FIG. 53.--_Pteronema darwinii_. The apex of the stomach is prolonged + into a brood pouch containing embryos.] + + 8. _Dendroclavidae._--Trophosome, polyp with filiform tentacles in + three or four whorls. _Dendroclava_, a hydroid, produces the medusa + known as _Turritopsis_. + + 9. _Clavidae_ (including the medusa-family _Tiaridae_ (figs. 27 and + 51). Trophosome, polyps with scattered filiform tentacles; gonosome, + medusae or gonophores, the medusae with hollow tentacles. _Clava_ + (fig. 5), a common British hydroid, produces gonophores; so also does + _Cordylophora_, a form inhabiting fresh or brackish water. _Turris_ + produces free medusae. _Amphinema_ is a medusan genus of unknown + hydroid. + + 10. _Bythotiaridae._--Trophosome unknown; gonosome, free medusae, with + deep, bell-shaped umbrella, with interradial gonads on the base of the + stomach, with branched radial canals, and correspondingly numerous + hollow tentacles. _Bythotiara_, _Sibogita_. + + 11. _Corynidae_ (= hydroid families _Corynidae_, _Syncorynidae_ and + _Cladocorynidae_ + medusan family _Sarsiidae_).--Trophosome polyps + with capitate tentacles, simple or branched, scattered or + verticillate; gonosome, free medusae or gonophores. _Coryne_, a common + British hydroid, produces gonophores; _Syncoryne_, indistinguishable + from it, produces medusae known as _Sarsia_ (fig. 51). _Cladocoryne_ + is another hydroid genus; _Codonium_ and _Dipurena_ (fig. 50) are + medusan genera. + + 12. _Myriothelidae._--The genus _Myriothela_ is a solitary polyp with + scattered capitate tentacles, producing sporosacs. + + 13. _Hydrolaridae._--Trophosome (only known in one genus), polyps with + two tentacles forming a creeping colony; gonosome, free medusae with + four, six or more radial canals, giving off one or more lateral + branches which run to the margin of the umbrella, with the stomach + produced into four, six or more lobes, upon which the gonads are + developed; the mouth with four lips or with a folded margin; the + tentacles simple, arranged evenly round the margin of the umbrella. + The remarkable hydroid _Lar_ (fig. 11) grows upon the tubes of the + worm _Sabella_ and produces a medusa known as _Willia_. Another + medusan genus is _Proboscidactyla_. + + 14. _Monobrachiidae._--The genus _Monobrachium_ is a colony-forming + hydroid which grows upon the shells of bivalve molluscs, each polyp + having but a single tentacle. It buds medusae, which, however, are as + yet only known in an immature condition (C. Mereschkowsky [41]). + + 15. _Ceratellidae._--Trophosome polyps forming branching colonies of + which the stem and main branches are thick and composed of a network + of anastomosing coenosarcal tubes covered by a common ectoderm and + supported by a thick chitinous perisarc; hydranths similar to those of + _Coryne_; gonosome, sessile gonophores. _Ceratella_, an exotic genus + from the coast of East Africa, New South Wales and Japan. The genera + _Dehitella_ Gray and _Dendrocoryne_ Inaba should perhaps be referred + to this family; the last-named is regarded by S. Goto [16] as the type + of a distinct family, _Dendrocorynidae_. + + Doubtful families, or forms difficult to classify, are: Pteronemidae, + Medusae of Cladonemid type, with hydroids for the most part unknown. + The British genus _Gemmaria_, however, is budded from a hydroid + referable to the family _Corynidae_. _Pteronema_ (fig. 53). + + _Nemopsidae_, for the floating polyp _Nemopsis_, very similar to + _Tubularia_ in character; the medusa, on the other hand, is very + similar to _Hippocrene_ (_Margelidae_). See C. Chun (HYDROZOA [1]). + + _Pelagohydridae_, for the floating polyp _Pelagohydra_, Dendy, from + New Zealand. The animal is a solitary polyp bearing a great number of + medusa-buds. The body, representing the hydranth of an ordinary + hydroid, has the aboral portion modified into a float, from which + hangs down a proboscis bearing the mouth. The float is covered with + long tentacles and bears the medusa-buds. The proboscis bears at its + extremity a circlet of smaller oral tentacles. Thus the affinities of + the hydranth are clearly, as Dendy points out, with a form such as + _Corymorpha_, which also is not fixed but only rooted in the mud. The + medusae, on the other hand, have the tentacles in four tufts of (in + the buds) five each, and thus resemble the medusae of the family + _Margelidae_. See A. Dendy [12]. + + [Illustration: _Fig. 54._--Diagram showing possible modifications of + the persons of a Calyptoblastic Hydromedusa. Letters a to h same as in + fig. 49. i, The horny cup or hydrotheca of the hydriform persons; l, + medusiform person springing from m, a modified, hydriform person + (blastostyle); n, the horny case or gonangium enclosing the + blastostyle and its buds. This and the hydrotheca i give origin to the + name _Calyptoblastea_. (After Allman.)] + + _Perigonimus._--This common British hydroid belongs by its characters + to the family _Bougainvillidae_; it produces, however, a medusa of the + genus _Tiara_ (fig. 52), referable to the family _Clavidae_; a fact + sufficient to indicate the tentative character of even the most modern + classifications of this order. + +SUB-ORDER II. HYDROIDEA CALYPTOBLASTEA (LEPTOMEDUSAE).--Trophosome with +polyps always differentiated into nutritive and reproductive individuals +(blastostyles) enclosed in hydrothecae and gonothecae respectively; with +sympodial type of budding. Gonosome with free medusae or gonophores; the +medusae typically with otocysts, sometimes with cordyli or ocelli (figs. +54, 55). + +[Illustration: FIG. 55.--View of the Oral Surface of one of the +_Leptomedusae_ (_Irene pellucida_, Haeckel), to show the numerous +tentacles and the otocysts. + + ge, Genital glands. + M, Manubrium. + ot, Otocysts. + rc, The four radiating canals. + Ve, The velum.] + +The calyptoblastic polyp of the nutritive type is very uniform in +character, its tendency to variation being limited, as it were, by the +enclosing hydrotheca. The hydranth almost always has a single circlet of +tentacles, like the _Bougainvillea_-type, in the preceding sub-order; an +exception is the curious genus _Clathrozoon_, in which the hydranth has +a single tentacle. The characteristic hydrotheca is formed by the bud at +an early stage (fig. 56); when complete it is an open cup, in which the +hydranth develops and can be protruded from the opening for the capture +of food, or is withdrawn into it for protection. Solitary polyps are +unknown in this sub-order; the colony may be creeping or arborescent in +form; if the latter, the budding of the polyps, as already stated, is of +the sympodial type, and either biserial, forming stems capable of +further branching, or uniserial, forming pinnules not capable of further +branching. In the biserial type the polyps on the two sides of the stem +have primitively an alternating, zigzag arrangement; but, by a process +of differential growth, quickened in the 1st, 3rd, 5th, &c., members of +the stem, and retarded in the 2nd, 4th, 6th, &c., members, the polyps +may assume secondarily positions opposite to one another on the two +sides of the stem. Other variations in the mode of growth or budding +bring about further differences in the building up of the colony, which +are not in all cases properly understood and cannot be described in +detail here. The stem may contain a single coenosarcal tube +("monosiphonic") or several united in a common perisarc +("polysiphonic"). An important variation is seen, in the form of the +hydrotheca itself, which may come off from the main stem by a stalk, as +in _Obelia_, or may be sessile, without a stalk, as in _Sertularia_. + +[Illustration: After Allman, _Gymnoblastic Hydroids_, by permission of +the council of the Ray Society. + +FIG. 56.--Diagrams to show the mode of formation of the Hydrotheca and +Gonotheca in Calyptoblastic Hydroids. A-D are stages common to both; +from D arises the hydrotheca (E) or the gonotheca (F); th, theca; st, +stomach; t, tentacles; m, mouth; mb, medusa-buds.] + +In many Calyptoblastea there occur also reduced defensive polyps or +dactylozoids, which in this sub-order have received the special name of +_sarcostyles_. Such are the "snake-like zoids" of _Ophiodes_ and other +genera, and as such are generally interpreted the "machopolyps" of the +_Plumularidea_. These organs are supported by cuplike structures of the +perisarc, termed nematophores, regarded as modified hydrothecae +supporting the specialized polyp-individuals. They are specially +characteristic of the family _Plumularidae_. + +The medusa-buds, as already stated, are always produced from +blastostyles, reduced non-nutritive polyps without mouth or tentacles. +An apparent, but not real, exception is _Halecium halecinum_, in which +the blastostyle is produced from the side of a nutritive polyp, and both +are enclosed in a common theca without a partition between them (Allman +[1] p. 50, fig. 24). The gonotheca is formed in its early stage in the +same way as the hydrotheca, but the remains of the hydranth persists as +an operculum closing the capsule, to be withdrawn when the medusae or +genital products are set free (fig. 56). + + The blastostyles, gonophores and gonothecae furnish a series of + variations which can best be considered as so many stages of + evolution. + + Stage 1, seen in _Obelia_. Numerous medusae are budded successively + within the gonotheca and set free; they swim off and mature in the + open sea (Allman [1], p. 48, figs. 18, 19). + + Stage 2, seen in _Gonothyraea_. Medusae, so-called "meconidia," are + budded but not liberated; each in turn, when it reaches sexual + maturity, is protruded from the gonotheca by elongation of the stalk, + and sets free the embryos, after which it withers and is replaced by + another (Allman [1], p. 57, fig. 28). + + Stage 3, seen in _Sertularia_.--The gonophores are reduced in varying + degree, it may be to sporosacs; they are budded successively from the + blastostyle, and each in turn, when ripe, protrudes the spadix through + the gonotheca (fig. 57, A, B). The spadix forms a gelatinous cyst, the + so-called acrocyst (ac), external to the gonotheca (gth), enclosing + and protecting the embryos. Then the spadix withers, leaving the + embryos in the acrocyst, which may be further protected by a so-called + marsupium, a structure formed by tentacle-like processes growing out + from the blastostyle to enclose the acrocyst, each such process being + covered by perisarc like a glove-finger secreted by it (fig. 57, C). + (Allman [1], pp. 50, 51, figs. 21-24; Weismann [58], p. 170, pl. ix., + figs. 7, 8.) + + Stage 4, seen in _Plumularidae_.--The generative elements are produced + in structures termed corbulae, formed by reduction and modification of + branches of the colony. Each corbula contains a central row of + blastostyles enclosed and protected by lateral rows of branches + representing stunted buds (Allman [1], p. 66, fig. 30). + +[Illustration: After Allman, _Gymnoblastic Hydroids_, by permission of +the council of the Ray Society. + +Fig. 57.--Diagrams to show the mode of formation of an Acrocyst and a +Marsupium. In A two medusa-buds are seen within the gonotheca (gth), the +upper more advanced than the lower one. In B the spadix of the upper bud +has protruded itself through the top of the gonotheca and the acrocyst +(ac) is secreted round it. In C the marsupium (m) is formed as +finger-like process from the summit of the blastostyle, enclosing the +acrocyst; b, medusa-buds on the blastostyle.] + +The _Leptomedusa_ in form is generally shallow, more or less +saucer-like, with velum less developed than in Anthomedusae (fig. 55). +The characteristic sense-organs are ectodermal otocysts, absent, +however, in some genera, in which case cordyli may replace them. When +otocysts are present, they are at least eight in number, situated +adradially, but are often very numerous. The cordyli are scattered on +the ring-canal. Ocelli, if present, are borne on the tentacle-bulbs. The +tentacles are usually hollow, rarely solid (_Obelia_). In number they +are rarely less than four, but in _Dissonema_ there are only two. +Primitively there are four perradial tentacles, to which may be added +four interradial, or they may become very numerous and are then +scattered evenly round the margin, never arranged in tufts or clusters. +In addition to tentacles, there may be marginal cirri (_Laodice_) with a +solid endodermal axis, spirally coiled, very contractile, and bearing a +terminal battery of nematocysts. The gonads are developed typically +beneath the radial canals or below the stomach or its pouches, often +stretching as long bands on to the base of the manubrium. In +_Octorchidae_ (fig. 58) each such band is interrupted, forming one mass +at the base of the manubrium and another below the radial canal in each +radius, in all eight separate gonad-masses, as the name implies. In some +Leptomedusae excretory "marginal tubercles" are developed on the +ring-canal. + + _Classification._---As in the Gymnoblastea, the difficulty of uniting + the hydroid and medusan systems into one scheme of classification is + very great in the present state of our knowledge. In a great many + Leptomedusae the hydroid stage is as yet unknown, and it is by no + means certain even that they possess one. It is quite possible that + some of these medusae will be found to be truly hypogenetic, that is + to say, with a life-cycle secondarily simplified by suppression of + metagenesis. At present, ten recent and one extinct family of + Calyptoblastea (Leptomedusae) may be recognized provisionally: + + 1. _Eucopidae_ (figs. 55, 59).--Trophosome with stalked hydrothecae; + gonosome, free medusae with otocysts and four, rarely six or eight, + unbranched radial canals. Two of the commonest British hydroids belong + to this family, _Obelia_ and _Clytia_. _Obelia_ forms numerous + polyserial stems of the characteristic zigzag pattern growing up from + a creeping basal stolon, and buds the medusa of the same name. In + _Clytia_ the polyps arise singly from the stolon, and the medusa is + known as _Phialidium_ (fig. 59). + + 2. _Aequoridae._--Trophosome only known in one genus (_Polycanna_), + and similar to the preceding; gonosome, free medusae with otocysts and + with at least eight radial canals, often a hundred or more, simple or + branched. _Aequorea_ is a common medusa. + + 3. _Thaumantidae._--Trophosome only known in one genus + (_Thaumantias_), similar to that of the _Eucopidae_; gonosome, free + medusae with otocysts inconspicuous or absent, with usually four, + sometimes eight, rarely more than eight, radial canals, simple and + unbranched, along which the gonads are developed, with numerous + tentacles bearing ocelli and with marginal sense-clubs. _Laodice_ and + _Thaumantias_ are representative genera. + + 4. _Berenicidae._--Trophosome unknown; gonosome, free medusae, with + four or six radial canals, bearing the gonads, with numerous + tentacles, between which occur sense-clubs, without otocysts. + _Berenice_, _Staurodiscus_, &c. + + [Illustration: After Haeckel, _System der Medusen_, by permission of + Gustav Fischer. + + FIG. 58.--_Octorchandra canariensis_, from life.] + + 5. _Polyorchidae._--Trophosome unknown; gonosome, free medusae of deep + form, with radial canals branched in a feathery manner, and bearing + gonads on the main canal, but not on the branches, with numerous + hollow tentacles bearing ocelli, and without otocysts. _Polyorchis_, + _Spirocodon_. + + 6. _Campanularidae.-_-Trophosome as in _Eucopidae_; gonosome, sessile + gonophores. Many common or well-known genera belong here, such as + _Halecium_, _Campanularia_, _Gonothyraea_, &c. + + 7. _Lafoëidae._--Trophosome as in the preceding; gonosome, free + medusae or gonophores, the medusae with large open otocysts. The + hydroid genus _Lafoëa_ is remarkable for producing gonothecae on the + hydrorhiza, each containing a blastostyle which bears a single + gonophore; this portion of the colony was formerly regarded as an + independent parasitic hydroid, and was named _Coppinia_. Medusan + genera are _Mitrocoma_, _Halopsis_, _Tiaropsis_ (fig. 29, &c.). + + (So far as the characters of the trophosome are concerned, the seven + preceding families are scarcely distinguishable, and they form a + section apart, contrasting sharply with the families next to be + mentioned, in none of which are free medusae liberated from the + colony, so that only the characters of the trophosome need be + considered.) + + [Illustration: After E. T. Browne, _Proc. Zool. Soc. of London_, 1896. + + FIG. 59.--Three stages in the development of _Phialidium temporarium_. + a, The youngest stage, is magnified about 22 diam.; b, older, is + magnified about 8 diam.; c, the adult medusa, is magnified.] + + 8. _Sertularidae._--Hydrothecae sessile, biserial, alternating or + opposite on the stem. _Sertularia_ and _Sertularella_ are two very + common genera of this family. + + 9. _Plumularidae._--Hydrothecae sessile, biserial on the main stem, + uniserial on the lateral branches or pinnules, which give the colony + its characteristic feathery form; with nematophores. A very abundant + and prolific family; well-known British genera are _Plumularia_, + _Antennularia_ and _Aglaophenia_. + + 10. _Hydroceratinidae_.--This family contains the single Australian + species _Clathrozoon wilsoni_ Spencer, in which a massive hydrorhiza + bears sessile hydrothecae, containing hydranths each with a single + tentacle, and numerous nematophores. See W. B. Spencer [53]. + + 11. _Dendrograptidae_, containing fossil (Silurian) genera, such as + _Dendrograptus_ and _Thamnograptus_, of doubtful affinities. + +[Illustration: FIG. 60.--Portion of the calcareous corallum of +_Millepora nodosa_, showing the cyclical arrangement of the pores +occupied by the "persons" or hydranths. About twice the natural size. +(From Moseley.)] + +ORDER III. Hydrocorallinae.--Metagenetic colony-forming Hydromedusae, in +which the polyp-colony forms a massive, calcareous _corallum_ into which +the polyps can be retracted; polyp-individuals always of two kinds, +gastrozoids and dactylozoids; gonosome either free medusae or sessile +gonophores. The trophosome consists of a mass of coenosarcal tubes +anastomosing in all planes. The interspaces between the tubes are filled +up by a solid mass of lime, consisting chiefly of calcium carbonate, +which replaces the chitinous perisarc of ordinary hydroids and forms a +stony corallum or _coenosteum_ (fig. 60). The surface of the coenosteum +is covered by a layer of common ectoderm, containing large nematocysts, +and is perforated by pores of two kinds, gastropores and dactylopores, +giving exit to gastrozoids and dactylozoids respectively, which are +lodged in vertical pore-canals of wider calibre than the coenosarcal +canals of the general network. The coenosteum increases in size by new +growth at the surface; and in the deeper, older portions of massive +forms the tissues die off after a certain time, only the superficial +region retaining its vitality down to a certain depth. The living +tissues at the surface are cut off from the underlying dead portions by +horizontal partitions termed _tabulae_, which are formed successively as +the coenosteum increases in age and size. If the coenosteum of +_Millepora_ be broken across, each pore-canal (perhaps better termed a +polyp-canal) is seen to be interrupted by a series of transverse +partitions, representing successive periods of growth with separation +from the underlying dead portions. + +[Illustration: FIG. 61.--Enlarged view of the surface of a living +_Millepora_, showing five dactylozooids surrounding a central +gastrozooid. (From Moseley.)] + +Besides the wider vertical pore-canals and the narrower, irregular +coenosarcal canals, the coenosteum may contain, in its superficial +portion, chambers or _ampullae_, in which the reproductive zoids +(medusae or gonophores) are budded from the coenosarc. + +The gastropores and dactylopores are arranged in various ways at the +surface, a common pattern being the formation of a cyclosystem (fig. +60), in which a central gastrozoid is surrounded by a ring of +dactylozoids (fig. 61). In such a system the dactylopores may be +confluent with the gastropore, so that the entire cyclosystem presents +itself as a single aperture subdivided by radiating partitions, thus +having a superficial resemblance to a madreporarian coral with its +radiating septa (figs. 62 and 63). + +[Illustration: FIG. 62.--Diagrams illustrating the successive stages in +the development of the cyclosystems of the _Stylasteridae_. (After +Moseley.) + + 1, _Sporadopora dichotoma_. + 2, 3, _Allopora nobilis_. + 4, _Allopora profunda_. + 5, _Allopora miniacea_. + 6, _Astylus subviridis_. + 7, _Distichopora coccinea_. + s, Style. + dp, Dactylopore. + gp, Gastropore. + b, In fig. 6, inner horseshoe-shaped mouth of gastropore.] + +The gastrozoids usually bear short capitate tentacles, four, six or +twelve in number; but in _Astylus_ (fig. 63) they have no tentacles. The +dactylozoids have no mouth; in _Milleporidae_ they have short capitate +tentacles, but lack tentacles in _Stylasteridae_. + +The gonosome consists of free medusae in _Milleporidae_, which are +budded from the apex of a dactylozoid in _Millepora murrayi_, but in +other species from the coenosarcal canals. The medusae are produced by +direct budding, without an entocodon in the bud. They are liberated in a +mature condition, and probably live but a short time, merely sufficient +to spread the species. The manubrium bearing the gonads is mouthless, +and the umbrella is without tentacles, sense-organs, velum or radial +canals. In the _Stylasteridae_ sessile gonophores are formed, always by +budding from the coenosarc. In _Distichopora_ the gonophores have radial +canals, but in other genera they are sporosacs with no trace of medusoid +structure. + +[Illustration: FIG. 63.--Portion of the corallum of _Astylus subviridis_ +(one of the Stylasteridae), showing cyclosystems placed at intervals on +the branches, each with a central gastropore and zone of slit-like +dactylopores. (After Moseley.)] + + _Classification._---Two families are known:-- + + 1. _Milleporidae._--Coenosteum massive, irregular in form; pores + scattered irregularly or in cyclosystems, without styles, with + transverse tabulae; free medusae. A single genus, _Millepora_ (figs. + 60, 61). + + 2. _Stylasteridae._--Coenosteum arborescent, sometimes fanlike, with + pores only on one face, or on the lateral margins of the branches; + gastropores with tabulae only in two genera, but with (except in + _Astylus_) a _style_, i.e. a conical, thorn-like projection from the + base of the pore, sometimes found also in dactylopores; sessile + gonophores. _Sporadopora_ has the pores scattered irregularly. + _Distichopora_ has the pores arranged in rows. _Stylaster_ has + cyclosystems. In _Allopora_ the cyclostems resemble the calyces of + Anthozoan corals. In _Cryptohelia_ the cyclosystem is covered by a cap + or operculum. In _Astylus_ (fig. 63) styles are absent. + + _Affinities of the Hydrocorallinae._--There can be no doubt that the + forms comprised in this order bear a close relationship to the + Hydroidea, especially the sub-order Gymnoblastea, with which they + should perhaps be classed in a natural classification. A + hydrocoralline may be regarded as a form of hydroid colony in which + the coenosarc forms a felt-work ramifying in all planes, and in which + the chitinous perisarc is replaced by a massive calcareous skeleton. + So far as the trophosome is concerned, the step from an encrusting + hydroid such as _Hydractinia_ to the hydrocoralline _Millepora_ is not + great. + + Hickson considers that the families _Milleporidae_ and _Stylasteridae_ + should stand quite apart from one another and should not be united in + one order. The nearest approach to the _Stylasteridae_ is perhaps to + be found in _Ceratella_, with its arborescent trophosome formed of + anastomosing coenosarcal tubes supported by a thick perisarc and + covered by a common ectoderm. _Ceratella_ stands in much the same + relation to the _Stylasteridae_ that _Hydractinia_ does to the + _Milleporidae_, in both cases the chitinous perisarc being replaced by + the solid coenosteum to which the hydrocorallines owe the second half + of their name. + +ORDER IV. Graptolitoidea (Rhabdophora, Allman).--This order has been +constituted for a peculiar group of palaeozoic fossils, which have been +interpreted as the remains of the skeletons of Hydrozoa of an extinct +type. + +A typical graptolite consists of an axis bearing a series of tooth-like +projections, like a saw. Each such projection is regarded as +representing a cup or hydrotheca, similar to those borne by a +calyptoblastic hydroid, such as _Sertularia_. The supposed hydrothecae +may be present on one side of the axis only (monoprionid) or on both +sides (diprionid); the first case may be conjectured to be the result of +uniserial (helicoid) budding, the second to be produced by biserial +(scorpioid) budding. In one division (_Retiolitidae_) the axis is +reticulate. In addition to the stems bearing cups, there are found +vesicles associated with them, which have been interpreted as gonothecae +or as floats, that is to say, air-bladders, acting as hydrostatic organs +for a floating polyp-colony. + +Since no graptolites are known living, or, indeed, since palaeozoic +times, the interpretation of their structure and affinities must of +necessity be extremely conjectural, and it is by no means certain that +they are Hydrozoa at all. It can only be said that their organization, +so far as the state of their preservation permits it to be ascertained, +offers closer analogies with the Hydrozoa, especially the +Calyptoblastea, than with any other existing group of the animal +kingdom. + + See the treatise of Delage and Hérouard (HYDROZOA, [4]), and the + article GRAPTOLITES. + +ORDER V. Trachylinea.--Hydromedusae without alternation of generations, +i.e. without a hydroid phase; the medusa develops directly from the +actinula larva, which may, however, multiply by budding. Medusae with +sense-organs represented by otocysts derived from modified tentacles +(tentaculocysts), containing otoliths of endodermal origin, and +innervated from the ex-umbral nerve-ring. + +This order, containing the typical oceanic medusae, is divided into two +sub-orders. + +SUB-ORDER 1. TRACHOMEDUSAE.--Tentacles given off from the margin of the +umbrella, which is entire, i.e. not lobed or indented; tentaculocysts +usually enclosed in vesicles; gonads on the radial canals. The medusae +of this order are characterized by the tough, rigid consistence of the +umbrella, due partly to the dense nature of the mesogloea, partly to the +presence of a marginal rim of chondral tissue, consisting of thickened +ectoderm containing great numbers of nematocysts, and forming, as it +were, a cushion-tyre supporting the edge of the umbrella. Prolongations +from the rim of chondral tissue may form clasps or _peronia_ supporting +the tentacles. The tentacles are primarily four in number, perradial, +alternating with four interradial tentaculocysts, but both tentacles and +sense-organs may be multiplied and the primary perradii may be six +instead of four (fig. 26). The tentacles are always solid, containing an +axis of endoderm-cells resembling notochordal tissue or +plant-parenchyma, and are but moderately flexible. The sense-organs are +tentaculocysts which are usually enclosed in vesicles and may be sunk +far below the surface. The gonads are on the radial canals or on the +stomach (_Ptychogastridae_), and each gonad may be divided into two by a +longitudinal sub-umbral muscle-tract. The radial canals are four, six, +eight or more, and in some genera blindly-ending centripetal canals are +present (fig. 26). The stomach may be drawn out into the manubrium, +forming a proboscis ("Magenstiel") of considerable length. + +The development of the Trachomedusae, so far as it is known, shows an +actinula-stage which is either free (larval) or passed over in the egg +(foetal) as in _Geryonia_; in no case does there appear to be a free +planula-stage. The actinula, when free, may multiply by larval budding, +but in all cases both the original actinula and all its descendants +become converted into medusae, so that there is no alternation of +generations. In _Gonionemus_ the actinula becomes attached and +polyp-like and reproduces by budding. + +[Illustration: After Haeckel, _System der Medusen_, by permission of +Gustav Fischer. + +FIG. 64. _Olindias mülleri._] + + The Trachomedusae are divided into the following families: + + 1. _Petasidae_ (_Petachnidae_).--Four radial canals, four gonads; + stomach not prolonged into the manubrium, which is relatively short; + tentaculocysts free. _Petasus_ and other genera make up this family, + founded by Haeckel, but no other naturalist has ever seen them, and it + is probable that they are simply immature forms of other genera. + + 2. _Olindiadae_, with four radial canals and four gonads; manubrium + short; ring-canals giving off blind centripetal canals; tentaculocysts + enclosed. _Olindias mülleri_ (fig. 64) is a common Mediterranean + species. Other genera are _Aglauropsis_, _Gossea_ and _Gonionemus_; + the last named bears adhesive suckers on the tentacles. Some doubt + attaches to the position of this family. It has been asserted that the + tentaculocysts are entirely ectodermal and that either the family + should be placed amongst the Leptomedusae, or should form, together + with certain Leptomedusae, an entirely distinct order. In + _Gonionemus_, however, the concrement-cells are endodermal. + + 3. _Trachynemidae._--Eight radial canals, eight gonads, stomach not + prolonged into manubrium; tentaculocysts enclosed. _Rhopalonema_, + _Trachynema_, &c. + + [Illustration: After E. T. Browne, _Proc. Zool. Soc. of London_. + + FIG. 65.--_Aglantha rosea_ (Forbes), a British medusa.] + + 4. _Ptychogastridae_ (_Pectyllidae_).--As in the preceding, but with + suckers on the tentacles. _Ptychogastria_ Allman (=_Pectyllis_), a + deep-sea form. + + 5. _Aglauridae._--Eight radial canals, two, four or eight gonads; + tentacles numerous; tentaculocysts free; stomach prolonged into + manubrium. _Aglaura_, _Aglantha_ (fig. 65), &c., with eight gonads; + _Stauraglaura_ with four; _Persa_ with two. _Amphogona_, + hermaphrodite, with male and female gonads on alternating radial + canals. + + 6. _Geryonidae._--Four or six radial canals; gonads band-like; stomach + prolonged into a manubrium of great length; tentaculocysts enclosed. + _Liriope_, &c., with four radial canals; _Geryonia_, _Carmarina_ (fig. + 26), &c., with six. + + 7. _Halicreidae._--Eight very broad radial canals; ex-umbrella often + provided with lateral outgrowths; tentacles differing in size, but in + a single row. _Halicreas_. + +SUB-ORDER 2. NARCOMEDUSAE.--Margin of the umbrella-lobed, tentacles +arising from the ex-umbrella at some distance from the margin; +tentaculocysts exposed, not enclosed in vesicles; gonads on the +sub-umbral floor of the stomach or of the gastric pouches. + +[Illustration: FIG. 66.--_Cunina rhododactyla_, one of the +_Narcomedusae_. (After Haeckel.) + + c, Circular canal. + h, "Otoporpae" or centripetal process of the marginal cartilaginous + ring connected with tentaculocyst. + k, Stomach. + l, Jelly of the disk. + r, Radiating canal (pouch of stomach). + tt, Tentacles. + tw, Tentacle root.] + +The Narcomedusae exhibit peculiarities of form and structure which +distinguish them at once from all other Hydromedusae. The umbrella is +shallow and has the margin supported by a rim of thickened ectoderm, as +in the Trachomedusae, but not so strongly developed. The tentacles are +not inserted on the margin of the umbrella, but arise high up on the +ex-umbral surface, and the umbrella is prolonged into lobes +corresponding to the interspaces between the tentacles. The condition of +things can be imagined by supposing that in a medusa primitively of +normal build, with tentacles at the margin, the umbrella has grown down +past the insertion of the tentacles. As a result of this extension of +the umbrellar margin, all structures belonging to this region, namely, +the ring-canal, the nerve-rings, and the rim of thickened ectoderm, do +not run an even course, but are thrown into festoons, caught up under +the insertion of each tentacle in such a way that the ring-canal and its +accompaniments form in each notch of the umbrellar margin an inverted V, +the apex of which corresponds to the insertion of the tentacle; in some +cases the limbs of the V may run for some distance parallel to one +another, and may be fused into one, giving a figure better compared to +an inverted Y. Thus the ectodermal rim runs round the edge of each lobe +of the umbrella and then passes upwards towards the base of the tentacle +from the re-entering angle between two adjacent lobes, to form with its +fellow of the next lobe a tentacle-clasp or _peronium_, i.e. a streak of +thickened ectoderm supporting the tentacle. Similarly the ring-canal +runs round the edge of the lobe as the so-called festoon-canal, and then +runs upwards under the peronium to the base of the tentacle as one of a +pair of peronial canals, the limbs of the V-like figure already +mentioned. The nerve-rings have a similar course. The tentaculocysts are +implanted round the margins of the lobes of the umbrella and may be +supported by prolongations of the ectodermal rim termed _otoporpae_ +(_Gehörspangen_). The radial canals are represented by wide gastric +pouches, and may be absent, so that the tentacles arise directly from +the stomach (_Solmaridae_). The tentacles are always solid, as in +Trachomedusae. + +The development of the Narcomedusae is in the main similar to that of +the Trachomedusae, but shows some remarkable features. In _Aeginopsis_ a +planula is formed by multipolar immigration. The two ends of the planula +become greatly lengthened and give rise to the two primary tentacles of +the actinula, of which the mouth arises from one side of the planula. +Hence the principal axis of the future medusa corresponds, not to the +longitudinal axis of the planula, but to a transverse axis. This is in +some degree parallel to the cases described above, in which a planula +gives rise to the hydrorhiza, and buds a polyp laterally. + +In _Cunina_ and allied genera the actinula, formed in the manner +described, has a hypostome of great length, quite disproportionate to +the size of the body, and is further endowed with the power of producing +buds from a stolon arising from the aboral side of the body. In these +species the actinula is parasitic upon another medusa; for instance, +_Cunoctantha octonaria_ upon _Turritopsis_, _C. proboscidea_ upon +_Liriope_ or _Geryonia_. The parasite effects a lodgment in the host +either by invading it as a free-swimming planula, or, apparently, in +other cases, as a spore-embryo which is captured and swallowed as food +by the host. The parasitic actinula is found attached to the proboscis +of the medusa; it thrusts its greatly elongated hypostome into the mouth +of the medusa and nourishes itself upon the food in the digestive cavity +of its host. At the same time it produces buds from an aboral stolon. +The buds become medusae by the direct method of budding described above. +In some cases the buds do not become detached at once, but the stolon +continues to grow and to produce more buds, forming a "bud-spike" +(_Knospenähre_), which consists of the axial stolon bearing medusa-buds +in all stages of development. In such cases the original parent-actinula +does not itself become a medusa, but remains arrested in development and +ultimately dies off, so that a true alternation of generations is +brought about. It is in these parasitic forms that we meet with the +method of reproduction by sporogony described above. + +In other Narcomedusae, e.g. _Cunoctantha fowleri_ Browne, buds are +formed from the sub-umbrella on the under side of the stomach pouches, +where later the gonads are developed. + + _Classification._--Three families of Narcomedusae are recognized (see + O. Maas [40]): + + [Illustration: After O. Maas, _Craspedoten Medusen der Siboga + Expedition_, by permission of E. S. Brill & Co. + + FIG. 67.--_Solmundella bitentaculata_ (Quoy and Gaimard).] + + 1. _Cunanthidae._--With broad gastric pouches which are simple, i.e. + undivided, and "pernemal," i.e. correspond in position with the + tentacles. _Cunina_ (fig. 66) with more than eight tentacles; + _Cunoctantha_ with eight tentacles, four perradial, four interradial. + + 2. _Aeginidae._--Radii a multiple of four, with radial gastric pouches + bifurcated or subdivided; the tentacles are implanted in the notch + between the two subdivisions of each (primary) gastric pouch, hence + the (secondary) gastric pouches appear to be "internemal" in position, + i.e. to alternate in position with the tentacles. _Aegina_, with four + tentacles and eight pouches; _Aeginura_ (fig. 25), with eight + tentacles and sixteen pouches; _Solmundella_ (fig. 67), with two + tentacles and eight pouches; _Aeginopsis_ (fig. 23), with two or four + tentacles and sixteen pouches. + + 3. _Solmaridae._--No gastric pouches; the numerous tentacles arise + direct from the stomach, into which also the peronial canals open, so + that the ring-canal is cut up into separate festoons. _Solmaris_, + _Pegantha_, _Polyxenia_, &c. To this family should be referred, + probably, the genus _Hydroctena_, described by C. Dawydov [11a] and + regarded by him as intermediate between Hydromedusae and Ctenophora. + See O. Maas [35]. + + _Appendix to the Trachylinae._ + + Of doubtful position, but commonly referred to the Trachylinae, are + the two genera of fresh-water medusae, _Limnocodium_ and _Limnocnida_. + + _Limnocodium sowerbyi_ was first discovered in the _Victoria regia_ + tank in the Botanic Gardens, Regent's Park, London. Since then it has + been discovered in other botanic gardens in various parts of Europe, + its two most recent appearances being at Lyons (1901) and Munich + (1905), occurring always in tanks in which the _Victoria regia_ is + cultivated, a fact which indicates that tropical South America is its + original habitat. In the same tanks a small hydroid, very similar to + _Microhydra_, has been found, which bears medusa-buds and is probably + the stock from which the medusa is budded. It is a remarkable fact + that all specimens of _Limnocodium_ hitherto seen have been males; it + may be inferred from this either that only one polyp-stock has been + introduced into Europe, from which all the medusae seen hitherto have + been budded, or perhaps that the female medusa is a sessile gonophore, + as in _Pennaria_. The male gonads are carried on the radial canals. + + _Limnocnida tanganyicae_ was discovered first in Lake Tanganyika, but + has since been discovered also in Lake Victoria and in the river + Niger. It differs from _Limnocodium_ in having practically no + manubrium but a wide mouth two-thirds the diameter of the umbrella + across. It buds medusae from the margin of the mouth in May and June, + and in August and September the gonads are formed in the place where + the buds arose. The hydroid phase, if any, is not known. + + Both these medusae have sense-organs of a peculiar type, which are + said to contain an endodermal axis like the sense-organs of + Trachylinae, but the fact has recently been called in question for + _Limnocodium_ by S. Goto, who considers the genus to be allied to + _Olindias_. Allman, on the other hand, referred _Limnocodium_ to the + Leptomedusae. + + In this connexion must be mentioned, finally, the medusae budded from + the fresh-water polyp _Microhydra_. The polyp-stages of _Limnocodium_ + and _Microhydra_ are extremely similar in character. In both cases the + hydranth is extremely reduced and has no tentacles, and the polyp + forms a colony by budding from the base. In _Limnocodium_ the body + secretes a gelatinous mucus to which adhere particles of mud, &c., + forming a protective covering. In _Microhydra_ no such protecting case + is formed. In view of the great resemblance between _Microhydra_ and + the polyp of _Limnocodium_, it might be expected that the medusae to + which they give origin would also be similar. As yet, however, the + medusa of _Microhydra_ has only been seen in an immature condition, + but it shows some well-marked differences from _Limnocodium_, + especially in the structure of the tentacles, which furnish useful + characters for distinguishing species amongst medusae. The possession + of a polyp-stage by _Limnocodium_ and _Microhydra_ furnishes an + argument against placing them in the Trachylinae. Their sense-organs + require renewed investigations. (Browne [10] and [10a].) + +ORDER VI. Siphonophora.--Pelagic floating Hydrozoa with great +differentiation of parts, each performing a special function; generally +regarded as colonies showing differentiation of individuals in +correspondence with a physiological division of labour. + +[Illustration: FIG. 68.--Diagram showing possible modifications of +medusiform and hydriform persons of a colony of _Siphonophora_. The +thick black line represents endoderm, the thinner line ectoderm. (After +Allman.) + + n, Pneumatocyst. + k, Nectocalyces (swimming bells). + l, Hydrophyllium (covering-piece). + i, Generative medusiform person. + g, Palpon with attached palpacle, h. + e, Siphon with branched grappling tentacle, f. + m, Stem.] + +A typical Siphonophore is a stock or _cormus_ consisting of a number of +_appendages_ placed in organic connexion with one another by means of a +_coenosarc_. The coenosarc does not differ in structure from that +already described in colonial Hydrozoa. It consists of a hollow tube, or +tubes, of which the wall is made up of the two body-layers, ectoderm and +endoderm, and the cavity is a continuation of the digestive cavities of +the nutritive and other appendages, i.e. of the coelenteron. The +coenosarc may consist of a single elongated tube or stolon, forming the +stem or axis of the cormus on which, usually, the appendages are +arranged in groups termed cormidia; or it may take the form of a compact +mass of ramifying, anastomosing tubes, in which case the cormus as a +whole has a compact form and _cormidia_ are not distinguishable. In the +Disconectae the coenosarc forms a spongy mass, the "_centradenia_," +which is partly hepatic in function, forming the so-called liver, and +partly excretory. + +The appendages show various types of form and structure corresponding to +different functions. The cormus is always differentiated into two parts; +an upper portion termed the _nectosome_, in which the appendages are +locomotor or hydrostatic in function, that is to say, serve for swimming +or floating; and a lower portion termed the _siphosome_, bearing +appendages which are nutritive, reproductive or simply protective in +function. + +Divergent views have been held by different authors both as regards the +nature of the cormus as a whole, and as regards the homologies of the +different types of appendages borne by it. + + The general theories of Siphonophoran morphology are discussed below, + but in enumerating the various types of appendages it is convenient to + discuss their morphological interpretation at the same time. + + [Illustration: After A. Agassiz, from Lankester's _Treatise on + Zoology_. + + FIG. 69.--_Porpita_, seen from above, showing the pneumatophore and + expanded palpons.] + + In the nectosome one or more of the following types of appendage + occur:-- + + 1. Swimming-bells, termed _nectocalyces_ or _nectophores_ (fig. 68, + k), absent in _Chondrophorida_ and _Cystophorida_; they are + contractile and resemble, both in appearance, structure and function, + the umbrella of a medusa, with radial canals, ring-canal and velum; + but they are without manubrium, tentacles or sense-organs, and are + always bilaterally symmetrical, a peculiarity of form related with the + fact that they are attached on one side to the stem. A given cormus + may bear one or several nectocalyces, and by their contractions they + propel the colony slowly along, like so many medusae harnessed + together. In cases where the cormus has no pneumatophore the topmost + swimming bell may contain an oil-reservoir or _oleocyst_. + + 2. The pneumatophore or air-bladder (fig. 68, n), for passive + locomotion, forming a float which keeps the cormus at or near the + surface of the water. The pneumatophore arises from the ectoderm as a + pit or invagination, part of which forms a gas-secreting gland, while + the rest gives rise to an air-sack lined by a chitinous cuticle. The + orifice of invagination forms a pore which may be closed up or may + form a protruding duct or funnel. As in the analogous swim-bladder of + fishes, the gas in the pneumatophore can be secreted or absorbed, + whereby the specific gravity of the body can be diminished or + increased, so as to cause it to float nearer the surface or at a + deeper level. Never more than one pneumatophore is found in a cormus, + and when present it is always situated at the highest point above the + swimming bells, if these are present also. In _Velella_ the + pneumatophore becomes of complex structure and sends air-tubes, lined + by a chitin and resembling tracheae, down into the compact coenosarc, + thus evidently serving a respiratory as well as a hydrostatic + function. + + Divergent views have been held as to the morphological significance of + the pneumatophore. E. Haeckel regarded the whole structure as a + glandular ectodermal pit formed on the ex-umbral surface of a + medusa-person. C. Chun and, more recently, R. Woltereck [59], on the + other hand, have shown that the ectodermal pit which gives rise to the + pneumatophore represents an entocodon. Hence the cavity of the + air-sack is equivalent to a sub-umbral cavity in which no manubrium is + formed, and the pore or orifice of invagination would represent the + margin of the umbrella. In the wall of the sack is a double layer of + endoderm, the space between which is a continuation of the + coelenteron. By coalescence of the endoderm-layers, the coelenteron + may be reduced to vessels, usually eight in number, opening into a + ring-sinus surrounding the pore. Thus the disposition of the + endoderm-cavities is roughly comparable to the gastrovascular system + of a medusa. + + The difference between the theories of Haeckel and Chun is connected + with a further divergence in the interpretation of the stem or axis of + the cormus. Haeckel regards it as the equivalent of the manubrium, and + as it is implanted on the blind end of the pneumatophore, such a view + leads necessarily to the air-sack and gland being a development on the + ex-umbral surface of the medusa-person. Chun and Woltereck, on the + other hand, regard the stem as a _stolo prolifer_ arising from the + aboral pole, that is to say, from the ex-umbrella, similar to that + which grows out from the ex-umbral surface of the embryo of the + Narcomedusae and produces buds, a view which is certainly supported by + the embryological evidence to be adduced shortly. + + In the siphosome the following types of appendages occur:-- + + 1. _Siphons_ or nutritive appendages, from which the order takes its + name; never absent and usually present in great numbers (fig. 68, e). + Each is a tube dilated at or towards the base and containing a mouth + at its extremity, leading into a stomach placed in the dilatation + already mentioned. The siphons have been compared to the manubrium of + a medusa-individual, or to polyps, and hence are sometimes termed + gastrozoids. + + 2. _Palpons_ (fig. 68, g), present in some genera, especially in + Physonectae; similar to the siphons but without a mouth, and purely + tactile in function, hence sometimes termed dactylozoids. If a distal + pore or aperture is present, it is excretory in function; such + varieties have been termed "cystons" by Haeckel. + + 3. _Tentacles_ ("_Fangfäden_"), always present, and implanted one at + the base of each siphon (fig. 68, f). The tentacles of siphonophores + may reach a great length and have a complex structure. They may bear + accessory filaments or _tentilla_ (f'), covered thickly with batteries + of nematocysts, to which these organisms owe their great powers of + offence and defence. + + 4. _Palpacles_ ("_Tastfäden_"), occurring together with palpons, one + implanted at the base of each palpon (fig. 68, h). Each palpacle is a + tactile filament, very extensile, without accessory filaments or + nematocysts. + + 5. _Bracts_ ("_hydrophyllia_"), occur in _Calycophorida_ and some + _Physophorida_ as scale-like appendages protecting other parts (fig. + 68, l). The mesogloea is greatly developed in them and they are often + of very tough consistency. By Haeckel they are considered homologous + with the umbrella of a medusa. + + [Illustration: From G. H. Fowler, after A. Agassiz, Lankester's + _Treatise on Zoology_. + + FIG. 70.--Diagram of the structure of _Velella_, showing the central + and peripheral thirds of a half-section of the colony, the middle + third being omitted. The ectoderm is indicated by close hatching, the + endoderm by light hatching, the mesogloea by thick black lines, the + horny skeleton of the pneumatophore and sail by dotting. + + BL, Blastostyle. + C, Centradenia. + D, Palpon. + EC, Edge of colony prolonged beyond the pneumatophore. + G, Cavity of the large central siphon. + M, Medusoid gonophores. + PN, Primary central chamber, and + PN', concentric chamber of the pneumatophore, showing an opening to + the exterior and a "trachea." + S, Sail.] + + 6. _Gonostyles_, appendages which produce by budding medusae or + gonophores, like the blastostyles of a hydroid colony. In their most + primitive form they are seen in _Velella_ as "gonosiphons," which + possess mouths like the ordinary sterile siphons and bud free medusae. + In other forms they have no mouths. They may be branched, so-called + "gonodendra," and amongst them may occur special forms of palpons, + "gonopalpons." The gonostyles have been compared to the blastostyles + of a hydroid colony, or to the manubrium of a medusa which produces + free or sessile medusa-buds. + + 7. _Gonophores_, produced either on the gonostyles already mentioned + or budded, as in hydrocorallines, from the coenosarc, i.e. the stem + (fig. 68, i.). They show every transition between free medusae and + sporosacs, as already described, for hydroid colonies. Thus in + _Velella_ free medusae are produced, which have been described as an + independent genus of medusae, _Chrysomitra_. In other types the + medusae may be set free in a mature condition as the so-called + "genital swimming bells," comparable to the _Globiceps of Pennaria_. + The most usual condition, however, is that in which sessile medusoid + gonophores or sporosacs are produced. + + The various types of appendages described in the foregoing may be + arranged in groups termed _cormidia_. In forms with a compact + coenosarc such as _Velella_, _Physalia_, &c., the separate cormidia + cannot be sharply distinguished, and such a condition is described + technically as one with "scattered" cormidia. In forms in which, on + the other hand, the coenosarc forms an elongated, tubular axis or + stem, the appendages are arranged as regularly recurrent cormidia + along it, and the cormidia are then said to be "ordinate." In such + cases the oldest cormidia, that is to say, those furthest from the + nectosome, may become detached (like the segments or proglottides of a + tape-worm) and swim off, each such detached cormidium then becoming a + small free cormus which, in many cases, has been given an independent + generic name. A cormidium may contain a single nutritive siphon + ("monogastric") or several siphons ("polygastric"): + + [Illustration: From G. H. Fowler, after G. Cuvier, Lankester's + _Treatise on Zoology_. + + FIG. 71.--Upper surface of _Velella_, showing pneumatophore and sail.] + + The following are some of the forms of cormidia that occur:-- + + 1. The _eudoxome_ (Calycophorida), consisting of a bract, siphon, + tentacle and gonophore; when free it is known as _Eudoxia_. + + 2. The _ersaeome_ (Calycophorida), made up of the same appendages as + the preceding type but with the addition of a nectocalyx; when free + termed _Ersaea_. + + 3. The _rhodalome_ of some _Rhodalidae_, consisting of siphon, + tentacle and one or more gonophores. + + 4. The _athorome_ of _Physophora_, &c., consisting of siphon, + tentacle, one or more palpons with palpacles, and one or more + gonophores. + + 5. The _crystallome_ of _Anthemodes_, &c., similar to the athorome but + with the addition of a group of bracts. + + [Illustration: FIG. 72.--A, _Diphyes campanulata_; B, a group of + appendages (cormidium) of the same _Diphyes_. (After C. Gegenbaur.) + + a, Axis of the colony. + m, Nectocalyx. + c, Sub-umbral cavity of nectocalyx. + v, Radial canals of nectocalyx. + o, Orifice of nectocalyx. + t, Bract. + n, Siphon. + g, Gonophore. + i, Tentacle.] + + _Embryology of the Siphonophora._--The fertilized ovum gives rise to a + parenchymula, with solid endoderm, which is set free as a + free-swimming planula larva, in the manner already described (see + HYDROZOA). The planula has its two extremities dissimilar + (Bipolaria-larva). The subsequent development is slightly different + according as the future cormus is headed by a pneumatophore + (Physophorida, Cystophorida) or by a nectocalyx (Calycophorida). + + (i.) Physophorida, for example _Halistemma_ (C. Chun, HYDROZOA [1]). + The planula becomes elongated and broader towards one pole, at which a + pit or invagination of the ectoderm arises. Next the pit closes up to + form a vesicle with a pore, and so gives rise to the pneumatophore. + From the broader portion of the planula an outgrowth arises which + becomes the first tentacle of the cormus. The endoderm of the planula + now acquires a cavity, and at the narrower pole a mouth is formed, + giving rise to the primary siphon. Thus from the original planula + three appendages are, as it were, budded off, while the planula itself + mostly gives rise to coenosarc, just as in some hydroids the planula + is converted chiefly into hydrorhiza. + + (ii.) Calycophorida, for example, _Muggiaea_. The planula develops, on + the whole, in a similar manner, but the ectodermal invagination + arises, not at the pole of the planula, but on the side of its broader + portion, and gives rise, not to a pneumatophore, but to a nectocalyx, + the primary swimming bell or _protocodon_ ("_Fallschirm_") which is + later thrown off and replaced by secondary swimming bells, + _metacodons_, budded from the coenosarc. + + From a comparison of the two embryological types there can be no doubt + on two points; first, that the pneumatophore and the protocodon are + strictly homologous, and, therefore if the nectocalyx is comparable to + the umbrella of a medusa, as seems obvious, the pneumatophore must be + so too; secondly, that the coenosarcal axis arises from the + ex-umbrella of the medusa and cannot be compared to a manubrium, but + is strictly comparable to the "bud-spike" of a Narcomedusan. + + _Theories of Siphonophore Morphology._--The many theories that have + been put forward as to the interpretation of the cormus and the + various parts are set forth and discussed in the treatise of Y. Delage + and E. Hérouard (HYDROZOA [4]) and more recently by R. Woltereck [59], + and only a brief analysis can be given here. + + [Illustration: After C. Gegenbaur. + + FIG. 73.--_Physophora hydrostatica._ + + a´, Pneumatocyst. + t, Palpons. + a, Axis of the colony. + m, Nectocalyx. + o, Orifice of nectocalyx. + n, Siphon. + g, Gonophore. + i, Tentacle.] + + In the first place the cormus has been regarded as a single individual + and its appendages as _organs_. This is the so-called "polyorgan" + theory, especially connected with the name of Huxley; but it must be + borne in mind that Huxley regarded all the forms produced, in any + animal, between one egg-generation and the next, as constituting in + the lump one single individual. Huxley, therefore, considered a + hydroid colony, for example, as a single individual, and each separate + polyp or medusa budded from it as having the value of an organ and not + of an individual. Hence Huxley's view is not so different from those + held by other authors as it seems to be at first sight. + + In more recent years Woltereck [59] has supported Huxley's view of + individuality, at the same time drawing a fine distinction between + "individual" and "person." The individual is the product of sexual + reproduction; a person is an individual of lower rank, which may be + produced asexually. A Siphonophore is regarded as a single individual + composed of numerous zoids, budded from the primary zoid (siphon) + produced from the planula. Any given zoid is a person-zoid if + equivalent to the primary zoid, an organ-zoid if equivalent only to a + part of it. Woltereck considers the siphonophores most nearly allied + to the Narcomedusae, producing like the buds from an aboral stolon, + the first bud being represented by the pneumatophore or protocodon, in + different cases. + + Contrasting, in the second place, with the polyorgan theory are the + various "polyperson" theories which interpret the Siphonophore cormus + as a colony composed of more or fewer individuals in organic union + with one another. On this interpretation there is still room for + considerable divergence of opinion as regards detail. To begin with, + it is not necessary on the polyperson theory to regard each appendage + as a distinct individual; it is still possible to compare appendages + with parts of an individual which have become separated from one + another by a process of "dislocation of organs." Thus a bract may be + regarded, with Haeckel, as a modified umbrella of a medusa, a siphon + as its manubrium, and a tentacle as representing a medusan tentacle + shifted in attachment from the margin to the sub-umbrella; or a siphon + may be compared with a polyp, of which the single tentacle has become + shifted so as to be attached to the coenosarc and so on. Some authors + prefer, on the other hand, to regard every appendage as a separate + individual, or at least as a portion of an individual, of which other + portions have been lost or obliterated. + + A further divergence of opinion arises from differences in the + interpretation of the persons composing the colony. It is possible to + regard the cormus (1) as a colony of medusa-persons, (2) as a colony + of polyp-persons, (3) as composed partly of one, partly of the other. + It is sufficient here to mention briefly the views put forward on this + point by C. Chun and R. Haeckel. + + Chun (HYDROZOA [1]) maintains the older views of Leuckart and Claus, + according to which the cormus is to be compared to a floating hydroid + colony. It may be regarded as derived from floating polyps similar to + _Nemopsis_ or _Pelagohydra_, which by budding produce a colony of + polyps and also form medusa-buds. The polyp-individuals form the + nutritive siphosome or trophosome. The medusa-buds are either fertile + or sterile. If fertile they become free medusae or sessile gonophores. + If sterile they remain attached and locomotor in function, forming the + nectosome, the pneumatophore and swimming-bells. + + Haeckel, on the other hand, is in accordance with Balfour in regarding + a Siphonophore as a medusome, that is to say, as a colony composed of + medusoid persons or organs entirely. Haeckel considers that the + Siphonophores have two distinct ancestral lines of evolution: + + 1. In the _Disconanthae_, i.e. in such forms as _Velella_, _Porpita_, + &c., the ancestor was an eight-rayed medusa (_Disconula_) which + acquired a pneumatophore as an ectodermal pit on the ex-umbrella, and + in which the organs (manubrium, tentacles, &c.) became secondarily + multiplied, just as they do in _Gastroblasta_ as the result of + incomplete fission. The nearest living allies of the ancestral + _Disconula_ are to be sought in the _Pectyllidae_. + + [Illustration: After Haeckel, from Lankester's _Treatise on Zoology_. + + FIG. 74.--_Stephalia corona_, a young colony. + + p, Pneumatophore. + n, Nectocalyx. + l, Aurophore. + lo, Orifice of the aurophore. + s, Siphon. + t, Tentacle.] + + 2. In the _Siphonanthae_, i.e. in all other Siphonophores, the + ancestral form was a _Siphonula_, a bilaterally symmetrical + Anthomedusa with a single long tentacle (cf. _Corymorpha_), which + became displaced from the margin to the sub-umbrella. The _Siphonula_ + produced buds on the manubrium, as many Anthomedusae are known to do, + and these by reduction or dislocation of parts gave rise to the + various appendages of the colony. Thus the umbrella of the _Siphonula_ + became the protocodon, and its manubrium, the axis or stolon, which, + by a process of dislocation of organs, escaped, as it were, from the + sub-umbrella through a cleft and became secondarily attached to the + ex-umbrella. It must be pointed out that, however probable Haeckel's + theory may be in other respects, there is not the slightest evidence + for any such cleft in the umbrella having been present at any time, + and that the embryological evidence, as already pointed out, is all + against any homology between the stem and a manubrium, since the + primary siphon does not become the stem, which arises from the + ex-umbral side of the protocodon and is strictly comparable to a + stolon. + +_Classification._--The Siphonophora may be divided, following Delage and +Hérouard, into four sub-orders: + +I. CHONDROPHORIDA (_Disconectae_ Haeckel, _Tracheophysae_ Chun). With an +apical chambered pneumatophore, from which tracheal tubes may take +origin (fig. 70); no nectocalyces or bracts; appendages all on the lower +side of the pneumatophore arising from a compact coenosarc, and +consisting of a central principal siphon, surrounded by gonosiphons, and +these again by tentacles. + + Three families: (1) _Discalidae_, for _Discalia_ and allied genera, + deep-sea forms not well known; (2) _Porpitidae_ for the familiar genus + _Porpita_ (fig. 69) and its allies; and (3) _Velellidae_, represented + by the well-known genus _Velella_ (figs. 70, 71), common in the + Mediterranean and other seas. + +II. CALYCOPHORIDA (_Calyconectae_, Haeckel). Without pneumatophore, with +one, two, rarely more nectocalyces. + + Three families: (1) _Monophyidae_, with a single nectocalyx; examples + _Muggiaea_, sometimes found in British seas, _Sphaeronectes_, &c.; (2) + _Diphyidae_, with two nectocalyces; examples _Diphyes_ (fig. 72), + _Praya_, _Abyla_, &c.; and (3) _Polyphyidae_, with numerous + nectocalyces; example _Hippopodius_, _Stephanophyes_ and other genera. + +[Illustration: From G. H. Fowler, modified after G. Cuvier and E. +Haeckel, Lankester's _Treatise on Zoology_. + +FIG. 75.--A. _Physalia_, general view, diagrammatic; B, cormidium of +Physalia; D, palpon; T, palpacle; G, siphon; GP, gonopalpon; M[male], +male gonophore; M[female], female gonophore, ultimately set free.] + +III. PHYSOPHORIDA (_Physonectae_ + _Auronectae_, Haeckel). With an +apical pneumatophore, not divided into chambers, followed by a series of +nectocalyces or bracts. + + A great number of families and genera are referred to this group, + amongst which may be mentioned specially--(1) _Agalmidae_, containing + the genera _Stephanomia_, _Agalma_, _Anthemodes_, _Halistemma_, &c.; + (2) _Apolemidae_, with the genus _Apolemia_ and its allies; (3) + _Forskaliidae_, with _Forskalia_ and allied forms; (4) + _Physophoridae_, for _Physophora_ (fig. 73) and other genera, (5) + _Anthophysidae_, for _Anthophysa_, _Athorybia_, &c.; and lastly the + two families (6) _Rhodalidae_ and (7) _Stephalidae_ (fig. 74), + constituting the group Auronectae of Haeckel. The Auronectae are + peculiar deep-sea forms, little known except from Haeckel's + descriptions, in which the large pneumatophore has a peculiar duct, + termed the aurophore, placed on its lower side in the midst of a + circle of swimming-bells. + +IV. CYSTOPHORIDA (_Cystonectae_, Haeckel). With a very large +pneumatophore not divided into chambers, but without nectocalyces or +bracts. Two sections can be distinguished, the Rhizophysina, with long +tubular coenosarc-bearing ordinate cormidia, and Physalina, with compact +coenosarc-bearing scattered cormidia. + + A type of the Rhizophysina is the genus _Rhizophysa_. The Physalina + comprise the families _Physalidae_ and _Epibulidae_, of which the + types are _Physalia_ (figs. 74, 75) and _Epibulia_, respectively. + _Physalia_, known commonly as the Portuguese man-of-war, is remarkable + for its great size, its brilliant colours, and its terrible stinging + powers. + + BIBLIOGRAPHY.--In addition to the works cited below, see the general + works cited in the article HYDROZOA, in some of which very full + bibliographies will be found. + + 1. G. J. Allman, "A Monograph of the Gymnoblastic or Tubularian + Hydroids," Ray Society (1871-1872); 2. A. Brauer, "Über die + Entwickelung von Hydra," _Zeitschr. f. wiss. Zool._ lii. (1891), pp. + 169-216, pls. ix.-xii.; 3. "Über die Entstehung der + Geschlechtsprodukte und die Entwickelung von Tubularia + mesembryanthemum Allm.," _t.c._ pp. 551-579, pls. xxxiii.-xxxv.; 4. W. + K. Brooks, "The Life-History of the Hydromedusae: a discussion of the + Origin of the Medusae, and of the significance of Metagenesis," _Mem. + Boston Soc. Nat. Hist._ iii. (1886), pp. 259-430, pis. xxxvii.-xliv.; + 5. "The Sensory Clubs of Cordyli of _Laodice_," _Journ. Morphology_, + x. (1895), pp. 287-304, pl. xvii.; 6. E. T. Browne, "On British + Hydroids and Medusae," _Proc. Zool. Soc._ (1896), pp. 459-500, pls. + xvi., xvii., (1897), pp. 816-835, pls. xlviii. xlix. 12 text-figs.; 7. + "Biscayan Medusae," _Trans. Linn. Soc._ x. (1906), pp. 163-187, pl. + xiii.; 8. "Medusae" in Herdman, _Rep. Pearl Oyster Fisheries, Gulf of + Manaar_, iv. (1905), pp. 131-166, 4 pls.; 9. 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"Revision des méduses + appartenant aux familles des _Cunanthidae_ et des _Aeginidae_, et + groupement nouveau des genres," _Bull. Mus. Monaco_, v. (1904), 8 pp.; + 37. "Revision der Cannotiden Haeckels," _SB. K. Bayer. Akad._ xxxiv. + (1904), pp. 421-445; 38. "Meduses," _Result. Camp. Sci. Monaco_, + xxviii. (1904), 71 pp., 6 pls.; 39. "Die craspedoten Medusen der + Siboga-Expedition," _Uitkomst. Siboga-Exped._ x. (1905), 84 pp., 14 + pls.; 40. "Die arktischen Medusen (ausschliesslich der + Polypomedusen)," _Fauna arctica_, iv. (1906), pp. 479-526; 41. C. + Mereschkowsky, "On a new Genus of Hydroids (_Monobrachium_) from the + White Sea, with a short description of other new Hydroids," _Ann. Mag. + Nat. Hist._ (4) xx. (1877), pp. 220-229, pls. v. vi.; 42. E. + Metchinkoft, "Studien über die Entwickelung der Medusen und + Siphonophoren," _Zeitschr. f. wiss. Zool._ xxiv. (1874), pp. 15-83, + pls. i.-xii.; 43. "Vergleichend-embryologische Studien" (_Geryoniden, + Cunina_), _ibid._ xxxvi. (1882), pp. 433-458, pl. xxviii.; 44. + _Embryologische Studien an Medusen_ (Vienna, 1886), 150 pp., 12 pls., + 10 figs.; 45. "Medusologische Mittheilungen," _Arb. zool. Inst. Wien_, + vi. (1886), pp. 237-266, pls. xxii. xxiii.; 46. L. Murbach, "Beiträge + zur Kenntnis der Anatomie und Entwickelung der Nesselorgane der + Hydroiden," _Arch. f. Naturgesch._ lx. i. (1894), pp. 217-254, pl. + xii.; 47. "Preliminary Note on the Life-History of _Gonionemus_," + _Journ. Morph._ xi. (1895), pp. 493-496; 48. L. Murbach and C. + Shearer, "On Medusae from the Coast of British Columbia and Alaska," + _Proc. Zool. Soc._ (1903), ii. pp. 164-191, pls. xvii.-xxii.; 49. H. + F. Perkins, "The Development of _Gonionema murbachii_," _Proc. Acad. + Nat. Sci. Philadelphia_ (1902), pp. 750-790, pls. xxxi-xxxiv.; 50. F. + Schaudinn, "Über Haleremita cumulans, n. g. n. sp., einen marinen + Hydroidpolypen," _SB. Ges. natforsch. Freunde Berlin_ (1894), pp. + 226-234, 8 figs.; 51. F. E. Schulze, "On the Structure and Arrangement + of the Soft Parts in _Euplectella aspergillum_" (_Amphibrachium_), + _Tr. R. Soc. Edinburgh_, xxix. (1880), pp. 661-673, pl. xvii.; 52. O. + Seeliger, "Über das Verhalten der Keimblätter bei der Knospung der + Cölenteraten," _Zeitschr. f. wiss. Zool._ lviii. (1894), pp. 152-188, + pls. vii.-ix.; 53. W. B. Spencer, "A new Family of Hydroidea + (_Clathrozoon_), together with a description of the Structure of a new + Species of _Plumularia_," _Trans. Roy. Soc. Victoria_ (1890), pp. + 121-140, 7 pls.; 54. M. Ussow, "A new Form of Fresh-water + Coelenterate" (_Polypodium_), _Ann. Mag. Nat. Hist._ (5) xviii. + (1886), pp. 110-124, pl. iv.; 55. E. Vanhöffen, "Versuch einer + natürlichen Gruppierung der Anthomedusen," _Zool. Anzeiger_, xiv. + (1891), pp. 439-446; 56. C. Viguier, "Études sur les animaux + inférieurs de la baie d'Alger" (_Tetraplatia_), _Arch. Zool. Exp. + Gen._ viii. (1890), pp. 101-142, pls. vii.-ix.; 57. J. Wagner, + "Recherches sur l'organisation de Monobrachium parasiticum Méréjk," + _Arch. biol._ x. (1890), pp. 273-309, pls. viii. ix.; 58. A. Weismann, + _Die Entstehung der Sexualzellen bei den Hydromedusen_ (Jena, 1883); + 59. R. Woltereck, "Beiträge zur Ontogenie und Ableitung des + Siphonophorenstocks," _Zeitschr. f. wiss. Zool._ lxxxii. (1905), pp. + 611-637, 21 text-figs.; 60. J. Wulfert, "Die Embryonalentwickelung von + Gonothyraea loveni Allm.," _Zeitschr. f. wiss. Zool._ lxxi. (1902), + pp. 296-326, pls. xvi.-xviii. (E. A. M.) + + +FOOTNOTES: + + [1] In some cases hydroids have been reared in aquaria from ova of + medusae, but these hydroids have not yet been found in the sea + (Browne [10 a]). + + [2] The numbers in square brackets [] refer to the bibliography at + the end of this article; but when the number is preceded by the word + Hydrozoa, it refers to the bibliography at the end of the article + HYDROZOA. + + + + +HYDROMETER (Gr. [Greek: hydôr], water, and [Greek: metron], a measure), +an instrument for determining the density of bodies, generally of +fluids, but in some cases of solids. When a body floats in a fluid under +the action of gravity, the weight of the body is equal to that of the +fluid which it displaces (see HYDROMECHANICS). It is upon this principle +that the hydrometer is constructed, and it obviously admits of two modes +of application in the case of fluids: either we may compare the weights +of floating bodies which are capable of displacing the same volume of +different fluids, or we may compare the volumes of the different fluids +which are displaced by the same weight. In the latter case, the +densities of the fluids will be inversely proportional to the volumes +thus displaced. + +The hydrometer is said by Synesius Cyreneus in his fifth letter to have +been invented by Hypatia at Alexandria,[1] but appears to have been +neglected until it was reinvented by Robert Boyle, whose "New Essay +Instrument," as described in the _Phil. Trans._ for June 1675, differs +in no essential particular from Nicholson's hydrometer. This instrument +was devised for the purpose of detecting counterfeit coin, especially +guineas and half-guineas. In the first section of the paper (_Phil. +Trans._ No. 115, p. 329) the author refers to a glass instrument +exhibited by himself many years before, and "consisting of a bubble +furnished with a long and slender stem, which was to be put into several +liquors, to compare and estimate their specific gravities." This seems +to be the first reference to the hydrometer in modern times. + +In fig. 1 C represents the instrument used for guineas, the circular +plates A representing plates of lead, which are used as ballast when +lighter coins than guineas are examined. B represents "a small glass +instrument for estimating the specific gravities of liquors," an account +of which was promised by Boyle in the following number of the _Phil. +Trans._, but did not appear. + +[Illustration: FIG. 1.--Boyle's New Essay Instrument.] + +The instrument represented at B (fig. 1), which is copied from Robert +Boyle's sketch in the _Phil. Trans._ for 1675, is generally known as the +common hydrometer. It is usually made of glass, the lower bulb being +loaded with mercury or small shot which serves as ballast, causing the +instrument to float with the stem vertical. The quantity of mercury or +shot inserted depends upon the density of the liquids for which the +hydrometer is to be employed, it being essential that the whole of the +bulb should be immersed in the heaviest liquid for which the instrument +is used, while the length and diameter of the stem must be such that the +hydrometer will float in the lightest liquid for which it is required. +The stem is usually divided into a number of equal parts, the divisions +of the scale being varied in different instruments, according to the +purposes for which they are employed. + + Let V denote the volume of the instrument immersed (i.e. of liquid + displaced) when the surface of the liquid in which the hydrometer + floats coincides with the lowest division of the scale, A the area of + the transverse section of the stem, l the length of a scale division, + n the number of divisions on the stem, and W the weight of the + instrument. Suppose the successive divisions of the scale to be + numbered 0, 1, 2 ... n starting with the lowest, and let w0, W1, w2 + ... w_n be the weights of unit volume of the liquids in which the + hydrometer sinks to the divisions 0, 1, 2 ... n respectively. Then, by + the principle of Archimedes, + + W = Vw0; or w0 = W/V. Also + + W = (V + lA)w1; or w1 = W/(V + lA), + + w_p = W/(V + plA), and + + w_n= W/(V + nlA), + + or the densities of the several liquids vary inversely as the + respective volumes of the instrument immersed in them; and, since the + divisions of the scale correspond to equal increments of volume + immersed, it follows that the densities of the several liquids in + which the instrument sinks to the successive divisions form a harmonic + series. + + If V = NlA then N expresses the ratio of the volume of the instrument + up to the zero of the scale to that of one of the scale-divisions. If + we suppose the lower part of the instrument replaced by a uniform bar + of the same sectional area as the stem and of volume V, the + indications of the instrument will be in no respect altered, and the + bottom of the bar will be at a distance of N scale-divisions below the + zero of the scale. + + In this case we have w_p = W/(N + p)lA; or the density of the liquid + varies inversely as N + p, that is, as the whole number of + scale-divisions between the bottom of the tube and the plane of + flotation. + + If we wish the successive divisions of the scale to correspond to + equal increments in the density of the corresponding liquids, then the + volumes of the instrument, measured up to the successive divisions of + the scale, must form a series in harmonical progression, the lengths + of the divisions increasing as we go up the stem. + + The greatest density of the liquid for which the instrument described + above can be employed is W/V, while the least density is W/(V + nlA), + or W/(V + v), where v represents the volume of the stem between the + extreme divisions of the scale. Now, by increasing v, leaving W and V + unchanged, we may increase the range of the instrument indefinitely. + But it is clear that if we increase A, the sectional area of the stem, + we shall diminish l, the length of a scale-division corresponding to a + given variation of density, and thereby proportionately diminish the + sensibility of the instrument, while diminishing the section A will + increase l and proportionately increase the sensibility, but will + diminish the range over which the instrument can be employed, unless + we increase the length of the stem in the inverse ratio of the + sectional area. Hence, to obtain great sensibility along with a + considerable range, we require very long slender stems, and to these + two objections apply in addition to the question of portability; for, + in the first place, an instrument with a very long stem requires a + very deep vessel of liquid for its complete immersion, and, in the + second place, when most of the stem is above the plane of flotation, + the stability of the instrument when floating will be diminished or + destroyed. The various devices which have been adopted to overcome + this difficulty will be described in the account given of the several + hydrometers which have been hitherto generally employed. + + The plan commonly adopted to obviate the necessity of inconveniently + long stems is to construct a number of hydrometers as nearly alike as + may be, but to load them differently, so that the scale-divisions at + the bottom of the stem of one hydrometer just overlap those at the top + of the stem of the preceding. By this means a set of six hydrometers, + each having a stem rather more than 5 in. long, will be equivalent to + a single hydrometer with a stem of 30 in. But, instead of employing a + number of instruments differing only in the weights with which they + are loaded, we may employ the same instrument, and alter its weight + either by adding mercury or shot to the interior (if it can be opened) + or by attaching weights to the exterior. These two operations are not + quite equivalent, since a weight added to the interior does not affect + the volume of liquid displaced when the instrument is immersed up to a + given division of the scale, while the addition of weights to the + exterior increases the displacement. This difficulty may be met, as in + Keene's hydrometer, by having all the weights of precisely the same + volume but of different masses, and never using the instrument except + with one of these weights attached. + +[Illustration: FIG. 2.--Clarke's Hydrometer.] + +The first hydrometer intended for the determination of the densities of +liquids, and furnished with a set of weights to be attached when +necessary, was that constructed by Mr Clarke (instrument-maker) and +described by J. T. Desaguliers in the _Philosophical Transactions_ for +March and April 1730, No. 413, p. 278. The following is Desaguliers's +account of the instrument (fig. 2):-- + + "After having made several fruitless trials with ivory, because it + imbibes spirituous liquors, and thereby alters its gravity, he (Mr + Clarke) at last made a copper hydrometer, represented in fig. 2, + having a brass wire of about 1 in. thick going through, and soldered + into the copper ball Bb. The upper part of this wire is filed flat on + one side, for the stem of the hydrometer, with a mark at m, to which + it sinks exactly in proof spirits. There are two other marks, A and B, + at top and bottom of the stem, to show whether the liquor be (1/10)th + above proof (as when it sinks to A), or (1/10)th under proof (as when + it emerges to B), when a brass weight such as C has been screwed on to + the bottom at c. There are a great many such weights, of different + sizes, and marked to be screwed on instead of C, for liquors that + differ more than (1/10)th from proof, so as to serve for the specific + gravities in all such proportions as relate to the mixture of + spirituous liquors, in all the variety made use of in trade. There are + also other balls for showing the specific gravities quite to common + water, which make the instrument perfect in its kind." + +Clarke's hydrometer, as afterwards constructed for the purposes of the +excise, was provided with thirty-two weights to adapt it to spirits of +different specific gravities, and eleven smaller weights, or "weather +weights" as they were called, which were attached to the instrument in +order to correct for variations of temperature. The weights were +adjusted for successive intervals of 5° F., but for degrees intermediate +between these no additional correction was applied. The correction for +temperature thus afforded was not sufficiently accurate for excise +purposes, and William Speer in his essay on the hydrometer (Tilloch's +_Phil. Mag._, 1802, vol. xiv.) mentions cases in which this imperfect +compensation led to the extra duty payable upon spirits which were more +than 10% over proof being demanded on spirits which were purposely +diluted to below 10% over proof in order to avoid the charge. Clarke's +hydrometer, however, remained the standard instrument for excise +purposes from 1787 until it was displaced by that of Sikes. + +Desaguliers himself constructed a hydrometer of the ordinary type for +comparing the specific gravities of different kinds of water +(Desaguliers's _Experimental Philosophy_, ii. 234). In order to give +great sensibility to the instrument, the large glass ball was made +nearly 3 in. in diameter, while the stem consisted of a wire 10 in. in +length and only (1/40)in. in diameter. The instrument weighed 4000 +grains, and the addition of a grain caused it to sink through an inch. +By altering the quantity of shot in the small balls the instrument could +be adapted for liquids other than water. + +To an instrument constructed for the same purpose, but on a still larger +scale than that of Desaguliers, A. Deparcieux added a small dish on the +top of the stem for the reception of the weights necessary to sink the +instrument to a convenient depth. The effect of weights placed in such a +dish or pan is of course the same as if they were placed within the bulb +of the instrument, since they do not alter the volume of that part which +is immersed. + +[Illustration: FIG. 3.--Nicholson's Hydrometer.] + +The first important improvement in the hydrometer after its reinvention +by Boyle was introduced by G. D. Fahrenheit, who adopted the second mode +of construction above referred to, arranging his instrument so as always +to displace the same volume of liquid, its weight being varied +accordingly. Instead of a scale, only a single mark is placed upon the +stem, which is very slender, and bears at the top a small scale pan into +which weights are placed until the instrument sinks to the mark upon its +stem. The volume of the displaced liquid being then always the same, its +density will be proportional to the whole weight supported, that is, to +the weight of the instrument together with the weights required to be +placed in the scale pan. + +Nicholson's hydrometer (fig. 3) combines the characteristics of +Fahrenheit's hydrometer and of Boyle's essay instrument.[2] The +following is the description given of it by W. Nicholson in the +_Manchester Memoirs_, ii. 374:-- + + "AA represents a small scale. It may be taken off at D. Diameter 1½ + in., weight 44 grains. + + "B a stem of hardened steel wire. Diameter 1/100 in. + + "E a hollow copper globe. Diameter 2(8/10) in. Weight with stem 369 + grains. + + "FF a stirrup of wire screwed to the globe at C. + + "G a small scale, serving likewise as a counterpoise. Diameter 1½ in. + Weight with stirrup 1634 grains. + + "The other dimensions may be had from the drawing, which is one-sixth + of the linear magnitude of the instrument itself. + + "In the construction it is assumed that the upper scale shall + constantly carry 1000 grains when the lower scale is empty, and the + instrument sunk in distilled water at the temperature of 60° Fahr. to + the middle of the wire or stem. The length of the stem is arbitrary, + as is likewise the distance of the lower scale from the surface of the + globe. But, the length of the stem being settled, the lower scale may + be made lighter, and, consequently, the globe less, the greater its + distance is taken from the surface of the globe; and the contrary." + +In comparing the densities of different liquids, it is clear that this +instrument is precisely equivalent to that of Fahrenheit, and must be +employed in the same manner, weights being placed in the top scale only +until the hydrometer sinks to the mark on the wire, when the specific +gravity of the liquid will be proportional to the weight of the +instrument together with the weights in the scale. + +In the subsequent portion of the paper above referred to, Nicholson +explains how the instrument may be employed as a thermometer, since, +fluids generally expanding more than the solids of which the instrument +is constructed, the instrument will sink as the temperature rises. + + To determine the density of solids heavier than water with this + instrument, let the solid be placed in the upper scale pan, and let + the weight now required to cause the instrument to sink in distilled + water at standard temperature to the mark B be denoted by w, while W + denotes the weight required when the solid is not present. Then W - w + is the weight of the solid. Now let the solid be placed in the lower + pan, care being taken that no bubbles of air remain attached to it, + and let w1 be the weight now required in the scale pan. This weight + will exceed w in consequence of the water displaced by the solid, and + the weight of the water thus displaced will be W1 - w, which is + therefore the weight of a volume of water equal to that of the solid. + Hence, since the weight of the solid itself is W - w, its density must + be (W - w)/(w1 - w). + +The above example illustrates how Nicholson's or Fahrenheit's hydrometer +may be employed as a weighing machine for small weights. + +In all hydrometers in which a part only of the instrument is immersed, +there is a liability to error in consequence of the surface tension, or +capillary action, as it is frequently called, along the line of contact +of the instrument and the surface of the liquid (see CAPILLARY ACTION). +This error diminishes as the diameter of the stem is reduced, but is +sensible in the case of the thinnest stem which can be employed, and is +the chief source of error in the employment of Nicholson's hydrometer, +which otherwise would be an instrument of extreme delicacy and +precision. The following is Nicholson's statement on this point:-- + + "One of the greatest difficulties which attends hydrostatical + experiments arises from the attraction or repulsion that obtains at + the surface of the water. After trying many experiments to obviate the + irregularities arising from this cause, I find reason to prefer the + simple one of carefully wiping the whole instrument, and especially + the stem, with a clean cloth. The weights in the dish must not be + esteemed accurate while there is either a cumulus or a cavity in the + water round the stem." + +It is possible by applying a little oil to the upper part of the bulb of +a common or of a Sikes's hydrometer, and carefully placing it in pure +water, to cause it to float with the upper part of the bulb and the +whole of the stem emerging as indicated in fig. 4, when it ought +properly to sink almost to the top of the stem, the surface tension of +the water around the circumference of the circle of contact, AA', +providing the additional support required. + +[Illustration: FIG. 4.] + + The universal hydrometer of G. Atkins, described in the _Phil. Mag._ + for 1808, xxxi. 254, is merely Nicholson's hydrometer with the screw + at C projecting through the collar into which it is screwed, and + terminating in a sharp point above the cup G. To this point soft + bodies lighter than water (which would float if placed in the cup) + could be attached, and thus completely immersed. Atkins's instrument + was constructed so as to weigh 700 grains, and when immersed to the + mark on the stem in distilled water at 60° F. it carried 300 grains in + the upper dish. The hydrometer therefore displaced 1000 grains of + distilled water at 60° F. and hence the specific gravity of any other + liquid was at once indicated by adding 700 to the number of grains in + the pan required to make the instrument sink to the mark on the stem. + The small divisions on the scale corresponded to differences of + (1/10)th of a grain in the weight of the instrument. + + The "Gravimeter," constructed by Citizen Guyton and described in + _Nicholson's Journal_, 4to, i. 110, differs from Nicholson's + instrument in being constructed of glass, and having a cylindrical + bulb about 21 centimetres in length and 22 millimetres in diameter. + Its weight is so adjusted that an additional weight of 5 grammes must + be placed in the upper pan to cause the instrument to sink to the mark + on the stem in distilled water at the standard temperature. The + instrument is provided with an additional piece, or "plongeur," the + weight of which exceeds 5 grammes by the weight of water which it + displaces; that is to say, it is so constructed as to weigh 5 grammes + in water, and consists of a glass envelope filled with mercury. It is + clear that the effect of this "plongeur," when placed in the lower + pan, is exactly the same as that of the 5 gramme weight in the upper + pan. Without the extra 5 grammes the instrument weighs about 20 + grammes, and therefore floats in a liquid of specific gravity .8. Thus + deprived of its additional weight it may be used for spirits. To use + the instrument for liquids of much greater density than water + additional weights must be placed in the upper pan, and the "plongeur" + is then placed in the lower pan for the purpose of giving to the + instrument the requisite stability. + + Charles's balance areometer is similar to Nicholson's hydrometer, + except that the lower basin admits of inversion, thus enabling the + instrument to be employed for solids lighter than water, the inverted + basin serving the same purpose as the pointed screw in Atkins's + modification of the instrument. + + Adie's sliding hydrometer is of the ordinary form, but can be adjusted + for liquids of widely differing specific gravities by drawing out a + sliding tube, thus changing the volume of the hydrometer while its + weight remains constant. + + The hydrometer of A. Baumé, which has been extensively used in France, + consists of a common hydrometer graduated in the following manner. + Certain fixed points were first determined upon the stem of the + instrument. The first of these was found by immersing the hydrometer + in pure water, and marking the stem at the level of the surface. This + formed the zero of the scale. Fifteen standard solutions of pure + common salt in water were then prepared, containing respectively 1, 2, + 3, ... 15% (by weight) of dry salt. The hydrometer was plunged in + these solutions in order, and the stem having been marked at the + several surfaces, the degrees so obtained were numbered 1, 2, 3, ... + 15. These degrees were, when necessary, repeated along the stem by the + employment of a pair of compasses till 80 degrees were marked off. The + instrument thus adapted to the determination of densities exceeding + that of water was called the hydrometer for salts. + + The hydrometer intended for densities less than that of water, or the + hydrometer for spirits, is constructed on a similar principle. The + instrument is so arranged that it floats in pure water with most of + the stem above the surface. A solution containing 10% of pure salt is + used to indicate the zero of the scale, and the point at which the + instrument floats when immersed in distilled water at 10° R. (54½° F.) + is numbered 10. Equal divisions are then marked off upwards along the + stem as far as the 50th degree. + + The densities corresponding to the several degrees of Baumé's + hydrometer are given by Nicholson (_Journal of Philosophy_, i. 89) as + follows:-- + + _Baumé's Hydrometer for Spirits. Temperature 10° R._ + + +--------+--------+--------+--------+--------+--------+ + |Degrees.|Density.|Degrees.|Density.|Degrees.|Density.| + +--------+--------+--------+--------+--------+--------+ + | 10 | 1.000 | 21 | .922 | 31 | .861 | + | 11 | .990 | 22 | .915 | 32 | .856 | + | 12 | .985 | 23 | .909 | 33 | .852 | + | 13 | .977 | 24 | .903 | 34 | .847 | + | 14 | .970 | 25 | .897 | 35 | .842 | + | 15 | .963 | 26 | .892 | 36 | .837 | + | 16 | .955 | 27 | .886 | 37 | .832 | + | 17 | .949 | 28 | .880 | 38 | .827 | + | 18 | .943 | 29 | .874 | 39 | .822 | + | 19 | .935 | 30 | .867 | 40 | .817 | + | 20 | .928 | | | | | + +--------+--------+--------+--------+--------+--------+ + + _Baume's Hydrometer for Salts._ + + +--------+--------+--------+--------+--------+--------+ + |Degrees.|Density.|Degrees.|Density.|Degrees.|Density.| + +--------+--------+--------+--------+--------+--------+ + | 0 | 1.000 | 27 | 1.230 | 51 | 1.547 | + | 3 | 1.020 | 30 | 1.261 | 54 | 1.594 | + | 6 | 1.040 | 33 | 1.295 | 57 | 1.659 | + | 9 | 1.064 | 36 | 1.333 | 60 | 1.717 | + | 12 | 1.089 | 39 | 1.373 | 63 | 1.779 | + | 15 | 1.114 | 42 | 1.414 | 66 | 1.848 | + | 18 | 1.140 | 45 | 1.455 | 69 | 1.920 | + | 21 | 1.170 | 48 | 1.500 | 72 | 2.000 | + | 24 | 1.200 | | | | | + +--------+--------+--------+--------+--------+--------+ + + Carrier's hydrometer was very similar to that of Baumé, Cartier having + been employed by the latter to construct his instruments for the + French revenue. The point at which the instrument floated in distilled + water was marked 10° by Cartier, and 30° on Carrier's scale + corresponded to 32° on Baumé's. + + Perhaps the main object for which hydrometers have been constructed is + the determination of the value of spirituous liquors, chiefly for + revenue purposes. To this end an immense variety of hydrometers have + been devised, differing mainly in the character of their scales. + + In Speer's hydrometer the stem has the form of an octagonal prism, and + upon each of the eight faces a scale is engraved, indicating the + percentage strength of the spirit corresponding to the several + divisions of the scale, the eight scales being adapted respectively to + the temperature 35°, 40°, 45°, 50°, 55°, 60°, 65° and 70° F. Four + small pins, which can be inserted into the counterpoise of the + instrument, serve to adapt the instrument to the temperatures + intermediate between those for which the scales are constructed. + William Speer was supervisor and chief assayer of spirits in the port + of Dublin. For a more complete account of this instrument see + Tilloch's _Phil. Mag._, xiv. 151. + + [Illustration: FIG. 5.--Jones's Hydrometer.] + + The hydrometer constructed by Jones, of Holborn, consists of a + spheroidal bulb with a rectangular stem (fig. 5). Between the bulb and + counterpoise is placed a thermometer, which serves to indicate the + temperature of the liquid, and the instrument is provided with three + weights which can be attached to the top of the stem. On the four + sides of the stem AD are engraved four scales corresponding + respectively to the unloaded instrument, and to the instrument loaded + with the respective weights. The instrument when unloaded serves for + the range from 74 to 47 over proof; when loaded with the first weight + it indicates from 46 to 13 over proof, with the second weight from 13 + over proof to 29 under proof, and with the third from 29 under proof + to pure water, the graduation corresponding to which is marked W at + the bottom of the fourth scale. One side of the stem AD is shown in + fig. 5, the other three in fig. 6. The thermometer is also provided + with four scales corresponding to the scales above mentioned. Each + scale has its zero in the middle corresponding to 60° F. If the + mercury in the thermometer stand above this zero the spirit must be + reckoned weaker than the hydrometer indicates by the number on the + thermometer scale level with the top of the mercury, while if the + thermometer indicate a temperature lower than the zero of the scale + (60° F.) the spirit must be reckoned stronger by the scale reading. At + the side of each of the four scales on the stem of the hydrometer is + engraved a set of small numbers indicating the contraction in volume + which would be experienced if the requisite amount of water (or + spirit) were added to bring the sample tested to the proof strength. + + [Illustration: FIG. 6.] + + The hydrometer constructed by Dicas of Liverpool is provided with a + sliding scale which can be adjusted for different temperatures, and + which also indicates the contraction in volume incident on bringing + the spirit to proof strength. It is provided with thirty-six different + weights which, with the ten divisions on the stem, form a scale from 0 + to 370. The employment of so many weights renders the instrument + ill-adapted for practical work where speed is an object. + + [Illustration: FIG. 7.--Atkins's Hydrometer.] + + This instrument was adopted by the United States in 1790, but was + subsequently discarded by the Internal Revenue Service for another + type. In this latter form the observations have to be made at the + standard temperature of 60° F., at which the graduation 100 + corresponds to proof spirit and 200 to absolute alcohol. The need of + adjustable weights is avoided by employing a set of five instruments, + graduated respectively 0°-100°, 80°-120°, 100°-140°, 130°-170°, + 160°-200°. The reading gives the volume of proof spirit equivalent to + the volume of liquor; thus the readings 80° and 120° mean that 100 + volumes of the test liquors contain the same amount of absolute + alcohol as 80 and 120 volumes of proof spirit respectively. Proof + spirit is defined in the United States as a mixture of alcohol and + water which contains equal volumes of alcohol and water at 60° F., the + alcohol having a specific gravity of 0.7939 at 60° as compared with + water at its maximum density. The specific gravity of proof spirit is + 0.93353 at 60°; and 100 volumes of the mixture is made from 50 volumes + of absolute alcohol and 53.71 volumes of water. + + Quin's universal hydrometer is described in the _Transactions of the + Society of Arts_, viii. 98. It is provided with a sliding rule to + adapt it to different temperatures, and has four scales, one of which + is graduated for spirits and the other three serve to show the + strengths of worts. The peculiarity of the instrument consists in the + pyramidal form given to the stem, which renders the scale-divisions + more nearly equal in length than they would be on a prismatic stem. + + Atkins's hydrometer, as originally constructed, is described in + _Nicholson's Journal_, 8vo, ii. 276. It is made of brass, and is + provided with a spheroidal bulb the axis of which is 2 in. in length, + the conjugate diameter being 1½ in. The whole length of the instrument + is 8 in., the stem square of about 1/8-in. side, and the weight about + 400 grains. It is provided with four weights, marked 1, 2, 3, 4, and + weighing respectively 20, 40, 61 and 84 grains, which can be attached + to the shank of the instrument at C (fig. 7) and retained there by the + fixed weight B. The scale engraved upon one face of the stem contains + fifty-five divisions, the top and bottom being marked 0 or zero and + the alternate intermediate divisions (of which there are twenty-six) + being marked with the letters of the alphabet in order. The four + weights are so adjusted that, if the instrument floats with the stem + emerging as far as the lower division 0 with one of the weights + attached, then replacing the weight by the next heavier causes the + instrument to sink through the whole length of the scale to the upper + division 0, and the first weight produces the same effect when applied + to the naked instrument. The stem is thus virtually extended to five + times its length, and the number of divisions increased practically to + 272. When no weight is attached the instrument indicates densities + from .806 to .843; with No. 1 it registers from .843 to .880, with No. + 2 from .880 to .918, with No. 3 from .918 to .958, and with No. 4 from + .958 to 1.000, the temperature being 55° F. It will thus be seen that + the whole length of the stem corresponds to a difference of density of + about .04, and one division to about .00074, indicating a difference + of little more than 1/3% in the strength of any sample of spirits. + + The instrument is provided with a sliding rule, with scales + corresponding to the several weights, which indicate the specific + gravity corresponding to the several divisions of the hydrometer scale + compared with water at 55° F. The slider upon the rule serves to + adjust the scale for different temperatures, and then indicates the + strength of the spirit in percentages over or under proof. The slider + is also provided with scales, marked respectively Dicas and Clarke, + which serve to show the readings which would have been obtained had + the instruments of those makers been employed. The line on the scale + marked "concentration" indicates the diminution in volume consequent + upon reducing the sample to proof strength (if it is _over proof_, + O.P.) or upon reducing proof spirit to the strength of the sample (if + it is _under proof_, U.P.). By applying the several weights in + succession in addition to No. 4 the instrument can be employed for + liquids heavier than water; and graduations on the other three sides + of the stem, together with an additional slide rule, adapt the + instrument for the determination of the strength of worts. + + Atkins subsequently modified the instrument (_Nicholson's Journal_, + 8vo, iii. 50) by constructing the different weights of different + shapes, viz. circular, square, triangular and pentagonal, instead of + numbering them 1, 2, 3 and 4 respectively, a figure of the weight + being stamped on the sliding rule opposite to every letter in the + series to which it belongs, thus diminishing the probability of + mistakes. He also replaced the letters on the stem by the + corresponding specific gravities referred to water as unity. Further + information concerning these instruments and the state of hydrometry + in 1803 will be found in Atkins's pamphlet _On the Relation between + the Specific Gravities and the Strength of Spirituous Liquors_ (1803); + or _Phil. Mag._ xvi. 26-33, 205-212, 305-312; xvii. 204-210 and + 329-341. + + In Gay-Lussac's alcoholometer the scale is divided into 100 parts + corresponding to the presence of 1, 2, ... % by volume of alcohol at + 15° C., the highest division of the scale corresponding to the purest + alcohol he could obtain (density .7947) and the lowest division + corresponding to pure water. A table provides the necessary + corrections for other temperatures. + + Tralles's hydrometer differs from Gay-Lussac's only in being graduated + at 4° C. instead of 15° C., and taking alcohol of density .7939 at + 15.5° C. for pure alcohol instead of .7947 as taken by Gay-Lussac + (Keene's _Handbook of Hydrometry_). + + In Beck's hydrometer the zero of the scale corresponds to density + 1.000 and the division 30 to density .850, and equal divisions on the + scale are continued as far as is required in both directions. + + [Illustration: FIG. 8.--Sike's Hydrometer.] + + In the centesimal hydrometer of Francoeur the volume of the stem + between successive divisions of the scale is always (1/100)th of the + whole volume immersed when the instrument floats in water at 4° C. In + order to graduate the stem the instrument is first weighed, then + immersed in distilled water at 4° C., and the line of flotation marked + zero. The first degree is then found by placing on the top of the stem + a weight equal to (1/100)th of the weight of the instrument, which + increases the volume immersed by (1/100)th of the original volume. The + addition to the top of the stem of successive weights, each (1/100)th + of the weight of the instrument itself, serves to determine the + successive degrees. The length of 100 divisions of the scale, or the + length of the uniform stem the volume of which would be equal to that + of the hydrometer up to the zero graduation, Francoeur called the + "modulus" of the hydrometer. He constructed his instruments of glass, + using different instruments for different portions of the scale + (Francoeur, _Traité d'aréométrie_, Paris, 1842). + + Dr Boriés of Montpellier constructed a hydrometer which was based upon + the results of his experiments on mixtures of alcohol and water. The + interval between the points corresponding to pure alcohol and to pure + water Boriés divided into 100 equal parts, though the stem was + prolonged so as to contain only 10 of these divisions, the other 90 + being provided for by the addition of 9 weights to the bottom of the + instrument as in Clarke's hydrometer. + + The instrument which has now been exclusively used for revenue + purposes for nearly a century is that associated with the name of + Bartholomew Sikes, who was correspondent to the Board of Excise from + 1774 to 1783, and for some time collector of excise for Hertfordshire. + + Sikes's hydrometer, on account of its similarity to that of Boriés, + appears to have been borrowed from that instrument. It is made of + gilded brass or silver, and consists of a spherical ball A (fig. 8), + 1.5 in. in diameter, below which is a weight B connected with the ball + by a short conical stem C. The stem D is rectangular in section and + about 3½ in. in length. This is divided into ten equal parts, each of + which is subdivided into five. As in Boriés's instrument, a series of + 9 weights, each of the form shown at E, serves to extend the scale to + 100 principal divisions. In the centre of each weight is a hole + capable of admitting the lowest and thickest end of the conical stem + C, and a slot is cut into it just wide enough to allow the upper part + of the cone to pass. Each weight can thus be dropped on to the lower + stem so as to rest on the counterpoise B. The weights are marked 10, + 20, ... 90; and in using the instrument that weight must be selected + which will allow it to float in the liquid with a portion only of the + stem submerged. Then the reading of the scale at the line of + flotation, added to the number on the weight, gives the reading + required. A small supernumerary weight F is added, which can be placed + upon the top of the stem. F is so adjusted that when the 60 weight is + placed on the lower stem the instrument sinks to the same point in + distilled water when F is attached as in proof spirit when F is + removed. The best instruments are now constructed for revenue purposes + of silver, heavily gilded, because it was found that saccharic acid + contained in some spirits attacked brass behind the gilding. + + The following table gives the specific gravities corresponding to the + principal graduations on Sikes's hydrometer at 60° F. and 62° F., + together with the corresponding strengths of spirits. The latter are + based upon the tables of Charles Gilpin, clerk to the Royal Society, + for which the reader is referred to the _Phil. Trans._ for 1794. + Gilpin's work is a model for its accuracy and thoroughness of detail, + and his results have scarcely been improved upon by more recent + workers. The merit of Sikes's system lies not so much in the + hydrometer as in the complete system of tables by which the readings + of the instrument are at once converted into percentage of + proof-spirit. + + _Table showing the Densities corresponding to the Indications of + Sike's Hydrometer._ + + +------------+------------------+------------------+ + | | 60° F. | 62° F. | + | +---------+--------+---------+--------+ + | Sike's | Proof | | Proof | | + |Indications.| Spirit |Density.| Spirit |Density.| + | |per cent.| |per cent.| | + +------------+---------+--------+---------+--------+ + | 0 | .815297 | 167.0 | .815400 | 166.5 | + | 1 | .816956 | 166.1 | .817059 | 165.6 | + | 2 | .818621 | 165.3 | .818725 | 164.8 | + | 3 | .820294 | 164.5 | .820397 | 163.9 | + | 4 | .821973 | 163.6 | .822077 | 163.1 | + | 5 | .823659 | 162.7 | .823763 | 162.3 | + | 6 | .825352 | 161.8 | .825457 | 161.4 | + | 7 | .827052 | 160.9 | .827157 | 160.5 | + | 8 | .828759 | 160.0 | .828864 | 159.6 | + | 9 | .830473 | 159.1 | .830578 | 158.7 | + | 10 | .832195 | 158.2 | .832300 | 157.8 | + | 11 | .833888 | 157.3 | .833993 | 156.8 | + | 12 | .835587 | 156.4 | .835692 | 155.9 | + | 13 | .837294 | 155.5 | .837400 | 155.0 | + | 14 | .839008 | 154.6 | .839114 | 154.0 | + | 15 | .840729 | 153.7 | .840835 | 153.1 | + | 16 | .842458 | 152.7 | .842564 | 152.1 | + | 17 | .844193 | 151.7 | .844299 | 151.1 | + | 18 | .845936 | 150.7 | .846042 | 150.1 | + | 19 | .847685 | 149.7 | .847792 | 149.1 | + | 20 | .849442 | 148.7 | .849549 | 148.1 | + | 20B | .849393 | 148.7 | .849500 | 148.1 | + | 21 | .851122 | 147.6 | .851229 | 147.1 | + | 22 | .852857 | 146.6 | .852964 | 146.1 | + | 23 | .854599 | 145.6 | .854707 | 145.1 | + | 24 | .856348 | 144.6 | .856456 | 144.0 | + | 25 | .858105 | 143.5 | .858213 | 142.9 | + | 26 | .859869 | 142.4 | .859978 | 141.8 | + | 27 | .861640 | 141.3 | .861749 | 140.8 | + | 28 | .863419 | 140.2 | .863528 | 139.7 | + | 29 | .865204 | 139.1 | .865313 | 138.5 | + | 30 | .866998 | 138.0 | .867107 | 137.4 | + | 30B | .866991 | 138.0 | .867100 | 137.4 | + | 31 | .868755 | 136.9 | .868865 | 136.2 | + | 32 | .870526 | 135.7 | .870636 | 135.1 | + | 33 | .872305 | 134.5 | .872415 | 133.9 | + | 34 | .874090 | 133.4 | .874200 | 132.8 | + | 35 | .875883 | 132.2 | .873994 | 131.6 | + | 36 | .877684 | 131.0 | .877995 | 130.4 | + | 37 | .879492 | 129.8 | .879603 | 129.1 | + | 38 | .881307 | 128.5 | .881419 | 127.9 | + | 39 | .883129 | 127.3 | .883241 | 126.7 | + | 40 | .884960 | 126.0 | .885072 | 125.4 | + | 40B | .884888 | 126.0 | .885000 | 125.4 | + | 41 | .886689 | 124.8 | .886801 | 124.2 | + | 42 | .888497 | 123.5 | .888609 | 122.9 | + | 43 | .890312 | 122.2 | .890425 | 121.6 | + | 44 | .892135 | 120.9 | .892248 | 120.3 | + | 45 | .893965 | 119.6 | .894078 | 119.0 | + | 46 | .895803 | 118.3 | .895916 | 117.6 | + | 47 | .897647 | 116.9 | .897761 | 116.3 | + | 48 | .899509 | 115.6 | .899614 | 114.9 | + | 49 | .901360 | 114.2 | .901417 | 113.5 | + | 50 | .903229 | 112.8 | .903343 | 112.1 | + | 50B | .903186 | 112.8 | .903300 | 112.1 | + | 51 | .905024 | 111.4 | .905138 | 110.7 | + | 52 | .906869 | 110.0 | .906983 | 109.3 | + | 53 | .908722 | 108.6 | .908837 | 107.9 | + | 54 | .910582 | 107.1 | .910697 | 106.5 | + | 55 | .912450 | 105.6 | .912565 | 105.0 | + | 56 | .914326 | 104.2 | .914441 | 103.5 | + | 57 | .916209 | 102.7 | .916323 | 102.0 | + | 58 | .918100 | 101.3 | .918216 | 100.5 | + | 59 | .919999 | 99.7 | .820115 | 98.9 | + | 60 | .921906 | 98.1 | .922022 | 97.4 | + | 60B | .921884 | 98.1 | .922000 | 97.4 | + | 61 | .923760 | 96.6 | .923877 | 95.9 | + | 62 | .925643 | 95.0 | .925760 | 94.2 | + | 63 | .927534 | 93.3 | .927652 | 92.6 | + | 64 | .929433 | 91.7 | .929550 | 90.9 | + | 65 | .931339 | 90.0 | .931457 | 89.2 | + | 66 | .933254 | 88.3 | .933372 | 87.5 | + | 67 | .935176 | 86.5 | .935294 | 85.8 | + | 68 | .937107 | 84.7 | .937225 | 84.0 | + | 69 | .939045 | 82.9 | .939163 | 82.2 | + | 70 | .940991 | 81.1 | .941110 | 80.3 | + | 70B | .940981 | 81.1 | .941100 | 80.3 | + | 71 | .942897 | 79.2 | .943016 | 78.4 | + | 72 | .944819 | 77.3 | .944938 | 76.5 | + | 73 | .946749 | 75.3 | .946869 | 74.5 | + | 74 | .948687 | 73.3 | .948807 | 72.5 | + | 75 | .950634 | 71.2 | .950753 | 70.4 | + | 76 | .952588 | 69.0 | .952708 | 68.2 | + | 77 | .954550 | 66.8 | .954670 | 66.0 | + | 78 | .956520 | 64.4 | .956641 | 63.5 | + | 79 | .958498 | 61.9 | .958619 | 61.1 | + | 80 | .960485 | 59.4 | .960606 | 58.5 | + | 80B | .960479 | 59.4 | .960600 | 58.5 | + | 81 | .962433 | 56.7 | .962555 | 55.8 | + | 82 | .964395 | 53.9 | .964517 | 53.0 | + | 83 | .966366 | 50.9 | .966488 | 50.0 | + | 84 | .968344 | 47.8 | .968466 | 47.0 | + | 85 | .970331 | 44.5 | .970453 | 43.8 | + | 86 | .972325 | 41.0 | .972448 | 40.4 | + | 87 | .974328 | 37.5 | .974451 | 36.9 | + | 88 | .976340 | 34.0 | .976463 | 33.5 | + | 89 | .978359 | 30.6 | .978482 | 30.1 | + | 90 | .980386 | 27.2 | .980510 | 26.7 | + | 90B | .980376 | 27.2 | .980500 | 26.7 | + | 91 | .982371 | 23.9 | .982496 | 23.6 | + | 92 | .984374 | 20.8 | .984498 | 20.5 | + | 93 | .986385 | 17.7 | .986510 | 17.4 | + | 94 | .988404 | 14.8 | .988529 | 14.5 | + | 95 | .990431 | 12.0 | .990557 | 11.7 | + | 96 | .992468 | 9.3 | .992593 | 9.0 | + | 97 | .994512 | 6.7 | .994637 | 6.5 | + | 98 | .996565 | 4.1 | .996691 | 4.0 | + | 99 | .998626 | 1.8 | .998752 | 1.6 | + | 100 |1.000696 | 0.0 |1.000822 | 0.0 | + +------------+---------+--------+---------+--------+ + + In the above table for Sikes's hydrometer two densities are given + corresponding to each of the degrees 20, 30, 40, 50, 60, 70, 80 and + 90, indicating that the successive weights belonging to the particular + instrument for which the table has been calculated do not quite agree. + The discrepancy, however, does not produce any sensible error in the + strength of the corresponding spirit. + + A table which indicates the weight per gallon of spirituous liquors + for every degree of Sikes's hydrometer is printed in 23 and 24 Vict. + c. 114, schedule B. This table differs slightly from that given above, + which has been abridged from the table given in Keene's _Handbook of + Hydrometry_, apparently on account of the equal divisions on Sikes's + scale having been taken as corresponding to equal increments of + density. + + Sikes's hydrometer was established for the purpose of collecting the + revenue of the United Kingdom by Act of Parliament, 56 Geo. III. c. + 140, by which it was enacted that "all spirits shall be deemed and + taken to be of the degree of strength which the said hydrometers + called Sikes's hydrometers shall, upon trial by any officer or + officers of the customs or excise, denote such spirits to be." This + act came into force on January 5, 1817, and was to have remained in + force until August 1, 1818, but was repealed by 58 Geo. III. c. 28, + which established Sikes's hydrometer on a permanent footing. By 3 and + 4 Will. IV. c. 52, § 123, it was further enacted that the same + instruments and methods should be employed in determining the duty + upon imported spirits as should in virtue of any Act of Parliament be + employed in the determination of the duty upon spirits distilled at + home. It is the practice of the officers of the inland revenue to + adjust Sikes's hydrometer at 62° F., that being the temperature at + which the imperial gallon is defined as containing 10 lb. avoirdupois + of distilled water. The specific gravity of any sample of spirits thus + determined, when multiplied by ten, gives the weight in pounds per + imperial gallon, and the weight of any bulk of spirits divided by this + number gives its volume at once in imperial gallons. + + Mr (afterwards Colonel) J. B. Keene, of the Hydrometer Office, London, + has constructed an instrument after the model of Sikes's, but provided + with twelve weights of different masses but equal volumes, and the + instrument is never used without having one of these attached. When + loaded with either of the lightest two weights the instrument is + specifically lighter than Sikes's hydrometer when unloaded, and it may + thus be used for specific gravities as low as that of absolute + alcohol. The volume of each weight being the same, the whole volume + immersed is always the same when it floats at the same mark whatever + weight may be attached. + + Besides the above, many hydrometers have been employed for special + purposes. Twaddell's hydrometer is adapted for densities greater than + that of water. The scale is so arranged that the reading multiplied by + 5 and added to 1000 gives the specific gravity with reference to water + as 1000. To avoid an inconveniently long stem, different instruments + are employed for different parts of the scale as mentioned above. + + The lactometer constructed by Dicas of Liverpool is adapted for the + determination of the quality of milk. It resembles Sikes's hydrometer + in other respects, but is provided with eight weights. It is also + provided with a thermometer and slide rule, to reduce the readings to + the standard temperature of 55° F. Any determination of density can be + taken only as affording prima facie evidence of the quality of milk, + as the removal of cream and the addition of water are operations which + tend to compensate each other in their influence on the density of the + liquid, so that the lactometer cannot be regarded as a reliable + instrument. + + The marine hydrometers, as supplied by the British government to the + royal navy and the merchant marine, are glass instruments with slender + stems, and generally serve to indicate specific gravities from 1.000 + to 1.040. Before being issued they are compared with a standard + instrument, and their errors determined. They are employed for taking + observations of the density of sea-water. + + The salinometer is a hydrometer originally intended to indicate the + strength of the brine in marine boilers in which sea-water is + employed. Saunders's salinometer consists of a hydrometer which floats + in a chamber through which the water from the boiler is allowed to + flow in a gentle stream, at a temperature of 200° F. The peculiarity + of the instrument consists in the stream of water, as it enters the + hydrometer chamber, being made to impinge against a disk of metal, by + which it is broken into drops, thus liberating the steam, which would + otherwise disturb the instrument. + + The use of Sikes's hydrometer necessitates the employment of a + considerable quantity of spirit. For the testing of spirits in bulk no + more convenient instrument has been devised, but where very small + quantities are available more suitable laboratory methods must be + adopted. + + In England, the Finance Act 1907 (7 Ed. VII. c. 13), section 4, + provides as follows: (1) The Commissioners of Customs and the + Commissioners of Inland Revenue may jointly make regulations + authorizing the use of any means described in the regulations for + ascertaining for any purpose the strength or weight of spirits. (2) + Where under any enactment Sykes's (sic) Hydrometer is directed to be + used or may be used for the purpose of ascertaining the strength or + weight of spirits, any means so authorized by regulations may be used + instead of Sykes's Hydrometer and references to Sykes's Hydrometer in + any enactment shall be construed accordingly. (3) Any regulations made + under this section shall be published in the London, Edinburgh and + Dublin Gazette, and shall take effect from the date of publication, or + such later date as may be mentioned in the regulations for the + purpose. (4) The expression "spirits" in this section has the same + meaning as in the Spirits Act 1880. (W. G.) + + +FOOTNOTES: + + [1] In _Nicholson's Journal_, iii. 89, Citizen Eusebe Salverte calls + attention to the poem "De Ponderibus et Mensuris" generally ascribed + to Rhemnius Fannius Palaemon, and consequently 300 years older than + Hypatia, in which the hydrometer is described and attributed to + Archimedes. + + [2] _Nicholson's Journal_, vol. i. p. 111, footnote. + + + + +HYDROPATHY, the name given, from the Greek, to the "water-cure," or the +treatment of disease by water, used outwardly and inwardly. Like many +descriptive names, the word "hydropathy" is defective and even +misleading, the active agents in the treatment being heat and cold, of +which water is little more than the vehicle, and not the only one. +Thermotherapeutics (or thermotherapy) is a term less open to objection. + +Hydropathy, as a formal system, dates from about 1829, when Vincenz +Priessnitz (1801-1851), a farmer of Gräfenberg in Silesia, Austria, +began his public career in the paternal homestead, extended so as to +accommodate the increasing numbers attracted by the fame of his cures. +Two English works, however, on the medical uses of water had been +translated into German in the century preceding the rise of the movement +under Priessnitz. One of these was by Sir John Floyer (1649-1734), a +physician of Lichfield, who, struck by the remedial use of certain +springs by the neighbouring peasantry, investigated the history of cold +bathing, and published in 1702 his [Greek: "Psychrolousia], _or the +History of Cold Bathing, both Ancient and Modern_." The book ran through +six editions within a few years, and the translation was largely drawn +upon by Dr J. S. Hahn of Silesia, in a work published in 1738, _On the +Healing Virtues of Cold Water, Inwardly and Outwardly applied, as proved +by Experience_. The other work was that of Dr James Currie (1756-1805) +of Liverpool, entitled _Medical Reports on the Effects of Water, Cold +and Warm, as a remedy in Fevers and other Diseases_, published in 1797, +and soon after translated into German by Michaelis (1801) and Hegewisch +(1807). It was highly popular, and first placed the subject on a +scientific basis. Hahn's writings had meanwhile created much enthusiasm +among his countrymen, societies having been everywhere formed to promote +the medicinal and dietetic use of water; and in 1804 Professor Örtel of +Ansbach republished them and quickened the popular movement by +unqualified commendation of water drinking as a remedy for all diseases. +In him the rising Priessnitz found a zealous advocate, and doubtless an +instructor also. + +At Gräfenberg, to which the fame of Priessnitz drew people of every rank +and many countries, medical men were conspicuous by their numbers, some +being attracted by curiosity, others by the desire of knowledge, but the +majority by the hope of cure for ailments which had as yet proved +incurable. Many records of experiences at Gräfenberg were published, all +more or less favourable to the claims of Priessnitz, and some +enthusiastic in their estimate of his genius and penetration; Captain +Claridge introduced hydropathy into England in 1840, his writings and +lectures, and later those of Sir W. Erasmus Wilson (1809-1884), James +Manby Gully (1808-1883) and Edward Johnson, making numerous converts, +and filling the establishments opened soon after at Malvern and +elsewhere. In Germany, France and America hydropathic establishments +multiplied with great rapidity. Antagonism ran high between the old +practice and the new. Unsparing condemnation was heaped by each on the +other; and a legal prosecution, leading to a royal commission of +inquiry, served but to make Priessnitz and his system stand higher in +public estimation. + +Increasing popularity diminished before long that timidity which had in +great measure prevented trial of the new method from being made on the +weaker and more serious class of cases, and had caused hydropathists to +occupy themselves mainly with a sturdy order of chronic invalids well +able to bear a rigorous regimen and the severities of unrestricted +crisis. The need of a radical adaptation to the former class was first +adequately recognized by John Smedley, a manufacturer of Derbyshire, +who, impressed in his own person with the severities as well as the +benefits of "the cold water cure," practised among his workpeople a +milder form of hydropathy, and began about 1852 a new era in its +history, founding at Matlock a counterpart of the establishment at +Gräfenberg. + +Ernst Brand (1826-1897) of Berlin, Räljen and Theodor von Jürgensen of +Kiel, and Karl Liebermeister (1833-1901) of Basel, between 1860 and +1870, employed the cooling bath in abdominal typhus with striking +results, and led to its introduction to England by Dr Wilson Fox. In the +Franco-German war the cooling bath was largely employed, in conjunction +frequently with quinine; and it now holds a recognized position in the +treatment of hyperpyrexia. The wet sheet pack has become part of medical +practice; the Turkish bath, introduced by David Urquhart (1805-1877) +into England on his return from the East, and ardently adopted by Dr +Richard Barter (1802-1870) of Cork, has become a public institution, +and, with the "morning tub" and the general practice of water drinking, +is the most noteworthy of the many contributions by hydropathy to public +health (see BATHS, ad fin.). + + The appliances and arrangements by means of which heat and cold are + brought to bear on the economy are--(a) Packings, hot and cold, + general and local, sweating and cooling; (b) hot air and steam baths; + (c) general baths, of hot water and cold; (d) sitz, spinal, head and + foot baths; (e) bandages (or compresses), wet and dry; also (f) + fomentations and poultices, hot and cold, sinapisms, stupes, rubbings + and water potations, hot and cold. + + (a) Packings.--The full pack consists of a wet sheet enveloping the + body, with a number of dry blankets packed tightly over it, including + a macintosh covering or not. In an hour or less these are removed and + a general bath administered. The pack is a derivative, sedative, + sudorific and stimulator of cutaneous excretion. There are numerous + modifications of it, notably the cooling pack, where the wrappings are + loose and scanty, permitting evaporation, and the application of + indefinite duration, the sheet being rewetted as it dries; this is of + great value in protracted febrile conditions. There are also local + packs, to trunk, limbs or head separately, which are derivative, + soothing or stimulating, according to circumstance and detail. + + (b) Hot air baths, the chief of which is the Turkish (properly, the + Roman) bath, consisting of two or more chambers ranging in temperature + from 120° to 212° or higher, but mainly used at 150° for curative + purposes. Exposure is from twenty minutes up to two hours according to + the effect sought, and is followed by a general bath, and occasionally + by soaping and shampooing. It is stimulating, derivative, depurative, + sudorific and alterative, powerfully promoting tissue change by + increase of the natural waste and repair. It determines the blood to + the surface, reducing internal congestions, is a potent diaphoretic, + and, through the extremes of heat and cold, is an effective nervous + and vascular stimulant and tonic. Morbid growths and secretions, as + also the uraemic, gouty and rheumatic diathesis, are beneficially + influenced by it. The full pack and Turkish bath have between them + usurped the place and bettered the function of the once familiar hot + bath. The Russian or steam bath and the lamp bath are primitive and + inferior varieties of the modern Turkish bath, the atmosphere of which + cannot be too dry and pure. + + (c) General baths comprise the rain (or needle), spray (or rose), + shower, shallow, plunge, douche, wave and common morning sponge baths, + with the dripping sheet, and hot and cold spongings, and are + combinations, as a rule, of hot and cold water. They are stimulating, + tonic, derivative and detergent. + + (d) Local baths comprise the sitz (or sitting), douche (or spouting), + spinal, foot and head baths, of hot or cold water, singly or in + combination, successive or alternate. The sitz, head and foot baths + are used "flowing" on occasion. The application of cold by "Leiter's + tubes" is effective for reducing inflammation (e.g. in meningitis and + in sunstroke); in these a network of metal or indiarubber tubing is + fitted to the part affected, and cold water kept continuously flowing + through them. Rapid alternations of hot and cold water have a powerful + effect in vascular stasis and lethargy of the nervous system and + absorbents, yielding valuable results in local congestions and chronic + inflammations. + + (e) Bandages (or compresses) are of two kinds,--_cooling_, of wet + material left exposed for evaporation, used in local inflammations and + fevers; and _heating_, of the same, covered with waterproof material, + used in congestion, external or internal, for short or long periods. + Poultices, warm, of bread, linseed, bran, &c., changed but twice in + twenty-four hours, are identical in action with the heating bandage, + and superior only in the greater warmth and consequent vital activity + their closer application to the skin ensures. + + (f) Fomentations and poultices, hot or cold, sinapisms, stupes, + rubefacients, irritants, frictions, kneadings, calisthenics, + gymnastics, electricity, &c., are adjuncts largely employed. + + BIBLIOGRAPHY.--Among the numerous earlier works on hydropathy, the + following are worth mention: Balbirnie, _Water Cure in Consumption_ + (1847), _Hydropathic Aphorisms_ (1856) and _A Plea for the Turkish + Bath_ (1862); Beni-Barde, _Traité d'hydrothérapie_ (1874); Claridge, + _Cold Water Cure, or Hydropathy_ (1841), _Facts and Evidence in + Support of Hydropathy_ (1843) and _Cold Water, Tepid Water and + Friction Cure_ (1849); Dunlop, _Philosophy of the Bath_ (1873); + Floyer, _Psychrolousia, or the History of Cold-Bathing_, &c. (1702); + J. S. Hahn (Schweidnitz), _Observations on the Healing Virtues of Cold + Water_ (1738); Hunter, _Hydropathy for Home Use_ (1879); E. W. Lane, + _Hydropathy, or the Natural System of Medical Treatment_ (1857); R. J. + Lane, _Life at the Water Cure_ (1851); Shew, _Hydropathic Family + Physician_ (1857); Smedley, _Practical Hydropathy_ (1879); Smethurst, + _Hydrotherapia, or the Water Cure_ (1843); Wainwright, _Inquiry into + the Nature and Use of Baths_ (1737); Weiss, _Handbook of Hydropathy_ + (1844); Wilson _Principles and Practice of the Cold Water Cure_ (1854) + and _The Water Cure_ (1859). A useful recent work dealing + comprehensively with the subject is Richard Metcalfe's _Rise and + Progress of Hydropathy_ (1906). + + + + +HYDROPHOBIA (Gr. [Greek: Hydor], water, and [Greek: phobos], fear; so +called from the symptom of dread of water), or RABIES (Lat. for +"madness"), an acute disease, occurring chiefly in certain of the lower +animals, particularly the canine species, and liable to be communicated +by them to other animals and to man. + +_In Dogs, &c._--The occurrence of rabies in the fox, wolf, hyaena, +jackal, raccoon, badger and skunk has been asserted; but there is every +probability that it is originally a disease of the dog. It is +communicated by inoculation to nearly all, if not all, warm-blooded +creatures. The transmission from one animal to another only certainly +takes place through inoculation with viruliferous matters. The malady is +generally characterized at a certain stage by an irrepressible desire in +the animal to act offensively with its natural weapons--dogs and other +carnivora attacking with their teeth, herbivora with their hoofs or +horns, and birds with their beaks, when excited ever so slightly. In the +absence of excitement the malady may run its course without any fit of +fury or madness. + + _Symptoms._--The disease has been divided into three stages or + periods, and has also been described as appearing in at least two + forms, according to the peculiarities of the symptoms. But, as a rule, + one period of the disease does not pass suddenly into another, the + transition being almost imperceptible; and the forms do not differ + essentially from each other, but appear merely to constitute varieties + of the same disease, due to the natural disposition of the animal, or + other modifying circumstances. These forms have been designated _true_ + or _furious rabies_ (Fr. _rage vrai_; Ger. _rasende Wuth_) and _dumb + rabies_ (Fr. _rage mue_; Ger. _stille Wuth_). + + The malady does not commence with fury and madness, but in a strange + and anomalous change in the habits of the dog: it becomes dull, + gloomy, and taciturn, and seeks to isolate itself in out-of-the-way + places, retiring beneath chairs and to odd corners. But in its + retirement it cannot rest: it is uneasy and fidgety, and no sooner has + it lain down than suddenly it jumps up in an agitated manner, walks + backwards and forwards several times, again lies down and assumes a + sleeping attitude, but has only maintained it for a few minutes when + it is once more moving about. Again it retires to its corner, to the + farthest recess it can find, and huddles itself up into a heap, with + its head concealed beneath its chest and fore-paws. This state of + continual agitation and inquietude is in striking contrast with its + ordinary habits, and should therefore receive attention. Not + unfrequently there are a few moments when the creature appears more + lively than usual, and displays an extraordinary amount of affection. + Sometimes there is a disposition to gather up straw, thread, bits of + wood, &c., which are industriously carried away; a tendency to lick + anything cold, as iron, stones, &c., is also observed in many + instances; and there is also a desire evinced to lick other animals. + Sexual excitement is also frequently an early symptom. At this period + no disposition to bite is observed; the animal is docile with its + master and obeys his voice, though not so readily as before, nor with + the same pleased countenance. There is something strange in the + expression of its face, and the voice of its owner is scarcely able to + make it change from a sudden gloominess to its usual animated aspect. + These symptoms gradually become more marked; the restlessness and + agitation increase. If on straw the dog scatters and pulls it about + with its paws, and if in a room it scratches and tumbles the cushions + or rugs on which it usually lies. It is incessantly on the move, + rambling about, scratching the ground, sniffing in corners and at the + doors, as if on the scent or seeking for something. It indulges in + strange movements, as if affected by some mental influences or a prey + to hallucinations. When not excited by any external influence it will + remain for a brief period perfectly still and attentive, as if + watching something, or following the movements of some creature on the + wall; then it will suddenly dart forward and snap at the vacant air, + as if pursuing an annoying object, or endeavouring to seize a fly. At + another time it throws itself, yelling and furious, against the wall, + as if it heard threatening voices on the other side, or was bent on + attacking an enemy. Nevertheless, the animal is still docile and + submissive, for its master's voice will bring it out of its frenzy. + But the saliva is already virulent, and the excessive affection which + it evinces at intervals, by licking the hands or face of those it + loves, renders the danger very great should there be a wound or + abrasion. Until a late period in the disease the master's voice has a + powerful influence over the animal. When it has escaped from all + control and wanders erratically abroad, ferocious and restless, and + haunted by horrid phantoms, the familiar voice yet exerts its + influence, and it is rare indeed that it attacks its master. + + There is no dread of water in the rabid dog; the animal is generally + thirsty, and if water be offered will lap it with avidity, and swallow + it at the commencement of the disease. And when, at a later period, + the constriction about the throat--symptomatic of the disease--renders + swallowing difficult, the dog will none the less endeavour to drink, + and the lappings are as frequent and prolonged when deglutition + becomes impossible. So little dread has the rabid dog of water that it + will ford streams and swim rivers; and when in the ferocious stage it + will even do this in order to attack other creatures on the opposite + side. + + At the commencement of the disease the dog does not usually refuse to + eat, and some animals are voracious to an unusual degree. But in a + short time it becomes fastidious, only eating what it usually has a + special predilection for. Soon, however, this gives place to a most + characteristic symptom--either the taste becomes extremely depraved or + the dog has a fatal and imperious desire to bite and ingest + everything. The litter of its kennel, wool from cushions, carpets, + stockings, slippers, wood, grass, earth, stones, glass, horse-dung, + even its own faeces and urine, or whatever else may come in its way, + are devoured. On examination of the body of a dog which has died of + rabies it is so common to find in the stomach a quantity of dissimilar + and strange matters on which the teeth have been exercised that, if + there was nothing known of the animal's history, there would be strong + evidence of its having been affected with the disease. When a dog, + then, is observed to gnaw and eat suchlike matters, though it exhibits + no tendency to bite, it should be suspected. + + The mad dog does not usually foam at the mouth to any great extent at + first. The mucus of the mouth is not much increased in quantity, but + it soon becomes thicker, viscid, and glutinous, and adheres to the + angles of the mouth, fauces and teeth. It is at this period that the + thirst is most ardent, and the dog sometimes furiously attempts to + detach the saliva with its paws; and if after a while it loses its + balance in these attempts and tumbles over, there can no longer be any + doubt as to the nature of the malady. There is another symptom + connected with the mouth in that form of the disease named "dumb + madness" which has frequently proved deceptive. The lower jaw drops in + consequence of paralysis of its muscles, and the mouth remains open. + The interior is dry from the air passing continually over it, and + assumes a deep red tint, somewhat masked by patches of dust or earth, + which more especially adhere to the upper surface of the tongue and to + the lips. The strange alteration produced in the dog's physiognomy by + its constantly open mouth and the dark colour of the interior is + rendered still more characteristic by the dull, sad, or dead + expression of the animal's eyes. In this condition the creature is not + very dangerous, because generally it could not bite if it + tried--indeed there does not appear to be much desire to bite in dumb + madness; but the saliva is none the less virulent, and accidental + inoculations with it, through imprudent handling, will prove as fatal + as in the furious form. The mouth should not be touched,--numerous + deaths having occurred through people thinking the dog had some + foreign substance lodged in its throat, and thrusting their fingers + down to remove it. The sensation of tightness which seems to exist at + the throat causes the dog to act as if a bone were fixed between its + teeth or towards the back of its mouth, and to employ its fore-paws as + if to dislodge it. This is a very deceptive symptom, and may prove + equally dangerous if caution be not observed. Vomiting of blood or a + chocolate-coloured fluid is witnessed in some cases, and has been + supposed to be due to the foreign substances in the stomach, which + abrade the lining membrane; this, however, is not correct, as it has + been observed in man. + + The voice of the rabid dog is very peculiar, and so characteristic + that to those acquainted with it nothing more is needed to prove the + presence of the disease. Those who have heard it once or twice never + forget its signification. Owing to the alterations taking place in the + larynx the voice becomes hoarse, cracked and stridulous, like that of + a child affected with croup--the "voix du coq," as the French have it. + A preliminary bark is made in a somewhat elevated tone and with open + mouth; this is immediately succeeded by five, six or eight decreasing + howls, emitted when the animal is sitting or standing, and always with + the nose elevated, which seem to come from the depths of the throat, + the jaws not coming together and closing the mouth during such + emission, as in the healthy bark. This alteration in the voice is + frequently the first observable indication of the malady, and should + at once attract attention. In dumb madness the voice is frequently + lost from the very commencement--hence the designation. + + The sensibility of the mad dog appears to be considerably diminished, + and the animal appears to have lost the faculty of expressing the + sensations it experiences: it is mute under the infliction of pain, + though there can be no doubt that it still has peripheral sensation to + some extent. Burning, beating and wounding produce much less effect + than in health, and the animal will even mutilate itself with its + teeth. Suspicion, therefore, should always strongly attach to a dog + which does not manifest a certain susceptibility to painful + impressions and receives punishment without any cry or complaint. + There is also reason for apprehension when a dog bites itself + persistently in any part of its body. A rabid dog is usually stirred + to fury at the sight of one of its own species; this test has been + resorted to by Henrie Marie Bouley (1814-1885) to dissipate doubts as + to the existence of the disease when the diagnosis is otherwise + uncertain. As soon as the suspected animal, if it is really rabid, + finds itself in the presence of another of its species it at once + assumes the aggressive, and, if allowed, will bite furiously. All + rabid animals indeed become excited, exasperated, and furious at the + sight of a dog, and attack it with their natural weapons, even the + timid sheep when rabid butts furiously at the enemy before which in + health it would have fled in terror. This inversion of sentiment is + sometimes valuable in diagnosing the malady; it is so common that it + may be said to be present in every case of rabies. When, therefore, a + dog, contrary to its habits and natural inclination, becomes suddenly + aggressive to other dogs, it is time to take precautions. + + In the large majority of instances the dog is inoffensive in the early + period of the disease to those to whom it is familiar. It then flies + from its home and either dies, is killed as "mad," or returns in a + miserable plight, and in an advanced stage of the malady, when the + desire to bite is irresistible. It is in the early stage that + sequestration and suppressive measures are most valuable. The dogs + which propagate the disease are usually those that have escaped from + their owners. After two or three days, frequently in about twelve + hours, more serious and alarming symptoms appear, ferocious instincts + are developed, and the desire to do injury is irrepressible. The + animal has an indefinable expression of sombre melancholy and cruelty. + The eyes have their pupils dilated, and emit flashes of light when + they are not dull and heavy; they always appear so fierce as to + produce terror in the beholder; they are red, and their sensibility to + light is increased; and wrinkles, which sometimes appear on the + forehead, add to the repulsive aspect of the animal. If caged it flies + at the spectator, emitting its characteristic howl or bark, and + seizing the iron bars with its teeth, and if a stick be thrust before + it this is grasped and gnawed. This fury is soon succeeded by + lassitude, when the animal remains insensible to every excitement. + Then all at once it rouses up again, and another paroxysm of fury + commences. The first paroxysm is usually the most intense, and the + fits vary in duration from some hours to a day, and even longer; they + are ordinarily briefer in trained and pet dogs than in those which are + less domesticated, but in all the remission is so complete after the + first paroxysm that the animals appear to be almost well, if not in + perfect health. During the paroxysms respiration is hurried and + laboured, but tranquil during the remissions. There is an increase of + temperature, and the pulse is quick and hard. When the animal is kept + in a dark place and not excited, the fits of fury are not observed. + Sometimes it is agitated and restless in the manner already described. + It never becomes really furious or aggressive unless excited by + external objects--the most potent of these, as has been said, being + another dog, which, however, if it be admitted to its cage, it may not + at once attack. The attacked animal rarely retaliates, but usually + responds to the bites by acute yells, which contrast strangely with + the silent anger of the aggressor, and tries to hide its head with its + paws or beneath the straw. These repeated paroxysms hurry the course + of the disease. The secretion and flowing of a large quantity of + saliva from the mouth are usually only witnessed in cases in which + swallowing has become impossible, the mouth being generally dry. At + times the tongue, nose and whole head appear swollen. Other dogs + frequently shun one which is rabid, as if aware of their danger. + + The rabid dog, if lodged in a room or kept in a house, is continually + endeavouring to escape; and when it makes its escape it goes freely + forward, as if impelled by some irresistible force. It travels + considerable distances in a short time, perhaps attacking every living + creature it meets--preferring dogs, however, to other animals, and + these to mankind; cats, sheep, cattle and horses are particularly + liable to be injured. It attacks in silence, and never utters a snarl + or a cry of anger; should it chance to be hurt in return it emits no + cry or howl of pain. The degree of ferocity appears to be related to + natural disposition and training. Some dogs, for instance, will only + snap or give a slight bite in passing, while others will bite + furiously, tearing the objects presented to them, or which they meet + in their way, and sometimes with such violence as to injure their + mouth and break their teeth, or even their jaws. If chained, they will + in some cases gnaw the chain until their teeth are worn away and the + bones laid bare. The rabid dog does not continue its progress very + long. Exhausted by fatigue and the paroxysms of madness excited in it + by the objects it meets, as well as by hunger, thirst, and also, no + doubt, by the malady, its limbs soon become feeble; the rate of + travelling is lessened and the walk is unsteady, while its drooping + tall, head inclined towards the ground, open mouth, and protruded + tongue (of a leaden colour or covered with dust) give the distressed + creature a very striking and characteristic physiognomy. In this + condition, however, it is much less to be dreaded than in its early + fits of fury, since it is no longer capable or desirous of altering + its course or going out of its way to attack an animal or a man not + immediately in the path. It is very probable that its fast-failing + vision, deadened scent, and generally diminished perception prevent + its being so readily impressed or excited by surrounding objects as it + previously was. To each paroxysm, which is always of short duration, + there succeeds a degree of exhaustion as great as the fits have been + violent and oft repeated. This compels the animal to stop; then it + shelters itself in obscure places--frequently in ditches by the + roadside--and lies there in a somnolescent state for perhaps hours. + There is great danger, nevertheless, in disturbing the dog at this + period; for when roused from its torpor it has sometimes sufficient + strength to inflict a bite. This period, which may be termed the + second stage, is as variable in its duration as the first, but it + rarely exceeds three or four days. The above-described phenomena + gradually merge into those of the third or last period, when symptoms + of paralysis appear, which are speedily followed by death. During the + remission in the paroxysms these paralytic symptoms are more + particularly manifested in the hind limbs, which appear as if unable + to support the animal's weight, and cause it to stagger about; or the + lower jaw becomes more or less drooping, leaving the parched mouth + partially open. Emaciation rapidly sets in, and the paroxysms diminish + in intensity, while the remissions become less marked. The physiognomy + assumes a still more sinister and repulsive aspect; the hair is dull + and erect; the flanks are retracted; the eyes lose their lustre and + are buried in the orbits, the pupil being dilated, and the cornea dull + and semi-opaque; very often, even at an early period, the eyes squint, + and this adds still more to the terrifying appearance of the poor dog. + The voice, if at all heard, is husky, the breathing laborious, and the + pulse hurried and irregular. Gradually the paralysis increases, and + the posterior extremities are dragged as if the animal's back were + broken, until at length it becomes general; it is then the prelude to + death. Or the dog remains lying in a state of stupor, and can only + raise itself with difficulty on the fore-limbs when greatly excited. + In this condition it may yet endeavour to bite at objects within its + reach. At times convulsions of a tetanic character appear in certain + muscles; at other times these are general. A comatose condition + ensues, and the rabid dog, if permitted to die naturally, perishes, in + the great majority of cases, from paralysis and asphyxia. + + In dumb madness there is paralysis of the lower jaw, which imparts a + curious and very characteristic physiognomy to the dog; the voice is + also lost, and the animal can neither eat nor drink. In this condition + the creature remains with its jaw pendent and the mouth consequently + wide open, showing the flaccid or swollen tongue covered with brownish + matter, and a stringy gelatinous-looking saliva lying between it and + the lower lip and coating the fauces, which sometimes appear to be + inflamed. Though the animal is unable to swallow fluids, the desire to + drink is nevertheless intense; for the creature will thrust its face + into the vessel of water in futile attempts to obtain relief, even + until the approach of death. Water may be poured down its throat + without inducing a paroxysm. The general physiognomy and demeanour of + the poor creature inspire the beholder with pity rather than fear. The + symptoms due to cerebral excitement are less marked than in the + furious form of the disease; the agitation is not so considerable, and + the restlessness, tendency to run away, and desire to bite are nearly + absent; generally the animal is quite passive. Not unfrequently one or + both eyes squint, and it is only when very much excited that the dog + may contrive to close its mouth. Sometimes there is swelling about the + pharynx and the neck; when the tongue shares in this complication it + hangs out of the mouth. In certain cases there is a catarrhal + condition of the membrane lining the nasal cavities, larynx, and + bronchi; sometimes the animal testifies to the existence of abdominal + pain, and the faeces are then soft or fluid. The other symptoms--such + as the rapid exhaustion and emaciation, paralysis of the posterior + limbs towards the termination of the disease, as well as the rapidity + with which it runs its course--are the same as in the furious form. + + The simultaneous occurrence of furious and dumb madness has frequently + been observed in packs of fox-hounds. Dumb madness differs, then, from + the furious type in the paralysis of the lower jaw, which hinders the + dog from biting, save in very exceptional circumstances; the ferocious + instincts are also in abeyance; and there is no tendency to + aggression. It has been calculated that from 15 to 20% of rabid dogs + have this particular form of the disease. Puppies and young dogs + chiefly have furious rabies. + + These are the symptoms of rabies in the dog; but it is not likely, nor + is it necessary, that they will all be present in every case. In other + species the symptoms differ more or less from those manifested by the + dog, but they are generally marked by a change in the manner and + habits of the creatures affected, with strong indications of nervous + disturbance, in the majority of species amounting to ferociousness and + a desire to injure, timid creatures becoming bold and aggressive. + +_In Human Beings._--The disease of hydrophobia has been known from early +times, and is alluded to in the works of Aristotle, Xenophon, Plutarch, +Virgil, Horace, Ovid and many others, as well as in those of the early +writers on medicine. Celsus gives detailed instructions respecting the +treatment of men who have been bitten by rabid dogs, and dwells on the +dangers attending such wounds. After recommending suction of the bitten +part by means of a dry cupping glass, and thereafter the application of +the actual cautery or of strong caustics, and the employment of baths +and various internal remedies, he says: "Idque cum ita per triduum +factum est, tutus esse homo a periculo videtur. Solet autem ex eo +vulnere, ubi parum occursum est, aquae timor nasci, [Greek: +hydrophobian] Graeci appellant. Miserrimum genus morbi; in quo simul +aeger et siti et aquae metu cruciatur; quo oppressis in angusto spes +est." Subsequently Galen described minutely the phenomena of +hydrophobia, and recommended the excision of the wounded part as a +protection against the disease. Throughout many succeeding centuries +little or nothing was added to the facts which the early physicians had +made known upon the subject. The malady was regarded with universal +horror and dread, and the unfortunate sufferers were generally abandoned +by all around them and left to their terrible fate. In later times the +investigations of Boerhaave, Gerard van Swieten (1700-1772), John +Hunter, François Magendie (1783-1855), Gilbert Breschet (1784-1845), +Virchow, Albert Reder, as also of William Youatt (1776-1847), George +Fleming, Meynell, Karl Hertwig (1798-1881), and others, have furnished +important information; but all these were put into the shade by the +researches of Pasteur. + +The disease is communicated by the secretions of the mouth of the +affected animal entering a wound or abrasion of the human skin or mucous +membrane. In the great majority of cases (90%) this is due to the bite +of a rabid dog, but bites of rabid cats, wolves, foxes, jackals, &c. are +occasionally the means of conveying the disease. Numerous popular +fallacies still prevail on the subject of hydrophobia. Thus it is +supposed that the bite of an angry dog may produce the disease, and all +the more if the animal should subsequently develop symptoms of rabies. +The ground for this erroneous notion is the fact, which is +unquestionable, that animals in whom rabies is in the stage of +incubation, during which there are few if any symptoms, may by their +bites convey the disease, though fortunately during this early stage +they are little disposed to bite. The bite of a non-rabid animal, +however enraged, cannot give rise to hydrophobia. + +The period of incubation of the disease, or that time which elapses +between the introduction of the virus and the development of the +symptoms, appears to vary in a remarkable degree, being in some cases as +short as a fortnight, and in others as long as several months or even +years. On an average it seems to be from about six weeks to three +months, but it mainly depends on the part bitten; bites on the head are +the most dangerous. The incubation period is also said to be shorter in +children. The rare instances of the appearance of hydrophobia many years +after the introduction of the poison are always more or less open to +question as to subsequent inoculation. + +When the disease is about to declare itself it not unfrequently happens +that the wound, which had quickly and entirely healed after the bite, +begins to exhibit evidence of irritation or inflammatory action, or at +least to be the seat of morbid sensations such as numbness, tingling or +itching. The symptoms characterizing the premonitory stage are great +mental depression and disquietude, together with restlessness and a kind +of indefinite fear. There is an unusual tendency to talk, and the +articulation is abrupt and rapid. Although in some instances the +patients will not acknowledge that they have been previously bitten, and +deny it with great obstinacy, yet generally they are well aware of the +nature of their malady, and speak despairingly of its consequences. +There is in this early stage a certain amount of constitutional +disturbance showing itself by feverishness, loss of appetite, +sleeplessness, headache, great nervous excitability, respiration of a +peculiar sighing or sobbing character, and even occasionally a +noticeable aversion to liquids. These symptoms--constituting what is +termed the melancholic stage--continue in general for one or two days, +when they are succeeded by the stage of excitement in which all the +characteristic phenomena of the malady are fully developed. Sometimes +the disease first shows itself in this stage, without antecedent +symptoms. + +The agitation of the sufferer now becomes greatly increased, and the +countenance exhibits anxiety and terror. There is noticed a marked +embarrassment of the breathing, but the most striking and terrible +features of this stage are the effects produced by attempts to swallow +fluids. The patient suffers from thirst and desires eagerly to drink, +but on making the effort is seized with a most violent suffocative +paroxysm produced by spasm of the muscles of swallowing and breathing, +which continues for several seconds, and is succeeded by a feeling of +intense alarm and distress. With great caution and determination the +attempt is renewed, but only to be followed with a repetition of the +seizure, until the unhappy sufferer ceases from sheer dread to try to +quench the thirst which torments him. Indeed the very thought of doing +so suffices to bring on a choking paroxysm, as does also the sound of +the running of water. The patient is extremely sensitive to any kind of +external impression; a bright light, a loud noise, a breath of cool air, +contact with any one, are all apt to bring on one of these seizures. But +besides these suffocative attacks there also occur general convulsions +affecting the whole muscular system of the body, and occasionally a +condition of tetanic spasm. These various paroxysms increase in +frequency and severity with the advance of the disease, but alternate +with intervals of comparative quiet, in which, however, there is intense +anxiety and more or less constant difficulty of breathing, accompanied +with a peculiar sonorous expiration, which has suggested the notion that +the patient barks like a dog. In many instances there is great mental +disturbance, with fits of maniacal excitement, in which he strikes at +every one about him, and accuses them of being the cause of his +sufferings--these attacks being succeeded by calm intervals in which he +expresses great regret for his violent behaviour. During all this stage +of the disease the patient is tormented with a viscid secretion +accumulating in his mouth, which from dread of swallowing he is +constantly spitting about him. There may also be noticed snapping +movements of the jaws as if he were attempting to bite, but these are in +reality a manifestation of the spasmodic action which affects the +muscles generally. There is no great amount of fever, but there is +constipation, diminished flow of urine, and often sexual excitement. + +After two or three days of suffering of the most terrible description +the patient succumbs, death taking place either in a paroxysm of +choking, or on the other hand in a tranquil manner from exhaustion, all +the symptoms having abated, and the power of swallowing returned before +the end. The duration of the disease from the first declaration of the +symptoms is generally from three to five days. + +Apart from the inoculation method (see below), the treatment of most +avail is that which is directed towards preventing the absorption of the +poison into the system. This may be accomplished by excision of the part +involved in the bite of the rabid animal, or, where this from its +locality is impracticable, in the application to the wound of some +chemical agent which will destroy the activity of the virus, such as +potassa fusa, lunar caustic (nitrate of silver), or the actual cautery +in the form of a red-hot wire. The part should be thoroughly acted on by +these agents, no matter what amount of temporary suffering this may +occasion. Such applications should be resorted to immediately after the +bite has been inflicted, or as soon thereafter as possible. Further, +even though many hours or days should elapse, these local remedies +should still be applied; for if, as appears probable, some at least of +the virus remains for long at the injured part, the removal or effectual +destruction of this may prevent the dread consequences of its +absorption. Every effort should be made to tranquillize and reassure the +patient. + +Two special points of interest have arisen in recent years in connexion +with this disease. One is the Pasteur treatment by inoculation with +rabic virus (see also PARASITIC DISEASES), and the other was the attempt +of the government to exterminate rabies in the British Isles by muzzling +dogs. + + + Pasteur treatment. + +The Pasteur treatment was first applied to human beings in 1885 after +prolonged investigation and experimental trial on animals. It is based +on the fact that a virus, capable of giving rabies by inoculation, can +be extracted from the tissues of a rabid animal and then intensified or +attenuated at pleasure. It appears that the strength of the rabic virus, +as determined by inoculation, is constant in the same species of animal, +but is modified by passing through another species. For instance, the +natural virus of dogs is always of the same strength, but when +inoculated into monkeys it becomes weakened, and the process of +attenuation can be carried on by passing the virus through a succession +of monkeys, until it loses the power of causing death. If this weakened +virus is then passed back through guinea-pigs, dogs or rabbits, it +regains its former strength. Again, if it be passed through a succession +of dogs it becomes intensified up to a maximum of strength which is +called the _virus fixe_. Pasteur further discovered that the strength +can be modified by temperature and by keeping the dried tissues of a +rabid animal containing the virus. Thus, if the spinal cord of a rabid +dog be preserved in a dry state, the virus loses strength day by day. +The system of treatment consists in making an emulsion of the cord and +graduating the strength of the dose by using a succession of cords, +which have been kept for a progressively diminishing length of time. +Those which have been kept for fourteen days are used as a +starting-point, yielding virus of a minimum strength. They are followed +by preparations of diminishing age and increasing strength, day by day, +up to the maximum, which is three days old. These are successively +injected into the circulatory system. The principle is the artificial +acquisition by the patient of resistance to the rabic virus, which is +presumed to be already in the system but has not yet become active, by +accustoming him gradually to its toxic effect, beginning with a weak +form and progressively increasing the dose. It is not exactly treatment +of the disease, because it is useless or nearly so when the disease has +commenced, nor is it exactly preventive, for the patient has already +been bitten. It must be regarded as a kind of anticipatory cure. The +cords are cut into sections and preserved dry in sterilized flasks +plugged with cotton-wool. Another method of preparing the inoculatory +virus, which has been devised by Guido Tizzoni and Eugenio Centanni, +consists in subjecting the _virus fixe_ to peptic digestion by diluted +gastric juice for varying periods of time. + +The first patient was treated by Pasteur's system in July 1885. He was +successively inoculated with emulsions made from cords that had been +kept fourteen and ten days, then eleven and eight days, then eight, +seven, six days, and so on. Two forms of treatment are now used--(1) the +"simple," in which the course from weak to strong virus is extended over +nine days; (2) the "intensive," in which the maximum is reached in seven +days. The latter is used in cases of very bad bites and those of some +standing, in which it is desirable to lose no time. Two days are +compressed into one at the commencement by making injections morning and +evening instead of once a day, so that the fifth-day cord is reached in +four days instead of six, as in the "simple" treatment. When the +maximum--the third-day cord--is reached the injections are continued +with fifth-, fourth-, and third-day cords. The whole course is fifteen +days in the simple treatment and twenty-one in the intensive. The doses +injected range from 1 to 3 cubic centimetres. Injections are made +alternately into the right and left flanks. The following table shows +the number treated from 1886 to 1905, with the mortality. + + +------+--------+-------+---------+ + | Year.|Patients|Deaths.|Mortality| + | |Treated.| |per cent.| + +------+--------+-------+---------+ + | 1886 | 2671 | 25 | .94 | + | 1887 | 1770 | 14 | .79 | + | 1888 | 1622 | 9 | .55 | + | 1889 | 1830 | 7 | .38 | + | 1890 | 1540 | 5 | .32 | + | 1891 | 1559 | 4 | .25 | + | 1892 | 1790 | 4 | .22 | + | 1893 | 1648 | 6 | .36 | + | 1894 | 1387 | 7 | .50 | + | 1895 | 1520 | 5 | .33 | + | 1896 | 1308 | 4 | .30 | + | 1897 | 1521 | 6 | .39 | + | 1898 | 1465 | 3 | .20 | + | 1899 | 1614 | 4 | .25 | + | 1900 | 1419 | 10 | .70 | + | 1901 | 1318 | 5 | .37 | + | 1902 | 1105 | 2 | .18 | + | 1903 | 630 | 4 | .65 | + | 1904 | 757 | 5 | .66 | + | 1905 | 727 | 4 | .54 | + +------+--------+-------+---------+ + +These figures do not include cases which develop hydrophobia during +treatment or within fifteen days after treatment is completed, for it is +held that persons who die within that period have their nervous centres +invaded by virus before the cure has time to act. The true mortality +should therefore be considerably higher. For instance, in 1898 three +deaths came within this category, which just doubles the mortality; and +in 1899 the additional deaths were six, bringing the mortality up to +two-and-a-half times that indicated in the table. When, however, the +additional deaths are included the results remain sufficiently striking, +if two assumptions are granted--(1) that all the persons treated have +been bitten by rabid animals; (2) that a large proportion of persons so +bitten usually have hydrophobia. Unfortunately, both these assumptions +lack proof, and therefore the evidence of the efficacy of the treatment +cannot be said to satisfy a strictly scientific standard. With regard to +the first point, the patients are divided into three categories--(1) +those bitten by an animal the rabidity of which is proved by the +development of rabies in other animals bitten by it or inoculated from +its spinal cord; (2) those bitten by an animal pronounced rabid on a +veterinary examination; (3) those bitten by an animal suspected of being +rabid. The number of patients in each category in 1898 was (1) 141, (2) +855, (3) 469; and in 1899 it was (1) 152, (2) 1099, (3) 363. As might be +expected, the vast majority came under the second and third heads, in +which the evidence of rabidity is doubtful or altogether lacking. With +regard to the second point, the proportion of persons bitten by rabid +animals who ordinarily develop hydrophobia has only been "estimated" +from very inadequate data. Otto Bollinger from a series of collected +statistics states that before the introduction of the Pasteur treatment, +of patients bitten by dogs undoubtedly rabid 47% died, the rate being +33% in those whose wounds had been cauterized and 83% when there had +been no local treatment. If the number of rabid dogs be compared with +the deaths from hydrophobia in any year or series of years, it can +hardly be very high. For instance, in 1895, 668 dogs, besides other +animals, were killed and certified to be rabid in England, and the +deaths from hydrophobia were twenty. Of course this proves nothing, as +the number of persons bitten is not known, but the difference between +the amount of rabies and of hydrophobia is suggestively great in view of +the marked propensity of rabid dogs to bite, nor is it accounted for by +the fact that some of the persons bitten were treated at the Institut +Pasteur. A comparison of the annual mortality from hydrophobia in France +before and after the introduction of the treatment would afford decisive +evidence as to its efficacy; but unfortunately no such comparison can be +made for lack of vital statistics in that country. The experience of the +Paris hospitals, however, points to a decided diminution of mortality. +On the whole it must be said, in the absence of further data, that the +Pasteur treatment certainly diminishes the danger of hydrophobia from +the bites of rabid animals. + +More recently treatment with an anti-rabic serum has been suggested (see +PARASITIC DISEASES). Victor Babes and Lepp and later Guido Tizzoni and +Eugenio Centanni have worked out a method of serum treatment curative +and protective. In this method not the rabic poison itself, as in the +Pasteur treatment, but the protective substance formed is injected into +the tissues. The serum of a vaccinated animal is capable of neutralizing +the power of the virus of rabies not only when mixed with the virus +before injection but even when injected simultaneously or within +twenty-four hours after the introduction of the virus. These authors +showed that the serum of a rabbit protects a rabbit better than does the +serum of a dog, and vice versa. At the end of twenty days' injections +they found they could obtain such a large quantity of anti-rabic +substance in the serum of an animal, that even 1 part of serum to 25,000 +of the body weight would protect an animal. This process differs from +that of Pasteur in so far as that in place of promoting the formation of +the antidote within the body of the patient, by a process of vaccination +with progressively stronger and stronger virus, this part of the process +is carried on in an animal, Babes using the dog and Centanni the sheep, +the blood serum of which is injected. This method of vaccination is +useful as a protective to those in charge of kennels. + + + Muzzling order in England. + +The attempt to stamp out rabies in Great Britain was an experiment +undertaken by the government in the public interest. The principal means +adopted were the muzzling of dogs in infected areas, and prolonged +quarantine for imported animals. The efficacy of dog-muzzling in +checking the spread of rabies and diminishing its prevalence has been +repeatedly proved in various countries. Liable as other animals may be +to the disease, in England at least the dog is pre-eminently the vehicle +of contagion and the great source of danger to human beings. There is a +difference of opinion on the way in which muzzling acts, though there +can be none as to the effect it produces in reducing rabies. Probably it +acts rather by securing the destruction of ownerless and stray--which +generally includes rabid--dogs than by preventing biting; for though it +may prevent snapping, even the wire-cage muzzle does not prevent furious +dogs from biting, and it is healthy, not rabid, dogs that wear the +muzzle. It has therefore been suggested that a collar would have the +same effect, if all collarless dogs were seized; but the evidence goes +to show that it has not, perhaps because rabid dogs are more likely to +stray from home with their collars, which are constantly worn, than with +muzzles which are not, and so escape seizure. Moreover, it is much +easier for the police to see whether a dog is wearing a muzzle or not +than it is to make sure about the collar. However this may be, the +muzzle has proved more efficacious, but it was not applied +systematically in England until a late date. Sometimes the regulations +were in the hands of the government, and sometimes they were left to +local authorities; in either case they were allowed to lapse as soon as +rabies had died down. In April 1897 the Board of Agriculture entered on +a systematic attempt to exterminate rabies by the means indicated. The +plan was to enforce muzzling over large areas in which the disease +existed, and to maintain it for six months after the occurrence of the +last case. In spite of much opposition and criticism, this was +resolutely carried out under Mr Walter Long, the responsible minister, +and met with great success. By the spring of 1899--that is, in two +years--the disease had disappeared in Great Britain, except for one area +in Wales; and, with this exception, muzzling was everywhere relaxed in +October 1899. It was taken off in Wales also in the following May, no +case having occurred since November 1899. Rabies was then pronounced +extinct. During the summer of 1900, however, it reappeared in Wales, and +several counties were again placed under the order. The year 1901 was +the third in succession in which no death from hydrophobia was +registered in the United Kingdom. In the ten years preceding 1899, 104 +deaths were registered, the death-rate reaching 30 in 1889 and averaging +29 annually. In 1902 two deaths from hydrophobia were registered. From +that date to June 1909 (the latest available for the purpose of this +article) no death from hydrophobia was notified in the United Kingdom. + + See _Annales de l'Institut Pasteur_, from 1886; _Journal of the Board + of Agriculture_, 1899; Makins, "Hydrophobia," in Treves's _System of + Surgery_; Woodhead, "Rabies," in Allbutt's _System of Medicine_. + + + + +HYDROSPHERE (Gr. [Greek: hydôr], water, and [Greek: sphaira], sphere), +in physical geography, a name given to the whole mass of the water of +the oceans, which fills the depressions in the earth's crust, and covers +nearly three-quarters of its surface. The name is used in distinction +from the atmosphere, the earth's envelope of air, the lithosphere (Gr. +[Greek: lithos], rock) or solid crust of the earth, and the centrosphere +or interior mass within the crust. To these "spheres" some writers add, +by figurative usage, the terms "biosphere," or life-sphere, to cover all +living things, both animals and plants, and "psychosphere," or +mind-sphere, covering all the products of human intelligence. + + + + +HYDROSTATICS (Gr. [Greek: hydôr], water, and the root [Greek: sta]-, to +cause to stand), the branch of hydromechanics which discusses the +equilibrium of fluids (see HYDROMECHANICS). + + + + +HYDROXYLAMINE, NH2OH, or hydroxy-ammonia, a compound prepared in 1865 by +W. C. Lossen by the reduction of ethyl nitrate with tin and hydrochloric +acid. In 1870 E. Ludwig and T. H. Hein (_Chem. Centralblatt_, 1870, 1, +p. 340) obtained it by passing nitric oxide through a series of bottles +containing tin and hydrochloric acid, to which a small quantity of +platinum tetrachloride has been added; the acid liquid is poured off +when the operation is completed, and sulphuretted hydrogen is passed in; +the tin sulphide is filtered off and the filtrate evaporated. The +residue is extracted by absolute alcohol, which dissolves the +hydroxylamine hydrochloride and a little ammonium chloride; this last +substance is removed as ammonium platino-chloride, and the residual +hydroxylamine hydrochloride is recrystallized. E. Divers obtains it by +mixing cold saturated solutions containing one molecular proportion of +sodium nitrate, and two molecular proportions of acid sodium sulphite, +and then adding a saturated solution of potassium chloride to the +mixture. After standing for twenty-four hours, hydroxylamine potassium +disulphonate crystallizes out. This is boiled for some hours with water +and the solution cooled, when potassium sulphate separates first, and +then hydroxylamine sulphate. E. Tafel (_Zeit. anorg. Chem._, 1902, 31, +p. 289) patented an electrolytic process, wherein 50% sulphuric acid is +treated in a divided cell provided with a cathode of amalgamated lead, +50% nitric acid being gradually run into the cathode compartment. Pure +anhydrous hydroxylamine has been obtained by C. A. Lobry de Bruyn from +the hydrochloride, by dissolving it in absolute methyl alcohol and then +adding sodium methylate. The precipitated sodium chloride is filtered, +and the solution of hydroxylamine distilled in order to remove methyl +alcohol, and finally fractionated under reduced pressure. The free base +is a colourless, odourless, crystalline solid, melting at about 30° C., +and boiling at 58° C. (under a pressure of 22 mm.). It deliquesces and +oxidizes on exposure, inflames in dry chlorine and is reduced to ammonia +by zinc dust. Its aqueous solution is strongly alkaline, and with acids +it forms well-defined stable salts. E. Ebler and E. Schott (_J. pr. +Chem._, 1908, 78, p. 289) regard it as acting with the formula NH2·OH +towards bases, and as NH3:O towards acids, the salts in the latter case +being of the oxonium type. It is a strong reducing agent, giving a +precipitate of cuprous oxide from alkaline copper solutions at ordinary +temperature, converting mercuric chloride to mercurous chloride, and +precipitating metallic silver from solutions of silver salts. With +aldehydes and ketones it forms oximes (q.v.). W. R. Dunstan (_Jour. +Chem. Soc._, 1899, 75, p. 792) found that the addition of methyl iodide +to a methyl alcohol solution of hydroxylamine resulted in the formation +of trimethyloxamine, N(CH3)3O. + + Many substituted hydroxylamines are known, substitution taking place + either in the [alpha] or [beta] position + + [beta] [alpha] + (NH2 · OH^). + + [beta]-phenylhydroxyl-amine, C6H5NH·OH·, is obtained in the reduction + of nitrobenzene in neutral solution (e.g. by the action of the + aluminium-mercury couple and water), but better, according to C. + Goldschmidt (_Ber._, 1896, 29, p. 2307) by dissolving nitrobenzene in + ten times its weight of ether containing a few cubic centimetres of + water, and heating with excess of zinc dust and anhydrous calcium + chloride for three hours on a water bath. It also appears as an + intermediate product in the electrolytic reduction of nitrobenzene in + sulphuric acid solution. By gentle oxidation it yields nitrosobenzene. + Derivatives of the type R2N·OH result in the action of the Grignard + reagent on amyl nitrite. Dihydroxy-ammonia or nitroxyl, NH(OH)2, a + very unstable and highly reactive substance, has been especially + studied by A. Angeli (see A. W. Stewart, _Recent Advances in Physical + and Inorganic Chemistry_, 1909). + + + + +HYDROZOA, one of the most widely spread and prolific groups of aquatic +animals. They are for the most part marine in habitat, but a familiar +fresh-water form is the common _Hydra_ of ponds and ditches, which gives +origin to the name of the class. The Hydrozoa comprise the hydroids, so +abundant on all shores, most of which resemble vegetable organisms to +the unassisted eye; the hydrocorallines, which, as their name implies, +have a massive stony skeleton and resemble corals; the jelly-fishes so +called; and the Siphonophora, of which the species best known by repute +is the so-called "Portuguese man-of-war" (_Physalia_), dreaded by +sailors on account of its terrible stinging powers. + +In external form and appearance the Hydrozoa exhibit such striking +differences that there would seem at first sight to be little in common +between the more divergent members of the group. Nevertheless there is +no other class in the animal kingdom with better marked characteristics, +or with more uniform morphological peculiarities underlying the utmost +diversity of superficial characters. + +All Hydrozoa, in the first place, exhibit the three structural features +distinctive of the Coelentera (q.v.). (1) The body is built up of two +layers only, an external protective and sensory layer, the ectoderm, and +an internal digestive layer, the endoderm. (2) The body contains but a +single internal cavity, the coelenteron or gastrovascular space, which +may be greatly ramified, but is not shut off into cavities distinct from +the central digestive space. (3) The generative cells are produced in +either the ectoderm or endoderm, and not in a third layer arising in the +embryo, distinct from the two primary layers; in other words, there is +no mesoderm or coelom. + +To these three characters the Hydrozoa add a fourth which is distinctive +of the subdivision of the Coelenterata termed the Cnidaria; that is to +say, they always possess peculiar stinging organs known as nettle-cells, +or _nematocysts_ (_Cnidae_), each produced in a cell forming an integral +part of the animal's tissues. The Hydrozoa are thus shown to belong to +the group of Coelenterata Cnidaria, and it remains to consider more +fully their distinctive features, and in particular those which mark +them off from the other main division of the Cnidaria, the Anthozoa +(q.v.), comprising the corals and sea-anemones. + +The great diversity, to which reference has already been made, in the +form and structure of the Hydrozoa is due to two principal causes. In +the first place, we find in this group two distinct types of person or +individual, the polyp and the medusa (qq.v.), each capable of a wide +range of variations; and when both polyp and medusa occur in the +life-cycle of the same species, as is frequently the case, the result is +an alternation of generations of a type peculiarly characteristic of the +class. In the second place, the power of non-sexual reproduction by +budding is practically of universal occurrence among the Hydrozoa, and +by the buds failing to separate from the parent stock, colonies are +produced, more or less complicated in structure and often of great size. +We find that polyps may either bud other polyps or may produce medusae, +and that medusae may bud medusae, though never, apparently, polyps. +Hence we have a primary subdivision of the colonies of Hydrozoa into +those produced by budding of polyps and those produced by budding of +medusae. The former may contain polyp-persons and medusa-persons, either +one kind alone or both kinds combined; the latter will contain only +medusa-persons variously modified. + +The morphology of the Hydrozoa reduces itself, therefore, to a +consideration of the morphology of the polyp, of the medusa and of the +colony. Putting aside the last-named, for a detailed account of which +see HYDROMEDUSAE, we can best deal with the peculiarities of the polyp +and medusa from a developmental point of view. + + In the development of the Hydrozoa, and indeed of the Cnidaria + generally, the egg usually gives rise to an oval larva which swims + about by means of a coating of cilia on the surface of the body. This + very characteristic larva is termed a _planula_, but though very + uniform externally, the planulae of different species, or of the same + species at different periods, do not always represent the same stage + of embryonic development internally. On examining more minutely the + course of the development, it is found that the ovum goes through the + usual process of cleavage, always total and regular in this group, and + so gives rise to a hollow sphere or ovoid with the wall composed of a + single layer of cells, and containing a spacious cavity, the + blastocoele or segmentation-cavity. This is the _blastula_ stage + occurring universally in all Metazoa, probably representing an + ancestral Protozoan colony in phylogeny. Next the blastula gives rise + to an internal mass of cells (fig. 1, hy) which come from the wall + either by immigration (fig. 1, A) or by splitting off (delamination). + The formation of an inner cell-mass converts the single-layered + blastula (monoblastula) into a double-layered embryo (diblastula) + which may be termed a parenchymula, since at first the inner cell-mass + forms an irregular parenchyma which may entirely fill up and + obliterate the segmentation cavity (fig. 1, B). At a later stage, + however, the cells of the inner mass arrange themselves in a definite + layer surrounding an internal cavity (fig. 1, C, al), which soon + acquires an opening to the exterior at one pole, and so forms the + characteristic embryonic stage of all Enterozoa known as the + _gastrula_ (fig. 2). In this stage the body is composed of two layers, + ectoderm (d) externally, and endoderm (c) internally, surrounding a + central cavity, the _archenteron_ (b), which communicates with the + exterior by a pore (a), the _blastopore_. + + Thus a planula larva may be a blastula, or but slightly advanced + beyond this stage, or it may be (and most usually is) a parenchymula; + or in some cases (Scyphomedusae) it may be a gastrula. It should be + added that the process of development, the gastrulation as it is + termed, may be shortened by the immigration of cells taking place at + one pole only, and in a connected layer with orderly arrangement, so + that the gastrula stage is reached at once from the blastula without + any intervening parenchymula stage. This is a process of gastrulation + by invagination which is found in all animals above the Coelenterata, + but which is very rare in the Cnidaria, and is known only in the + Scyphomedusae amongst the Hydrozoa. + + [Illustration: From Balfour, after Kowalewsky. + + FIG. 1.--Formation of the Diblastula of _Eucope_ (one of the + Calyptoblastic _Hydromedusae_) by immigration. A, B, C, three + successive stages. _ep_, Ectoderm; _hy_, endoderm; _al_, enteric + cavity.] + + After the gastrula stage, which is found as a developmental stage in + all Enterozoa, the embryo of the Hydrozoa proceeds to develop + characters which are peculiar to the Coelenterata only. Round the + blastopore hollow outgrowths, variable in number, arise by the + evagination of the entire body-wall, both ectoderm and endoderm. Each + outgrowth contains a prolongation of the archenteric cavity (compare + figs. 2 and 3, A). In this way is formed a ring of tentacles, the most + characteristic organs of the Cnidaria. They surround a region which is + termed the peristome, and which contains in the centre the blastopore, + which becomes the adult mouth. The archenteron becomes the + gastrovascular system or coelenteron. Between the ectoderm and + endoderm a gelatinous supporting layer, termed the mesogloea, makes + its appearance. The gastrula has now become an _actinula_, which may + be termed the distinctive larva of the Cnidaria, and doubtless + represents in a transitory manner the common ancestor of the group. In + no case known, however, does the actinula become the adult, sexually + mature individual, but always undergoes further modifications, whereby + it develops into either a polyp or a medusa. + + [Illustration: From Gegenbaur's _Elements of Comparative Anatomy_. + + FIG. 2.--Diagram of a Diblastula. + + a, Blastopore. + b, Archenteric cavity. + c, Endoderm. + d, Ectoderm.] + + To become a polyp, the actinula (fig. 3, A) becomes attached to some + firm object by the pole farthest from the mouth, and its growth + preponderates in the direction of the principal axis, that is to say, + the axis passing through the mouth (fig. 3, _a-b_). As a result the + body becomes columnar in form (fig. 3, B), and without further change + passes into the characteristic polyp-form (see POLYP). + + [Illustration: FIG. 3.--Diagram showing the change of the Actinula (A) + into a Polyp (B); _a-b_, principal (vertical) axis; _c-d_, horizontal + axis. The endoderm is shaded, the ectoderm is left clear.] + + It is convenient to distinguish two types of polyp by the names hydro + polyp and anthopolyp, characteristic of the Hydrozoa and Anthozoa + respectively. In the hydropolyp the body is typically elongated, the + height of the column being far greater than the diameter. The + peristome is relatively small and the mouth is generally raised on a + projecting spout or _hypostome_. The ectoderm loses entirely the + ciliation which it had in the planula and actinula stages and commonly + secretes on its external surface a protective or supporting + investment, the perisarc. Contrasting with this, the anthopolyp is + generally of squat form, the diameter often exceeding the height; the + peristome is wide, a hypostome is lacking, and the ectoderm, or so + much of it as is exposed, i.e. not covered by secretion of skeletal or + other investment, retains its ciliation throughout life. The internal + structural differences are even more characteristic. In the hydropolyp + the blastopore of the embryo forms the adult mouth situated at the + extremity of the hypostome, and the ectoderm and endoderm meet at this + point. In the anthopolyp the blastopore is carried inwards by an + in-pushing of the body-wall of the region of the peristome, so that + the adult mouth is an opening leading into a short ectodermal + oesophagus or stomodaeum, at the bottom of which is the blastopore. + Further, in the hydropolyp the digestive cavity either remains simple + and undivided and circular in transverse section, or may show ridges + projecting internally, which in this case are formed of endoderm + alone, without any participation of the mesogloea. In the anthopolyp, + on the other hand, the digestive cavity is always subdivided by + so-called mesenteries, in-growths of the endoderm containing vertical + lamellae of mesogloea (see ANTHOZOA). In short, the hydropolyp is + characterized by a more simple type of organization than the + anthopolyp, and is in most respects less modified from the actinula + type of structure. + + [Illustration: FIG. 4.--Diagram showing the change of the Actinula + into a Medusa. A, Vertical section of the actinula; _a-b_ and _c-d_ as + in fig. 3, B, transitional stage, showing preponderating growth in the + horizontal plane. C, C', D, D', two types of medusa organization; C + and D are composite sections, showing a radius (R) on one side, an + interradius (IR) on the other; C' and D' are plans; the mouth and + manubrium are indicated at the centre, leading into the gastral cavity + subdivided by the four areas of concrescence in each interradius (IR). + t, tentacle; g.p, gastric pouch; r.c, radial canal not present in C + and C'; c.c, circular or ring-canal; e.l, endoderm-lamella formed by + concrescence. For a more detailed diagram of medusa-structure see + article MEDUSA.] + + Returning now to the actinula, this form may, as already stated, + develop into a medusa, a type of individual found only in the + Hydrozoa, as here understood. To become a medusa, the actinula grows + scarcely at all in the direction of the principal axis, but greatly + along a plane at right angles to it. Thus the body becomes + umbrella-shaped, the concave side representing the peristome, and the + convex side the column, of the polyp. Hence the tentacles are found at + the edge of the umbrella, and the hypostome forms usually a projecting + tube, with the mouth at the extremity, forming the _manubrium_ or + handle of the umbrella. The medusa has a pronounced radial symmetry, + and the positions of the primary tentacles, usually four in number, + mark out the so-called _radii_, alternating with which are four + _interradii_. The ectoderm retains its ciliation only in the sensory + organs. The mesogloea becomes enormously increased in quantity (hence + the popular name "jelly-fish"), and in correlation with this the + endoderm-layer lining the coelenteron becomes pressed together in the + interradial areas and undergoes concrescence, forming a more or less + complicated gastrovascular system (see MEDUSA). It is sufficient to + state here that the medusa is usually a free-swimming animal, floating + mouth downwards on the open seas, but in some cases it may be attached + by its aboral pole, like a polyp, to some firm basis, either + temporarily or permanently. + + Thus the development of the two types of individual seen in the + Hydrozoa may be summarized as follows:-- + + / Egg + | | + Free | Blastula + | | + "Planula" < Parenchymula + | | + Stage | Gastrula + | | + \ Actinula + / \ + / \ + Polyp Medusa + + This development, though probably representing the primitive sequence + of events, is never actually found in its full extent, but is always + abbreviated by omission or elimination of one or more of the stages. + We have already seen that the parenchymula stage is passed over when + the gastrulation is of the invaginate type. On the other hand, the + parenchymula may develop directly into the actinula or even into the + polyp, with suppression of the intervening steps. Great apparent + differences may also be brought about by variations in the period at + which the embryo is set free as a larva, and since two free-swimming + stages, planula and actinula, are unnecessary, one or other of them is + always suppressed. A good example of this is seen in two common genera + of British hydroids, _Cordylophora_ and _Tabularia_. In _Cordylophora_ + the embryo is set free at the parenchymula stage as a planula which + fixes itself and develops into a polyp, both gastrula and actinula + stages being suppressed. In _Tubularia_, on the other hand, the + parenchymula develops into an actinula within the maternal tissues, + and is then set free, creeps about for a time, and after fixing + itself, changes into a polyp; hence in this case the planula-stage, as + a free larva, is entirely suppressed. + + The Hydrozoa may be defined, therefore, as Cnidaria in which two types + of individual, the polyp and the medusa, may be present, each type + developed along divergent lines from the primitive actinula form. The + polyp (hydropolyp) is of simple structure and never has an ectodernal + oesophagus or mesenteries.[1] The general ectoderm loses its cilia, + which persist only in the sensory cells, and it frequently secretes + external protective or supporting structures. An internal mesogloeal + skeleton is not found. + + The class is divisible into two main divisions or sub-classes, + Hydromedusae and Scyphomedusae, of which definitions and detailed + systematic accounts will be found under these headings. + + GENERAL WORKS ON HYDROZOA.--C. Chun, "Coelenterata (Hohlthiere)," + _Bronn's Klassen und Ordnungen des Thier-Reichs_ ii. 2 (1889 et seq.); + Y. Delage, and E. Hérouard, _Traité de zoologie concrète_, ii. part 2, + _Les Coelentérés_ (1901); G. H. Fowler, "The Hydromedusae and + Scyphomedusae" in E. R. Lankester's _Treatise on Zoology_, ii. + chapters iv. and v. (1900); S. J. Hickson, "Coelenterata and + Ctenophora," _Cambridge Natural History_, i. chapters x.-xv. (1906). + (E. A. M.) + + +FOOTNOTE: + + [1] See further under SCYPHOMEDUSAE. + + + + +HYENA, a name applicable to all the representatives of the mammalian +family _Hyaenidae_, a group of Carnivora (q.v.) allied to the civets. +From all other large Carnivora except the African hunting-dog, hyenas +are distinguished by having only four toes on each foot, and are further +characterized by the length of the fore-legs as compared with the hind +pair, the non-retractile claws, and the enormous strength of the jaws +and teeth, which enables them to break the hardest bones and to retain +what they have seized with unrelaxing grip. + +[Illustration: FIG. 1.--The Striped Hyena (_Hyaena striata_).] + +[Illustration: FIG. 2.--The Spotted Hyena (_Hyaena crocuta_).] + +The striped hyena (_Hyaena striata_) is the most widely distributed +species, being found throughout India, Persia, Asia Minor, and North and +East Africa, the East African form constituting a distinct race, _H. +striata schillingsi_; while there are also several distinct Asiatic +races. The species resembles a wolf in size, and is greyish-brown In +colour, marked with indistinct longitudinal stripes of a darker hue, +while the legs are transversely striped. The hairs on the body are long, +especially on the ridge of the neck and back, where they form a distinct +mane, which is continued along the tail. Nocturnal in habits, it prefers +by day the gloom of caves and ruins, or of the burrows which it +occasionally forms, and issues forth at sunset, when it commences its +unearthly howling. When the animal is excited, the howl changes into +what has been compared to demoniac laughter, whence the name of +"laughing-hyena." These creatures feed chiefly on carrion, and thus +perform useful service by devouring remains which might otherwise +pollute the air. Even human dead are not safe from their attacks, their +powerful claws enabling them to gain access to newly interred bodies in +cemeteries. Occasionally (writes Dr W. T. Blanford) sheep or goats, and +more often dogs, are carried off, and the latter, at all events, are +often taken alive to the animal's den. This species appears to be +solitary in habits, and it is rare to meet with more than two together. +The cowardice of this hyena is proverbial; despite its powerful teeth, +it rarely attempts to defend itself. A very different animal is the +spotted hyena, _Hyaena (Crocuta) crocuta_, which has the sectorial teeth +of a more cat-like type, and is marked by dark-brown spots on a +yellowish ground, while the mane is much less distinct. At the Cape it +was formerly common, and occasionally committed great havoc among the +cattle, while it did not hesitate to enter the Kaffir dwellings at +night and carry off children sleeping by their mothers. By persistent +trapping and shooting, its numbers have now been considerably reduced, +with the result, however, of making it exceedingly wary, so that it is +not readily caught in any trap with which it has had an opportunity of +becoming acquainted. Its range extends from Abyssinia to the Cape. The +Abyssinian form has been regarded as a distinct species, under the name +of _H. liontiewi_, but this, like various more southern forms, is but +regarded as a local race. The brown hyena (_H. brunnea_) is South +African, ranging to Angola on the west and Kilimanjaro on the east. In +size it resembles the striped hyena, but differs in appearance, owing to +the fringe of long hair covering the neck and fore part of the back. The +general hue is ashy-brown, with the hair lighter on the neck (forming a +collar), chest and belly; while the legs are banded with dark brown. +This species is not often seen, as it remains concealed during the day. +Those frequenting the coast feed on dead fish, crabs and an occasional +stranded whale, though they are also a danger to the sheep and cattle +kraal. Strand-wolf is the local name at the Cape. + +Although hyenas are now confined to the warmer regions of the Old World, +fossil remains show that they had a more northerly range during Tertiary +times; the European cave-hyena being a form of the spotted species, +known as _H. crocuta spelaea_. Fossil hyenas occur in the Lower Pliocene +of Greece, China, India, &c.; while remains indistinguishable from those +of the striped species have been found in the Upper Pliocene of England +and Italy. + + + + +HYÈRES, a town in the department of the Var in S.E. France, 11 m. by +rail E. of Toulon. In 1906 the population of the commune was 17,790, of +the town 10,464; the population of the former was more than doubled in +the last decade of the 19th century. Hyères is celebrated (as is also +its fashionable suburb, Costebelle, nearer the seashore) as a winter +health resort. The town proper is situated about 2½ m. from the +seashore, and on the south-western slope of a steep hill (669 ft., +belonging to the Maurettes chain, 961 ft.), which is one of the +westernmost spurs of the thickly wooded Montagnes des Maures. It is +sheltered from the north-east and east winds, but is exposed to the cold +north-west wind or _mistral_. Towards the south and south-east a fertile +plain, once famous for its orange groves, but now mainly covered by +vineyards and farms, stretches to the sea, while to the south-west, +across a narrow valley, rises a cluster of low hills, on which is the +suburb of Costebelle. The older portion of the town is still surrounded, +on the north and east, by its ancient, though dilapidated medieval +walls, and is a labyrinth of steep and dirty streets. The more modern +quarter which has grown up at the southern foot of the hill has handsome +broad boulevards and villas, many of them with beautiful gardens, filled +with semi-tropical plants. Among the objects of interest in the old town +are: the house (Rue Rabaton, 7) where J. B. Massillon (1663-1742), the +famous pulpit orator, was born; the parish church of St Louis, built +originally in the 13th century by the Cordelier or Franciscan friars, +but completely restored in the earlier part of the 19th century; and the +site of the old château, on the summit of the hill, now occupied by a +villa. The plain between the new town and the sea is occupied by large +nurseries, an excellent _jardin d'acclimatation_, and many market +gardens, which supply Paris and London with early fruits and vegetables, +especially artichokes, as well as with roses in winter. There are +extensive salt beds (_salines_) both on the peninsula of Giens, S. of +the town, and also E. of the town. To the east of the Giens peninsula is +the fine natural harbour of Hyères, as well as three thinly populated +islands (the Stoechades of the ancients), Porquerolles, Port Cros and Le +Levant, which are grouped together under the common name of Îles +d'Hyères. + +The town of Hyères seems to have been founded in the 10th century, as a +place of defence against pirates, and takes its name from the aires +(_hierbo_ in the Provençal dialect), or threshing-floors for corn, which +then occupied its site. It passed from the possession of the viscounts +of Marseilles to Charles of Anjou, count of Provence, and brother of St +Louis (the latter landed here in 1254, on his return from Egypt). The +château was dismantled by Henri IV., but thanks to its walls, the town +resisted in 1707 an attack made by the duke of Savoy. + + See Ch. Lenthéric, _La Provence Maritime ancienne et moderne_ (chap. + 5) (Paris, 1880). (W. A. B. C.) + + + + +HYGIEIA, in Greek mythology, the goddess of health. It seems probable +that she was originally an abstraction, subsequently personified, rather +than an independent divinity of very ancient date. The question of the +original home of her worship has been much discussed. The oldest traces +of it, so far as is known at present, are to be found at Titane in the +territory of Sicyon, where she was worshipped together with Asclepius, +to whom she appears completely assimilated, not an independent +personality. Her cult was not introduced at Epidaurus till a late date, +and therefore, when in 420 B.C. the worship of Asclepius was introduced +at Athens coupled with that of Hygieia, it is not to be inferred that +she accompanied him from Epidaurus, or that she is a Peloponnesian +importation at all. It is most probable that she was invented at the +time of the introduction of Asclepius, after the sufferings caused by +the plague had directed special attention to sanitary matters. The +already existing worship of Athena Hygieia had nothing to do with +Hygieia the goddess of health, but merely denoted the recognition of the +power of healing as one of the attributes of Athena, which gradually +became crystallized into a concrete personality. At first no special +relationship existed between Asclepius and Hygieia, but gradually she +came to be regarded as his daughter, the place of his wife being already +secured by Epione. Later Orphic hymns, however, and Herodas iv. 1-9, +make her the wife of Asclepius. The cult of Hygieia then spread +concurrently with that of Asclepius, and was introduced at Rome from +Epidaurus in 293, by which time she may have been admitted (which was +not the case before) into the Epidaurian family of the god. Her proper +name as a Romanized Greek importation was Valetudo, but she was +gradually identified with Salus, an older genuine Italian divinity, to +whom a temple had already been erected in 302. While in classical times +Asclepius and Hygieia are simply the god and goddess of health, in the +declining years of paganism they are protecting divinities generally, +who preserve mankind not only from sickness but from all dangers on land +and sea. In works of art Hygieia is represented, together with +Asclepius, as a maiden of benevolent appearance, wearing the chiton and +giving food or drink to a serpent out of a dish. + + See the article by H. Lechat in Daremberg and Saglio's _Dictionnaire + des antiquités_, with full references to authorities; and E. Thrämer + in Roscher's _Lexikon der Mythologie_, with a special section on the + modern theories of Hygieia. + + + + +HYGIENE (Fr. _hygiène_, from Gr. [Greek: hygiainein], to be healthy), +the science of preserving health, its practical aim being to render +"growth more perfect, decay less rapid, life more vigorous, death more +remote." The subject is thus a very wide one, embracing all the agencies +which affect the physical and mental well-being of man, and it requires +acquaintance with such diverse sciences as physics, chemistry, geology, +engineering, architecture, meteorology, epidemiology, bacteriology and +statistics. On the personal or individual side it involves consideration +of the character and quality of food and of water and other beverages; +of clothing; of work, exercise and sleep; of personal cleanliness, of +special habits, such as the use of tobacco, narcotics, &c.; and of +control of sexual and other passions. In its more general and public +aspects it must take cognizance of meteorological conditions, roughly +included under the term climate; of the site or soil on which dwellings +are placed; of the character, materials and arrangement of dwellings, +whether regarded individually or in relation to other houses among which +they stand; of their heating and ventilation; of the removal of excreta +and other effete matters; of medical knowledge relating to the incidence +and prevention of disease; and of the disposal of the dead. + + These topics will be found treated in such articles as DIETETICS, + FOOD, FOOD-PRESERVATION, ADULTERATION, WATER, HEATING, VENTILATION, + SEWERAGE, BACTERIOLOGY, HOUSING, CREMATION, &c. For legal enactments + which concern the sanitary well-being of the community, see PUBLIC + HEALTH. + + + + +HYGINUS, eighth pope. It was during his pontificate (c. 137-140) that +the gnostic heresies began to manifest themselves at Rome. + + + + +HYGINUS (surnamed GROMATICUS, from _gruma_, a surveyor's measuring-rod), +Latin writer on land-surveying, flourished in the reign of Trajan (A.D. +98-117). Fragments of a work on legal boundaries attributed to him will +be found in C. F. Lachmann, _Gromatici Veteres_, i. (1848). + + A treatise on Castrametation (_De Munitionibus Castrorum_), also + attributed to him, is probably of later date, about the 3rd century + A.D. (ed. W. Gemoll, 1879; A. von Domaszewski, 1887). + + + + +HYGINUS, GAIUS JULIUS, Latin author, a native of Spain (or Alexandria), +was a pupil of the famous Cornelius Alexander Polyhistor and a freedman +of Augustus, by whom he was made superintendent of the Palatine library +(Suetonius, _De Grammaticis_, 20). He is said to have fallen into great +poverty in his old age, and to have been supported by the historian +Clodius Licinus. He was a voluminous author, and his works included +topographical and biographical treatises, commentaries on Helvius Cinna +and the poems of Virgil, and disquisitions on agriculture and +bee-keeping. All these are lost. + + Under the name of Hyginus two school treatises on mythology are + extant: (1) _Fabularum Liber_, some 300 mythological legends and + celestial genealogies, valuable for the use made by the author of the + works of Greek tragedians now lost; (2) _De Astronomia_, usually + called _Poetica Astronomica_, containing an elementary treatise on + astronomy and the myths connected with the stars, chiefly based on the + [Greek: Katasterismoi] of Eratosthenes. Both are abridgments and both + are by the same hand; but the style and Latinity and the elementary + mistakes (especially in the rendering of the Greek originals) are held + to prove that they cannot have been the work of so distinguished a + scholar as C. Julius Hyginus. It is suggested that these treatises are + an abridgment (made in the latter half of the 2nd century) of the + _Genealogiae_ of Hyginus by an unknown grammarian, who added a + complete treatise on mythology. + + EDITIONS.--_Fabulae_, by M. Schmidt (1872); _De Astronomia_, by B. + Bunte (1875); see also Bunte, _De C. Julii Hygini, Augusti Liberti, + Vita et Scriptis_ (1846). + + + + +HYGROMETER (Gr. [Greek: hygros], moist, [Greek: metron], a measure), an +instrument for measuring the absolute or relative amount of moisture in +the atmosphere; an instrument which only qualitatively determines +changes in the humidity is termed a "hygroscope." The earlier +instruments generally depended for their action on the contraction or +extension of substances when exposed to varying degrees of moisture; +catgut, hair, twisted cords and wooden laths, all of which contract with +an increase in the humidity and vice versa, being the most favoured +materials. The familiar "weather house" exemplifies this property. This +toy consists of a house provided with two doors, through which either a +man or woman appears according as the weather is about to be wet or +fine. This action is effected by fixing a catgut thread to the base on +which the figures are mounted, in such a manner that contraction of the +thread rotates the figures so that the man appears and extension so that +the woman appears. + + Many of the early forms are described in C. Hutton, _Math. and Phil. + Dictionary_ (1815). The modern instruments, which utilize other + principles, are described in METEOROLOGY: II. _Methods and Apparatus_. + + + + +HYKSOS, or "SHEPHERD KINGS," the name of the earliest invaders of Egypt +of whom we have definite evidence in tradition. Josephus (c. _Apion._ i. +14), who identifies the Hyksos with the Israelites, preserves a passage +from the second book of Manetho giving an account of them. (It may be +that Josephus had it, not direct from Manetho's writings, but through +the garbled version of some Alexandrine compiler.) In outline it is as +follows. In the days of a king of Egypt named Timaeus the land was +suddenly invaded from the east by men of ignoble race, who conquered it +without a struggle, destroyed cities and temples, and slew or enslaved +the inhabitants. At length they elected a king named Salatis, who, +residing at Memphis, made all Egypt tributary, and established garrisons +in different parts, especially eastwards, fearing the Assyrians. He +built also a great fortress at Avaris, in the Sethroite nome, east of +the Bubastite branch of the Nile. Salatis was followed in succession by +Beon, Apachnas, Apophis, Jannas and Asses. These six kings reigned 198 +years and 10 months, and all aimed at extirpating the Egyptians. Their +whole race was named Hyksos, i.e. "shepherd kings," and some say they +were Arabs (another explanation found by Josephus is "captive +shepherds"). When they and their successors had held Egypt for 511 +years, the kings of the Thebais and other parts of Egypt rebelled, and a +long and mighty war began. Misphragmuthosis worsted the "Shepherds" and +shut them up in Avaris; and his son Thutmosis, failing to capture the +stronghold, allowed them to depart; whereupon they went forth, 240,000 +in number, established themselves in Judea and built Jerusalem. + +In Manetho's list of kings, the six above named (with many variations in +detail) form the XVth dynasty, and are called "six foreign Phoenician +kings." The XVIth dynasty is of thirty-two "Hellenic (_sic?_) shepherd +kings," the seventeenth is of "shepherds and Theban kings" (reigning +simultaneously). The lists vary greatly in different versions, but the +above seems the most reasonable selection of readings to be made. For +"Hellenic" see below. The supposed connexion with the Israelites has +made the problem of the Hyksos attractive, but light is coming upon it +very slowly. In 1847 E. de Rougé proved from a fragment of a story in +the papyri of the British Museum, that Apopi was one of the latest of +the Hyksos kings, corresponding to Aphobis; he was king of the "pest" +and suppressed the worship of the Egyptian gods, and endeavoured to make +the Egyptians worship his god Setekh or Seti; at the same time an +Egyptian named Seqenenre reigned in Thebes, more or less subject to +Aphobis. The city of Hawari (Avaris) was also mentioned in the fragment. + +In 1850 a record of the capture of this city from the Hyksos by Ahmosi, +the founder of the eighteenth dynasty, was discovered by the same +scholar. A large class of monuments was afterwards attributed to the +Hyksos, probably in error. Some statues and sphinxes, found in 1861 by +Mariette at Tanis (in the north-east of the Delta), which had been +usurped by later kings, had peculiar "un-Egyptian" features. One of +these bore the name of Apopi engraved lightly on the shoulder; this was +evidently a usurper's mark, but from the whole circumstances it was +concluded that these, and others of the same type of features found +elsewhere, must have belonged to the Hyksos. This view held the field +until 1893, when Golénischeff produced an inferior example bearing its +original name, which showed that in this case it represented Amenemhe +III. In consequence it is now generally believed that they all belong to +the twelfth dynasty. Meanwhile a headless statue of a king named Khyan, +found at Bubastis, was attributed on various grounds to the Hyksos, the +soundest arguments being his foreign name and the boastful un-Egyptian +epithet "beloved of his _ka_," where "beloved of Ptah" or some other god +was to be expected. His name was immediately afterwards recognized on a +lion found as far away from Egypt as Bagdad. Flinders Petrie then +pointed out a group of kings named on scarabs of peculiar type, which, +including Khyan, he attributed to the period between the Old Kingdom and +the New, while others were in favour of assigning them all to the +Hyksos, whose appellation seemed to be recognizable in the title +Hek-khos, "ruler of the barbarians," borne by Khyan. The extraordinary +importance of Khyan was further shown by the discovery of his name on a +jar-lid at Cnossus in Crete. Semitic features were pointed out in the +supposed Hyksos names, and Petrie was convinced of their date by his +excavations of 1905-1906 in the eastern Delta. Avaris is generally +assigned to the region towards Pelusium on the strength of its being +located in the Sethroite nome by Josephus, but Petrie thinks it was at +Tell el-Yahudiyeh (Yehudia), where Hyksos scarabs are common. From the +remains of fortifications there he argues that the Hyksos were +uncivilized desert people, skilled in the use of the bow, and must thus +have destroyed by their archery the Egyptian armies trained to fight +hand-to-hand; further, that their hordes were centered in Syria, but +were driven thence by a superior force in the East to take refuge in the +islands and became a sea-power--whence the strange description +"Hellenic" in Manetho, which most editors have corrected to [Greek: +alloi], "others." Besides the statue of Khyan, blocks of granite with +the name of Apopi have been found in Upper Egypt at Gebelen and in +Lower Egypt at Bubastis. The celebrated Rhind mathematical papyrus was +copied in the reign of an Apopi from an original of the time of Amenemhe +III. Large numbers of Hyksos scarabs are found in Upper and Lower Egypt, +and they are not unknown in Palestine. Khyan's monuments, inconspicuous +as they are, actually extend over a wider area--from Bagdad to +Cnossus--than those of any other Egyptian king. + +It is certain that this mysterious people were Asiatic, for they are +called so by the Egyptians. Though Seth was an Egyptian god, as god of +the Hyksos he represents some Asiatic deity. The possibility of a +connexion between the Hyksos and the Israelites is still admitted in +some quarters. Hatred of these impious foreigners, of which there is +some trace in more than one text, aroused amongst the Egyptians (as +nothing ever did before or since) that martial spirit which carried the +armies of Tethmosis to the Euphrates. + + Besides the histories of Egypt, see J. H. Breasted, _Ancient Records + of Egypt_; Historical Documents ii. 4, 125; G. Maspero, _Contes + populaires_, 3me éd. p. 236; W. M. F. Petrie, _Hyksos and Israelite + Cities_, p. 67; Golénischeff in _Recueil de travaux_, xv. p. 131. + (F. Ll. G.) + + + + +HYLAS, In Greek legend, son of Theiodamas, king of the Dryopians in +Thessaly, the favourite of Heracles and his companion on the Argonautic +expedition. Having gone ashore at Kios in Mysia to fetch water, he was +carried off by the nymphs of the spring in which he dipped his pitcher. +Heracles sought him in vain, and the answer of Hylas to his +thrice-repeated cry was lost in the depths of the water. Ever +afterwards, in memory of the threat of Heracles to ravage the land if +Hylas were not found, the inhabitants of Kios every year on a stated day +roamed the mountains, shouting aloud for Hylas (Apollonius Rhodius i. +1207; Theocritus xiii.; Strabo xii. 564; Propertius i. 20; Virgil, +_Ecl._ vi. 43). But, although the legend is first told in Alexandrian +times, the "cry of Hylas" occurs long before as the "Mysian cry" in +Aeschylus (_Persae_, 1054), and in Aristophanes (_Plutus_, 1127) "to cry +Hylas" is used proverbially of seeking something in vain. Hylas, like +Adonis and Hyacinthus, represents the fresh vegetation of spring, or the +water of a fountain, which dries up under the heat of summer. It is +suggested that Hylas was a harvest deity and that the ceremony gone +through by the Kians was a harvest festival, at which the figure of a +boy was thrown into the water, signifying the dying vegetation-spirit of +the year. + + See G. Türk in _Breslauer Philologische Abhandlungen_, vii. (1895); W. + Mannhardt, _Mythologische Forschungen_ (1884). + + + + +HYLOZOISM (Gr. [Greek: hylê], matter, [Greek: zôê], life), in +philosophy, a term applied to any system which explains all life, +whether physical or mental, as ultimately derived from matter ("cosmic +matter," _Weldstoff_). Such a view of existence has been common +throughout the history of thought, and especially among physical +scientists. Thus the Ionian school of philosophy, which began with +Thales, sought for the beginning of all things in various material +substances, water, air, fire (see IONIAN SCHOOL). These substances were +regarded as being in some sense alive, and taking some active part in +the development of being. This primitive hylozoism reappeared in +modified forms in medieval and Renaissance thought, and in modern times +the doctrine of materialistic monism is its representative. Between +modern materialism and hylozoism proper there is, however, the +distinction that the ancients, however vaguely, conceived the elemental +matter as being in some sense animate if not actually conscious and +conative. + + + + +HYMEN, or HYMENAEUS, originally the name of the song sung at marriages +among the Greeks. As usual the name gradually produced the idea of an +actual person whose adventures gave rise to the custom of this song. He +occurs often in association with Linus and Ialemus, who represent +similar personifications, and is generally called a son of Apollo and a +Muse. As the son of Dionysus and Aphrodite, he was regarded as a god of +fruitfulness. In Attic legend he was a beautiful youth who, being in +love with a girl, followed her in a procession to Eleusis disguised as a +woman, and saved the whole band from pirates. As reward he obtained the +girl in marriage, and his happy married life caused him ever afterwards +to be invoked in marriage songs (Servius on Virgil, _Aen._ i. 651). +According to another story, he was a youth who was killed by the fall of +his house on his wedding day; hence he was invoked, to propitiate him +and avert a similar fate from others (Servius, loc. cit.). He is +represented in works of art as an effeminate-looking, winged youth, +carrying a bridal torch and wearing a nuptial veil. The marriage song +was sung, with musical accompaniment, during the procession of the bride +from her parents' house to that of the bridegroom, Hymenaeus being +invoked at the end of each portion. + + See R. Schmidt, _De Hymenaeo el Talasio_ (1886), and J. A. Hild in + Daremberg and Saglis's _Dictionnaire des antiquités_. + + + + +HYMENOPTERA (Gr. [Greek: hymên], a membrane, and [Greek: pteron], a +wing), a term used in zoological classification for one of the most +important orders of the class _Hexapoda_ (q.v.). The order was founded +by Linnaeus (_Systema Naturae_, 1735), and is still recognized by all +naturalists in the sense proposed by him, to include the saw-flies, +gall-flies, ichneumon-flies and their allies, ants, wasps and bees. The +relationship of the Hymenoptera to other orders of insects is discussed +in the article HEXAPODA, but it may be mentioned here that in structure +the highest members of the order are remarkably specialized, and that in +the perfection of their instincts they stand at the head of all insects +and indeed of all invertebrate animals. About 30,000 species of +Hymenoptera are now known. + +[Illustration: After C. L. Marlatt, _Bur. Ent. Bull. 3, N.S., U.S. Dept. +Agric._ + +FIG. 1.--A, Front of head of Saw-fly (_Pachynematus_); a, labrum; b, +clypeus; c, vertex; d, d, antennal cavities. C and D, Mandibles. E, +First maxilla; a, cardo; b, stipes; c, galea; d, lacinia; e, palp. B, +Second maxillae (Labium); a, mentum; b, ligula (between the two galeae); +c, c, palps. Magnified.] + +[Illustration: FIG. 2.--Jaws of Hive-bee (_Apis mellifica_). Magnified +about 6½ times. a, mandible; b, c, palp and lacinia of first maxilla; d, +e, g, h, mentum, palp, fused laciniae (ligula or "tongue") and galea of +2nd maxillae.] + +[Illustration: After C. Janet, _Mem. Soc. Zool. France_ (1898). + +FIG. 3.--Median section through mid-body of female Red Ant (_Myrmica +rubra_). H, Head; 1, 2, 3, the thoracic segments; i., ii., the first and +second abdominal segments; i., being the propodeum.] + + _Characters._--In all Hymenoptera the mandibles (fig. 1, C, D) are + well developed, being adapted, as in the more lowly winged insects, + such as the Orthoptera, for biting. The more generalized Hymenoptera + have the second maxillae but slightly modified, their inner lobes + being fused to form a _ligula_ (fig. 1, B, b). In the higher families + this structure becomes elongated (fig. 2, g) so as to form an + elaborate sucking-organ or "tongue." These insects are able, + therefore, to bite as well as to suck, whereas most insects which have + acquired the power of suction have lost that of biting. Both fore- and + hind-wings are usually present, both pairs being membranous, the + hind-wings small and not folded when at rest, each provided along the + costa with a row of curved hooks which catch on to a fold along the + dorsum of the adjacent fore-wing during flight. A large number of + Hymenoptera are, however, entirely wingless--at least as regards one + sex or form of the species. One of the most remarkable features is the + close union of the foremost abdominal segment (fig. 3, i.) with the + metathorax, of which it often seems to form a part, the apparent first + abdominal segment being, in such case, really the second (fig. 3, + ii.). The true first segment, which undergoes a more or less complete + fusion with the thorax is known as the "median segment" or + _propodeum_. In female Hymenoptera the typical insectan ovipositor + with its three pairs of processes is well developed, and in the higher + families this organ becomes functional as a sting (fig. 5),--used for + offence and defence. As regards their life history, all Hymenoptera + undergo a "complete" metamorphosis. The larva is soft-skinned + (eruciform), being either a caterpillar (fig. 6, b) or a legless grub + (fig. 7, a), and the pupa is free (fig. 7, c), i.e. with the + appendages not fixed to the body, as is the case in the pupa of most + moths. + + [Illustration: FIG. 4.--Fore-Wings of Hymenoptera. + + 1. Tenthredinidae (_Hylotoma_)-- 1, marginal; 2, appendicular; 3, 4, + 5, 6, radial or submarginal; 7, 8, 9, median or discoidal; 10, + sub-costal; 11, 12, cubital or branchial; and 13, anal or lanceolate + cellules; a, b, c, submarginal nervures; d, basal nervures; e, f, + recurrent nervures; st, stigma; co, costa. + 2. Cynipidae (_Cynips_). + 3. Chalcididae (_Perilampus_). + 4. Proctotrypidae (_Codrus_). + 5. Mymaridae (_Mymar_). + 6. Braconidae (_Bracon_). + 7. Ichneumonidae (_Trogus_). + 8. Chrysididae (_Cleptes_). + 9. Formicidae (_Formica_). + 10. Vespidae (_Vespa_). + 11. Apidae (_Apathus_).] + + _Structure._--The head of a hymenopterous insect bears three simple + eyes (ocelli) on the front and vertex in addition to the large + compound eyes. The feelers are generally simple in type, rarely + showing serrations or prominent appendages; but one or two basal + segments are frequently differentiated to form an elongate "scape," + the remaining segments--carried at an elbowed angle to the + scape--making up the "flagellum"; the segments of the flagellum often + bear complex sensory organs. The general characters of the jaws have + been mentioned above, and in detail there is great variation in these + organs among the different families. The sucking tongue of the + Hymenoptera has often been compared with the hypopharynx of other + insects. According to D. Sharp, however, the hypopharynx is present in + all Hymenoptera as a distinct structure at the base of the "tongue," + which must be regarded as representing the fused laciniae of the + second maxillae. In the thorax the pronotum and prosternum are closely + associated with the mesothorax, but the pleura of the prothorax are + usually shifted far forwards, so that the fore-legs are inserted just + behind the head. A pair of small plates--the tegulae--are very + generally present at the bases of the fore-wings. The union of the + first abdominal segment with the metathorax has been already + mentioned. The second (so-called "first") abdominal segment is often + very constricted, forming the "waist" so characteristic of wasps and + ants for example. The constriction of this segment and its very + perfect articulation with the propodeum give great mobility to the + abdomen, so that the ovipositor or sting can be used with the greatest + possible accuracy and effect. + + Mention has already been made of the series of curved hooks along the + costa of the hind-wing; by means of this arrangement the two wings of + a side are firmly joined together during flight, which thus becomes + particularly accurate. The wings in the Hymenoptera show a marked + reduction in the number of nervures as compared with more primitive + insects. The main median nervure, and usually also the sub-costal + become united with the radial, while the branches of radial, median + and cubital nervures pursuing a transverse or recurrent course across + the wing, divide its area into a number of areolets or "cells," that + are of importance in classification. Among many of the smaller + Hymenoptera we find that the wings are almost destitute of nervures. + In the hind-wings--on account of their reduced size--the nervures are + even more reduced than in the fore-wings. + + The legs of Hymenoptera are of the typical insectan form, and the foot + is usually composed of five segments. In many families the trochanter + appears to be represented by two small segments, there being thus an + extra joint in the leg. It is almost certain that the distal of these + two segments really belongs to the thigh, but the ordinary + nomenclature will be used in the present article, as this character is + of great importance in discriminating families, and the two segments + in question are referred to the trochanter by most systematic writers. + + [Illustration: After C. Janet, _Aiguillon de la Myrmica rubra_ (Paris, + 1898). + + FIG. 5.--Ovipositor or Sting of Red Ant (_Myrmica rubra_) Queen. + Magnified. The right sheath C (outer process of the ninth abdominal + segment--9) is shown in connexion with the guide B formed by the inner + processes of the 9th segment. The stylet A (process of the 8th + abdominal segment--8) is turned over to show its groove a, which works + along the tongue or rail b.] + + The typical insectan ovipositor, so well developed among the + Hymenoptera, consists of three pairs of processes (gonapophyses) two + of which belong to the ninth abdominal segment and one to the eighth. + The latter are the cutting or piercing stylets (fig. 5, A) of the + ovipositor, while the two outer processes of the ninth segment are + modified into sheaths or feelers (fig. 5, C) and the two inner + processes form a guide (fig. 5, B) on which the stylets work, tongues + or rails on the "guide" fitting accurately into longitudinal grooves + on the stylet. In the different families of the Hymenoptera, there are + various modifications of the ovipositor, in accord with the habits of + the insects and the purposes to which the organ is put. The sting of + wasps, ants and bees is a modified ovipositor and is used for + egg-laying by the fertile females, as well as for defence. Most male + Hymenoptera have processes which form claspers or genital armature. + These processes are not altogether homologous with those of the + ovipositor, being formed by inner and outer lobes of a pair of + structures on the ninth abdominal segment. + + Many points of interest are to be noted in the internal structure of + the Hymenoptera. The gullet leads into a moderate-sized crop, and + several pairs of salivary glands open into the mouth. The crop is + followed by a proventriculus which, in the higher Hymenoptera, forms + the so-called "honey stomach," by the contraction of whose wails the + solid and liquid food can be separated, passed on into the digestive + stomach, or held in the crop ready for regurgitation into the mouth. + Behind the digestive stomach are situated, as usual, intestine and + rectum, and the number of kidney (Malpighian) tubes varies from only + six to over a hundred, being usually great. + + In the female, each ovary consists of a large number of ovarian tubes, + in which swollen chambers containing the egg-cells alternate with + smaller chambers enclosing nutrient material. In connexion with the + ovipositor are two poison-glands, one acid and the other alkaline in + its secretion. The acid gland consists of one, two or more tubes, with + a cellular coat of several layers, opening into a reservoir whence + the duct leads to the exterior. The alkaline gland is an irregular + tube with a single cellular layer, its duct opening alongside that of + the acid reservoir. These glands are most strongly developed when the + ovipositor is modified into a sting. + + _Development._--Parthenogenesis is of normal occurrence in the + life-cycle of many Hymenoptera. There are species of gall-fly in which + males are unknown, the unfertilized eggs always developing into + females. On the other hand, in certain saw-flies and among the higher + families, the unfertilized eggs, capable of development, usually give + rise to male insects (see BEE). The larvae of most saw-flies feeding + on the leaves of plants are caterpillars (fig. 6, b) with numerous + abdominal pro-legs, but in most families of Hymenoptera the egg is + laid in such a situation that an abundant food-supply is assured + without exertion on the part of the larva, which is consequently a + legless grub, usually white in colour, and with soft flexible cuticle + (fig. 7, a). The organs and instincts for egg-laying and + food-providing are perhaps the most remarkable features in the economy + of the Hymenoptera. Gall-fly grubs are provided with vegetable food + through the eggs being laid by the mother insect within plant tissues. + The ichneumon pierces the body of a caterpillar and lays her eggs + where the grubs will find abundant animal food. A digging-wasp hunts + for insect prey and buries it with the egg, while a true wasp feeds + her brood with captured insects, as a bird her fledglings. Bees store + honey and pollen to serve as food for their young. Thus we find + throughout the order a degree of care for offspring unreached by other + insects, and this family-life has, in the best known of the + Hymenoptera--ants, wasps and bees--developed into an elaborate social + organization. + +_Social Life._--The development of a true insect society among the +Hymenoptera is dependent on a differentiation among the females between +individuals with well-developed ovaries ("queens") whose special +function is reproduction; and individuals with reduced or aborted +ovaries ("workers") whose duty is to build the nest, to gather food and +to tend and feed the larvae. Among the wasps the workers may only differ +from the queens in size, and individuals intermediate between the two +forms of female may be met with. Further, the queen wasp, and also the +queen humble-bee, commences unaided the work of building and founding a +new nest, being afterwards helped by her daughters (the workers) when +these have been developed. In the hive-bee and among ants, on the other +hand, there are constant structural distinctions between queen and +worker, and the function of the queen bee in a hive is confined to +egg-laying, the labour of the community being entirely done by the +workers. Many ants possess several different forms of worker, adapted +for special duties. Details of this fascinating subject are given in the +special articles ANT, BEE and WASP (q.v.). + +_Habits and Distribution._--Reference has been already made to the +various methods of feeding practised by Hymenoptera in the larval stage, +and the care taken of or for the young throughout the order leads in +many cases to the gathering of such food by the mother or nurse. Thus, +wasps catch flies; worker ants make raids and carry off weak insects of +many kinds; bees gather nectar from flowers and transform it into honey +within their stomachs--largely for the sake of feeding the larvae in the +nest. The feeding habits of the adult may agree with that of the larva, +or differ, as in the ease of wasps which feed their grubs on flies, but +eat principally vegetable food themselves. The nest-building habit is +similarly variable. Digging wasps make simple holes in the ground; many +burrowing bees form branching tunnels; other bees excavate timber or +make their brood-chambers in hollow plant-stems; wasps work up with +their saliva vegetable fibres bitten off tree-bark to make paper; social +bees produce from glands in their own bodies the wax whence their +nest-chambers are built. The inquiline habit ("cuckoo-parasitism"), when +one species makes use of the labour of another by invading the nest and +laying her eggs there, is of frequent occurrence among Hymenoptera; and +in some cases the larva of the intruder is not content with taking the +store of food provided, but attacks and devours the larva of the host. + +Most Hymenoptera are of moderate or small size, the giants of the +order--certain saw-flies and tropical digging-wasps--never reach the bulk +attained by the largest beetles, while the wing-spread is narrow compared +with that of many dragon-flies and moths. On the other hand, there are +thousands of very small species, and the tiny "fairy-flies" +(_Mymaridae_), whose larvae live as parasites in the eggs of various +insects, are excessively minute for creatures of such complex +organization. Hymenoptera are probably less widely distributed than +Aptera, Coleoptera or Diptera, but they are to be found in all except the +most inhospitable regions of the globe. The order is, with few +exceptions, terrestrial or aerial in habit. Comparatively only a few +species are, for part of their lives, denizens of fresh water; these, as +larvae, are parasitic on the eggs or larvae of other aquatic insects, the +little hymenopteron, _Polynema natans_, one of the "fairy-flies"--swims +through the water by strokes of her delicate wings in search of a +dragon-fly's egg in which to lay her own egg, while the rare _Agriotypus_ +dives after the case of a caddis-worm. It is of interest that the waters +have been invaded by the parasitic group of the Hymenoptera, since in +number of species this is by far the largest of the order. No group of +terrestrial insects escapes their attacks--even larvae boring in wood are +detected by ichneumon flies with excessively long ovipositors. Not a few +cases are known in which a parasitic larva is itself pierced by the +ovipositor of a "hyperparasite," and even the offspring of the latter may +itself fall a victim to the attack of a "tertiary parasite." + + _Fossil History._--Very little is known of the history of the + Hymenoptera previous to the Tertiary epoch, early in which, as we know + from the evidence of many Oligocene and Miocene fossils, all the more + important families had been differentiated. Fragments of wings from + the Lias and Oolitic beds have been referred to ants and bees, but the + true nature of these remains is doubtful. + +_Classification._--Linnaeus divided the Hymenoptera into two +sections--the Terebrantia, whose females possess a cutting or piercing +ovipositor, and the Aculeata, in which the female organ is modified into +a sting. This nomenclature was adopted by P. A. Latreille and has been +in general use until the present day. A closely similar division of the +order results from T. Hartig's character drawn from the +trochanter--whether of two segments or undivided--the groups being +termed respectively Ditrocha and Monotrocha. But the most natural +division is obtained by the separation of the saw-flies as a primitive +sub-order, characterized by the imperfect union of the first abdominal +segment with the thorax, and by the broad base of the abdomen, so that +there is no median constriction or "waist," and by the presence of +thoracic legs--usually also of abdominal pro-legs--in the larva. All the +other families of Hymenoptera, including the gall-flies, ichneumons and +aculeates, have the first abdominal segment closely united with the +thorax, the second abdominal segment constricted so as to form a narrow +stalk or "waist," and legless larvae without a hinder outlet to the +food-canal. These two sub-orders are usually known as the +_Sessiliventra_ and _Petioliventra_ respectively, but the names +_Symphyta_ and _Apocrita_ proposed in 1867 by C. Gerstaecker have +priority, and should not be replaced. + + + _Symphyta._ + + This sub-order, characterized by the "sessile," broad-based abdomen, + whose first segment is imperfectly united with the thorax, and by the + usually caterpillar-like larvae with legs, includes the various groups + of saw-flies. Three leading families may be mentioned. The _Cephidae_, + or stem saw-flies, have an elongate pronotum, a compressed abdomen, + and a single spine on the shin of the fore-leg. The soft, white larvae + have the thoracic legs very small and feed in the stems of various + plants. _Cephus pygmaeus_ is a well-known enemy of corn crops. The + _Siricidae_ ("wood-wasps") are large elongate insects also with one + spine on each fore-shin, but with the pronotum closely joined to the + mesothorax. The ovipositor is long and prominent, enabling the female + insect to lay her eggs in the wood of trees, where the white larvae, + whose legs are excessively short, tunnel and feed. These insects are + adorned with bands of black and yellow, or with bright metallic + colours, and on account of their large size and formidable ovipositors + they often cause needless alarm to persons unfamiliar with their + habits. The _Tenthredinidae_, or true saw-flies, are distinguished by + two spines on each fore-shin, while the larvae are usually + caterpillars, with three pairs of thoracic legs, and from six to eight + pairs of abdominal pro-legs the latter not possessing the hooks found + on the pro-legs of lepidopterous caterpillars. Most saw-fly larvae + devour leaves, and the beautifully serrate processes of the ovipositor + are well adapted for egg-laying in plant tissues. Some saw-fly larvae + are protected by a slimy secretion (fig. 6, c) and a few live + concealed in galls. In the form of the feelers, the wing-neuration and + minor structural details there is much diversity among the saw-flies. + They have been usually regarded as a single family, but W. H. Ashmead + has lately differentiated eleven families of them. + + + _Apocrita._ + + This sub-order includes the vast majority of the Hymenoptera, + characterized by the narrowly constricted waist in the adult and by + the legless condition of the larva. The trochanter is simple in some + genera and divided in others. With regard to the minor divisions of + this group, great difference of opinion has prevailed among students. + In his recent classification Ashmead (1901) recognizes seventy-nine + families arranged under eight "super-families." The number of species + included in this division is enormous, and the multiplication of + families is, to some extent, a natural result of increasingly close + study. But the distinctions between many of these rest on + comparatively slight characters, and it is likely that the future + discovery of new genera may abolish many among such distinctions as + may now be drawn. It seems advisable, therefore, in the present + article to retain the wider conception of the family that has hitherto + contented most writers on the Hymenoptera. Ashmead's "super-families" + have, however, been adopted as--founded on definite structural + characters--they probably indicate relationship more nearly than the + older divisions founded mostly on habit. The Cynipoidea include the + gall-flies and their parasitic relations. In the Chalcidoidea, + Ichneumonoidea and Proctotrypoidea will be found nearly all the + "parasitic Hymenoptera" of older classifications. The Formicoidea are + the ants. The group of Fossores, or "digging-wasps," is divided by + Ashmead, one section forming the Sphecoidea, while the other, together + with the Chrysidae and the true wasps, make up the Vespoidea. The + Apoidea consists of the bees only. + + [Illustration: After Marlatt, _Ent. Circ._ 26, U.S. Dept. Agric. + + FIG. 6.--a, Pear Saw-fly (_Eriocampoides limacina_); b, larva without, + and c, with its slimy protective coat; e, cocoon; f, larva before + pupation; g, pupa, magnified; d, leaves with larvae.] + + [Illustration: After Howard, _Ent. Tech. Bull._ 5 U.S. Dept. Agric. + + FIG. 7.--Chalcid (_Dibrachys boucheanus_), a hyper-parasite. + + a, Larva. + d, Its head more highly magnified. + b, Female fly. + c, Pupa of male. + e, Feeler.] + + _Cynipoidea._--In this division the ovipositor issues from the ventral + surface of the abdomen; the pronotum reaches back to the tegulae; the + trochanter has two segments; the fore-wing (fig. 4, 2) has no stigma, + but one or two areolets. The feelers with twelve to fifteen segments + are thread-like and straight. All the insects included in this group + are small and form two families--the Cynipidae and the Figitidae. They + are the "gall-flies," many of the species laying eggs in various + plant-tissues where the presence of the larva causes the formation of + a pathological growth or gall, always of a definite form and + characteristic of the species; the "oak-apple" and the bedeguar of + the rose are familiar examples. Other flies of this group have the + inquiline habit, laying their eggs in the galls of other species, + while others again pierce the cuticle of maggots or aphids, in whose + bodies their larvae live as parasites. + + _Chalcidoidea._--This division resembles the Cynipoidea in the + position of the ovipositor, and in the two segmented trochanters. The + fore-wing also has no stigma, and the whole wing is almost destitute + of nervures and areolets, while the pronotum does not reach back to + the tegulae, and the feelers are elbowed (fig. 7). The vast majority + of this group, including nearly 5000 known species, are usually + reckoned as a single family, the _Chalcididae_, comprising small + insects, often of bright metallic colours, whose larvae are parasitic + in insects of various orders. The "fig-insects," whose presence in + ripening figs is believed essential to the proper development of the + fruit, belong to _Blastophaga_ and other genera of this family. They + are remarkable in having wingless males and winged females. The + "polyembryonic" development of an _Encyrtus_, as studied by P. + Marchal, is highly remarkable. The female lays her egg in the egg of a + small ermine moth (_Hyponomeuta_) and the egg gives rise not to a + single embryo but to a hundred, which develop as the host-caterpillar + develops, being found at a later stage within the latter enveloped in + a flexible tube. + + The _Mymaridae_ or "fairy-flies" are distinguished from the + _Chalcididae_ by their narrow fringed wings (figs. 4, 5) and by the + situation of the ovipositor just in front of the tip of the abdomen. + They are among the most minute of all insects and their larvae are + probably all parasitic in insects' eggs. + + [Illustration: After Riley and Howard, _Insect Life_, vol. i. + + FIG. 8.--Ichneumon Fly (_Rhyssa per-suasoria_) ovipositing.] + + _Ichneumonoidea._--The ten thousand known species included in this + group agree with the Cynipoidea and Chalcidoidea in the position of + the ovipositor and in the jointed trochanters, but are distinguished + by the fore-wing possessing a distinct stigma and usually a typical + series of nervures and areolets (figs. 4, 8). Many of the species are + of fair size. They lay their eggs (fig. 8) in the bodies of insects + and their larvae belonging to various orders. A few small families + such as the _Evaniidae_ and the _Stephanidae_ are included here, but + the vast majority of the group fall into two large families, the + _Ichneumonidae_ and the _Braconidae_, the former distinguished by the + presence of two median (or discoidal) cells in the fore-wing (figs. 4, + 7), while the latter has only one (figs. 4, 6). Not a few of these + insects, however, are entirely wingless. On account of their work in + destroying plant-eating insects, the ichneumon-flies are of great + economic importance. + + _Proctotrypoidea._--This group may be distinguished from the preceding + by the position of the ovipositor at the extreme apex of the abdomen, + and from the groups that follow (with very few exceptions) by the + jointed trochanters of the legs. The pronotum reaches back to the + tegulae. The _Pelecinidae_--included here by Ashmead--are large + insects with remarkably elongate abdomens and undivided trochanters. + All the other members of the group may be regarded as forming a single + family--the _Proctotrypidae_, including an immense number of small + parasitic Hymenoptera, not a few of which are wingless. Of special + interest are the transformations of _Platygaster_, belonging to this + family, discovered by M. Ganin, and familiarized to English readers + through the writings of Sir J. Lubbock (Lord Avebury). The first larva + is broad in front and tapers behind to a "tail" provided with two + divergent processes, so that it resembles a small crustacean. It lives + in the grub of a gall-midge and it ultimately becomes changed into the + usual white and fleshy hymenopterous larva. The four succeeding + sections, in which the ovipositor is modified into a sting (always + exserted from the tip of the abdomen) and the trochanters are with few + exceptions simple, form the _Aculeata_ of Linnaeus. + + _Formicoidea._--The ants which form this group are readily + distinguished by the differentiation of the females into winged + "queens" and wingless "workers." The pronotum extends back to the + wing-bases, and the "waist" is greatly constricted and marked by one + or two "nodes." The differentiation of the females leads to a complex + social life, the nesting habits of ants and the various industries + that they pursue being of surpassing interest (see ANT). + + _Vespoidea._--This section includes a number of families characterized + by the backward extension of the prothorax to the tegulae and + distinguished from the ants by the absence of "nodes" at the base of + the abdomen. The true wasps have the fore-wings folded lengthwise when + at rest and the fore-legs of normal build--not specialized for + digging. The _Vespidae_ or social wasps have "queens" and "workers" + like the ants, but both these forms of female are winged; the claws on + their fret are simple. In the _Eumenidae_ or solitary wasps the female + sex is undifferentiated, and the foot claws are toothed. (For the + habits of these insects see WASP.) The _Chrysididae_ or ruby wasps are + small insects with a very hard cuticle exhibiting brilliant metallic + colours--blue, green and crimson. Only three or four abdominal + segments are visible, the hinder segments being slender and retracted + to form a telescope-like tube in which the ovipositor lies. When the + ovipositor is brought into use this tube is thrust out. The eggs are + laid in the nests of various bees and wasps, the chrysid larva living + as a "cuckoo" parasite. The _Trigonalidae_, a small family whose + larvae are parasitic in wasps' nests, also probably belong here. + + The other families of the _Vespoidea_ belong to the series of + "Fossores" or digging-wasps. In two of the families--the _Mutillidae_ + and _Thynnidae_--the females are wingless and the larvae live as + parasites in the larvae of other insects; the female _Mutilla_ enters + bumble-bees' nests and lays her eggs in the bee-grubs. In the other + families both sexes are winged, and the instinct and industry of the + females are among the most wonderful in the Hymenoptera. They make + burrows wherein they place insects or spiders which they have caught + and stung, laying their eggs beside the victim so that the young + larvae find themselves in presence of an abundant and appropriate + food-supply. Valuable observations on the habits of these insects are + due to J. H. Fabre and G. W. and E. Peckham. The prey is sometimes + stung in the neighbourhood of the nerve ganglia, so that it is + paralysed but not killed, the grub of the fossorial wasp devouring its + victim alive; but this instinct varies in perfection, and in many + cases the larva flourishes equally whether its prey be killed or not. + The females have a wonderful power of finding their burrows on + returning from their hunting expeditions. Among the Vespoid families + of fossorial wasps, the _Pompilidae_ are the most important. They are + recognizable by their slender and elongate hind-legs; many of them + provision their burrows with spiders. The _Sapygidae_ are parasitic on + bees, while the _Scoliidae_ are large, robust and hairy insects, many + of which prey upon the grubs of chafers. + + _Sphecoidea._--In this division are included the rest of the + "digging-wasps," distinguished from the _Vespoidea_ by the short + pronotum not reaching backward to the tegulae. They have usually been + reckoned as forming a single, very large family--the _Sphegidae_--but + ten or twelve subdivisions of the group are regarded as distinct + families by Ashmead and others. Great diversity is shown in the + details of structure, habits and nature of the prey. Species of + _Sphex_, studied by Fabre, provisioned their brood-chambers with + crickets. _Pelopoeus_ hunts spiders, while _Ammophila_ catches + caterpillars for the benefit of her young. Fabre states that the + last-named insect uses a stone for the temporary closing of her + burrow, and the Peckhams have seen a female _Ammophila_ take a stone + between her mandibles and use it as a hammer for pounding down the + earth over her finished nest. The habits of _Bembex_ are of especial + interest. The female, instead of provisioning her burrow with a supply + of food that will suffice the larva for its whole life, brings fresh + flies with which she regularly feeds her young. In this instinct we + have a correspondence with the habits of social wasps and bees. Yet it + may be thought that the usual instinct of the "digging-wasps" to + capture and store up food in an underground burrow for the benefit of + offspring which they will never see is even more surprising. The habit + of some genera is to catch the prey before making their tunnel, but + more frequently the insect digs her nest, and then hunts for prey to + put into it. + + _Apoidea._--The bees which make up this group agree with the + Sphecoidea in the short pronotum, but may be distinguished from all + other Hymenoptera by the widened first tarsal segment and the plumose + hairs on head and body. They are usually regarded as forming a single + family--the _Apidae_--but there is very great diversity in structural + details, and Ashmead divides them into fourteen families. The + "tongue," for example, is short and obtuse or emarginate in _Colletes_ + and _Prosopis_, while in all other bees it is pointed at the tip. But + in _Andrena_ and its allies it is comparatively short, while in the + higher genera, such as _Apis_ and _Bombus_, it is elongate and + flexible, forming a most elaborate and perfect organ for taking liquid + food. Bees feed on honey and pollen. Most of the genera are "solitary" + in habit, the female sex being undifferentiated; but among the + humble-bees and hive-bees we find, as in social wasps and ants, the + occurrence of workers, and the consequent elaboration of a wonderful + insect-society. (See BEE.) + + BIBLIOGRAPHY.--The literature of several special families of the + Hymenoptera will be found under the articles ANT, BEE, ICHNEUMON-FLY, + WASP, &c., referred to above. Among earlier students on structure may + be mentioned P. A. Latreille, _Familles naturelles du règne animal_ + (Paris, 1825), who recognized the nature of the "median segment." C. + Gerstaecker (_Arch. f. Naturg._ xx., 1867) and F. Brauer (_Sitzb. K. + Akad. Wiss. Wien._ lxxxv., 1883) should also be consulted on this + subject. For internal anatomy, specially the digestive organs, see L. + Dufour, _Mém. savants étrangers_, vii. (1841), and _Ann. Sci. Nat. + Zool._ (4), i. 1854. For nervous system H. Viallanes, _Ann. Sci. Nat. + Zool._ (7), ii. iv. 1886-1887, and F. C. Kenyon, _Journ. Comp. + Neurol._ vi., 1896. For poison and other glands, see L. Bordas, _Ann. + Sci. Nat. Zool._ (7) xix., 1895. For the sting and ovipositor H. + Dewitz, _Zeits. wiss. Zool._ xxv., 1874, xxviii., 1877, and F. Zander, + _ib._ lxvi., 1899. For male genital armature S. A. Peytoureau, + _Morphologie de l'armure génitale des insectes_ (Bordeaux, 1895), + and E. Zander, Zeits. wiss. Zool. lxvii., 1900. The systematic student + of Hymenoptera is greatly helped by C. G. de Dalla Torre's _Catalogus + Hymenopterorum_ (10 vols., Leipzig, 1893-1902). For general + classifications see F. W. Konow, _Entom. Nachtr._ (1897), and W. H. + Ashmead, _Proc. U.S. Nat. Mus._ xxiii., 1901; the latter paper deals + also especially with the Ichneumonoidea of the globe. For habits and + life histories of Hymenoptera see J. Lubbock (Lord Avebury), _Ants, + Bees and Wasps_ (9th ed., London, 1889); C. Janet, _Études sur les + fourmis, les guêpes et les abeilles_ (Paris, &c., 1893 and onwards); + and G. W. and E. G. Peckham, _Instincts and Habits of Solitary Wasps_ + (Madison, Wis. U.S.A., 1898). Monographs of most of the families of + British Hymenoptera have now been published. For saw-flies and + gall-flies, see P. Cameron's _British Phytophagous Hymenoptera_ (4 + vols., London, _Roy. Soc._, 1882-1893). For Ichneumonoidea, C. + Morley's _Ichneumons of Great Britain_ (Plymouth, 1903, &c.), and T. + A. Marshall's "British Braconidae," _Trans. Entom. Soc._, 1885-1899. + The smaller parasitic Hymenoptera have been neglected in this country + since A. H. Haliday's classical papers _Entom. Mag._ i.-v., + (1833-1838) but Ashmead's "North American Proctotrypidae" (_Bull. U.S. + Nat. Mus._ xlv., 1893) is valuable for the European student. For the + Fossores, wasps, ants and bees see E. Saunders, _Hymenoptera Aculeata + of the British Islands_ (London, 1896). Exhaustive references to + general systematic works will be found in de Dalla Torre's _Catalogue_ + mentioned above. Of special value to English students are C. T. + Bingham's _Fauna of British India_, "Hymenoptera" (London, 1897 and + onwards), and P. Cameron's volumes on Hymenoptera in the _Biologia + Centrali-Americana_. F. Smith's _Catalogues of Hymenoptera in the + British Museum_ (London, 1853-1859) are well worthy of study. + (G. H. C.) + + + + +HYMETTUS (Ital. Monte Matto, hence the modern name Trello Vouni), a +mountain in Attica, bounding the Athenian plain on the S.E. Height, 3370 +ft. It was famous in ancient times for its bees, which gathered honey of +peculiar flavour from its aromatic herbs; their fame still persists. The +spring mentioned by Ovid (_Ars Amat._ iii. 687) is probably to be +recognized near the monastery of Syriani or Kaesariani on the western +slope. This may be identical with that known as [Greek: Kyllon Pêra], +said to be a remedy for barrenness in women. The marble of Hymettus, +which often has a bluish tinge, was used extensively for building in +ancient Athens, and also, in early times, for sculpture; but the white +marble of Pentelicus was preferred for both purposes. + + See E. Dodwell, _Classical and Topographical Tour_ (1819), i. 483. + + + + +HYMNS.--1. _Classical Hymnody._--The word "hymn" ([Greek: hymnos]) was +employed by the ancient Greeks[1] to signify a song or poem composed in +honour of gods, heroes or famous men, or to be recited on some joyful, +mournful or solemn occasion. Polymnia was the name of their lyric muse. +Homer makes Alcinous entertain Odysseus with a "hymn" of the minstrel +Demodocus, on the capture of Troy by the wooden horse. The _Works and +Days_ of Hesiod begins with an invocation to the Muses to address hymns +to Zeus, and in his _Theogonia_ he speaks of them as singing or +inspiring "hymns" to all the divinities, and of the bard as "their +servant, hymning the glories of men of old, and of the gods of Olympus." +Pindar calls by this name odes, like his own, in praise of conquerors at +the public games of Greece. The Athenian dramatists (Euripides most +frequently) use the word and its cognate verbs in a similar manner; they +also describe by them metrical oracles and apophthegms, martial, festal +and hymeneal songs, dirges and lamentations or incantations of woe. + +Hellenic hymns, according to this conception of them, have come down to +us, some from a very early and others from a late period of Greek +classical literature. Those which passed by the name of Homer[2] were +already old in the time of Thucydides. They are mythological poems +(several of them long), in hexameter verse--some very interesting. That +to Apollo contains a traditionary history of the origin and progress of +the Delphic worship; those on Hermes and on Dionysus are marked by much +liveliness and poetical fancy. Hymns of a like general character, but of +less interest (though these also embody some fine poetical traditions of +the Greek mythology, such as the story of Teiresias, and that of the +wanderings of Leto), were written in the 3rd century before Christ, by +Callimachus of Cyrene. Cleanthes, the successor of Zeno, composed (also +in hexameters) an "excellent and devout hymn" (as it is justly called by +Cudworth, in his _Intellectual System_) to Zeus, which is preserved in +the _Eclogae_ of Stobaeus, and from which Aratus borrowed the words, +"For we are also His offspring," quoted by St Paul at Athens. The +so-called Orphic hymns, in hexameter verse, styled [Greek: teletai], or +hymns of initiation into the "mysteries" of the Hellenic religion, are +productions of the Alexandrian school,--as to which learned men are not +agreed whether they are earlier or later than the Christian era. + +The Romans did not adopt the word "hymn"; nor have we many Latin poems +of the classical age to which it can properly be applied. There are, +however, a few--such as the simple and graceful "Dianae sumus in fide" +("Dian's votaries are we") of Catullus, and "Dianam tenerae dicite +virgines" ("Sing to Dian, gentle maidens") of Horace--which approach +much more nearly than anything Hellenic to the form and character of +modern hymnody. + +2. _Hebrew Hymnody._--For the origin and idea of Christian hymnody we +must look, not to Gentile, but to Hebrew sources. St Augustine's +definition of a hymn, generally accepted by Christian antiquity, may be +summed up in the words, "praise to God with song" ("cum cantico"); Bede +understood the "canticum" as properly requiring metre; though he thought +that what in its original language was a true hymn might retain that +character in an unmetrical translation. Modern use has enlarged the +definition; Roman Catholic writers extend it to the praises of saints; +and the word now comprehends rhythmical prose as well as verse, and +prayer and spiritual meditation as well as praise. + +The modern distinction between psalms and hymns is arbitrary (see +PSALMS). The former word was used by the LXX. as a generic designation, +probably because it implied an accompaniment by the psaltery (said by +Eusebius to have been of very ancient use in the East) or other +instruments. The cognate verb "psallere" has been constantly applied to +hymns, both in the Eastern and in the Western Church; and the same +compositions which they described generically as "psalms" were also +called by the LXX. "odes" (i.e. songs) and "hymns." The latter word +occurs, e.g. in Ps. lxxii. 20 ("the hymns of David the son of Jesse"), +in Ps. lxv. 1, and also in the Greek titles of the 6th, 54th, 55th, 67th +and 76th (this numbering of the psalms being that of the English +version, not of the LXX.). The 44th chapter of Ecclesiasticus, "Let us +now praise famous men," &c., is entitled in the Greek [Greek: paterôn +hymnos], "The Fathers' Hymn." Bede speaks of the whole book of Psalms as +called "liber hymnorum," by the universal consent of Hebrews, Greeks and +Latins. + +In the New Testament we find our Lord and His apostles singing a hymn +([Greek: hymnêsantes exêlthon]), after the institution of the Lord's +Supper; St Paul and Silas doing the same ([Greek: hymnoun ton theon]) in +their prison at Philippi; St James recommending psalm-singing ([Greek: +psalletô]), and St Paul "psalms and hymns and spiritual songs" ([Greek: +psalmois kai hymnois kai ôdais pneumatikais]) St Paul also, in the 14th +chapter of the first epistle to the Corinthians, speaks of singing +([Greek: psalô]) and of every man's psalm ([Greek: hekastos hymôn +psalmon echei]). In a context which plainly has reference to the +assemblies of the Corinthian Christians for common worship. All the +words thus used were applied by the LXX. to the Davidical psalms; it is +therefore possible that these only may be intended, in the different +places to which we have referred. But there are in St Paul's epistles +several passages (Eph. v. 14; 1 Tim. iii. 16; 1 Tim. vi. 15, 16; 2 Tim. +ii. 11, 12) which have so much of the form and character of later +Oriental hymnody as to have been supposed by Michaelis and others to be +extracts from original hymns of the Apostolic age. Two of them are +apparently introduced as quotations, though not found elsewhere in the +Scriptures. A third has not only rhythm, but rhyme. The thanksgiving +prayer of the assembled disciples, recorded in Acts iv., is both in +substance and in manner poetical; and in the canticles, "Magnificat," +"Benedictus," &c., which manifestly followed the form and style of +Hebrew poetry, hymns or songs, proper for liturgical use, have always +been recognized by the church. + +3. _Eastern Church Hymnody._--The hymn of our Lord, the precepts of the +apostles, the angelic song at the nativity, and "Benedicite omnia opera" +are referred to in a curious metrical prologue to the hymnary of the +Mozarabic Breviary as precedents for the practice of the Western Church. +In this respect, however, the Western Church followed the Eastern, in +which hymnody prevailed from the earliest times. + + + Therapeutae. + +Philo describes the Theraputae (q.v.) of the neighbourhood of Alexandria +as composers of original hymns, which (as well as old) were sung at +their great religious festivals--the people listening in silence till +they came to the closing strains, or refrains, at the end of a hymn or +stanza (the "acroteleutia" and "ephymnia"), in which all, women as well +as men, heartily joined. These songs, he says, were in various metres +(for which he uses a number of technical terms); some were choral, some +not; and they were divided into variously constructed strophes or +stanzas. Eusebius, who thought that the Theraputae were communities of +Christians, says that the Christian practice of his own day was in exact +accordance with this description. + + + Antiphonal singing. + +The practice, not only of singing hymns, but of singing them +antiphonally, appears, from the well-known letter of Pliny to Trajan, to +have been established in the Bithynian churches at the beginning of the +2nd century. They were accustomed "stato die ante lucem convenire, +carmenque Christo, quasi Deo, dicere _secum invicem_." This agrees well, +in point of time, with the tradition recorded by the historian Socrates, +that Ignatius (who suffered martyrdom about A.D. 107) was led by a +vision or dream of angels singing hymns in that manner to the Holy +Trinity to introduce antiphonal singing into the church of Antioch, from +which it quickly spread to other churches. There seems to be an allusion +to choral singing in the epistle of Ignatius himself to the Romans, +where he exhorts them, "[Greek: choros genomenoi]" ("having formed +themselves into a choir"), to "sing praise to the Father in Christ +Jesus." A statement of Theodoret has sometimes been supposed to refer +the origin of antiphonal singing to a much later date; but this seems to +relate only to the singing of Old Testament Psalms ([Greek: tên +Dauidikên melôdian]), the alternate chanting of which, by a choir +divided into two parts, was (according to that statement) first +introduced into the church of Antioch by two monks famous in the history +of their time, Flavianus and Diodorus, under the emperor Constantius II. + + + 2nd century. + + 3rd century. + +Other evidence of the use of hymns in the 2nd century is contained in a +fragment of Caius, preserved by Eusebius, which refers to "all the +psalms and odes written by faithful brethren from the beginning," as +"hymning Christ, the Word of God, as God." Tertullian also, in his +description of the "Agapae," or love-feasts, of his day, says that, +after washing hands and bringing in lights, each man was invited to come +forward and sing to God's praise something either taken from the +Scriptures or of his own composition ("ut quisque de Sacris Scripturis +vel proprio ingenio potest"). George Bull, bishop of St David's, +believed one of those primitive compositions to be the hymn appended by +Clement of Alexandria to his _Paedagogus_; and Archbishop Ussher +considered the ancient morning and evening hymns, of which the use was +enjoined by the _Apostolical Constitutions_, and which are also +mentioned in the "Tract on Virginity" printed with the works of St +Athanasius, and in St Basil's treatise upon the Holy Spirit, to belong +to the same family. Clement's hymn, in a short anapaestic metre, +beginning [Greek: stomion pôlôn adaôn] (or, according to some editions, +[Greek: basileu hagiôn, loge pandamatôr]--translated by the Rev. A. +Chatfield, "O Thou, the King of Saints, all-conquering Word"), is rapid, +spirited and well-adapted for singing. The Greek "Morning Hymn" (which, +as divided into verses by Archbishop Ussher in his treatise _De +Symbolis_, has a majestic rhythm, resembling a choric or dithyrambic +strophe) is the original form of "Gloria in Excelsis," still said or +sung, with some variations, in all branches of the church which have not +relinquished the use of liturgies. The Latin form of this hymn (of which +that in the English communion office is an exact translation) is said, +by Bede and other ancient writers, to have been brought into use at Rome +by Pope Telesphorus, as early as the time of the emperor Hadrian. A +third, the Vesper or "Lamp-lighting" hymn ("[Greek: phôs hilaron hagias +doxês]"--translated by Canon Bright "Light of Gladness, Beam Divine"), +holds its place to this day in the services of the Greek rite. In the +3rd century Origen seems to have had in his mind the words of some other +hymns or hymn of like character, when he says (in his treatise _Against +Celsus_): "We glorify in hymns God and His only begotten Son; as do also +the Sun, the Moon, the Stars and all the host of heaven. All these, in +one Divine chorus, with the just among men, glorify in hymns God who is +over all, and His only begotten Son." So highly were these compositions +esteemed in the Syrian churches that the council which deposed Paul of +Samosata from the see of Antioch in the time of Aurelian justified that +act, in its synodical letter to the bishops of Rome and Alexandria, on +this ground (among others) that he had prohibited the use of hymns of +that kind, by uninspired writers, addressed to Christ. + +After the conversion of Constantine, the progress of hymnody became +closely connected with church controversies. There had been in Edessa, +at the end of the 2nd or early in the 3rd century, a Gnostic writer of +conspicuous ability, named Bardesanes, who was succeeded, as the head of +his sect or school, by his son Harmonius. Both father and son wrote +hymns, and set them to agreeable melodies, which acquired, and in the +4th century still retained, much local popularity. Ephraem Syrus, the +first voluminous hymn-writer whose works remain to us, thinking that the +same melodies might be made useful to the faith, if adapted to more +orthodox words, composed to them a large number of hymns in the Syriac +language, principally in tetrasyllabic, pentasyllable and heptasyllabic +metres, divided into strophes of from 4 to 12, 16 and even 20 lines +each. When a strophe contained five lines, the fifth was generally an +"ephymnium," detached in sense, and consisting of a prayer, invocation, +doxology or the like, to be sung antiphonally, either in full chorus or +by a separate part of the choir. The _Syriac Chrestomathy_ of August +Hahn (Leipzig, 1825), and the third volume of H. A. Daniel's _Thesaurus +Hymnologicus_ (Leipzig, 1841-1856), contain specimens of these hymns. +Some of them have been translated into (unmetrical) English by the Rev. +Henry Burgess (_Select Metrical Hymns of Ephrem Syrus_, &c., 1853). A +considerable number of those so translated are on subjects connected +with death, resurrection, judgment, &c., and display not only Christian +faith and hope, but much simplicity and tenderness of natural feeling. +Theodoret speaks of the spiritual songs of Ephraem as very sweet and +profitable, and as adding much, in his (Theodoret's) time, to the +brightness of the commemorations of martyrs in the Syrian Church. + +The Greek hymnody contemporary with Ephraem followed, with some licence, +classical models. One of its favourite metres was the Anacreontic; but +it also made use of the short anapaestic, Ionic, iambic and other +lyrical measures, as well as the hexameter and pentameter. Its principal +authors were Methodius, bishop of Olympus, who died about A.D. 311, +Synesius, who became bishop of Ptolemais in Cyrenaica in 410, and +Gregory Nazianzen, for a short time (380-381) patriarch of +Constantinople. The merits of these writers have been perhaps too much +depreciated by the admirers of the later Greek "Melodists." They have +found an able English translator in the Rev. Allen Chatfield (_Songs and +Hymns of Earliest Greek Christian Poets_, London, 1876). Among the most +striking of their works are [Greek: mnôeo Christe] ("Lord Jesus, think +of me"), by Synesius; [Greek: se ton aphthiton monarchên] ("O Thou, the +One Supreme") and [Greek: ti soi theleis genesthai] ("O soul of mine, +repining"), by Gregory; also [Greek: anôthen parthenoi] ("The Bridegroom +cometh"), by Methodius. There continued to be Greek metrical +hymn-writers, in a similar style, till a much later date. Sophronius, +patriarch of Jerusalem in the 7th century, wrote seven Anacreontic +hymns; and St John Damascene, one of the most copious of the second +school of "Melodists," was also the author of some long compositions in +trimeter iambics. + + + Period of Arian controversy. + +An important development of hymnody at Constantinople arose out of the +Arian controversy. Early in the 4th century Athanasius had rebuked, not +only the doctrine of Arius, but the light character of certain hymns by +which he endeavoured to make that doctrine popular. When, towards the +close of that century (398), St John Chrysostom was raised to the +metropolitan see, the Arians, who were still numerous at Constantinople, +had no places of worship within the walls; but they were in the habit of +coming into the city at sunset on Saturdays, Sundays and the greater +festivals, and congregating in the porticoes and other places of public +resort, where they sung, all night through, antiphonal songs, with +"acroteleutia" (closing strains, or refrains), expressive of Arian +doctrine, often accompanied by taunts and insults to the orthodox. +Chrysostom was apprehensive that this music might draw some of the +simpler church people to the Arian side; he therefore organized, in +opposition to it, under the patronage and at the cost of Eudoxia, the +empress of Arcadius (then his friend), a system of nightly processional +hymn-singing, with silver crosses, wax-lights and other circumstances of +ceremonial pomp. Riots followed, with bloodshed on both sides, and with +some personal injury to the empress's chief eunuch, who seems to have +officiated as conductor or director of the church musicians. This led to +the suppression, by an imperial edict, of all public Arian singing; +while in the church the practice of nocturnal hymn-singing on certain +solemn occasions, thus first introduced, remained an established +institution. + + + Greek system of hymnody. + +It is not improbable that some rudiments of the peculiar system of +hymnody which now prevails throughout the Greek communion, and whose +affinities are rather to the Hebrew and Syriac than to the classical +forms, may have existed in the church of Constantinople, even at that +time. Anatolius, patriarch of Constantinople in the middle of the 5th +century, was the precursor of that system; but the reputation of being +its proper founder belongs to Romanos, of whom little more is known than +that he wrote hymns still extant, and lived towards the end of that +century. The importance of that system in the services of the Greek +church may be understood from the fact that Dr J. M. Neale computed +four-fifths of the whole space (about 5000 pages) contained in the +different service-books of that church to be occupied by hymnody, all in +a language or dialect which has ceased to be anywhere spoken. + + The system has a peculiar technical terminology, in which the words + "troparion," "ode," "canon" and "hirmus" ([Greek: eirmos]) chiefly + require explanation. + + The _troparion_ is the unit of the system, being a strophe or stanza, + seen, when analysed, to be divisible into verses or clauses, with + regulated caesuras, but printed in the books as a single prose + sentence, without marking any divisions. The following (turned into + English, from a "canon" by John Mauropus) may be taken as an example: + "The never-sleeping Guardian, | the patron of my soul, | the guide of + my life, | allotted me by God, | I hymn thee, Divine Angel | of + Almighty God." Dr Neale and most other writers regard all these + "troparia" as rhythmical or modulated prose. Cardinal J. B. Pitra, on + the other hand, who in 1867 and 1876 published two learned works on + this subject, maintains that they are really metrical, and governed by + definite rules of prosody, of which he lays down sixteen. According to + him, each "troparion" contains from three to thirty-three verses; each + verse varies from two to thirteen syllables, often in a continuous + series, uniform, alternate or reciprocal, the metre being always + syllabic, and depending, not on the quantity of vowels or the position + of consonants, but on an harmonic series of accents. + + In various parts of the services solitary troparia are sung, under + various names, "contacion," "oecos," "cathisma," &c., which mark + distinctions either in their character or in their use. + + An _ode_ is a song or hymn compounded of several similar + "troparia,"--usually three, four or five. To these is always prefixed + a typical or standard "troparion," called the _hirmus_, by which the + syllabic measure, the periodic series of accents, and in fact the + whole structure and rhythm of the stanzas which follow it are + regulated. Each succeeding "troparion" in the same "ode" contains the + same number of verses, and of syllables in each verse, and similar + accents on the same or equivalent syllables. The "hirmus" may either + form the first stanza of the "ode" itself, or (as is more frequently + the case) may be taken from some other piece; and, when so taken, it + is often indicated by initial words only, without being printed at + length. It is generally printed within commas, after the proper rubric + of the "ode." A hymn in irregular "stichera" or stanzas, without a + "hirmus," is called "idiomelon." A system of three or four odes is + "triodion" or "tetraodion." + + A _canon_ is a system of eight (theoretically nine) connected odes, + the second being always suppressed. Various pauses, relieved by the + interposition of other short chants or readings, occur during the + singing of a whole "canon." The final "troparion" in each ode of the + series is not unfrequently detached in sense (like the "ephymnia" of + Ephraem Syrus), particularly when it is in the (very common) form of a + "theotokion," or ascription of praise to the mother of our Lord, and + when it is a recurring refrain or burden. + +There were two principal periods of Greek hymnography constructed on +these principles--the first that of Romanos and his followers, extending +over the 6th and 7th centuries, the second that of the schools which +arose during the Iconoclastic controversy in the 8th century, and which +continued for some centuries afterwards, until the art itself died out. + + + School of Romanos. + +The works of the writers of the former period were collected in +_Tropologia_, or church hymn-books, which were held in high esteem till +the 10th century, when they ceased to be regarded as church-books, and +so fell into neglect. They are now preserved only in a very small number +of manuscripts. From three of these, belonging to public libraries at +Moscow, Turin and Rome, Cardinal Pitra has printed, in his _Analecta_, a +number of interesting examples, the existence of which appears to have +been unknown to Dr Neale, and which, in the cardinal's estimation, are +in many respects superior to the "canons," &c., of the modern Greek +service-books, from which all Neale's translations (except some from +Anatolius) are taken. Cardinal Pitra's selections include twenty-nine +works by Romanos, and some by Sergius, and nine other known, as well as +some unknown, authors. He describes them as having generally a more +dramatic character than the "melodies" of the later period, and a much +more animated style; and he supposes that they may have been originally +sung with dramatic accompaniments, by way of substitution for the +theatrical performances of Pagan times. As an instance of their peculiar +character, he mentions a Christmas or Epiphany hymn by Romanos, in +twenty-five long strophes, in which there is, first, an account of the +Nativity and its accompanying wonders, and then a dialogue between the +wise men, the Virgin mother and Joseph. The magi arrive, are admitted, +describe the moral and religious condition of Persia and the East, and +the cause and adventures of their journey, and then offer their gifts. +The Virgin intercedes for them with her Son, instructs them in some +parts of Jewish history, and ends with a prayer for the salvation of the +world. + + + Melodists. + +The controversies and persecutions of the 8th and succeeding centuries +turned the thoughts of the "melodists" of the great monasteries of the +Studium at Constantinople and St Saba in Palestine and their followers, +and those of the adherents of the Greek rite in Sicily and South Italy +(who suffered much from the Saracens and the Normans), into a less +picturesque but more strictly theological course; and the influence of +those controversies, in which the final success of the cause of "Icons" +was largely due to the hymns, as well as to the courage and sufferings, +of these confessors, was probably the cause of their supplanting, as +they did, the works of the older school. Cardinal Pitra gives them the +praise of having discovered a graver and more solemn style of chant, and +of having done much to fix the dogmatic theology of their church upon +its present lines of near approach to the Roman. + +Among the "melodists" of this latter Greek school there were many saints +of the Greek church, several patriarchs and two emperors--Leo the +Philosopher, and Constantine Porphyrogenitus, his son. Their greatest +poets were Theodore and Joseph of the Studium, and Cosmas and John +(called Damascene) of St Saba. Neale translated into English verse +several selected portions, or centoes, from the works of these and +others, together with four selections from earlier works by Anatolius. +Some of his translations--particularly "The day is past and over," from +Anatolius, and "Christian, dost thou see them," from Andrew of +Crete--have been adopted into hymn-books used in many English churches; +and the hymn "Art thou weary," which is rather founded upon than +translated from one by Stephen the Sabaite, has obtained still more +general popularity. + +4. _Western Church Hymnody._--It was not till the 4th century that Greek +hymnody was imitated in the West, where its introduction was due to two +great lights of the Latin Church--St Hilary of Poitiers and St Ambrose +of Milan. + +Hilary was banished from his see of Poitiers in 356, and was absent from +it for about four years, which he spent in Asia Minor, taking part +during that time in one of the councils of the Eastern Church. He thus +had full opportunity of becoming acquainted with the Greek church music +of that day; and he wrote (as St Jerome, who was thirty years old when +Hilary died, and who was well acquainted with his acts and writings, and +spent some time in or near his diocese, informs us) a "book of hymns," +to one of which Jerome particularly refers, in the preface to the second +book of his own commentary on the epistle to the Galatians. Isidore, +archbishop of Seville, who presided over the fourth council of Toledo, +in his book on the offices of the church, speaks of Hilary as the first +Latin hymn-writer; that council itself, in its 13th canon, and the +prologue to the Mozarabic hymnary (which is little more than a +versification of the canon), associate his name, in this respect, with +that of Ambrose. A tradition, ancient and widely spread, ascribed to him +the authorship of the remarkable "Hymnum dicat turba fratrum, hymnum +cantus personet" ("Band of brethren, raise the hymn, let your song the +hymn resound"), which is a succinct narrative, in hymnal form, of the +whole gospel history; and is perhaps the earliest example of a strictly +didactic hymn. Both Bede and Hincmar much admired this composition, +though the former does not mention, in connexion with it, the name of +Hilary. The private use of hymns of such a character by Christians in +the West may probably have preceded their ecclesiastical use; for Jerome +says that in his day those who went into the fields might hear "the +ploughman at his hallelujahs, the mower at his hymns, and the +vine-dresser singing David's psalms." Besides this, seven shorter +metrical hymns attributed to Hilary are still extant. + + + Ambrose. + +Of the part taken by Ambrose, not long after Hilary's death, in bringing +the use of hymns into the church of Milan, we have a contemporary +account from his convert, St Augustine. Justina, mother of the emperor +Valentinian, favoured the Arians, and desired to remove Ambrose from his +see. The "devout people," of whom Augustine's mother, Monica, was one, +combined to protect him, and kept guard in the church. "Then," says +Augustine, "it was first appointed that, after the manner of the Eastern +churches, hymns and psalms should be sung, lest the people should grow +weary and faint through sorrow; which custom has ever since been +retained, and has been followed by almost all congregations in other +parts of the world." He describes himself as moved to tears by the +sweetness of these "hymns and canticles":--"The voices flowed into my +ears; the truth distilled into my heart; I overflowed with devout +affections, and was happy." To this time, according to an uncertain but +not improbable tradition which ascribed the composition of the "Te Deum" +to Ambrose, and connected it with the conversion of Augustine, is to be +referred the commencement of the use in the church of that sublime +unmetrical hymn. + +It is not, however, to be assumed that the hymnody thus introduced by +Ambrose was from the first used according to the precise order and +method of the later Western ritual. To bring it into (substantially) +that order and method appears to have been the work of St Benedict. +Walafrid Strabo, the earliest ecclesiastical writer on this subject (who +lived at the beginning of the 9th century), says that Benedict, on the +constitution of the religious order known by his name (about 530), +appointed the Ambrosian hymns to be regularly sung in his offices for +the canonical hours. Hence probably originated the practice of the +Italian churches, and of others which followed their example, to sing +certain hymns (Ambrosian, or by the early successors of the Ambrosian +school) daily throughout the week, at "Vespers," "Lauds" and "Nocturns," +and on some days at "Compline" also--varying them with the different +ecclesiastical seasons and festivals, commemorations of saints and +martyrs and other special offices. Different dioceses and religious +houses had their own peculiarities of ritual, including such hymns as +were approved by their several bishops or ecclesiastical superiors, +varying in detail, but all following the same general method. The +national rituals, which were first reduced into a form substantially +like that which has since prevailed, were probably those of Lombardy and +of Spain, now known as the "Ambrosian" and the "Mozarabic." The age and +origin of the Spanish ritual are uncertain, but it is mentioned in the +7th century by Isidore, bishop of Seville. It contained a copious +hymnary, the original form of which may be regarded as canonically +approved by the fourth council of Toledo (633). By the 13th canon of +that council, an opinion (which even then found advocates) against the +use in churches of any hymns not taken from the Scriptures--apparently +the same opinion which had been held by Paul of Samosata--was censured; +and it was ordered that such hymns should be used in the Spanish as well +as in the Gallican churches, the penalty of excommunication being +denounced against all who might presume to reject them. + +The hymns of which the use was thus established and authorized were +those which entered into the daily and other offices of the church, +afterwards collected in the "Breviaries"; in which the hymns "proper" +for "the week," and for "the season," continued for many centuries, with +very few exceptions, to be derived from the earliest epoch of Latin +Church poetry--reckoning that epoch as extending from Hilary and Ambrose +to the end of the pontificate of Gregory the Great. The "Ambrosian" +music, to which those hymns were generally sung down to the time of +Gregory, was more popular and congregational than the "Gregorian," which +then came into use, and afterwards prevailed. In the service of the mass +it was not the general practice, before the invention of sequences in +the 9th century, to sing any hymns, except some from the Scriptures +esteemed canonical, such as the "Song of the Three Children" +("Benedicite omnia opera"). But to this rule there were, according to +Walafrid Strabo, some occasional exceptions; particularly in the case of +Paulinus, patriarch of Aquileia under Charlemagne, himself a +hymn-writer, who frequently used hymns, composed by himself or others, +in the eucharistic office, especially in private masses. + +Some of the hymns called "Ambrosian" (nearly 100 in number) are beyond +all question by Ambrose himself, and the rest probably belong to his +time or to the following century. Four, those beginning "Aeterne rerum +conditor" ("Dread Framer of the earth and sky"), "Deus Creator omnium" +("Maker of all things, glorious God"), "Veni Redemptor Gentium" +("Redeemer of the nations, come") and "Jam surgit hora tertia" ("Christ +at this hour was crucified"), are quoted as works of Ambrose by +Augustine. These, and others by the hand of the same master, have the +qualities most valuable in hymns intended for congregational use. They +are short and complete in themselves; easy, and at the same time +elevated in their expression and rhythm; terse and masculine in thought +and language; and (though sometimes criticized as deficient in +theological precision) simple, pure and not technical in their rendering +of the great facts and doctrines of Christianity, which they present in +an objective and not a subjective manner. They have exercised a powerful +influence, direct or indirect, upon many of the best works of the same +kind in all succeeding generations. With the Ambrosian hymns are +properly classed those of Hilary, and the contemporary works of Pope +Damasus I. (who wrote two hymns in commemoration of saints), and of +Prudentius, from whose _Cathemerina_ ("Daily Devotions") and +_Peristephana_ ("Crown-songs for Martyrs"), all poems of considerable, +some of great length--about twenty-eight hymns, found in various +Breviaries, were derived. Prudentius was a layman, a native of +Saragossa, and it was in the Spanish ritual that his hymns were most +largely used. In the Mozarabic Breviary almost the whole of one of his +finest poems (from which most churches took one part only, beginning +"Corde natus ex parentis") was appointed to be sung between Easter and +Ascension-Day, being divided into eight or nine hymns; and on some of +the commemorations of Spanish saints long poems from his _Peristephana_ +were recited or sung at large. He is entitled to a high rank among +Christian poets, many of the hymns taken from his works being full of +fervour and sweetness, and by no means deficient in dignity or strength. + + + 5th and 6th centuries. + +These writers were followed in the 5th and early in the 6th century by +the priest Sedulius, whose reputation perhaps exceeded his merit; Elpis, +a noble Roman lady (considered, by an erroneous tradition, to have been +the wife of the philosophic statesman Boetius); Pope Gelasius I.; and +Ennodius, bishop of Pavia. Sedulius and Elpis wrote very little from +which hymns could be extracted; but the small number taken from their +compositions obtained wide popularity, and have since held their ground. +Gelasius was of no great account as a hymn-writer; and the works of +Ennodius appear to have been known only in Italy and Spain. The latter +part of the 6th century produced Pope Gregory the Great and Venantius +Fortunatus, an Italian poet, the friend of Gregory, and the favourite of +Radegunda, queen of the Franks, who died (609) bishop of Poitiers. +Eleven hymns of Gregory, and twelve or thirteen (mostly taken from +longer poems) by Fortunatus, came into general use in the Italian, +Gallican and British churches. Those of Gregory are in a style hardly +distinguishable from the Ambrosian; those of Fortunatus are graceful, +and sometimes vigorous. He does not, however, deserve the praise given +to him by Dr Neale, of having struck out a new path in Latin hymnody. On +the contrary, he may more justly be described as a disciple of the +school of Prudentius, and as having affected the classical style, at +least as much as any of his predecessors. + + The poets of this primitive epoch, which closed with the 6th century, + wrote in the old classical metres, and made use of a considerable + variety of them--anapaestic, anacreontic, hendecasyllabic, asclepiad, + hexameters and pentameters and others. Gregory and some of the + Ambrosian authors occasionally wrote in sapphics; but the most + frequent measure was the iambic dimeter, and, next to that, the + trochaic. The full alcaic stanza does not appear to have been used for + church purposes before the 16th century, though some of its elements + were. In the greater number of these works, a general intention to + conform to the rules of Roman prosody is manifest; but even those + writers (like Prudentius) in whom that conformity was most decided + allowed themselves much liberty of deviation from it. Other works, + including some of the very earliest, and some of conspicuous merit, + were of the kind described by Bede as not metrical but + "rhythmical"--i.e. (as he explains the term "rhythm"), "modulated to + the ear in imitation of different metres." It would be more correct to + call them metrical--(e.g. still trochaic or iambic, &c., but, + according to new laws of syllabic quantity, depending entirely on + accent, and not on the power of vowels or the position of + consonants)--laws by which the future prosody of all modern European + nations was to be governed. There are also, in the hymns of the + primitive period (even in those of Ambrose), anticipations--irregular + indeed and inconstant, but certainly not accidental--of another great + innovation, destined to receive important developments, that of + assonance or rhyme, in the final letters or syllables of verses. + Archbishop Trench, in the introduction to his _Sacred Latin Poetry_, + has traced the whole course of the transition from the ancient to the + modern forms of versification, ascribing it to natural and necessary + causes, which made such changes needful for the due development of the + new forms of spiritual and intellectual life, consequent upon the + conversion of the Latin-speaking nations to Christianity. + + + 6th century downwards. + +From the 6th century downwards we see this transformation making +continual progress, each nation of Western Christendom adding, from time +to time, to the earlier hymns in its service-books others of more recent +and frequently of local origin. For these additions, the commemorations +of saints, &c., as to which the devotion of one place often differed +from that of another, offered especial opportunities. This process, +while it promoted the development of a medieval as distinct from the +primitive style, led also to much deterioration in the quality of +hymns, of which, perhaps, some of the strongest examples may be found in +a volume published in 1865 by the Irish Archaeological Society from a +manuscript in the library of Trinity College, Dublin. It contains a +number of hymns by Irish saints of the 6th, 7th and 8th centuries--in +several instances fully rhymed, and in one mixing Erse and Latin +barbarously together, as was not uncommon, at a much later date, in +semi-vernacular hymns of other countries. The Mozarabic Breviary, and +the collection of hymns used in the Anglo-Saxon churches, published in +1851 by the Surtees Society (chiefly from a Benedictine MS. In the +college library of Durham, supplemented by other MSS. in the British +Museum), supply many further illustrations of the same decline of +taste:--such Sapphics, e.g., as the "Festum insigne prodiit coruscum" of +Isidore, and the "O veneranda Trinitas laudanda" of the Anglo-Saxon +books. The early medieval period, however, from the time of Gregory the +Great to that of Hildebrand, was far from deficient in the production of +good hymns, wherever learning flourished. Bede in England, and Paul "the +Deacon"--the author of a fairly classical sapphic ode on St John the +Baptist--in Italy, were successful followers of the Ambrosian and +Gregorian styles. Eleven metrical hymns are attributed to Bede by +Cassander; and there are also in one of Bede's works (_Collectanea et +flores_) two rhythmical hymns of considerable length on the Day of +Judgment, with the refrains "In tremendo die" and "Attende homo," both +irregularly rhymed, and, in parts, not unworthy of comparison with the +"Dies Irae." Paulinus, patriarch of Aquileia, contemporary with Paul, +wrote rhythmical trimeter iambics in a manner peculiar to himself. +Theodulph, bishop of Orleans (793-835), author of the famous +processional hymn for Palm Sunday in hexameters and pentameters, +"Gloria, laus, et honor tibi sit, Rex Christe Redemptor" ("Glory and +honour and laud be to Thee, King Christ the Redeemer"), and Hrabanus +Maurus, archbishop of Mainz, the pupil of Alcuin, and the most learned +theologian of his day, enriched the church with some excellent works. +Among the anonymous hymns of the same period there are three of great +beauty, of which the influence may be traced in most, if not all, of the +"New Jerusalem" hymns of later generations, including those of Germany +and Great Britain:--"Urbs beata Hierusalem" ("Blessed city, heavenly +Salem"); "Alleluia piis edite laudibus" ("Alleluias sound ye in strains +of holy praise"--called, from its burden, "Alleluia perenne"); and +"Alleluia dulce carmen" ("Alleluia, song of sweetness"), which, being +found in Anglo-Saxon hymnaries certainly older than the Conquest, cannot +be of the late date assigned to it, in his _Mediaeval Hymns and +Sequences_, by Neale. These were followed by the "Chorus novae +Hierusalem" ("Ye Choirs of New Jerusalem") of Fulbert, bishop of +Chartres. This group of hymns is remarkable for an attractive union of +melody, imagination, poetical colouring and faith. It represents, +perhaps, the best and highest type of the middle school, between the +severe Ambrosian simplicity and the florid luxuriance of later times. + + + Veni Creator. + + Notker. + +Another celebrated hymn, which belongs to the first medieval period, is +the "Veni Creator Spiritus" ("Come, Holy Ghost, our souls inspire"). The +earliest recorded occasion of its use is that of a translation (898) of +the relics of St Marcellus, mentioned in the _Annals_ of the Benedictine +order. It has since been constantly sung throughout Western Christendom +(as versions of it still are in the Church of England), as part of the +appointed offices for the coronation of kings, the consecration and +ordination of bishops and priests, the assembling of synods and other +great ecclesiastical solemnities. It has been attributed--probably in +consequence of certain corruptions in the text of Ekkehard's _Life of +Notker_ (a work of the 13th century)--to Charlemagne. Ekkehard wrote in +the Benedictine monastery of St Gall, to which Notker belonged, with +full access to its records; and an ignorant interpolator, regardless of +chronology, added, at some later date, the word "Great" to the name of +"the emperor Charles," wherever it was mentioned in that work. The +biographer relates that Notker--a man of a gentle, contemplative nature, +observant of all around him, and accustomed to find spiritual and +poetical suggestions in common sights and sounds--was moved by the +sound of a mill-wheel to compose his "sequence" on the Holy Spirit, +"Sancti Spiritus adsit nobis gratia" ("Present with us ever be the Holy +Spirit's grace"); and that, when finished, he sent it as a present to +"the emperor Charles," who in return sent him back, "by the same +messenger," the hymn "Veni Creator," which (says Ekkehard) the same +"Spirit had inspired him to write" ("Sibi idem Spiritus inspiraverat"). +If this story is to be credited--and, from its circumstantial and almost +dramatic character, it has an air of truth--the author of "Veni Creator" +was not Charlemagne, but his grandson the emperor Charles the Bald. +Notker himself long survived that emperor, and died in 912. + + + Sequences. + +The invention of "sequences" by Notker may be regarded as the beginning +of the later medieval epoch of Latin hymnody. In the eucharistic +service, in which (as has been stated) hymns were not generally used, it +had been the practice, except at certain seasons, to sing "laud," or +"Alleluia," between the epistle and the gospel, and to fill up what +would otherwise have been a long pause, by extending the cadence upon +the two final vowels of the "Alleluia" into a protracted strain of +music. It occurred to Notker that, while preserving the spirit of that +part of the service, the monotony of the interval might be relieved by +introducing at that point a chant of praise specially composed for the +purpose. With that view he produced the peculiar species of rhythmical +composition which obtained the name of "sequentia" (probably from +following after the close of the "Alleluia"), and also that of "prosa," +because its structure was originally irregular and unmetrical, +resembling in this respect the Greek "troparia," and the "Te Deum," +"Benedicite" and canticles. That it was in some measure suggested by the +forms of the later Greek hymnody seems probable, both from the +intercourse (at that time frequent) between the Eastern and Western +churches, and from the application by Ekkehard, in his biography and +elsewhere (e.g. in Lyndwood's _Provinciale_), of some technical terms, +borrowed from the Greek terminology, to works of Notker and his school +and to books containing them. + + Dr Neale, in a learned dissertation prefixed to his collection of + sequences from medieval Missals, and enlarged in a Latin letter to H. + A. Daniel (printed in the fifth volume of Daniel's _Thesaurus + hymnologicus_), investigated the laws of caesura and modulation which + are discoverable in these works. Those first brought into use were + sent by their author to Pope Nicholas I., who authorized their use, + and that of others composed after the same model by other brethren of + St Gall, in all churches of the West. + + Although the sequences of Notker and his school, which then rapidly + passed into most German, French and British Missals, were not + metrical, the art of "assonance" was much practised in them. Many of + those in the Sarum and French Missals have every verse, and even every + clause or division of a verse, ending with the same vowel "a"--perhaps + with some reference to the terminal letter of "Alleluia." Artifices + such as these naturally led the way to the adaptation of the same kind + of composition to regular metre and fully developed rhyme. Neale's + full and large collection, and the second volume of Daniel's + _Thesaurus_, contain numerous examples, both of the "proses," properly + so called, of the Notkerian type, and of those of the later school, + which (from the religious house to which its chief writer belonged) + has been called "Victorine." Most Missals appear to have contained + some of both kinds. In the majority of those from which Neale's + specimens are taken, the metrical kind largely prevailed; but in some + (e.g. those of Sarum and Liége) the greater number were Notkerian. + +Of the sequence on the Holy Ghost, sent by Notker (according to +Ekkehard) to Charles the Bald, Neale says that it "was in use all over +Europe, even in those countries, like Italy and Spain, which usually +rejected sequences"; and that, "in the Missal of Palencia, the priest +was ordered to hold a white dove in his hands, while intoning the first +syllables, and then to let it go." Another of the most remarkable of +Notker's sequences, beginning "Media in vita" ("In the midst of life we +are in death"), is said to have been suggested to him while observing +some workmen engaged in the construction of a bridge over a torrent near +his monastery. Catherine Winkworth (_Christian Singers of Germany_, +1869) states that this was long used as a battle-song, until the custom +was forbidden, on account of its being supposed to exercise a magical +influence. A translation of it ("Mitten wir im Leben sind") is one of +Luther's funeral hymns; and all but the opening sentence of that part of +the burial service of the Church of England which is directed to be +"said or sung" at the grave, "while the corpse is made ready to be laid +into the earth," is taken from it. + +The "Golden Sequence," "Veni, sancte Spiritus" ("Holy Spirit, Lord of +Light"), is an early example of the transition of sequences from a +simply rhythmical to a metrical form. Archbishop Trench, who esteemed it +"the loveliest of all the hymns in the whole circle of Latin sacred +poetry," inclined to give credit to a tradition which ascribes its +authorship to Robert II., king of France, son of Hugh Capet. Others have +assigned to it a later date--some attributing it to Pope Innocent III., +and some to Stephen Langton, archbishop of Canterbury. Many +translations, in German, English and other languages, attest its merit. +Berengarius of Tours, St Bernard of Clairvaux and Abelard, in the 11th +century and early in the 12th, followed in the same track; and the art +of the Victorine school was carried to its greatest perfection by Adam +of St Victor (who died between 1173 and 1194)--"the most fertile, and" +(in the concurrent judgment of Archbishop Trench and Neale) "the +greatest of the Latin hymnographers of the Middle Ages." The +archbishop's selection contains many excellent specimens of his works. + + + Dies Irae. + + Stabat Mater. + + Aquinas. + +But the two most widely celebrated of all this class of +compositions--works which have exercised the talents of the greatest +musical composers, and of innumerable translators in almost all +languages--are the "Dies Irae" ("That day of wrath, that dreadful day"), +by Thomas of Celano, the companion and biographer of St Francis of +Assisi, and the "Stabat Mater dolorosa" ("By the cross sad vigil +keeping") of Jacopone, or Jacobus de Benedictis, a Franciscan humorist +and reformer, who was persecuted by Pope Boniface VIII. for his satires +on the prelacy of the time, and died in 1306. Besides these, the 13th +century produced the famous sequence "Lauda Sion salvatorem" ("Sion, +lift thy voice and sing"), and the four other well-known sacramental +hymns of St Thomas Aquinas, viz. "Pange lingua gloriosi corporis +mysterium" ("Sing, my tongue, the Saviour's glory"), "Verbum supernum +prodiens" ("The Word, descending from above"--not to be confounded with +the Ambrosian hymn from which it borrowed the first line), "Sacris +solemniis juncta sint gaudia" ("Let us with hearts renewed our grateful +homage pay"), and "Adoro Te devote, latens Deitas" ("O Godhead hid, +devoutly I adore Thee")--a group of remarkable compositions, written by +him for the then new festival of Corpus Christi, of which he induced +Pope Urban IV. (1261-1265) to decree the observance. In these (of which +all but "Adoro Te devote" passed rapidly into breviaries and missals) +the doctrine of transubstantiation is set forth with a wonderful degree +of scholastic precision; and they exercised, probably, a not unimportant +influence upon the general reception of that dogma. They are undoubtedly +works of genius, powerful in thought, feeling and expression. + + + Medieval hymns. + +These and other medieval hymn-writers of the 12th and 13th centuries may +be described, generally, as poet-schoolmen. Their tone is contemplative, +didactic, theological; they are especially fertile and ingenious in the +field of mystical interpretation. Two great monasteries in the East had, +in the 8th and 9th centuries, been the principal centres of Greek +hymnology; and, in the West, three monasteries--St Gall, near Constance +(which was long the especial seat of German religious literature), Cluny +in Burgundy and St Victor, near Paris--obtained a similar distinction. +St Gall produced, besides Notker, several distinguished sequence +writers, probably his pupils--Hartmann, Hermann and Gottschalk--to the +last of whom Neale ascribes the "Alleluiatic Sequence" ("Cantemus cuncti +melodum nunc Alleluia"), well known in England through his translation, +"The strain upraise of joy and praise." The chief poets of Cluny were +two of its abbots, Odo and Peter the Venerable (1122-1156), and one of +Peter's monks, Bernard of Morlaix, who wrote the remarkable poem on +"Contempt of the World" in about 3000 long rolling "leonine-dactylic" +verses, from parts of which Neale's popular hymns, "Jerusalem the +golden," &c., are taken. The abbey of St Victor, besides Adam and his +follower Pistor, was destined afterwards to produce the most popular +church poet of the 17th century. + + + Bernard of Clairvaux. + +There were other distinguished Latin hymn-writers of the later medieval +period besides those already mentioned. The name of St Bernard of +Clairvaux cannot be passed over with the mere mention of the fact that +he was the author of some metrical sequences. He was, in truth, the +father, in Latin hymnody, of that warm and passionate form of devotion +which some may consider to apply too freely to Divine Objects the +language of human affection, but which has, nevertheless, been popular +with many devout persons, in Protestant as well as Roman Catholic +churches. F. von Spee, "Angelus Silesius," Madame Guyon, Bishop Ken, +Count Zinzendorf and Frederick William Faber may be regarded as +disciples in this school. Many hymns, in various languages, have been +founded upon St Bernard's "Jesu dulcis memoria" ("Jesu, the very thought +of Thee"), "Jesu dulcedo cordium" ("Jesu, Thou joy of loving hearts") +and "Jesu Rex admirabilis" ("O Jesu, King most wonderful")--three +portions of one poem, nearly 200 lines long. Pietro Damiani, the friend +of Pope Gregory VII, Marbode, bishop of Rennes, in the 11th, Hildebert, +archbishop of Tours, in the 12th, and St Bonaventura in the 13th +centuries, are other eminent men who added poetical fame as +hymnographers to high public distinction. + +Before the time of the Reformation, the multiplication of sequences +(often as unedifying in matter as unpoetical in style) had done much to +degrade the common conception of hymnody. In some parts of France, +Portugal, Sardinia and Bohemia, their use in the vernacular language had +been allowed. In Germany also there were vernacular sequences as early +as the 12th century, specimens of which may be seen in the third chapter +of C. Winkworth's _Christian Singers of Germany_. Scoffing parodies upon +sequences are said to have been among the means used in Scotland to +discredit the old church services. After the 15th century they were +discouraged at Rome. They retained for a time some of their old +popularity among German Protestants, and were only gradually +relinquished in France. A new "prose," in honour of St Maxentia, is +among the compositions of Jean Baptiste Santeul; and Dr Daniel's second +volume closes with one written in 1855 upon the dogma of the Immaculate +Conception. + + + Roman revision of hymns. + + The taste of the Renaissance was offended by all deviations from + classical prosody and Latinity. Pope Leo X. directed the whole body of + the hymns in use at Rome to be reformed; and the _Hymni novi + ecclesiastici juxta veram metri et Latinitatis normam_, prepared by + Zacharie Ferreri (1479-1530), a Benedictine of Monte Cassino, + afterwards a Carthusian and bishop of Guardia, to whom Leo had + committed that task, appeared at Rome in 1525, with the sanction of a + later pope, Clement VII. The next step was to revise the whole Roman + Breviary. That undertaking, after passing through several stages under + different popes (particularly Pius V. and Clement VIII.), was at last + brought to a conclusion by Urban VIII., in 1631. From this revised + Breviary a large number of medieval hymns, both of the earlier and the + later periods, were excluded; and in their places many new hymns, + including some by Pope Urban himself, and some by Cardinal Bellarmine + and another cardinal (Silvius Antonianus) were introduced. The hymns + of the primitive epoch, from Hilary to Gregory the Great, for the most + part retained their places (especially in the offices for every day of + the week); and there remained altogether from seventy to eighty of + earlier date than the 11th century. Those, however, which were so + retained were freely altered, and by no means generally improved. The + revisers appointed by Pope Urban (three learned Jesuits--Strada, + Gallucci and Petrucci) professed to have made "as few changes as + possible" in the works of Ambrose, Gregory, Prudentius, Sedulius, + Fortunatus and other "poets of great name." But some changes, even in + those works, were made with considerable boldness; and the pope, in + the "constitution" by which his new book was promulgated, boasted + that, "with the exception of a very small number ('perpaucis'), which + were either prose or merely rhythmical, all the hymns had been made + conformable to the laws of prosody and Latinity, those which could not + be corrected by any milder method being entirely rewritten." The + latter fate befel, among others, the beautiful "Urbs beata + Hierusalem," which now assumed the form (to many, perhaps, better + known), of "Caelestis urbs Jerusalem." Of the "very few" which were + spared, the chief were "Ave maris stella" ("Gentle star of ocean"), + "Dies Irae," "Stabat Mater dolorosa," the hymns of Thomas Aquinas, + two of St Bernard and one Ambrosian hymn, "Jesu nostra Redemptio" ("O + Jesu, our Redemption"), which approaches nearer than others to the + tone of St Bernard. A then recent hymn of St Francis Xavier, with + scarcely enough merit of any kind to atone for its neglect of prosody, + "O Deus, ego amo Te" ("O God, I love Thee, not because"), was at the + same time introduced without change. This hymnary of Pope Urban VIII. + is now in general use throughout the Roman Communion. + + + Parisian revisions. + + The Parisian hymnary underwent three revisions--the first in 1527, + when a new "Psaltery with hymns" was issued. In this such changes only + were made as the revisers thought justifiable upon the principle of + correcting supposed corruptions of the original text. Of these, the + transposition, "Urbs Jerusalem beata," instead of "Urbs beata + Hierusalem," may be taken as a typical example. The next revision was + in 1670-1680, under Cardinal Péréfixe, preceptor of Louis XIV., and + Francis Harlay, successively archbishops of Paris, who employed for + this purpose Claude Santeul, of the monastery of St Magloire, and, + through him, obtained the assistance of other French scholars, + including his more celebrated brother, Jean Baptiste Santeul, of the + abbey of St Victor--better known as "Santolius Victorinus." The third + and final revision was completed in 1735, under the primacy of + Cardinal Archbishop de Vintimille, who engaged for it the services of + Charles Coffin, then rector of the university of Paris. Many old hymns + were omitted in Archbishop Harlay's Breviary, and a large number of + new compositions, by the Santeuls and others, was introduced. It + still, however, retained in their old places (without further changes + than had been made in 1527) about seventy of earlier date than the + 11th century--including thirty-one Ambrosian, one by Hilary, eight by + Prudentius, seven by Fortunatus, three by Paul the Deacon, two each by + Sedulius, Elpis, Gregory and Hrabanus Maurus, "Veni Creator" and "Urbs + Jerusalem beata." Most of these disappeared in 1735, although Cardinal + Vintimille, in his preface, professed to have still admitted the old + hymns, except when the new were better--("veteribus hymnis locus datus + est, nisi quibus, ob sententiarum vim, elegantiam verborum, et + teneriores pietatis sensus, recentiores anteponi satius visum est"). + The number of the new was, at the same time, very largely increased. + Only twenty-one more ancient than the 16th century remained, of which + those belonging to the primitive epoch were but eight, viz. four + Ambrosian, two by Fortunatus and one each by Prudentius and Gregory. + The number of Jean Baptiste Santeul's hymns rose to eighty-nine; those + by Coffin--including some old hymns, e.g. "Jam lucis orto sidere" + ("Once more the sun is beaming bright"), which he substantially + re-wrote--were eighty-three; those of other modern French writers, + ninety-seven. Whatever opinion may be entertained of the principles on + which these Roman and Parisian revisions proceeded, it would be unjust + to deny very high praise as hymn-writers to several of their poets, + especially to Coffin and Jean Baptiste Santeul. The noble hymn by + Coffin, beginning-- + + "O luce qui mortalibus "O Thou who in the light dost dwell, + Lates inaccessa, Deus, To mortals unapproachable, + Praesente quo sancti tremunt Where angels veil them from Thy rays, + Nubuntque vultus angeli," And tremble as they gaze," + + and several others of his works, breathe the true Ambrosian spirit; + and though Santeul (generally esteemed the better poet of the two) + delighted in alcaics, and did not greatly affect the primitive manner, + there can be no question as to the excellence of such hymns as his + "Fumant Sabaeis templa vaporibus" ("Sweet incense breathes around"), + "Stupete gentes, fit Deus hostia" ("Tremble, ye Gentile lands"), + "Hymnis dum resonat curia caelitum" ("Ye in the house of heavenly + morn"), and "Templi sacratas pande, Sion, fores" ("O Sion, open wide + thy gates"). It is a striking testimony to the merits of those writers + that such accomplished translators as the Rev. Isaac Williams and the + Rev. John Chandler appear (from the title-page of the latter, and the + prefaces of both) to have supposed their hymns to be "ancient" and + "primitive." Among the other authors associated with them, perhaps the + first place is due to the Abbé Besnault, of Sens, who contributed to + the book of 1735 the "Urbs beata vera pacis Visio Jerusalem," in the + opinion of Neale "much superior" to the "Caelestis urbs Jerusalem" of + the Roman Breviary. This stood side by side with the "Urbs Jerusalem + beata" of 1527 (in the office for the dedication of churches) till + 1822, when the older form was at last finally excluded by Archbishop + de Quelen. + + The Parisian Breviary of 1735 remained in use till the national French + service-books were superseded (as they have lately been, generally, if + not universally) by the Roman. Almost all French dioceses followed, + not indeed the Breviary, but the example, of Paris; and before the end + of the 18th century the ancient Latin hymnody was all but banished + from France. + + + Modern Latin hymns. + + In some parts of Germany, after the Reformation, Latin hymns continued + to be used even by Protestants. This was the case at Halberstadt until + quite a recent date. In England, a few are still occasionally used in + the older universities and colleges. Some, also, have been composed in + both countries since the Reformation. The "Carmina lyrica" of Johann + Jakob Balde, a native of Alsace, and a Jesuit priest in Bavaria, have + received high commendation from very eminent German critics, + particularly Herder and Augustus Schlegel. Some of the Latin hymns of + William Alard (1572-1645), a Protestant refugee from Belgium, and + pastor in Holstein, have been thought worthy of a place in Archbishop + Trench's selection. Two by W. Petersen (printed at the end of + Haberkorn's supplement to Jacobi's _Psalmodia Germanica_) are good in + different ways--one, "Jesu dulcis amor meus" ("Jesus, Thee my soul + doth love"), being a gentle melody of spiritual devotion, and the + other, entitled _Spes Sionis_, violently controversial against Rome. + An English hymn of the 17th century, in the Ambrosian style, "Te Deum + Patrem colimus" ("Almighty Father, just and good"), is sung on every + May-Day morning by the choristers of Magdalen College, Oxford, from + the top of the tower of their chapel; and another in the style of the + Renaissance, of about the same date, "Te de profundis, summe Rex" + ("Thee from the depths, Almighty King"), long formed part of a grace + formerly sung by the scholars of Winchester College. + + + Luther. + +5. _German Hymnody._--Luther was a proficient in and a lover of music. +He desired (as he says in the preface to his hymn-book of 1545) that +this "beautiful ornament" might "in a right manner serve the great +Creator and His Christian people." The persecuted Bohemian or Hussite +Church, then settled on the borders of Moravia under the name of "United +Brethren," had sent to him, on a mission in 1522, Michael Weiss, who not +long afterwards published a number of German translations from old +Bohemian hymns (known as those of the "Bohemian Brethren"), with some of +his own. These Luther highly approved and recommended. He himself, in +1522, published a small volume of eight hymns, which was enlarged to 63 +in 1527, and to 125 in 1545. He had formed what he called a "house +choir" of musical friends, to select such old and popular tunes (whether +secular or ecclesiastical) as might be found suitable, and to compose +new melodies, for church use. His fellow labourers in this field +(besides Weiss) were Justus Jonas, his own especial colleague; Paul +Eber, the disciple and friend of Melanchthon; John Walther, choirmaster +successively to several German princes, and professor of arts, &c., at +Wittenberg; Nicholas Decius, who from a monk became a Protestant teacher +in Brunswick, and translated the "Gloria in Excelsis," &c.; and Paul +Speratus, chaplain to Duke Albert of Prussia in 1525. Some of their +works are still popular in Germany. Weiss's "Funeral Hymn," "Nun lasst +uns den Leib begraben" ("Now lay we calmly in the grave"); Eber's "Herr +Jesu Christ, wahr Mensch und Gott" ("Lord Jesus Christ, true Man and +God"), and "Wenn wir in höchsten Nöthen sein" ("When in the hour of +utmost need"); Walther's "New Heavens and new Earth" ("Now fain my +joyous heart would sing"); Decius's "To God on high be thanks and +praise"; and Speratus's "Salvation now has come for all," are among +those which at the time produced the greatest effect, and are still best +remembered. + +Luther's own hymns, thirty-seven in number (of which about twelve are +translations or adaptations from Latin originals), are for the principal +Christian seasons; on the sacraments, the church, grace, death, &c.; and +paraphrases of seven psalms, of a passage in Isaiah, and of the Lord's +Prayer, Ten Commandments, Creed, Litany and "Te Deum." There is also a +very touching and stirring song on the martyrdom of two youths by fire +at Brussels, in 1523-1524. Homely and sometimes rugged in form, and for +the most part objective in tone, they are full of fire, manly simplicity +and strong faith. Three rise above the rest. One for Christmas, "Vom +Himmel hoch da komm ich her" ("From Heaven above to earth I come"), has +a reverent tenderness, the influence of which may be traced in many +later productions on the same subject. That on salvation through Christ, +of a didactic character, "Nun freuet euch, lieben Christen g'mein" +("Dear Christian people, now rejoice"), is said to have made many +conversions, and to have been once taken up by a large congregation to +silence a Roman Catholic preacher in the cathedral of Frankfort. +Pre-eminent above all is the celebrated paraphrase of the 46th Psalm: +"Ein' feste Burg ist unser Gott" ("A sure stronghold our God is +He")--"the production" (as Ranke says) "of the moment in which Luther, +engaged in a conflict with a world of foes, sought strength in the +consciousness that he was defending a divine cause which could never +perish." Carlyle compares it to "a sound of Alpine avalanches, or the +first murmur of earthquakes." Heine called it "the Marseillaise of the +Reformation." + +Luther spent several years in teaching his people at Wittenberg to sing +these hymns, which soon spread over Germany. Without adopting the +hyperbolical saying of Coleridge, that "Luther did as much for the +Reformation by his hymns as by his translation of the Bible," it may +truly be affirmed, that, among the secondary means by which the success +of the Reformation was promoted, none was more powerful. They were sung +everywhere--in the streets and fields as well as the churches, in the +workshop and the palace, "by children in the cottage and by martyrs on +the scaffold." It was by them that a congregational character was given +to the new Protestant worship. This success they owed partly to their +metrical structure, which, though sometimes complex, was recommended to +the people by its ease and variety; and partly to the tunes and melodies +(many of them already well known and popular) to which they were set. +They were used as direct instruments of teaching, and were therefore, in +a large measure, didactic and theological; and it may be partly owing to +this cause that German hymnody came to deviate, so soon and so generally +as it did, from the simple idea expressed in the ancient Augustinian +definition, and to comprehend large classes of compositions which, in +most other countries, would be thought hardly suitable for church use. + + + Followers of Luther + +The principal hymn-writers of the Lutheran school, in the latter part of +the 16th century, were Nikolaus Selnecker, Herman and Hans Sachs, the +shoemaker of Nuremberg, also known in other branches of literature. All +these wrote some good hymns. They were succeeded by men of another sort, +to whom F. A. Cunz gives the name of "master-singers," as having raised +both the poetical and the musical standard of German +hymnody:--Bartholomäus Ringwaldt, Ludwig Helmbold, Johannes Pappus, Martin +Schalling, Rutilius and Sigismund Weingartner. The principal topics of +their hymns (as if with some foretaste of the calamities which were soon +to follow) were the vanity of earthly things, resignation to the Divine +will, and preparation for death and judgment. The well-known English hymn, +"Great God, what do I see and hear," is founded upon one by Ringwaldt. Of +a quite different character were two of great beauty and universal +popularity, composed by Philip Nicolai, a Westphalian pastor, during a +pestilence in 1597, and published by him, with fine chorales, two years +afterwards. One of these (the "Sleepers wake! a voice is calling," of +Mendelssohn's oratorio, _St Paul_) belongs to the family of Advent or New +Jerusalem hymns. The other, a "Song of the believing soul concerning the +Heavenly Bridegroom" ("Wie schön leucht't uns der Morgenstern"--"O morning +Star, how fair and bright"), became the favourite marriage hymn of +Germany. + + + Period of Thirty Years' War. + +The hymns produced during the Thirty Years' War are characteristic of +that unhappy time, which (as Miss Winkworth says) "caused religious men +to look away from this world," and made their songs more and more +expressive of personal feelings. In point of refinement and graces of +style, the hymn-writers of this period excelled their predecessors. +Their taste was chiefly formed by the influence of Martin Opitz, the +founder of what has been called the "first Silesian school" of German +poetry, who died comparatively young in 1639, and who, though not of any +great original genius, exercised much power as a critic. Some of the +best of these works were by men who wrote little. In the famous +battle-song of Gustavus Adolphus, published (1631) after the victory of +Breitenfeld, for the use of his army, "Verzage nicht du Häuflein klein" +("Fear not, O little flock, the foe"), we have almost certainly a +composition of the hero-king himself, the versification corrected by his +chaplain Jakob Fabricius (1593-1654) and the music composed by Michael +Altenburg, whose name has been given to the hymn. This, with Luther's +paraphrase of the 67th Psalm, was sung by Gustavus and his soldiers +before the battle of Lützen in 1632. Two very fine hymns, one of prayer +for deliverance and peace, the other of trust in God under calamities, +were written about the same time by Matthäus Löwenstern, a saddler's +son, poet, musician and statesman, who was ennobled after the peace by +the emperor Ferdinand III. Martin Rinckhart, in 1636, wrote the "Chorus +of God's faithful children" ("Nun danket alle Gott"--"Now thank we all +our God"), introduced by Mendelssohn in his "Lobgesang," which has been +called the "Te Deum" of Germany, being usually sung on occasions of +public thanksgiving. Weissel, in 1635, composed a beautiful Advent hymn +("Lift up your heads, ye mighty gates"), and J. M. Meyfart, professor of +theology at Erfurt, in 1642, a fine adaptation of the ancient "Urbs +beata Hierusalem." The hymn of trust in Providence by George Neumark, +librarian to that duke of Weimar ("Wer nur den lieben Gott lässt +walten"--"Leave God to order all thy ways"), is scarcely, if at all, +inferior to that of Paul Gerhardt on the same theme. Paul Flemming, a +great traveller and lover of nature, who died in 1639, also wrote +excellent compositions, coloured by the same tone of feeling; and some, +of great merit, were composed, soon after the close of the war, by +Louisa Henrietta, electress of Brandenburg, granddaughter of the famous +admiral Coligny, and mother of the first king of Prussia. With these may +be classed (though of later date) a few striking hymns of faith and +prayer under mental anxiety, by Anton Ulrich, duke of Brunswick. + + + Rist. + + Dach. + +The most copious, and in their day most esteemed, hymn-writers of the +first half of the 17th century, were Johann Heermann and Johann Rist. +Heermann, a pastor in Silesia, the theatre (in a peculiar degree) of war +and persecution, experienced in his own person a very large share of the +miseries of the time, and several times narrowly escaped a violent +death. His _Devoti musica cordis_, published in 1630, reflects the +feelings natural under such circumstances. With a correct style and good +versification, his tone is subjective, and the burden of his hymns is +not praise, but prayer. Among his works (which enter largely into most +German hymn-books), two of the best are the "Song of Tears" and the +"Song of Comfort," translated by Miss Winkworth in her _Christian +Singers of Germany_. Rist published about 600 hymns, "pressed out of +him," as he said, "by the cross." He was a pastor, and son of a pastor, +in Holstein, and lived after the peace to enjoy many years of +prosperity, being appointed poet-laureate to the emperor and finally +ennobled. The bulk of his hymns, like those of other copious writers, +are of inferior quality; but some, particularly those for Advent, +Epiphany, Easter Eve and on Angels, are very good. They are more +objective than those of Heermann, and written, upon the whole, in a more +manly spirit. Next to Heermann and Rist in fertility of production, and +above them in poetical genius, was Simon Dach, professor of poetry at +Königsberg, who died in 1659. Miss Winkworth ranks him high among German +poets, "for the sweetness of form and depth of tender contemplative +emotion to be found in his verses." + + + Gerhardt. + + Franck. + + Scheffler. + +The fame of all these writers was eclipsed in the latter part of the +same century by three of the greatest hymnographers whom Germany has +produced--Paul Gerhardt (1604-1676), Johann Franck (1618-1677) and +Johann Scheffler (1624-1677), the founder of the "second Silesian +school," who assumed the name of "Angelus Silesius." Gerhardt is by +universal consent the prince of Lutheran poets. His compositions, which +may be compared, in many respects, to those of the _Christian Year_, are +lyric poems, of considerable length, rather than hymns, though many +hymns have been taken from them. They are, with few exceptions, +subjective, and speak the language of individual experience. They occupy +a middle ground between the masculine simplicity of the old Lutheran +style and the highly wrought religious emotion of the later pietists, +towards whom they on the whole incline. Being nearly all excellent, it +is not easy to distinguish among the 123 those which are entitled to the +highest praise. Two, which were written one during the war and the other +after the conclusion of peace, "Zeuch ein zu deinen Thoren" ("Come to +Thy temple here on earth"), and "Gottlob, nun ist erschollen" ("Thank +God, it hath resounded"), are historically interesting. Of the rest, one +is well known and highly appreciated in English through Wesley's +translation, "Commit thou all thy ways"; and the evening and +spring-tide hymns ("Now all the woods are sleeping" and "Go forth, my +heart, and seek delight") show an exquisite feeling for nature; while +nothing can be more tender and pathetic than "Du bist zwar mein und +bleibest mein" ("Thou'rt mine, yes, still thou art mine own"), on the +death of his son. Franck, who was burgomaster of Guben in Lusatia, has +been considered by some second only to Gerhardt. If so, it is with a +great distance between them. His approach to the later pietists is +closer than that of Gerhardt. His hymns were published, under the title +of _Geistliche und weltliche Gedichte_, in 1674, some of them being +founded on Ambrosian and other Latin originals. Miss Winkworth gives +them the praise of a condensed and polished style and fervid and +impassioned thought. It was after his conversion to Roman Catholicism +that Scheffler adopted the name of "Angelus Silesius," and published in +1657 his hymns, under a fantastic title, and with a still more fantastic +preface. Their keynote is divine love; they are enthusiastic, intense, +exuberant in their sweetness, like those of St Bernard among medieval +poets. An adaptation of one of them, by Wesley, "Thee will I love, my +Strength, my Tower," is familiar to English readers. Those for the first +Sunday after Epiphany, for Sexagesima Sunday and for Trinity Sunday, in +_Lyra Germanica_, are good examples of his excellences, with few of his +defects. His hymns are generally so free from the expression, or even +the indirect suggestion, of Roman Catholic doctrine, that it has been +supposed they were written before his conversion, though published +afterwards. The evangelical churches of Germany found no difficulty in +admitting them to that prominent place in their services which they have +ever since retained. + + + Pietists. + +Towards the end of the 17th century, a new religious school arose, to +which the name of "Pietists" was given, and of which Philipp Jakob +Spener was esteemed the founder. He and his pupils and successors, +August Hermann Francke and Anastasius Freylinghausen, all wrote hymns. +Spener's hymns are not remarkable, and Francke's are not numerous. +Freylinghausen was their chief singer; his rhythm is lively, his music +florid; but, though his book attained extraordinary popularity, he was +surpassed in solid merit by other less fertile writers of the same +school. The "Auf hinauf zu deiner Freude" ("Up, yes, upward to thy +gladness") of Schade may recall to an English reader a hymn by Seagrave, +and more than one by Lyte; the "Malabarian hymn" (as it was called by +Jacobi) of Johann Schütz, "All glory to the Sovereign Good," has been +popular in England as well as Germany; and one of the most exquisite +strains of pious resignation ever written is "Whate'er my God ordains is +right," by Samuel Rodigast. + + + Neander. + +Joachim Neander, a schoolmaster at Düsseldorf, and a friend of Spener +and Schütz (who died before the full development of the "Pietistic" +school), was the first man of eminence in the "Reformed" or Calvinistic +Church who imitated Lutheran hymnody. This he did, while suffering +persecution from the elders of his own church for some other religious +practices, which he had also learnt from Spener's example. As a poet, he +is sometimes deficient in art; but there is feeling, warmth and +sweetness in many of his "Bundeslieder" or "Songs of the Covenant," and +they obtained general favour, both in the Reformed and in Lutheran +congregations. The Summer Hymn ("O Thou true God alone") and that on the +glory of God in creation ("Lo, heaven and earth and sea and air") are +instances of his best style. + + + Schmolke. + + Dessler. + + Hiller. + + Arnold. + + Tersteegen. + + Zinzendorf. + +With the "Pietists" may be classed Benjamin Schmolke and Dessler, +representatives of the "Orthodox" division of Spener's school; Philipp +Friedrich Hiller, their leading poet in South Germany; Gottfried Arnold +and Gerhard Tersteegen, who were practically independent of +ecclesiastical organization, though connected, one with the "Orthodox" +and the other with the "Reformed" churches; and Nikolaus Ludwig, Graf +von Zinzendorf. Schmolke, a pastor in Silesia, called the Silesian Rist +(1672-1737), was perhaps the most voluminous of all German hymn-writers. +He wrote 1188 religious poems and hymns, a large proportion of which do +not rise above mediocrity. His style, if less refined, is also less +subjective and more simple than that of most of his contemporaries. +Among his best and most attractive works, which indeed, it would be +difficult to praise too highly, are the "Hosianna David's Sohn," for +Palm Sunday--much resembling a shorter hymn by Jeremy Taylor; and the +Ascension, Whitsuntide and Sabbath hymns--"Heavenward doth our journey +tend," "Come deck our feast to-day," and "Light of light, enlighten me." +Dessler was a greater poet than Schmolke. Few hymns, of the subjective +kind, are better than his "I will not let Thee go, Thou Help in time of +need," "O Friend of souls, how well is me," and "Now, the pearly gates +unfold." Hiller (1699-1769), was a pastor in Württemberg who, falling +into ill-health during the latter part of his ministry, published a +_Geistliche Liederhöstlein_ in a didactic vein, with more taste than +power, but (as Miss Winkworth says) in a tone of "deep, thoughtful, +practical piety." They were so well adapted to the wants of his people +that to this day Hiller's Casket is prized, next to their Bibles, by the +peasantry of Württemberg; and the numerous emigrants from that part of +Germany to America and other foreign countries generally take it with +them wherever they go. Arnold, a professor at Giessen, and afterwards a +pastor in Brandenburg, was a man of strong will, uncompromising +character and austere views of life, intolerant and controversial +towards those whose doctrine or practice he disapproved, and more +indifferent to separatism and sectarianism than the "orthodox" generally +thought right. His hymns, like those of Augustus M. Toplady, whom in +these respects he resembled, unite with considerable strength more +gentleness and breadth of sympathy than might be expected from a man of +such a character. Tersteegen (1697-1769), who never formally separated +himself from the "Reformed" communion, in which he was brought up, but +whose sympathies were with the Moravians and with Zinzendorf, was, of +all the more copious German hymn-writers after Luther, perhaps the most +remarkable man. Pietist, mystic and missionary, he was also a great +religious poet. His 111 hymns were published In 1731, in a volume called +_Geistlicher Blumengärtlein inniger_ Seelen. They are intensely +individual, meditative and subjective. Wesley's adaptations of two--"Lo! +God is here; let us adore," and "Thou hidden Love of God, whose +source"--are well known. Among those translated by Miss Winkworth, "O +God, O Spirit, Light of all that live," and "Come, brethren, let us go," +are specimens which exhibit favourably his manner and power. Miss Cox +speaks of him as "a gentle heaven-inspired soul, whose hymns are the +reflection of a heavenly, happy life, his mind being full of a +child-like simplicity"; and his own poem on the child-character, which +Miss Winkworth has appropriately connected with Innocents' day ("Dear +Soul, couldst thou become a child")--one of his best compositions, +exquisitely conceived and expressed--shows that this was in truth the +ideal which he sought to realize. The hymns of Zinzendorf are often +disfigured by excess in the application of the language and imagery of +human affections to divine objects; and this blemish is also found in +many later Moravian hymns. But one hymn, at least, of Zinzendorf may be +mentioned with unqualified praise, as uniting the merits of force, +simplicity and brevity--"Jesu, geh voran" ("Jesus, lead the way"), which +is taught to most children of religious parents in Germany. Wesley's +"Jesus, Thy blood and righteousness" is a translation from Zinzendorf. + + + Gellert. + +The transition from Tersteegen and Zinzendorf to Gellert and Klopstock +marks strongly the reaction against Pietism which took place towards the +middle of the 18th century. The _Geistlichen Oden und Lieder_ of +Christian F. Gellert were published in 1757, and are said to have been +received with an enthusiasm almost like that which "greeted Luther's +hymns on their first appearance." It is a proof of the moderation both +of the author and of his times that they were largely used, not only by +Protestant congregations, but in those German Roman Catholic churches in +which vernacular services had been established through the influence of +the emperor Joseph II. They became the model which was followed by most +succeeding hymn-writers, and exceeded all others in popularity till the +close of the century, when a new wave of thought was generated by the +movement which produced the French Revolution. Since that time they have +been, perhaps, too much depreciated. They are, indeed, cold and +didactic, as compared with Scheffler or Tersteegen; but there is +nevertheless in them a spirit of genuine practical piety; and, if not +marked by genius, they are pure in taste, and often terse, vigorous and +graceful. + + + Klopstock. + +Klopstock, the author of the _Messiah_, cannot be considered great as a +hymn-writer, though his "Sabbath Hymn" (of which there is a version in +_Hymns from the Land of Luther_) is simple and good. Generally his hymns +(ten of which are translated in Sheppard's _Foreign Sacred Lyre_) are +artificial and much too elaborate. + + + Fouqué. + +Of the "romantic" school, which came in with the French Revolution, the +two leading writers are Friedrich Leopold von Hardenberg, called +"Novalis," and Friedrich de la Motte Fouqué, the celebrated author of +_Undine_ and _Sintram_--both romance-writers, as well as poets. The +genius of Novalis was early lost to the world; he died in 1801, not +thirty years old. Some of his hymns are very beautiful; but even in such +works as "Though all to Thee were faithless," and "If only He is mine," +there is a feeling of insulation and of despondency as to good in the +actual world, which was perhaps inseparable from his ecclesiastical +idealism. Fouqué survived till 1843. In his hymns there is the same deep +flow of feeling, richness of imagery and charm of expression which +distinguishes his prose works. The two missionary hymns--"Thou, solemn +Ocean, rollest to the strand," and "In our sails all soft and +sweetly"--and the exquisite composition which finds its motive in the +gospel narrative of blind Bartimeus, "Was du vor tausend Jahren" (finely +translated both by Miss Winkworth and by Miss Cox), are among the best +examples. + + + Spitta. + +The later German hymn-writers of the 19th century belong, generally, to +the revived "Pietistic" school. Some of the best, Johann Baptist von +Albertini, Friedrich Adolf Krummacher, and especially Karl Johann +Philipp Spitta (1801-1859) have produced works not unworthy of the fame +of their nation. Mr Massie, the able translator of Spitta's _Psalter und +Harfe_ (Leipzig, 1833), speaks of it as having "obtained for him in +Germany a popularity only second to that of Paul Gerhardt." In Spitta's +poems (for such they generally are, rather than hymns) the subjective +and meditative tone is tempered, not ungracefully, with a didactic +element; and they are not disfigured by exaggerated sentiment, or by a +too florid and rhetorical style. + +6. _British Hymnody._--After the Reformation, the development of hymnody +was retarded, in both parts of Great Britain, by the example and +influence of Geneva. Archbishop Cranmer appears at one time to have been +disposed to follow Luther's course, and to present to the people, in an +English dress, some at least of the hymns of the ancient church. In a +letter to King Henry VIII. (October 7, 1544), among some new +"processions" which he had himself translated, into English, he mentions +the Easter hymn, "Salve, festa dies, toto memorabilis aevo" ("Hail, glad +day, to be joyfully kept through all generations"), of Fortunatus. In +the "Primer" of 1535 (by Marshall) and the one of 1539 (by Bishop Hilsey +of Rochester, published by order of the vicar-general Cromwell) there +had been several rude English hymns, none of them taken from ancient +sources. King Henry's "Primer" of 1545 (commanded by his injunction of +the 6th of May 1545 to be used throughout his dominions) was formed on +the model of the daily offices of the Breviary; and it contains English +metrical translations from some of the best-known Ambrosian and other +early hymns. But in the succeeding reign different views prevailed. A +new direction had been given to the taste of the "Reformed" +congregations in France and Switzerland by the French metrical +translation of the Old Testament Psalms, which appeared about 1540. This +was the joint work of Clement Marot, valet or groom of the chamber to +Francis I., and Theodore Beza, then a mere youth, fresh from his studies +at Orleans. + + + Marot's Psalms. + +Marot's psalms were dedicated to the French king and the ladies of +France, and, being set to popular airs, became fashionable. They were +sung by Francis himself, the queen, the princesses and the courtiers, +upon all sorts of secular occasions, and also, more seriously and +religiously, by the citizens and the common people. They were soon +perceived to be a power on the side of the Reformation. Calvin, who had +settled at Geneva in the year of Marot's return to Paris, was then +organizing his ecclesiastical system. He rejected the hymnody of the +breviaries and missals, and fell back upon the idea, anciently held by +Paul of Samosata, and condemned by the fourth council of Toledo, that +whatever was sung in churches ought to be taken out of the Scriptures. +Marot's Psalter, appearing thus opportunely, was introduced into his new +system of worship, and appended to his catechism. On the other hand, it +was interdicted by the Roman Catholic priesthood. Thus it became a badge +to the one party of the "reformed" profession, and to the other of +heresy. + + + Sternhold and Hopkins. + +The example thus set produced in England the translation commonly known +as the "Old Version" of the Psalms. It was begun by Thomas Sternhold, +whose position in the household of Henry VIII., and afterwards of Edward +VI., was similar to that of Marot with Francis I., and whose services to +the former of those kings were rewarded by a substantial legacy under +his will. Sternhold published versions of nineteen Psalms, with a +dedication to King Edward, and died soon afterwards. A second edition +appeared in 1551, with eighteen more Psalms added, of Sternhold's +translating, and seven others by John Hopkins, a Suffolk clergyman. The +work was continued during Queen Mary's reign by British refugees at +Geneva, the chief of whom were William Whittingham, afterwards dean of +Durham, who succeeded John Knox as minister of the English congregation +there, and William Kethe or Keith, said by Strype to have been a +Scotsman. They published at Geneva in 1556 a service-book, containing +fifty-one English metrical psalms, which number was increased, in later +editions, to eighty-seven. On the accession of Queen Elizabeth, this +Genevan Psalmody was at once brought into use in England--first +(according to a letter of Bishop Jewell to Peter Martyr, dated 5th March +1560) in one London church, from which it quickly spread to others both +in London and in other cities. Jewell describes the effect produced by +large congregations, of as many as 6000 persons, young and old, women +and children, singing it after the sermons at St Paul's Cross--adding, +"Id sacrificos et diabolum aegre habet; vident enim sacras conciones hoc +pacto profundius descendere in hominum animos." The first edition of the +completed "Old Version" (containing forty Psalms by Sternhold, +sixty-seven by Hopkins, fifteen by Whittingham, six by Kethe and the +rest by Thomas Norton the dramatist, Robert Wisdom, John Marckant and +Thomas Churchyard) appeared in 1562. + + In the meantime, the Books of Common Prayer, of 1549, 1552 and 1559, + had been successively established as law by the acts of uniformity of + Edward VI. and Queen Elizabeth. In these no provision was made for the + use of any metrical psalm or hymn on any occasion whatever, except at + the consecration of bishops and the ordination of priests, in which + offices (first added in 1552) an English version of "Veni Creator" + (the longer of the two now in use) was appointed to be "said or sung." + The canticles, "Te Deum," "Benedicite," the Nicene and Athanasian + Creeds, the "Gloria in Excelsis," and some other parts of the + communion and other special offices were also directed to be "said or + sung"; and, by general rubrics, the chanting of the whole service was + allowed. + + The silence, however, of the rubrics in these books as to any other + singing was not meant to exclude the use of psalms not expressly + appointed, when they could be used without interfering with the + prescribed order of any service. It was expressly provided by King + Edward's first act of uniformity (by later acts made applicable to the + later books) that it should be lawful "for all men, as well in + churches, chapels, oratories or other places, to use openly any psalms + or prayers taken out of the Bible, at any due time, not letting or + omitting thereby the service, or any part thereof, mentioned in the + book." And Queen Elizabeth, by one of the injunctions issued in the + first year of her reign, declared her desire that the provision made, + "in divers collegiate and also some parish churches, for singing in + the church, so as to promote the laudable service of music," should + continue. After allowing the use of "a modest and distinct song in all + parts of the common prayers of the church, so that the same may be as + plainly understanded as if it were read without singing," the + injunction proceeded thus--"And yet, nevertheless, for the comforting + of such that delight in music, it may be permitted that in the + beginning or in the end of the Common Prayer, either at morning or + evening, there may be sung an hymn, or such like song to the praise of + Almighty God, in the best sort of melody and music that may be + conveniently devised, having respect that the sentence" (i.e. sense) + "of hymn may be understanded and perceived." + + The "Old Version," when published (by John Daye, for the Stationers' + Company, "cum gratia et privilegio Regiae Majestatis"), bore upon the + face of it that it was "newly set forth, and allowed to be sung of the + people in churches, before and after morning and evening prayer, as + also before and after the sermon." The question of its authority has + been at different times much debated, chiefly by Peter Heylyn and + Thomas Warton on one side (both of whom disliked and disparaged it), + and by William Beveridge, bishop of St Asaph, and the Rev. H. J. Todd + on the other. Heylyn says, it was "permitted rather than allowed," + which seems to be a distinction without much difference. "Allowance," + which is all that the book claimed for itself, is authorization by way + of permission, not of commandment. Its publication in that form could + hardly have been licensed, nor could it have passed into use as it did + without question, throughout the churches of England, unless it had + been "allowed" by some authority then esteemed to be sufficient. + Whether that authority was royal or ecclesiastical does not appear, + nor (considering the proviso in King Edward's act of uniformity, and + Queen Elizabeth's injunctions) is it very important. No inference can + justly be drawn from the inability of inquirers, in Heylyn's time or + since, to discover any public record bearing upon this subject, many + public documents of that period having been lost. + +In this book, as published in 1562, and for many years afterwards, there +were (besides the versified Psalms) eleven metrical versions of the "Te +Deum," canticles, Lord's Prayer (the best of which is that of the +"Benedicite"); and also "Da pacem, Domine," a hymn suitable to the +times, rendered into English from Luther; two original hymns of praise, +to be sung before morning and evening prayer; two penitential hymns (one +of them the "humble lamentation of a sinner"); and a hymn of faith, +beginning, "Lord, in Thee is all my trust." In these respects, and also +in the tunes which accompanied the words (stated by Dr Charles Burney, +in his _History of Music_, to be German, and not French), there was a +departure from the Genevan platform. Some of these hymns, and some of +the psalms also (e.g. those by Robert Wisdom, being alternative +versions), were omitted at a later period; and many alterations and +supposed amendments were from time to time made by unknown hands in the +psalms which remained, so that the text, as now printed, is in many +places different from that of 1562. + + + Scotch Psalms. + +In Scotland, the General Assembly of the kirk caused to be printed at +Edinburgh in 1564, and enjoined the use of, a book entitled _The Form of +Prayers and Ministry of the Sacraments used in the English Church at +Geneva, approved and received by the Church of Scotland; whereto, +besides that was in the former books, are also added sundry other +prayers, with the whole Psalms of David in English metre_. This +contained, from the "Old Version," translations of forty Psalms by +Sternhold, fifteen by Whittingham, twenty-six by Kethe and thirty-five +by Hopkins. Of the remainder two were by John Pulleyn (one of the +Genevan refugees, who became archdeacon of Colchester); six by Robert +Pont, Knox's son-in-law, who was a minister of the kirk, and also a lord +of session; and fourteen signed with the initials I. C., supposed to be +John Craig; one was anonymous, eight were attributed to N., two to M. +and one to T. N. respectively. + +So matters continued in both churches until the Civil War. During the +interval, King James I. conceived the project of himself making a new +version of the Psalms, and appears to have translated thirty-one of +them--the correction of which, together with the translation of the +rest, he entrusted to Sir William Alexander, afterwards earl of +Stirling. Sir William having completed his task, King Charles I. had it +examined and approved by several archbishops and bishops of England, +Scotland and Ireland, and caused it to be printed in 1631 at the Oxford +University Press, as the work of King James; and, by an order under the +royal sign manual, recommended its use in all churches of his dominions. +In 1634 he enjoined the Privy Council of Scotland not to suffer any +other psalms, "of any edition whatever," to be printed in or imported +into that kingdom. In 1636 it was republished, and was attached to the +famous Scottish service-book, with which the troubles began in 1637. It +need hardly be added that the king did not succeed in bringing this +Psalter into use in either kingdom. + +When the Long Parliament undertook, in 1642, the task of altering the +liturgy, its attention was at the same time directed to psalmody. It had +to judge between two rival translations of the Psalms--one by Francis +Rouse, a member of the House of Commons, afterwards one of Cromwell's +councillors and finally provost of Eton; the other by William Barton, a +clergyman of Leicester. The House of Lords favoured Barton, the House of +Commons Rouse, who had made much use of the labours of Sir William +Alexander. Both versions were printed by order of parliament, and were +referred for consideration to the Westminster Assembly. They decided in +favour of Rouse. His version, as finally amended, was published in 1646, +under an order of the House of Commons dated 14th November 1645. In the +following year it was recommended by the parliament to the General +Assembly at Edinburgh, who appointed a committee, with large powers, to +prepare a revised Psalter, recommending to their consideration not only +Rouse's book but that of 1564, and two other versions (by Zachary Boyd +and Sir William Mure of Rowallan), then lately executed in Scotland. The +result of the labours of this committee was the "Paraphrase" of the +Psalms, which, in 1649-1650, by the concurrent authority of the General +Assembly and the committee of estates, was ordered to be exclusively +used throughout the church of Scotland. Some use was made in the +preparation of this book of the versions to which the attention of the +revisers had been directed, and also of Barton's; but its basis was that +of Rouse. It was received in Scotland with great favour, which it has +ever since retained; and it is fairly entitled to the praise of striking +a tolerable medium between the rude homeliness of the "Old," and the +artificial modernism of the "New" English versions--perhaps as great a +success as was possible for such an undertaking. Sir Walter Scott is +said to have dissuaded any attempt to alter it, and to have pronounced +it, "with all its acknowledged occasional harshness, so beautiful, that +any alterations must eventually prove only so many blemishes." No +further step towards any authorized hymnody was taken by the kirk of +Scotland till the following century. + +In England, two changes bearing on church hymnody were made upon the +revision of the prayer-book after the Restoration, in 1661-1662. One was +the addition, in the offices for consecrating bishops and ordaining +priests, of the shorter version of "Veni Creator" ("Come, Holy Ghost, +our souls inspire"), as an alternative form. The other, and more +important, was the insertion of the rubric after the third collect, at +morning and evening prayer: "In quires and places where they sing, here +followeth the anthem." By this rubric synodical and parliamentary +authority was given for the interruption, at that point, of the +prescribed order of the service by singing an anthem, the choice of +which was left to the discretion of the minister. Those actually used, +under this authority, were for some time only unmetrical passages of +scripture, set to music by Blow, Purcell and other composers, of the +same kind with the anthems still generally sung in cathedral and +collegiate churches. But the word "anthem" had no technical +signification which could be an obstacle to the use under this rubric of +metrical hymns. + + + Tate and Brady. + +The "New Version" of the Psalms, by Dr Nicholas Brady and the +poet-laureate Nahum Tate (both Irishmen), appeared in 1696, under the +sanction of an order in council of William III., "allowing and +permitting" its use "in all such churches, chapels and congregations as +should think fit to receive it." Dr Compton, bishop of London, +recommended it to his diocese. No hymns were then appended to it; but +the authors added a "supplement" in 1703, which received an exactly +similar sanction from an order in council of Queen Anne. In that +supplement there were several new versions of the canticles, and of the +"Veni Creator"; a variation of the old "humble lamentation of a sinner"; +six hymns for Christmas, Easter and Holy Communion (all versions or +paraphrases of scripture), which are still usually printed at the end of +the prayer-books containing the new version; and a hymn "on the divine +use of music"--all accompanied by tunes. The authors also reprinted, +with very good taste, the excellent version of the "Benedicite" which +appeared in the book of 1562. Of the hymns in this "supplement," one +("While shepherds watched their flocks by night") greatly exceeded the +rest in merit. It has been ascribed to Tate, but it has a character of +simplicity unlike the rest of his works. + + + Old and new versions compared. + +The relative merits of the "Old" and "New" versions have been very +variously estimated. Competent judges have given the old the praise, which +certainly cannot be accorded to the new, of fidelity to the Hebrew. In +both, it must be admitted, that those parts which have poetical merit are +few and far between; but a reverent taste is likely to be more offended by +the frequent sacrifice, in the new, of depth of tone and accuracy of sense +to a fluent commonplace correctness of versification and diction, than by +any excessive homeliness in the old. In both, however, some psalms, or +portions of psalms, are well enough rendered to entitle them to a +permanent place in the hymn-books--especially the 8th, and parts of the +18th Psalm, by Sternhold; the 57th, 84th and 100th, by Hopkins; the 23rd, +34th and 36th, and part of the 148th, by Tate and Brady. + +The judgment which a fastidious critic might be disposed to pass upon +both these books may perhaps be considerably mitigated by comparing them +with the works of other labourers in the same field, of whom Holland, in +his interesting volumes entitled _Psalmists of Great Britain_, +enumerates above 150. Some of them have been real poets--the celebrated +earl of Surrey, Sir Philip Sidney and his sister the countess of +Pembroke, George Sandys, George Wither, John Milton and John Keble. In +their versions, as might be expected, there are occasional gleams of +power and beauty, exceeding anything to be found in Sternhold and +Hopkins, or Tate and Brady; but even in the best these are rare, and +chiefly occur where the strict idea of translation has been most widely +departed from. In all of them, as a rule, the life and spirit, which in +prose versions of the psalms are so wonderfully preserved, have +disappeared. The conclusion practically suggested by so many failures is +that the difficulties of metrical translation, always great, are in this +case insuperable; and that, while the psalms like other parts of +scripture are abundantly suggestive of motive and material for +hymnographers, it is by assimilation and adaptation, and not by any +attempt to transform their exact sense into modern poetry, that they may +be best used for this purpose. + + The order in council of 1703 is the latest act of any public authority + by which an express sanction has been given to the use of psalms or + hymns in the Church of England. At the end, indeed, of many + Prayer-books, till about the middle of the 19th century, there were + commonly found, besides some of the hymns sanctioned by that order in + council, or of those contained in the book of 1562, a sacramental and + a Christmas hymn by Doddridge; a Christmas hymn (varied by Martin + Madan) from Charles Wesley; an Easter hymn of the 18th century, + beginning "Jesus Christ has risen to-day"; and abridgments Bishop + Ken's Morning and Evening Hymns. These additions first began to be + made in or about 1791, in London editions of the Prayer-book and + Psalter, at the mere will and pleasure (so far as appears) of the + printers. They had no sort of authority. + + + English congregational hymnody. + +In the state of authority, opinion and practice disclosed by the +preceding narrative may be found the true explanation of the fact that, +in the country of Chaucer, Spenser, Shakespeare and Milton, and +notwithstanding the example of Germany, no native congregational hymnody +worthy of the name arose till after the commencement of the 18th +century. Yet there was no want of appreciation of the power and value +of congregational church music. Milton could write, before 1645:-- + + "There let the pealing organ blow + To the full-voiced quire below + In service high, and anthems clear, + As may with sweetness through mine ear + Dissolve me into ecstasies, + And bring all Heaven before mine eyes." + +Thomas Mace, in his _Music's Monument_ (1676), thus described the effect +of psalm-singing before sermons by the congregation in York Minster on +Sundays, during the siege of 1644: "When that vast concording unity of +the whole congregational chorus came thundering in, even so as it made +the very ground shake under us, oh, the unutterable ravishing soul's +delight! in the which I was so transported and wrapt up in high +contemplations that there was no room left in my whole man, body, soul +and spirit, for anything below divine and heavenly raptures; nor could +there possibly be anything to which that very singing might be truly +compared, except the right apprehension or conceiving of that glorious +and miraculous quire, recorded in the scriptures at the dedication of +the temple." Nor was there any want of men well qualified, and by the +turn of their minds predisposed, to shine in this branch of literature. +Some (like Sandys, Boyd and Barton) devoted themselves altogether to +paraphrases of other scriptures as well as the psalms. Others (like +George Herbert, and Francis and John Quarles) moralized, meditated, +soliloquized and allegorized in verse. Without reckoning these, there +were a few, even before the Restoration, who came very near to the ideal +of hymnody. + + + Wedderburn. + +First in time is the Scottish poet John Wedderburn, who translated +several of Luther's hymns, and in his _Compendious Book of Godly and +Spiritual Songs_ added others of his own (or his brothers') composition. +Some of these poems, published before 1560, are of uncommon excellence, +uniting ease and melody of rhythm, and structural skill, with grace of +expression, and simplicity, warmth and reality of religious feeling. +Those entitled "Give me thy heart," "Go, heart," and "Leave me not," +which will be found in a collection of 1860 called _Sacred Songs of +Scotland_, require little, beyond the change of some archaisms of +language, to adapt them for church or domestic use at the present day. + + + Dickson. + +Next come the two hymns of "The new Jerusalem," by an English Roman +Catholic priest signing himself F. B. P. (supposed to be "Francis Baker, +Presbyter"), and by another Scottish poet, David Dickson, of which the +history is given by Dr Bonar in his edition of Dickson's work. This +(Dickson's), which begins "O mother dear, Jerusalem," and has long been +popular in Scotland, is a variation and amplification by the addition of +a large number of new stanzas of the English original, beginning +"Jerusalem, my happy home," written in Queen Elizabeth's time, and +printed (as appears by a copy in the British Museum) about 1616, when +Dickson was still young. Both have an easy natural flow, and a simple +happy rendering of the beautiful scriptural imagery upon the subject, +with a spirit of primitive devotion uncorrupted by medieval +peculiarities. The English hymn of which some stanzas are now often sung +in churches is the true parent of the several shorter forms,--all of +more than common merit,--which, in modern hymn-books, begin with the +same first line, but afterwards deviate from the original. Kindred to +these is the very fine and faithful translation, by Dickson's +contemporary Drummond of Hawthornden of the ancient "Urbs beata +Hierusalem" ("Jerusalem, that place divine"). Other ancient hymns (two +of Thomas Aquinas, and the "Dies Irae") were also well translated, in +1646, by Richard Crashaw, after he had become a Roman Catholic and had +been deprived by the parliament of his fellowship at Cambridge. + + + Wither. + +Conspicuous among the sacred poets of the first two Stuart reigns in +England was George Wither. His _Hymnes and Songs of the Church_ appeared +in 1622-1623, under a patent of King James I., by which they were +declared "worthy and profitable to be inserted, in convenient manner and +due place, into every English Psalm-book to metre." His _Hallelujah_ +(in which some of the former _Hymnes and Songs_ were repeated) followed +in 1641. Some of the _Hymnes and Songs_ were set to music by Orlando +Gibbons, and those in both books were written to be sung, though there +is no evidence that the author contemplated the use of any of them in +churches. They included hymns for every day in the week (founded, as +those contributed nearly a century afterwards by Charles Coffin to the +Parisian Breviary also were, upon the successive works of the days of +creation); hymns for all the church seasons and festivals, including +saints' days; hymns for various public occasions; and hymns of prayer, +meditation and instruction, for all sorts and conditions of men, under a +great variety of circumstances--being at once a "Christian Year" and a +manual of practical piety. Many of them rise to a very high point of +excellence,--particularly the "general invitation to praise God" ("Come, +O come, in pious lays"), with which _Hallelujah_ opens; the +thanksgivings for peace and for victory, the Coronation Hymn, a +Christmas, an Epiphany, and an Easter Hymn, and one for St Bartholomew's +day (Hymns 1, 74, 75, and 84 in part i., and 26, 29, 36 and 54 in part +ii. of _Hallelujah_). + + + Cosin. + +John Cosin, afterwards bishop of Durham, published in 1627 a volume of +"Private Devotions," for the canonical hours and other occasions. In +this there are seven or eight hymns of considerable merit,--among them a +very good version of the Ambrosian "Jam lucis orto sidere," and the +shorter version of the "Veni Creator," which was introduced after the +Restoration into the consecration and ordination services of the Church +of England. + + + Milton. + +The hymns of Milton (on the Nativity, Passion, Circumcision and "at a +Solemn Music"), written about 1629, in his early manhood, were probably +not intended for singing; but they are odes full of characteristic +beauty and power. + + + Jeremy Taylor. + +During the Commonwealth, in 1654, Jeremy Taylor published at the end of +his _Golden Grove_, twenty-one hymns, described by himself as +"celebrating the mysteries and chief festivals of the year, according to +the manner of the ancient church, fitted to the fancy and devotion of +the younger and pious persons, apt for memory, and to be joined, to +their other prayers." Of these, his accomplished editor, Bishop Heber, +justly says:-- + + "They are in themselves, and on their own account, very interesting + compositions. Their metre, indeed, which is that species of spurious + Pindaric which was fashionable with his contemporaries, is an + obstacle, and must always have been one, to their introduction into + public or private psalmody; and the mixture of that alloy of conceits + and quibbles which was an equally frequent and still greater + defilement of some of the finest poetry of the 17th century will + materially diminish their effect as devotional or descriptive odes. + Yet, with all these faults, they are powerful, affecting, and often + harmonious; there are many passages of which Cowley need not have been + ashamed, and some which remind us, not disadvantageously, of the + corresponding productions of Milton." + +He mentions particularly the advent hymn ("Lord, come away"), part of +the hymn "On heaven," and (as "more regular in metre, and in words more +applicable to public devotion") the "Prayer for Charity" ("Full of +mercy, full of love"). + + + Restoration period. + +The epoch of the Restoration produced in 1664 Samuel Crossman's _Young +Man's Calling_, with a few "Divine Meditations" in verse attached to it; +in 1668 John Austin's _Devotions in the ancient way of offices, with +psalms, hymns and prayers for every day in the week and every holyday in +the year_; and in 1681 Richard Baxter's _Poetical Fragments_. In these +books there are altogether seven or eight hymns, the whole or parts of +which are extremely good: Crossman's "New Jerusalem" ("Sweet place, +sweet place alone"), one of the best of that class, and "My life's a +shade, my days"; Austin's "Hark, my soul, how everything," "Fain would +my thoughts fly up to Thee," "Lord, now the time returns," "Wake all my +hopes, lift up your eyes"; and Baxter's "My whole, though broken heart, +O Lord," and "Ye holy angels bright." Austin's _Offices_ (he was a Roman +Catholic) seem to have attracted much attention. Theophilus Dorrington, +in 1686, published variations of them under the title of _Reformed_ +_Devotions_; George Hickes, the non-juror, wrote one of his numerous +recommendatory prefaces to S. Hopton's edition; and the Wesleys, in +their earliest hymn-book, adopted hymns from them, with little +alteration. These writers were followed by John Mason in 1683, and +Thomas Shepherd in 1692,--the former, a country clergyman, much esteemed +by Baxter and other Nonconformists; the latter himself a Nonconformist, +who finally emigrated to America. Between these two men there was a +close alliance, Shepherd's _Penitential Cries_ being published as an +addition to the _Spiritual Songs_ of Mason. Their hymns came into early +use in several Nonconformist congregations; but, with the exception of +one by Mason ("There is a stream which issues forth"), they are not +suitable for public singing. In those of Mason there is often a very +fine vein of poetry; and later authors have, by extracts or centoes from +different parts of his works (where they were not disfigured by his +general quaintness), constructed several hymns of more than average +excellence. + +Three other eminent names of the 17th century remain to be mentioned, +John Dryden, Bishop Ken and Bishop Simon Patrick; with which may be +associated that of Addison, though he wrote in the 18th century. + + + Dryden, Ken. + + Patrick + + Addison. + +Dryden's translation of "Veni Creator" a cold and laboured performance, +is to be met with in many hymn-books. Abridgments of Ken's morning and +evening hymns are in all. These, with the midnight hymn, which is not +inferior to them, first appeared In 1697, appended to the third edition +of the author's _Manual of Prayers for Winchester Scholars_. Between +these and a large number of other hymns (on the attributes of God, and +for the festivals of the church) published by Bishop Ken after 1703 the +contrast is remarkable. The universal acceptance of the morning and +evening hymns is due to their transparent simplicity, warm but not +overstrained devotion, and extremely popular style. Those afterwards +published have no such qualities. They are mystical, florid, stiff, +didactic and seldom poetical, and deserve the neglect into which they +have fallen. Bishop Patrick's hymns were chiefly translations from the +Latin, most of them from Prudentius. The best is a version of "Alleluia +dulce carmen." Of the five attributed to Addison, not more than three +are adapted to public singing; one ("The spacious firmament on high") is +a very perfect and finished composition, taking rank among the best +hymns in the English language.[3] + +From the preface to Simon Browne's hymns, published in 1720, we learn +that down to the time of Dr Watts the only hymns known to be "in common +use, either in private families or in Christian assemblies," were those +of Barton, Mason and Shepherd, together with "an attempt to turn some of +George Herbert's poems into common metre," and a few sacramental hymns +by authors now forgotten, named Joseph Boyse (1660-1728) and Joseph +Stennett. Of the 1410 authors of original British hymns enumerated in +Daniel Sedgwick's catalogue, published in 1863, 1213 are of later date +than 1707; and, if any correct enumeration could be made of the total +number of hymns of all kinds published in Great Britain before and after +that date, the proportion subsequent to 1707 would be very much larger. + + +The English Independents, as represented by Dr Isaac Watts, have a just +claim to be considered the real founders of modern English hymnody. +Watts was the first to understand the nature of the want, and, by the +publication of his _Hymns_ in 1707-1709, and _Psalms_ (not translations, +but hymns founded on psalms) in 1709, he led the way in providing for +it. His immediate followers were Simon Browne and Philip Doddridge. +Later in the 18th century, Joseph Hart, Thomas Gibbons, Miss Anne +Steele, Samuel Medley, Samuel Stennett, John Ryland, Benjamin Beddome +and Joseph Swain succeeded to them. + + + Watts. + +Among these writers, most of whom produced some hymns of merit, and +several are extremely voluminous, Isaac Watts and Philip Doddridge are +pre-eminent. It has been the fashion with some to disparage Watts, as if +he had never risen above the level of his _Hymns for Little Children_. +No doubt his taste is often faulty, and his style very unequal, but, +looking to the good, and disregarding the large quantity of inferior +matter, it is probable that more hymns which approach to a very high +standard of excellence, and are at the same time suitable for +congregational use, may be found in his works than in those of any other +English writer. Such are "When I survey the wondrous cross," "Jesus +shall reign where'er the sun" (and also another adaptation of the same +72nd Psalm), "Before Jehovah's awful throne" (first line of which, +however, is not his, but Wesley's), "Joy to the world, the Lord is +come," "My soul, repeat His praise," "Why do we mourn departing +friends," "There is a land of pure delight," "Our God, our help in ages +past," "Up to the hills I lift mine eyes," and many more. It is true +that in some of these cases dross is found in the original poems mixed +with gold; but the process of separation, by selection without change, +is not difficult. As long as pure nervous English, unaffected fervour, +strong simplicity and liquid yet manly sweetness are admitted to be +characteristics of a good hymn, works such as these must command +admiration. + + + Doddridge. + +Doddridge is, generally, much more laboured and artificial; but his +place also as a hymn-writer ought to be determined, not by his failures, +but by his successes, of which the number is not inconsiderable. In his +better works he is distinguished by a graceful and pointed, sometimes +even a noble style. His "Hark, the glad sound, the Saviour comes" (which +is, indeed, his masterpiece), is as sweet, vigorous and perfect a +composition as can anywhere be found. Two other hymns, "How gentle God's +commands," and that which, in a form slightly varied, became the "O God +of Bethel, by whose hand," of the Scottish "Paraphrases," well represent +his softer manner. + +Of the other followers in the school of Watts, Miss Anne Steele +(1717-1778) is the most popular and perhaps the best. Her hymn beginning +"Far from these narrow scenes of night" deserves high praise, even by +the side of other good performances on the same subject. + +The influence of Watts was felt in Scotland, and among the first whom it +reached there was Ralph Erskine. This seems to have been after the +publication of Erskine's _Gospel Sonnets_, which appeared in 1732, five +years before he joined his brother Ebenezer in the Secession Church. The +_Gospel Sonnets_ became, as some have said, a "people's classic"; but +there is in them very little which belongs to the category of hymnody. +More than nineteen-twentieths of this very curious book are occupied +with what are, in fact, theological treatises and catechisms, mystical +meditations on Christ as a bridegroom or husband, and spiritual enigmas, +paradoxes, and antithetical conceits, versified, it is true, but of a +quality of which such lines as-- + + "Faith's certain by fiducial arts, + Sense by its evidential facts," + +may be taken as a sample. The grains of poetry scattered through this +large mass of Calvinistic divinity are very few; yet in one short +passage of seven stanzas ("O send me down a draught of love"), the fire +burns with a brightness so remarkable as to justify a strong feeling of +regret that the gift which this writer evidently had in him was not more +often cultivated. Another passage, not so well sustained, but of +considerable beauty (part of the last piece under the title "The +believer's soliloquy"), became afterwards, in the hands of John +Berridge, the foundation of a very striking hymn ("O happy saints, who +walk in light"). + +After his secession, Ralph Erskine published two paraphrases of the +"Song of Solomon," and a number of other "Scripture songs," paraphrased, +in like manner, from the Old and New Testaments. In these the influence +of Watts became very apparent, not only by a change in the writer's +general style, but by the direct appropriation of no small quantity of +matter from Dr Watts's hymns, with variations which were not always +improvements. His paraphrases of I Cor. i. 24; Gal. vi. 14; Heb. vi. +17-19; Rev. v. 11, 12, vii. 10-17, and xii. 7-12 are little else than +Watts transformed. One of these (Rev. vii. 10-17) is interesting as a +variation and improvement, intermediate between the original and the +form which it ultimately assumed as the 66th "Paraphrase" of the Church +of Scotland, of Watts's "What happy men or angels these," and "These +glorious minds, how bright they shine." No one can compare it with its +ultimate product, "How bright these glorious spirits shine," without +perceiving that William Cameron followed Erskine, and only added finish +and grace to his work,--both excelling Watts, in this instance, in +simplicity as well as in conciseness. + + + Scottish paraphrases. + +Of the contributions to the authorized "Paraphrases" (with the +settlement of which committees of the General Assembly of the Church of +Scotland were occupied from 1745, or earlier, till 1781), the most +noteworthy, besides the two already mentioned, were those of John +Morrison and those claimed for Michael Bruce. The obligations of these +"Paraphrases" to English hymnody, already traced in some instances (to +which may be added the adoption from Addison of three out of the five +"hymns" appended to them), are perceptible in the vividness and force +with which these writers, while adhering with a severe simplicity to the +sense of the passages of Scripture which they undertook to render, +fulfilled the conception of a good original hymn. Morrison's "The race +that long in darkness pined" and "Come, let us to the Lord our God," and +Bruce's "Where high the heavenly temple stands" (if this was really +his), are well entitled to that praise. The advocates of Bruce in the +controversy, not yet closed, as to the poems said to have been entrusted +by him to John Logan, and published by Logan in his own name, also claim +for him the credit of having varied the paraphrase "Behold, the mountain +of the Lord," from its original form, as printed by the committee of the +General Assembly in 1745, by some excellent touches. + + + Methodist hymns. + +Attention must now be directed to the hymns produced by the "Methodist" +movement, which began about 1738, and which afterwards became divided, +between those esteemed Arminian, under John Wesley, those who adhered to +the Moravians, when the original alliance between that body and the +founders of Methodism was dissolved, and the Calvinists, of whom +Whitfield was the leader, and Selina, countess of Huntingdon, the +patroness. Each of these sections had its own hymn-writers, some of whom +did, and others did not, secede from the Church of England. The +Wesleyans had Charles Wesley, Robert Seagrave and Thomas Olivers; the +Moravians, John Cennick, with whom, perhaps, may be classed John Byrom, +who imbibed the mystical ideas of some of the German schools; the +Calvinists, Augustus Montague Toplady, John Berridge, William Williams, +Martin Madan, Thomas Haweis, Rowland Hill, John Newton and William +Cowper. + + + Charles Wesley. + +Among all these writers, the palm undoubtedly belongs to Charles Wesley. +In the first volume of hymns published by the two brothers are several +good translations from the German, believed to be by John Wesley, who, +although he translated and adapted, is not supposed to have written any +original hymns; and the influence of German hymnody, particularly of the +works of Paul Gerhardt, Scheffler, Tersteegen and Zinzendorf, may be +traced in a large proportion of Charles Wesley's works. He is more +subjective and meditative than Watts and his school; there is a didactic +turn, even in his most objective pieces, as, for example, in his +Christmas and Easter hymns; most of his works are supplicatory, and his +faults are connected with the same habit of mind. He is apt to repeat +the same thoughts, and to lose force by redundancy--he runs sometimes +even to a tedious length; his hymns are not always symmetrically +constructed, or well balanced and finished off. But he has great truth, +depth and variety of feeling; his diction is manly and always to the +point; never florid, though sometimes passionate and not free from +exaggeration; often vivid and picturesque. Of his spirited style there +are few better examples than "O for a thousand tongues to sing," "Blow +ye the trumpet, blow," "Rejoice, the Lord is King" and "Come, let us +join our friends above"; of his more tender vein, "Happy soul, thy days +are ended"; and of his fervid contemplative style (without going beyond +hymns fit for general use), "O Thou who earnest from above," "Forth in +Thy name, O Lord, I go" and "Eternal beam of light divine." With those +whose taste is for hymns in which warm religious feelings are warmly and +demonstratively expressed, "Jesus, lover of my soul," is as popular as +any of these. + + + Olivers. + +Of the other Wesleyan hymn-writers, Olivers, originally a Welsh +shoemaker and afterwards a preacher, is the most remarkable. He is the +author of only two works, both odes, in a stately metre, and from their +length unfit for congregational singing, but one of them, "The God of +Abraham praise," an ode of singular power and beauty. + + + Cennick, Hammond, Byrom. + +The Moravian Methodists produced few hymns now available for general +use. The best are Cennick's "Children of the heavenly King" and +Hammond's "Awake and sing the song of Moses and the Lamb," the former of +which (abridged), and the latter as varied by Madan, are found in many +hymn-books, and are deservedly esteemed. John Byrom, whose name we have +thought it convenient to connect with these, though he did not belong to +the Moravian community, was the author of a Christmas hymn ("Christians +awake, salute the happy morn") which enjoys great popularity; and also +of a short subjective hymn, very fine both in feeling and in expression, +"My spirit longeth for Thee within my troubled breast." + + + Toplady. + +The contributions of the Calvinistic Methodists to English hymnody are +of greater extent and value. Few writers of hymns had higher gifts than +Toplady, author of "Rock of ages," by some esteemed the finest in the +English language. He was a man of ardent temperament, enthusiastic zeal, +strong convictions and great energy of character. "He had," says one of +his biographers, "the courage of a lion, but his frame was brittle as +glass." Between him and John Wesley there was a violent opposition of +opinion, and much acrimonious controversy; but the same fervour and zeal +which made him an intemperate theologian gave warmth, richness and +spirituality to his hymns. In some of them, particularly those which, +like "Deathless principle, arise," are meditations after the German +manner, and not without direct obligation to German originals, the +setting is somewhat too artificial; but his art is never inconsistent +with a genuine flow of real feeling. Others (e.g. "When languor and +disease invade" and "Your harps, ye trembling saints") fail to sustain +to the end the beauty with which they began, and would have been better +for abridgment. But in all these, and in most of his other works, there +is great force and sweetness, both of thought and language, and an easy +and harmonious versification. + + + Berridge, Williams and R. Hill. + +Berridge, William Williams (1717-1791) and Rowland Hill, all men +remarkable for eccentricity, activity and the devotion of their lives to +the special work of missionary preaching, though not the authors of many +good hymns, composed, or adapted from earlier compositions, some of +great merit. One of Berridge, adapted from Erskine, has been already +mentioned; another, adapted from Watts, is "Jesus, cast a look on me." +Williams, a Welshman, who wrote "Guide me, O Thou great Jehovah," was +especially an apostle of Calvinistic Methodism in his own country, and +his hymns are still much used in the principality. Rowland Hill wrote +the popular hymn beginning "Exalted high at God's right hand." + + + Cowper and Newton. + +If, however, the number as well as the quality of good hymns available +for general use is to be regarded, the authors of the _Olney Hymns_ are +entitled to be placed at the head of all the writers of this Calvinistic +school. The greater number of the _Olney Hymns_ are, no doubt, homely +and didactic; but to the best of them, and they are no inconsiderable +proportion, the tenderness of Cowper and the manliness of John Newton +(1725-1807) give the interest of contrast, as well as that of sustained +reality. If Newton carried to some excess the sound principle laid down +by him, that "perspicuity, simplicity and ease should be chiefly +attended to, and the imagery and colouring of poetry, if admitted at +all, should be indulged very sparingly and with great judgment," if he +is often dry and colloquial, he rises at other times into +"soul-animating strains," such as "Glorious things of thee are spoken, +Zion, city of our God"; and sometimes (as in "Approach, my soul, the +mercy seat") rivals Cowper himself in depth of feeling. Cowper's hymns +in this book are, almost without exception, worthy of his name. Among +them are "Hark, my soul, it is the Lord," "There is a fountain filled +with blood," "Far from the world, O Lord, I flee," "God moves in a +mysterious way" and "Sometimes a light surprises." Some, perhaps, even +of these, and others of equal excellence (such as "O for a closer walk +with God"), speak the language of a special experience, which, in +Cowper's case, was only too real, but which could not, without a degree +of unreality not desirable in exercises of public worship, be applied to +themselves by all ordinary Christians. + + + 19th-century hymns. + + R. Grant. + + Bowdler. + +During the first quarter of the 19th century there were not many +indications of the tendency, which afterwards became manifest, to +enlarge the boundaries of British hymnody. _The Remains of Henry Kirke +White_, published by Southey in 1807, contained a series of hymns, some +of which are still in use; and a few of Bishop Heber's hymns and those +of Sir Robert Grant, which, though offending rather too much against +John Newton's canon, are well known and popular, appeared between 1811 +and 1816, in the _Christian Observer_. In John Bowdler's Remains, +published soon after his death in 1815, there are a few more of the +same, perhaps too scholarlike, character. But the chief hymn-writers of +that period were two clergymen of the Established Church--one in +Ireland, Thomas Kelly, and the other in England, William Hurn--who both +became Nonconformists, and the Moravian poet, James Montgomery +(1771-1854), a native of Scotland. + + + Kelly. + +Kelly was the son of an Irish judge, and in 1804 published a small +volume of ninety-six hymns, which grew in successive editions till, in +the last before his death in 1854, they amounted to 765. There is, as +might be expected, in this great number a large preponderance of the +didactic and commonplace. But not a few very excellent hymns may be +gathered from them. Simple and natural, without the vivacity and +terseness of Watts or the severity of Newton, Kelly has some points in +common with both those writers, and he is less subjective than most of +the "Methodist" school. His hymns beginning "Lo! He comes, let all adore +Him," and "Through the day Thy love hath spared us," have a rich, +melodious movement; and another, "We sing the praise of Him who died," +is distinguished by a calm, subdued power, rising gradually from a +rather low to a very high key. + + + Hurn. + +Hurn published in 1813 a volume of 370 hymns, which were afterwards +increased to 420. There is little in them which deserves to be saved +from oblivion; but one at least, "There is a river deep and broad," may +bear comparison with the best of those which have been produced upon the +same, and it is rather a favourite, theme. + + + Montgomery. + +The _Psalms and Hymns_ of James Montgomery were published in 1822 and +1825, though written earlier. More cultivated and artistic than Kelly, +he is less simple and natural. His "Hail to the Lord's Anointed," "Songs +of praise the angels sang" and "Mercy alone can meet my case" are among +his most successful efforts. + + + Collections of hymns. + +During this period, the collections of miscellaneous hymns for +congregational use, of which the example was set by the Wesleys, +Whitfield, Toplady and Lady Huntingdon, had greatly multiplied; and with +them the practice (for which, indeed, too many precedents existed in the +history of Latin and German hymnody) of every collector altering the +compositions of other men without scruple, to suit his own doctrine or +taste; with the effect, too generally, of patching and disfiguring, +spoiling and emasculating the works so altered, substituting neutral +tints for natural colouring, and a dead for a living sense. In the +Church of England the use of these collections had become frequent in +churches and chapels, principally in cities and towns, where the +sentiments of the clergy approximated to those of the Nonconformists. In +rural parishes, when the clergy were not of the "Evangelical" school, +they were generally held in disfavour; for which, even if doctrinal +prepossessions had not entered into the question, the great want of +taste and judgment often manifested in their compilation, and perhaps +also the prevailing mediocrity of the bulk of the original compositions +from which most of them were derived, would be enough to account. In +addition to this, the idea that no hymns ought to be used in any +services of the Church of England, except prose anthems after the third +collect, without express royal or ecclesiastical authority, continued +down to that time largely to prevail among high churchmen. + + + Heber, Milman, Keble. + + Mant. + + Newman. + +Two publications, which appeared almost simultaneously in 1827--Bishop +Heber's _Hymns_, with a few added by Dean Milman, and John Keble's +_Christian Year_ (not a hymn-book, but one from which several admirable +hymns have been taken, and the well-spring of many streams of thought +and feeling by which good hymns have since been produced)--introduced a +new epoch, breaking down the barrier as to hymnody which had till then +existed between the different theological schools of the Church of +England. In this movement Richard Mant, bishop of Down, was also one of +the first to co-operate. It soon received a great additional impulse +from the increased attention which, about the same time, began to be +paid to ancient hymnody, and from the publication in 1833 of Bunsen's +_Gesangbuch_. Among its earliest fruits was the _Lyra apostolica_, +containing hymns, sonnets and other devotional poems, most of them +originally contributed by some of the leading authors of the _Tracts for +the Times_ to the _British Magazine_; the finest of which is the +pathetic "Lead, kindly Light, amid th' encircling gloom," by Cardinal +Newman--well known, and universally admired. From that time hymns and +hymn-writers rapidly multiplied in the Church of England, and in +Scotland also. Nearly 600 authors whose publications were later than +1827 are enumerated in Sedgwick's catalogue of 1863, and about half a +million hymns are now in existence. Works, critical and historical, upon +the subject of hymns, have also multiplied; and collections for church +use have become innumerable--several of the various religious +denominations, and many of the leading ecclesiastical and religious +societies, having issued hymn-books of their own, in addition to those +compiled for particular dioceses, churches and chapels, and to books +(like _Hymns Ancient and Modern_, published 1861, supplemented 1889, +revised edition, 1905) which have become popular without any sanction +from authority. To mention all the authors of good hymns since the +commencement of this new epoch would be impossible; but probably no +names could be chosen more fairly representative of its characteristic +merits, and perhaps also of some of its defects, than those of Josiah +Conder and James Edmeston among English Nonconformists; Henry Francis +Lyte and Charlotte Elliott among evangelicals in the Church of England; +John Mason Neale and Christopher Wordsworth, bishop of Lincoln, among +English churchmen of the higher school; Arthur Penrhyn Stanley, Edward +H. Plumptre, Frances Ridley Havergal; and in Scotland, Dr Horatius +Bonar, Dr Norman Macleod and Dr George Matheson. American hymn-writers +belong to the same schools, and have been affected by the same +influences. Some of them have enjoyed a just reputation on both sides +of the Atlantic. Among those best known are John Greenleaf Whittier, +Bishop Doane, Dr W. A. Muhlenberg and Thomas Hastings; and it is +difficult to praise too highly such works as the Christmas hymn, "It +came upon the midnight clear," by Edmund H. Sears; the Ascension hymn, +"Thou, who didst stoop below," by Mrs S. E. Miles; two by Dr Ray Palmer, +"My faith looks up to Thee, Thou Lamb of Calvary," and "Jesus, Thou joy +of loving hearts," the latter of which is the best among several good +English versions of "Jesu, dulcedo, cordium"; and "Lord of all being, +throned afar," by Oliver Wendell Holmes. + +The more modern "Moody and Sankey" hymns (see Moody, D. L.) popularized +a new Evangelical type, and the Salvation Army has carried this still +farther. + +7. _Conclusion._--The object aimed at in this article has been to trace +the general history of the principal schools of ancient and modern +hymnody, and especially the history of its use in the Christian church. +For this purpose it has not been thought necessary to give any account +of the hymns of Racine, Madame Guyon and others, who can hardly be +classed with any school, nor of the works of Caesar Malan of Geneva +(1787-1864) and other quite modern hymn-writers of the Reformed churches +in Switzerland and France. + +On a general view of the whole subject, hymnody is seen to have been a +not inconsiderable factor in religious worship. It has been sometimes +employed to disseminate and popularize particular views, but its spirit +and influence has been, on the whole, catholic. It has embodied the +faith, trust and hope, and no small part of the inward experience, of +generation after generation of men, in many different countries and +climates, of many different nations, and in many varieties of +circumstances and condition. Coloured, indeed, by these differences, and +also by the various modes in which the same truths have been apprehended +by different minds and sometimes reflecting partial and imperfect +conceptions of them, and errors with which they have been associated in +particular churches, times and places, its testimony is, nevertheless, +generally the same. It has upon it a stamp of genuineness which cannot +be mistaken. It bears witness to the force of a central attraction more +powerful than all causes of difference, which binds together times +ancient and modern, nations of various race and language, churchmen and +nonconformists, churches reformed and unreformed; to a true fundamental +unity among good Christians; and to a substantial identity in their +moral and spiritual experience. (S.) + + The regular practice of hymnody in English musical history dates from + the beginning of the 16th century. Luther's verses were adapted + sometimes to ancient church melodies, sometimes to tunes of secular + songs, and sometimes had music composed for them by himself and + others. Many rhyming Latin hymns are of earlier date whose tunes are + identified with them, some of which tunes, with the subject of their + Latin text, are among the Reformer's appropriations; but it was he who + put the words of praise and prayer into the popular mouth, associated + with rhythmical music which aided to imprint the words upon the memory + and to enforce their enunciation. In conjunction with his friend + Johann Walther, Luther issued a collection of poems for choral singing + in 1524, which was followed by many others in North Germany. The + English versions of the Psalms by Sternhold and Hopkins and their + predecessors, and the French version by Clement Marot and Theodore + Beza, were written with the same purpose of fitting sacred minstrelsy + to the voice of the multitude. Goudimel in 1566 and Claudin le Jeune + in 1607 printed harmonizations of tunes that had then become standard + for the Psalms, and in England several such publications appeared, + culminating in Thomas Ravenscroft's famous collection, _The Whole Book + of Psalms_ (1621); in all of these the arrangements of the tunes were + by various masters. The English practice of hymn-singing was much + strengthened on the return of the exiled reformers from Frankfort and + Geneva, when it became so general that, according to Bishop Jewell, + thousands of the populace who assembled at Paul's Cross to hear the + preaching would join in the singing of psalms before and after the + sermon. + + The placing of the choral song of the church within the lips of the + people had great religious and moral influence; it has had also its + great effect upon art, shown in the productions of the North German + musicians ever since the first days of the Reformation, which abound + in exercises of scholarship and imagination wrought upon the tunes of + established acceptance. Some of these are accompaniments to the tunes + with interludes between the several strains, and some are + compositions for the organ or for orchestral instruments that consist + of such elaboration of the themes as is displayed in accompaniments to + voices, but of far more complicated and extended character. A special + art-form that was developed to a very high degree, but has passed into + comparative disuse, was the structure of all varieties of counterpoint + extemporaneously upon the known hymn-tunes (chorals), and several + masters acquired great fame by success in its practice, of whom J. A. + Reinken (1623-1722), Johann Pachelbel (1653-1706), Georg Boehm and the + great J. S. Bach are specially memorable. The hymnody of North Germany + has for artistic treatment a strong advantage which is unpossessed by + that of England, in that for the most part the same verses are + associated with the same tunes, so that, whenever the text or the + music is heard, either prompts recollection of the other, whereas in + England tunes were always and are now often composed to metres and not + to poems; any tune in a given metre is available for every poem in the + same, and hence there are various tunes to one poem, and various poems + to one tune.[4] In England a tune is named generally after some + place--as "York," "Windsor," "Dundee,"--or by some other unsignifying + word; in North Germany a tune is mostly named by the initial words of + the verses to which it is allied, and consequently, whenever it is + heard, whether with words or without, it necessarily suggests to the + hearer the whole subject of that hymn of which it is the musical + moiety undivorceable from the literary half. Manifold as they are, + knowledge of the choral tunes is included in the earliest schooling of + every Lutheran and every Calvinist in Germany, which thus enables all + to take part in performance of the tunes, and hence expressly the + definition of "choral." Compositions grounded on the standard tune are + then not merely school exercises, but works of art which link the + sympathies of the writer and the listener, and aim at expressing the + feeling prompted by the hymn under treatment. + + BIBLIOGRAPHY: I. Ancient.--George Cassander, _Hymni ecclesiastici_ + (Cologne, 1556); Georgius Fabricius, _Poëtarum veterum + ecclesiasticorum_ (Frankfort, 1578); Cardinal J. M. Thomasius, + _Hymnarium in Opera_, ii. 351 seq. (Rome, 1747); A. J. Rambach, + _Anthologie christlicher Gesänge_ (Altona, 1817); H. A. Daniel, + _Thesaurus hymnologicus_ (Leipzig, 5 vols., 1841-1856); J. M. Neale, + _Hymni ecclesiae et sequentiae_ (London, 1851-1852); and _Hymns of the + Eastern Church_ (1863). The dissertation prefixed to the second volume + of the _Acta sanctorum_ of the Bollandists; Cardinal J. B. Pitra, + _Hymnographie de l'église grecque_ (1867), _Analecta sacra_ (1876); W. + Christ and M. Paranikas, _Anthologia Graeca carminum Christianorum_ + (Leipzig, 1871); F. A. March, _Latin Hymns with English Notes_ (New + York, 1875); R. C. Trench, _Sacred Latin Poetry_ (London, 4th ed., + 1874); J. Pauly, _Hymni breviarii Romani_ (Aix-la-Chapelle, 3 vols., + 1868-1870); Pimont, _Les Hymnes du bréviaire romain_ (vols. 1-3, + 1874-1884, unfinished); A. W. F. Fischer, _Kirchenlieder-Lexicon_ + (Gotha, 1878-1879); J. Kayser, _Beiträge zur Geschichte der ältesten + Kirchenhymnen_ (1881); M. Manitius, _Geschichte der christlichen + lateinischen Poesie_ (Stuttgart, 1891); John Julian, _Dictionary of + Hymnology_ (1892, new ed. 1907). For criticisms of metre, see also + Huemer, _Untersuchungen über die ältesten christlichen Rhythmen_ + (1879); E. Bouvy, _Poètes et mélodes_ (Nîmes, 1886); C. Krumbacher, + _Geschichte der byzantinischen Literatur_ (Munich, 1897, p. 700 seq.); + J. M. Neale, Latin dissertation prefixed to Daniel's _Thesaurus_, vol. + 5; and D. J. Donahoe, _Early Christian Hymns_ (London, 1909). + + II. Medieval.--Walafrid Strabo's treatise, ch. 25, _De hymnis, &c._; + Radulph of Tongres, _De psaltario observando_ (14th century); + Clichtavaens, _Elucidatorium ecclesiasticum_ (Paris, 1556); Faustinus + Arevalus, _Hymnodia Hispanica_ (Rome, 1786); E. du Méril, _Poésies + populaires latines antérieures au XIII^e siècle_ (Paris, 1843); J. + Stevenson, _Latin Hymns of the Anglo-Saxon Church_ (Surtees Society, + Durham, 1851); Norman, _Hymnarium Sarisburiense_ (London, 1851); J. D. + Chambers, _Psalter, &c._, according to the Sarum use (1852); F. J. + Mone, _Lateinische Hymnen des Mittelalters_ (Freiburg, 3 vols., + 1853-1855); Ph. Wackernagel, _Das deutsche Kirchenlied von der + ältesten Zeit bis zum Anfang des 17. Jahrhunderts_, vol. i. (Leipzig, + 1864); E. Dümmler, _Poëtae latini aevi Carolini_ (1881-1890); the + _Hymnologische Beiträge: Quellen und Forschungen zur Geschichte der + lateinischen Hymnendichtung_, edited by C. Blume and G. M. Dreves + (Leipzig, 1897); G. C. F. Mohnike, _Hymnologische Forschungen_; + Klemming, _Hymni et sequentiae in regno Sueciae_ (Stockholm, 4 vols., + 1885-1887); _Das katholische deutsche Kirchenlied_ (vol. i. by K. + Severin Meister, 1862, vol. ii. by W. Baumker, 1883); the "Hymnodia + Hiberica," _Spanische Hymnen des Mittelalters_, vol. xvi. (1894); the + "Hymnodia Gotica," _Mozarabische Hymnen des altspanischen Ritus_, vol. + xxvii. (1897); J. Dankó, _Vetus hymnarium ecclesiasticae Hungariae_ + (Budapest, 1893); J. H. Bernard and R. Atkinson, _The Irish Liber + Hymnorum_ (2 vols., London, 1898); C. A. J. Chevalier, _Poésie + liturgique du moyen âge_ (Paris, 1893). + + III. Modern.--J. C. Jacobi, _Psalmodia Germanica_ (1722-1725 and 1732, + with supplement added by J. Haberkorn, 1765); F. A. Cunz, _Geschichte + des deutschen Kirchenliedes_ (Leipzig, 1855); Baron von Bunsen, + _Versuch eines allgemeinen Gesang- und Gebetbuches_ (1833) and + _Allgemeines evangelisches Gesang- und Gebetbuch_ (1846); Catherine + Winkworth, _Christian Singers of Germany_ (1869) and _Lyra Germanica_ + (1855); Catherine H. Dunn, _Hymns from the German_ (1857); Frances E. + Cox, _Sacred Hymns from the German_ (London, 1841); Massie, _Lyra + domestica_ (1860); _Appendix on Scottish Psalmody_ in D. Laing's + edition of Baillie's _Letters and Journals_ (1841-1842); J. and C. + Wesley, _Collection of Psalms and Hymns_ (1741); Josiah Miller, _Our + Hymns, their Authors and Origin_ (1866); John Gadsby, _Memoirs of the + Principal Hymn-writers_ (3rd ed., 1861); L. C. Biggs, Annotations to + _Hymns Ancient and Modern_ (1867); Daniel Sedgwick, _Comprehensive + Index of Names of Original Authors of Hymns_ (2nd ed., 1863); R. E. + Prothero, _The Psalms in Human Life_ (1907); C. J. Brandt and L. + Helweg, _Den danske Psalmedigtning_ (Copenhagen, 1846-1847); J. N. + Skaar, _Norsk Salmehistorie_ (Bergen, 1879-1880); H. Schück, _Svensk + Literaturhistoria_ (Stockholm, 1890); Rudolf Wolkan, _Geschichte der + deutschen Literatur in Böhmen_, 246-256, and _Das deutsche Kirchenlied + der böhm. Brüder_ (Prague, 1891); Zahn, _Die geistlichen Lieder der + Brüder in Böhmen, Mähren u. Polen_ (Nuremberg, 1875); and J. Müller, + "Bohemian Brethren's Hymnody," in J. Julian's _Dictionary of + Hymnology_. + + For account of hymn-tunes, &c., see W. Cowan and James Love, _Music of + the Church Hymnody and the Psalter in Metre_ (London, 1901); and + Dickinson, _Music in the History of the Western Church_ (New York, + 1902); S. Kümmerle, _Encyklopädie der evangelischen Kirchenmusik_ (4 + vols., 1888-1895); Chr. Palmer, _Evangelische Hymnologie_ (Stuttgart, + 1865); and P. Urto Kornmüller, _Lexikon der kirchlichen Tonkunst_ + (1891). + + +FOOTNOTES: + + [1] The history of the "hymn" naturally begins with Greece, but it + may be found in some form much earlier; Assyria and Egypt have left + specimens, while India has the Vedic hymns, and Confucius collected + "praise songs" in China. + + [2] See GREEK LITERATURE. + + [3] The authorship of this and of one other, "When all thy mercies, O + my God," has been made a subject of controversy,--being claimed for + Andrew Marvell (who died in 1678), in the preface to Captain E. + Thompson's edition (1776) of Marvell's _Works_. But this claim does + not appear to be substantiated. The editor did not give his readers + the means of judging as to the real age, character or value of a + manuscript to which he referred; he did not say that these portions + of it were in Marvell's handwriting; he did not even himself include + them among Marvell's poems, as published in the body of his edition; + and he advanced a like claim on like grounds to two other poems, in + very different styles, which had been published as their own by + Tickell and Mallet. It is certain that all the five hymns were first + made public in 1712, in papers contributed by Addison to the + _Spectator_ (Nos. 441, 453, 465, 489, 513), in which they were + introduced in a way which might have been expected if they were by + the hand which wrote those papers, but which would have been + improbable, and unworthy of Addison, if they were unpublished works + of a writer of so much genius, and such note in his day, as Marvell. + They are all printed as Addison's in Dr Johnson's _British Poets_. + + [4] The old tune for the 100th Psalm and Croft's tune for the 104th + are almost the only exceptions, unless "God save the King" may be + classed under "hymnody." In Scotland also the tune for the 124th + Psalm is associated with its proper text. + + + + +HYPAETHROS (Gr. [Greek: hypaithros], beneath the sky, in the open air, +[Greek: hypo], beneath, and [Greek: aithêr], air), the Greek term quoted +by Vitruvius (iii. 2) for the opening in the middle of the roof of +decastyle temples, of which "there was no example in Rome, but one in +Athens in the temple of Jupiter Olympius, which is octastyle." But at +the time he wrote (c. 25 B.C.) the cella of this temple was unroofed, +because the columns which had been provided to carry, at all events, +part of the ceiling and roof had been taken away by Sulla in 80 B.C. The +decastyle temple of Apollo Didymaeus near Miletus was, according to +Strabo (c. 50 B.C.), unroofed, on account of the vastness of its cella, +in which precious groves of laurel bushes were planted. Apart from these +two examples, the references in various writers to an opening of some +kind in the roofs of temples dedicated to particular deities, and the +statement of Vitruvius, which was doubtless based on the writings of +Greek authors, that in decastyle or large temples the centre was open to +the sky and without a roof (_medium autem sub divo est sine tecto_), +render the existence of the hypaethros probable in some cases; and +therefore C. R. Cockerell's discovery in the temple at Aegina of two +fragments of a coping-stone, in which there were sinkings on one side to +receive the tiles and covering tiles, has been of great importance in +the discussion of this subject. In the conjectural restoration of the +opaion or opening in the roof shown in Cockerell's drawing, it has been +made needlessly large, having an area of about one quarter of the +superficial area of the cella between the columns, and since in the +Pantheon at Rome the relative proportions of the central opening in the +dome and the area of the Rotunda are 1: 22, and the light there is +ample, in the clearer atmosphere of Greece it might have been less. The +larger the opening the more conspicuous would be the notch in the roof +which is so greatly objected to; in this respect T. J. Hittorff would +seem to be nearer the truth when, in his conjectural restoration of +Temple R. at Selinus, he shows an opaion about half the relative size +shown in Cockerell's of that at Aegina, the coping on the side elevation +being much less noticeable. The problem was apparently solved in another +way at Bassae, where, in the excavations of the temple of Apollo by +Cockerell and Baron Haller von Hallerstein, three marble tiles were +found with pierced openings in them about 18 in. by 10 in.; five of +these pierced tiles on either side would have amply lighted the interior +of the cella, and the amount of rain passing through (a serious element +to be considered in a country where torrential rains occasionally fall) +would not be very great or more than could be retained to dry up in the +cella sunk pavement. In favour of both these methods of lighting the +interior of the cella, the sarcophagus tomb at Cyrene, about 20 ft. +long, carved in imitation of a temple, has been adduced, because, on the +top of the roof and in its centre, there is a raised coping, and a +similar feature is found on a tomb found near Delos; an example from +Crete now in the British Museum shows a pierced tile on each side of +the roof, and a large number of pierced tiles have been found in +Pompeii, some of them surrounded with a rim identical with that of the +marble tiles at Bassae. On the other hand, there are many authorities, +among them Dr W. Dörpfeld, who have adhered to their original opinion +that it was only through the open doorway that light was ever admitted +into the cella, and with the clear atmosphere of Greece and the +reflections from the marble pavement such lighting would be quite +sufficient. There remains still another source of light to be +considered, that passing through the Parian marble tiles of the roof; +the superior translucency of Parian to any other marble may have +suggested its employment for the roofs of temples, and if, in the framed +ceilings carried over the cella, openings were left, some light from the +Parian tile roof might have been obtained. It is possibly to this that +Plutarch refers when describing the ceiling and roof of the temple of +Demeter at Eleusis, where the columns in the interior of the temple +carried a ceiling, probably constructed of timbers crossing one another +at right angles, and one or more of the spaces was left open, which +Xenocles surmounted by a roof formed of tiles. + + James Fergusson put forward many years ago a conjectural restoration + in which he adopted a clerestory above the superimposed columns inside + the cella; in order to provide the light for these windows he + indicated two trenches in the roof, one on each side, and pointed out + that the great Hall of Columns at Karnak was lighted in this way with + clerestory windows; but in the first place the light in the latter was + obtained over the flat roofs covering lower portions of the hall, and + in the second place, as it rarely rains in Thebes, there could be no + difficulty about the drainage, while in Greece, with the torrential + rains and snow, these trenches would be deluged with water, and with + all the appliances of the present day it would be impossible to keep + these clerestory windows watertight. There is, however, still another + objection to Fergusson's theory; the water collecting in these + trenches on the roof would have to be discharged, for which + Fergusson's suggestions are quite inadequate, and the gargoyles shown + in the cella wall would make the peristyle insupportable just at the + time when it was required for shelter. No drainage otherwise of any + kind has ever been found in any Greek temple, which is fatal to + Fergusson's view. Nor is it in accordance with the definition "open to + the sky." English cathedrals and churches are all lighted by + clerestory windows, but no one has described them as open to the sky, + and although Vitruvius's statements are sometimes confusing, his + description is far too clear to leave any misunderstanding as to the + lighting of temples (where it was necessary on account of great + length) through an opening in the roof. + + There is one other theory which has been put forward, but which can + only apply to non-peristylar temples,--that light and air was admitted + through the metopes, the apertures between the beams crossing the + cella,--and it has been assumed that because Orestes was advised in + one of the Greek plays to climb up and look through the metopes of the + temple, these were left open; but if Orestes could look in, so could + the birds, and the statue of the god would be defiled. The metopes + were probably filled in with shutters of some kind which Orestes knew + how to open. (R. P. S.) + + + + +HYPALLAGE (Gr. [Greek: hypallagê], interchange or exchange), a +rhetorical figure, in which the proper relation between two words +according to the rules of syntax are inverted. The stock instance is +that in Virgil, _Aen._ iii. 61, where _dare classibus austros_, to give +winds to the fleet, is put for _dare classes austris_, to give the fleet +to the winds. The term is also loosely applied to figures of speech +properly known as "metonymy" and, generally, to any striking turn of +expression. + + + + +HYPATIA ([Greek: Hypatia]) (c. A.D. 370-415) mathematician and +philosopher, born in Alexandria, was the daughter of Theon, also a +mathematician and philosopher, author of scholia on Euclid and a +commentary on the _Almagest_, in which it is suggested that he was +assisted by Hypatia (on the 3rd book). After lecturing in her native +city, Hypatia ultimately became the recognized head of the Neoplatonic +school there (c. 400). Her great eloquence and rare modesty and beauty, +combined with her remarkable intellectual gifts, attracted to her +class-room a large number of pupils. Among these was Synesius, +afterwards (c. 410) bishop of Ptolemaïs, several of whose letters to +her, full of chivalrous admiration and reverence, are still extant. +Suidas, misled by an incomplete excerpt in Photius from the life of +Isidorus (the Neoplatonist) by Damascius, states that Hypatia was the +wife of Isidorus; but this is chronologically impossible, since Isidorus +could not have been born before 434 (see Hoche in _Philologus_). Shortly +after the accession of Cyril to the patriarchate of Alexandria in 412, +owing to her intimacy with Orestes, the pagan prefect of the city, +Hypatia was barbarously murdered by the Nitrian monks and the fanatical +Christian mob (March 415). Socrates has related how she was torn from +her chariot, dragged to the Caesareum (then a Christian church), +stripped naked, done to death with oyster-shells ([Greek: ostrakois +aneilon,] perhaps "cut her throat") and finally burnt piecemeal. Most +prominent among the actual perpetrators of the crime was one Peter, a +reader; but there seems little reason to doubt Cyril's complicity (see +CYRIL OF ALEXANDRIA). + +Hypatia, according to Suidas, was the author of commentaries on the +_Arithmetica_ of Diophantus of Alexandria, on the Conics of Apollonius +of Perga and on the astronomical canon (of Ptolemy). These works are +lost; but their titles, combined with expressions in the letters of +Synesius, who consulted her about the construction of an astrolabe and a +hydroscope, indicate that she devoted herself specially to astronomy and +mathematics. Little is known of her philosophical opinions, but she +appears to have embraced the intellectual rather than the mystical side +of Neoplatonism, and to have been a follower of Plotinus rather than of +Porphyry and Iamblichus. Zeller, however, in his _Outlines of Greek +Philosophy_ (1886, Eng. trans. p. 347), states that "she appears to have +taught the Neoplatonic doctrine in the form in which Iamblichus had +stated it." A Latin letter to Cyril on behalf of Nestorius, printed in +the _Collectio nova conciliorum_, i. (1623), by Stephanus Baluzius +(Étienne Baluze, q.v.), and sometimes attributed to her, is undoubtedly +spurious. The story of Hypatia appears in a considerably disguised yet +still recognizable form in the legend of St Catherine as recorded in the +Roman _Breviary_ (November 25), and still more fully in the +_Martyrologies_ (see A. B. Jameson, _Sacred and Legendary Art_ (1867) +ii. 467.) + + The chief source for the little we know about Hypatia is the account + given by Socrates (_Hist. ecclesiastica_, vii. 15). She is the subject + of an epigram by Palladas in the Greek Anthology (ix. 400). See + Fabricius, _Bibliotheca Graeca_ (ed. Harles), ix. 187; John Toland, + _Tetradymus_ (1720); R. Hoche in _Philologus_ (1860), xv. 435; + monographs by Stephan Wolf (Czernowitz, 1879), H. Ligier (Dijon, 1880) + and W. A. Meyer (Heidelberg, 1885), who devotes attention to the + relation of Hypatia to the chief representatives of Neoplatonism; J. + B. Bury, _Hist. of the Later Roman Empire_ (1889), i. 208,317; A. + Güldenpenning, _Geschichte des oströmischen Reiches unter Arcadius und + Theodosius II._ (Halle, 1885), p. 230; Wetzer and Welte, + _Kirchenlexikon_, vi. (1889), from a Catholic standpoint. The story of + Hypatia also forms the basis of the well-known historical romance by + Charles Kingsley (1853). + + + + +HYPERBATON (Gr. [Greek: huperbaton], a stepping over), the name of a +figure of speech, consisting of a transposition of words from their +natural order, such as the placing of the object before instead of after +the verb. It is a common method of securing emphasis. + + + + +HYPERBOLA, a conic section, consisting of two open branches, each +extending to infinity. It may be defined in several ways. The _in +solido_ definition as the section of a cone by a plane at a less +inclination to the axis than the generator brings out the existence of +the two infinite branches if we imagine the cone to be double and to +extend to infinity. The _in plano_ definition, i.e. as the conic having +an eccentricity greater than unity, is a convenient starting-point for +the Euclidian investigation. In projective geometry it may be defined as +the conic which intersects the line at infinity in two real points, or +to which it is possible to draw two real tangents from the centre. +Analytically, it is defined by an equation of the second degree, of +which the highest terms have real roots (see CONIC SECTION). + + While resembling the parabola in extending to infinity, the curve has + closest affinities to the ellipse. Thus it has a real centre, two + foci, two directrices and two vertices; the transverse axis, joining + the vertices, corresponds to the major axis of the ellipse, and the + line through the centre and perpendicular to this axis is called the + conjugate axis, and corresponds to the minor axis of the ellipse; + about these axes the curve is symmetrical. The curve does not appear + to intersect the conjugate axis, but the introduction of imaginaries + permits us to regard it as cutting this axis in two unreal points. + Calling the foci S, S´, the real vertices A, A´, the extremities of + the conjugate axis B, B' and the centre C, the positions of B, B´ are + given by AB = AB´ = CS. If a rectangle be constructed about AA´ and + BB´, the diagonals of this figure are the "asymptotes" of the curve; + they are the tangents from the centre, and hence touch the curve at + infinity. These two lines may be pictured in the _in solido_ + definition as the section of a cone by a plane through its vertex and + parallel to the plane generating the hyperbola. If the asymptotes be + perpendicular, or, in other words, the principal axes be equal, the + curve is called the rectangular hyperbola. The hyperbola which has for + its transverse and conjugate axes the transverse and conjugate axes of + another hyperbola is said to be the conjugate hyperbola. + + Some properties of the curve will be briefly stated: If PN be the + ordinate of the point P on the curve, AA' the vertices, X the meet of + the directrix and axis and C the centre, then PN²: AN·NA´: : SX²: + AX·A´X, i.e. PN² is to AN·NA´ in a constant ratio. The circle on AA' + as diameter is called the auxiliarly circle; obviously AN·NA' equals + the square of the tangent to this circle from N, and hence the ratio + of PN to the tangent to the auxiliarly circle from N equals the ratio + of the conjugate axis to the transverse. We may observe that the + asymptotes intersect this circle in the same points as the + directrices. An important property is: the difference of the focal + distances of any point on the curve equals the transverse axis. The + tangent at any point bisects the angle between the focal distances of + the point, and the normal is equally inclined to the focal distances. + Also the auxiliarly circle is the locus of the feet of the + perpendiculars from the foci on any tangent. Two tangents from any + point are equally inclined to the focal distance of the point. If the + tangent at P meet the conjugate axis in t, and the transverse in N, + then Ct. PN = BC²; similarly if g and G be the corresponding + intersections of the normal, PG : Pg : : BC² : AC². A diameter is a + line through the centre and terminated by the curve: it bisects all + chords parallel to the tangents at its extremities; the diameter + parallel to these chords is its conjugate diameter. Any diameter is a + mean proportional between the transverse axis and the focal chord + parallel to the diameter. Any line cuts off equal distances between + the curve and the asymptotes. If the tangent at P meets the asymptotes + in R, R', then CR·CR´ = CS². The geometry of the rectangular hyperbola + is simplified by the fact that its principal axes are equal. + + Analytically the hyperbola is given by ax² + 2hxy + by² + 2gx + 2fy + + c = 0 wherein ab > h². Referred to the centre this becomes Ax² + 2Hxy + + By² + C = 0; and if the axes of coordinates be the principal axes of + the curve, the equation is further simplified to Ax² - By² = C, or if + the semi-transverse axis be a, and the semi-conjugate b, x²/a² - y²/b² + = 1. This is the most commonly used form. In the rectangular hyperbola + a = b; hence its equation is x² - y² = 0. The equations to the + asymptotes are x/a = ±y/b and x = ±y respectively. Referred to the + asymptotes as axes the general equation becomes xy = k²; obviously the + axes are oblique in the general hyperbola and rectangular in the + rectangular hyperbola. The values of the constant k² are ½(a² + b²) + and ½a² respectively. (See GEOMETRY: _Analytical_; _Projective_.) + + + + +HYPERBOLE (from Gr. [Greek: hyperballein], to throw beyond), a figure of +rhetoric whereby the speaker expresses more than the truth, in order to +produce a vivid impression; hence, an exaggeration. + + + + +HYPERBOREANS ([Greek: Hyperboreoi, Hyperboreioi]), a mythical people +intimately connected with the worship of Apollo. Their name does not +occur in the _Iliad_ or the _Odyssey_, but Herodotus (iv. 32) states +that they were mentioned in Hesiod and in the _Epigoni_, an epic of the +Theban cycle. According to Herodotus, two maidens, Opis and Arge, and +later two others, Hyperoche and Laodice, escorted by five men, called by +the Delians Perphereës, were sent by the Hyperboreans with certain +offerings to Delos. Finding that their messengers did not return, the +Hyperboreans adopted the plan of wrapping the offerings in wheat-straw +and requested their neighbours to hand them on to the next nation, and +so on, till they finally reached Delos. The theory of H. L. Ahrens, that +Hyperboreans and Perphereës are identical, is now widely accepted. In +some of the dialects of northern Greece (especially Macedonia and +Delphi) [phi] had a tendency to become [beta]. The original form of +[Greek: Perpherees] was [Greek: hyperpheretai] or [Greek: hyperphoroi] +("those who carry over"), which becoming [Greek: hyperboroi] gave rise +to the popular derivation from [Greek: boreas] ("dwellers beyond the +north wind"). The Hyperboreans were thus the bearers of the sacrificial +gifts to Apollo over land and sea, irrespective of their home, the name +being given to Delphians, Thessalians, Athenians and Delians. It is +objected by O. Schröder that the form [Greek: Perpherees] requires a +passive meaning, "those who are carried round the altar," perhaps +dancers like the whirling dervishes; distinguishing them from the +Hyperboreans, he explains the latter as those who live "above the +mountains," that is, in heaven. Under the influence of the derivation +from [Greek: boreas], the home of the Hyperboreans was placed in a +region beyond the north wind, a paradise like the Elysian plains, +inaccessible by land or sea, whither Apollo could remove those mortals +who had lived a life of piety. It was a land of perpetual sunshine and +great fertility; its inhabitants were free from disease and war. The +duration of their life was 1000 years, but if any desired to shorten it, +he decked himself with garlands and threw himself from a rock into the +sea. The close connexion of the Hyperboreans with the cult of Apollo may +be seen by comparing the Hyperborean myths, the characters of which by +their names mostly recall Apollo or Artemis (Agyieus, Opis, Hecaergos, +Loxo), with the ceremonial of the Apolline worship. No meat was eaten at +the Pyanepsia; the Hyperboreans were vegetarians. At the festival of +Apollo at Leucas a victim flung himself from a rock into the sea, like +the Hyperborean who was tired of life. According to an Athenian decree +(380 B.C.) asses were sacrificed to Apollo at Delphi, and Pindar +(_Pythia_, x. 33) speaks of "hecatombs of asses" being offered to him by +the Hyperboreans. As the latter conveyed sacrificial gifts to Delos +hidden in wheat-straw, so at the Thargelia a sheaf of corn was carried +round in procession, concealing a symbol of the god (for other +resemblances see Crusius's article). Although the Hyperborean legends +are mainly connected with Delphi and Delos, traces of them are found in +Argos (the stories of Heracles, Perseus, Io), Attica, Macedonia, Thrace, +Sicily and Italy (which Niebuhr indeed considers their original home). +In modern times the name has been applied to a group of races, which +includes the Chukchis, Koryaks, Yukaghirs, Ainus, Gilyaks and +Kamchadales, inhabiting the arctic regions of Asia and America. But if +ever ethnically one, the Asiatic and American branches are now as far +apart from each other as they both are from the Mongolo-Tatar stock. + + See O. Crusius in Roscher's _Lexikon der Mythologie_; O. Schröder in + _Archiv für Religionswissenschaft_ (1904), viii. 69; W. Mannhardt, + _Wald- und Feldkulte_ (1905); L. R. Farnell, _Cults of the Greek + States_ (1907), iv. 100. + + + + +HYPEREIDES (c. 390-322 B.C.), one of the ten Attic orators, was the son +of Glaucippus, of the deme of Collytus. Having studied under Isocrates, +he began life as a writer of speeches for the courts, and in 360 he +prosecuted Autocles, a general charged with treason in Thrace (frags. +55-65, Blass). At the time of the so-called "Social War" (358-355) he +accused Aristophon, then one of the most influential men at Athens, of +malpractices (frags. 40-44, Blass), and impeached Philocrates (343) for +high treason. From the peace of 346 to 324 Hypereides supported +Demosthenes in the struggle against Macedon; but in the affair of +Harpalus he was one of the ten public prosecutors of Demosthenes, and on +the exile of his former leader he became the head of the patriotic party +(324). After the death of Alexander, he was the chief promoter of the +Lamian war against Antipater and Craterus. After the decisive defeat at +Crannon (322), Hypereides and the other orators, whose surrender was +demanded by Antipater, were condemned to death by the Athenian partisans +of Macedonia. Hypereides fled to Aegina, but Antipater's emissaries +dragged him from the temple of Aeacus, where he had taken refuge, and +put him to death; according to others, he was taken before Antipater at +Athens or Cleonae. His body was afterwards removed to Athens for burial. + +Hypereides was an ardent pursuer of "the beautiful," which in his time +generally meant pleasure and luxury. His temper was easy-going and +humorous; and hence, though in his development of the periodic sentence +he followed Isocrates, the essential tendencies of his style are those +of Lysias, whom he surpassed, however, in the richness of his vocabulary +and in the variety of his powers. His diction was plain and forcible, +though he occasionally indulged in long compound words probably borrowed +from the Middle Comedy, with which, and with the everyday life of his +time, he was in full sympathy. His composition was simple. He was +specially distinguished for subtlety of expression, grace and wit, as +well as for tact in approaching his case and handling his subject +matter. Sir R. C. Jebb sums up the criticism of pseudo-Longinus (_De +sublimitate_, 34) in the phrase--"Hypereides was the Sheridan of +Athens." + + Seventy-seven speeches were attributed to Hypereides, of which + twenty-five were regarded as spurious even by ancient critics. It is + said that a MS. of most of the speeches was in existence in the 16th + century in the library of Matthias Corvinus, king of Hungary, at Ofen, + but was destroyed at the capture of the city by the Turks in 1526. + Only a few fragments were known until comparatively recent times. In + 1847 large fragments of his speeches Against _Demosthenes_ (see above) + and _For Lycophron_ (incidentally interesting as elucidating the order + of marriage processions and other details of Athenian life, and the + Athenian government of Lemnos), and the whole of the _For Euxenippus_ + (c. 330, a _locus classicus_ on [Greek: eisangeliai] or state + prosecutions), were found in a tomb at Thebes in Egypt, and in 1856 a + considerable portion of a [Greek: logos epitaphios], a _Funeral + Oration_ over Leosthenes and his comrades who had fallen in the Lamian + war, the best extant specimen of epideictic oratory (see BABINGTON, + CHURCHILL). Towards the end of the century further discoveries were + made of the conclusion of the speech _Against Philippides_ (dealing + with a [Greek: graphê paranomôn], or indictment for the proposal of an + unconstitutional measure, arising out of the disputes of the + Macedonian and anti-Macedonian parties at Athens), and of the whole of + the _Against Athenogenes_ (a perfumer accused of fraud in the sale of + his business). These have been edited by F. G. Kenyon (1893). An + important speech that is lost is the _Deliacus_ (frags. 67-75, Blass) + on the presidency of the Delian temple claimed by both Athens and + Delos, which was adjudged by the Amphictyons to Athens. + + On Hypereides generally see pseudo-Plutarch, _Decem oratorum vitae_; + F. Blass, _Attische Beredsamkeit_, iii.; R. C. Jebb, _Attic Orators_, + ii. 381. A full list of editions and articles is given in F. Blass, + _Hyperidis orationes sex cum ceterarum fragmentis_ (1894, Teubner + series), to which may be added I. Bassi, _Le Quattro Orazioni di + Iperide_ (introduction and notes, 1888), and J. E. Sandys in + _Classical Review_ (January 1895) (a review of the editions of Kenyon + and Blass). For the discourse against Athenogenes see H. Weil, _Études + sur l'antiquité grecque_ (1900). + + + + +HYPERION, in Greek mythology, one of the Titans, son of Uranus and Gaea +and father of Helios, the sun-god (Hesiod, _Theog._ 134, 371; +Apollodorus i. 1. 2). In the well-known passage in Shakespeare +(_Hamlet_, i. 2: "Hyperion to a satyr," where as in other poets the +vowel -_i_- though really long, is shortened for metrical reasons) +Hyperion is used for Apollo as expressive of the idea of beauty. The +name is often used as an epithet of Helios, who is himself sometimes +called simply Hyperion. It is explained as (1) he who moves above +([Greek: hyper-iôn]), but the quantity of the vowel is against this; (2) +he who is above ([Greek: hyperi-ôn]). Others take it to be a patronymic +in form, like [Greek: Kroniôn, Moliôn]. + + + + +HYPERSTHENE, a rock-forming mineral belonging to the group of +orthorhombic pyroxenes. It differs from the other members (enstatite +[q.v.] and bronzite) of this group in containing a considerable amount +of iron replacing magnesium: the chemical formula is (Mg, Fe)SiO3. +Distinctly developed crystals are rare, the mineral being usually found +as foliated masses embedded in those igneous rocks--norite, +hypersthene-andesite, &c.--of which it forms an essential constituent. +The coarsely grained labradorite-hypersthene-rock (norite) of the island +of St Paul off the coast of Labrador has furnished the most typical +material; and for this reason the mineral has been known as "Labrador +hornblende" or paulite. The colour is brownish-black, and the pleochrism +strong; the hardness is 6, and the specific gravity 3.4-3.5. On certain +surfaces it displays a brilliant copper-red metallic sheen or schiller, +which has the same origin as the bronzy sheen of bronzite (q.v.), but is +even more pronounced. Like bronzite, it is sometimes cut and polished +for ornamental purposes. (L. J. S.) + + + + +HYPERTROPHY (Gr. [Greek: hyper], over, and [Greek: trophê], +nourishment), a term in medicine employed to designate an abnormal +increase in bulk of one or more of the organs or component tissues of +the body (see PATHOLOGY). In its strict sense this term can only be +applied where the increase affects the natural textures of a part, and +is not applicable where the enlargement is due to the presence of some +extraneous morbid formation. Hypertrophy of a part may manifest itself +either by simply an increase in the size of its constituents, or by this +combined with an increase in their number (hyperplasia). In many +instances both are associated. + +The conditions giving rise to hypertrophy are the reverse of those +described as producing Atrophy (q.v.). They are concisely stated by Sir +James Paget as being chiefly or only three, namely: (1) the increased +exercise of a part in its healthy functions; (2) an increased +accumulation in the blood of the particular materials which a part +appropriates to its nutrition or in secretion; and (3) an increased +afflux of healthy blood. + +Illustrations are furnished of the first of these conditions by the high +development of muscular tissue under habitual active exercise; of the +second in the case of obesity, which is an hypertrophy of the fatty +tissues, the elements of which are furnished by the blood; and of the +third in the occasional overgrowth of hair in the neighbourhood of parts +which are the seat of inflammation. Obviously therefore, in many +instances, hypertrophy cannot be regarded as a deviation from health, +but rather on the contrary as indicative of a high degree of nutrition +and physical power. Even in those cases where it is found associated +with disease, it is often produced as a salutary effort of nature to +compensate for obstructions or other difficulties which have arisen in +the system, and thus to ward off evil consequences. No better example of +this can be seen than in the case of certain forms of heart disease, +where from defect at some of the natural orifices of that organ the +onward flow of the blood is interfered with, and would soon give rise to +serious embarrassment to the circulation, were it not that behind the +seat of obstruction the heart gradually becomes hypertrophied, and thus +acquires greater propelling power to overcome the resistance in front. +Again, it has been noticed, in the case of certain double organs such as +the kidneys, that when one has been destroyed by disease the other has +become hypertrophied to such a degree as enables it to discharge the +functions of both. + +Hypertrophy may, however, in certain circumstances constitute a disease, +as in goitre and elephantiasis (q.v.), and also in the case of certain +tumours and growths (such as cutaneous excrescences, fatty tumours, +mucous polypi, &c.), which are simply enlargements of normal textures. +Hypertrophy does not in all cases involve an increase in bulk; for, just +as in atrophy there may be no diminution in the size of the affected +organ, so in hypertrophy there may be no increase. This is apt to be the +case where certain only of the elements of an organ undergo increase, +while the others remain unaffected or are actually atrophied by the +pressure of the hypertrophied tissue, as is seen in the disease known as +cirrhosis of the liver. + +A spurious hypertrophy is observed in the rare disease to which G. B. +Duchenne applied the name of _pseudo-hypertrophic paralysis_. This +ailment, which appears to be confined to children, consists essentially +of a progressive loss of power accompanied with a remarkable enlargement +of certain muscles or groups of muscles, more rarely of the whole +muscular system. This increase of bulk is, however, not a true +hypertrophy, but rather an excessive development of connective tissue in +the substance of the muscles, the proper texture of which tends in +consequence to undergo atrophy or degeneration. The appearance presented +by a child suffering from this disease is striking. The attitude and +gait are remarkably altered, the child standing with shoulders thrown +back, small of the back deeply curved inwards, and legs wide apart, +while walking is accompanied with a peculiar swinging or rocking +movement. The calves of the legs, the buttocks, the muscles of the back, +and occasionally other muscles, are seen to be unduly enlarged, and +contrast strangely with the general feebleness. The progress of the +disease is marked by increasing failure of locomotory power, and +ultimately by complete paralysis of the limbs. The malady is little +amenable to treatment, and, although often prolonged for years, +generally proves fatal before the period of maturity. + + + + +HYPNOTISM, a term now in general use as covering all that pertains to +the art of inducing the hypnotic state, or hypnosis, and to the study of +that state, its conditions, peculiarities and effects. Hypnosis is a +condition, allied to normal sleep (Gr. [Greek: hypnos]), which can be +induced in a large majority of normal persons. Its most characteristic +and constant symptom is the increased suggestibility of the subject (see +SUGGESTION). Other symptoms are very varied and differ widely in +different subjects and in the same subject at different times. There can +be no doubt that the increased suggestibility and all the other symptoms +of hypnosis imply some abnormal condition of the brain of a temporary +and harmless nature. It would seem that in all ages and in almost all +countries individuals have occasionally fallen into abnormal states of +mind more or less closely resembling the hypnotic state, and have +thereby excited the superstitious wonder of their fellows. In some cases +the state has been deliberately induced, in others it has appeared +spontaneously, generally under the influence of some emotional +excitement. The most familiar of these allied states is the somnambulism +or sleep-walking to which some persons seem to be hereditarily disposed. +Of a rather different type are the states of ecstasy into which +religious enthusiasts have occasionally fallen and which were especially +frequent among the peoples of Europe during the middle ages. While in +this condition individuals have appeared to be insensitive to all +impressions made on their sense-organs, even to such as would excite +acute pain in normal persons, have been capable of maintaining rigid +postures for long periods of time, have experienced vivid +hallucinations, and have produced, through the power of the imagination, +extraordinary organic changes in the body, such as the bloody stigmata +on the hands and feet in several well-attested instances. It has been +proved in recent years that effects of all these kinds may be produced +by hypnotic suggestion. Different again, but closely paralleled by some +subjects in hypnosis, is the state of _latah_ into which a certain +proportion of persons of the Malay race are liable to fall. These +persons, if their attention is suddenly and forcibly drawn to any other +person, will begin to imitate his every action and attitude, and may do +so in spite of their best efforts to restrain their imitative movements. +Among the half-bred French-Canadians of the forest regions of Canada +occur individuals, known as "jumpers," who are liable to fall suddenly +into a similar state of abject imitativeness, and the same peculiar +behaviour has been observed among some of the remote tribes of Siberia. + +The deliberate induction of states identical with, or closely allied to, +hypnosis is practised by many barbarous and savage peoples, generally +for ceremonial purposes. Thus, certain dervishes of Algiers are said to +induce in themselves, by the aid of the sound of drums, monotonous songs +and movements, a state in which they are insensitive to pain, and a +similar practice of religious devotees is reported from Tibet. Perhaps +the most marvellous achievement among well-attested cases of this sort +is that of certain _yogis_ of Hindustan; by long training and practice +they seem to acquire the power of arresting almost completely all their +vital functions. An intense effort of abstraction from the impressions +of the outer world, a prolonged fixation of the eyes upon the nose or in +some other strained position and a power of greatly slowing the +respiration, these seem to be important features of their procedure for +the attainment of their abnormal states. + +In spite of the wide distribution in time and space, and the not very +infrequent occurrence, of these instances of states identical with or +allied to hypnosis, some three centuries of enthusiastic investigation +and of bitter controversy were required to establish the occurrence of +the hypnotic state among the facts accepted by the world of European +science. Scientific interest in them may be traced back at least as far +as the end of the 16th century. Paracelsus had founded the "sympathetic +system" of medicine, according to which the stars and other bodies, +especially magnets, influence men by means of a subtle emanation or +fluid that pervades all space. J. B. van Helmont, a distinguished man of +science of the latter part of the 16th century, extended this doctrine +by teaching that a similar magnetic fluid radiates from men, and that it +can be guided by their wills to influence directly the minds and bodies +of others. In the middle of the 17th century there appeared in England +several persons who claimed to have the power of curing diseases by +stroking with the hand. Notable amongst these was Valentine Greatrakes, +of Affane, in the county of Waterford, Ireland, who was born in +February 1628, and who attracted great attention in England by his +supposed power of curing the king's evil, or scrofula. Many of the most +distinguished scientific and theological men of the day, such as Robert +Boyle and R. Cudworth, witnessed and attested the cures supposed to be +effected by Greatrakes, and thousands of sufferers crowded to him from +all parts of the kingdom. About the middle of the 18th century John +Joseph Gassner, a Roman Catholic priest in Swabia, took up the notion +that the majority of diseases arose from demoniacal possession, and +could only be cured by exorcism. His method was undoubtedly similar to +that afterwards followed by Mesmer and others, and he had an +extraordinary influence over the nervous systems of his patients. +Gassner, however, believed his power to be altogether supernatural. + +But it was not until the latter part of the 18th century that the +doctrine of a magnetic fluid excited great popular interest and became +the subject of fierce controversy in the scientific world. F. A. Mesmer +(q.v.), a physician of Vienna, was largely instrumental in bringing the +doctrine into prominence. He developed it by postulating a specialized +variety of magnetic fluid which he called _animal magnetism_; and he +claimed to be able to cure many diseases by means of this animal +magnetism, teaching, also, that it may be imparted to and stored up in +inert objects, which are thereby rendered potent to cure disease. + +It would seem that Mesmer himself was not acquainted with the artificial +somnambulism which for nearly a century was called mesmeric or magnetic +sleep, and which is now familiar as hypnosis of a well-marked degree. It +was observed and described about the year 1780 by the marquis de +Puységur, a disciple of Mesmer, who showed that, while subjects were in +this state, not only could some of their diseases be cured, but also +their movements could be controlled by the "magnetizer," and that they +usually remembered nothing of the events of the period of sleep when +restored to normal consciousness. These are three of the most important +features of hypnosis, and the modern study of hypnotism may therefore be +said to have been initiated at this date by Puységur. For, though it is +probable that this state had often been induced by the earlier +magnetists, they had not recognized that the peculiar behaviour of their +patients resulted from their being plunged into this artificial sleep, +but had attributed all the symptoms they observed to the direct physical +action of external agents upon the patients. + +The success of Mesmer and his disciples, especially great in the +fashionable world, led to the appointment in Paris of a royal commission +for the investigation of their claims. The commission, which included +men of great eminence, notably A. L. Lavoisier and Benjamin Franklin, +reported in the year 1784 that it could not accept the evidence for the +existence of the magnetic fluid; but it did not express an opinion as to +the reality of the cures said to be effected by its means, nor as to the +nature of the magnetic sleep. This report and the social upheavals of +the following years seem to have abolished the public interest in +"animal magnetism" for the space of one generation; after which +Alexandre Bertrand, a Parisian physician, revived it by his acute +investigations and interpretations of the phenomena. Bertrand was the +first to give an explanation of the facts of the kind that is now +generally accepted. He exhibited the affinity of the "magnetic sleep" to +ordinary somnambulism, and he taught that the peculiar effects are to be +regarded as due to the suggestions of the operator working themselves +out in the mind and body of the "magnetized" subject, i.e. he regarded +the influence of the magnetizer as exerted in the first instance on the +mind of the subject and only indirectly through the mind upon the body. +Shortly after this revival of public interest, namely in the year 1831, +a committee of the Academy of Medicine of Paris reported favourably upon +"magnetism" as a therapeutic agency, and before many years had elapsed +it was extensively practised by the physicians of all European +countries, with few exceptions, of which England was the most notable. +Most of the practitioners of this period adhered to the doctrine of the +magnetic fluid emanating from the operator to his patient, and the +acceptance of this doctrine was commonly combined with belief in +phrenology, astrology and the influence of metals and magnets, +externally applied, in curing disease and in producing a variety of +strange sensations and other affections of the mind. These beliefs, +claiming to rest upon carefully observed facts, were given a new +elaboration and a more imposing claim to be scientifically established +by the doctrine of _odylic force_ propounded by Baron Karl von +Reichenbach. In this mass of ill-based assertion and belief the valuable +truths of "animal magnetism" and the psychological explanations of them +given by Bertrand were swamped and well-nigh lost sight of. For it was +this seemingly inseparable association between the facts of hypnotism +and these bizarre practices and baseless beliefs that blinded the larger +and more sober part of the scientific world, and led them persistently +to assert that all this group of alleged phenomena was a mass of +quackery, fraud and superstition. And the fact that magnetism was +practised for pecuniary gain, often in a shameless manner, by exponents +who claimed to cure by its means every conceivable ill, rendered this +attitude on the part of the medical profession inevitable and perhaps +excusable, though not justifiable. It was owing to this baleful +association that John Elliotson, one of the leading London physicians of +that time, who became an ardent advocate of "magnetism" and who founded +and edited the _Zoist_ in the interests of the subject, was driven out +of the profession. This association may perhaps be held, also, to excuse +the hostile attitude of the medical profession towards James Esdaile, a +surgeon, who, practising in a government hospital in Calcutta among the +natives of India, performed many major operations, such as the +amputation of limbs, painlessly and with the most excellent results by +aid of the "magnetic" sleep. For both Elliotson and Esdaile, though +honourable practitioners, accepted the doctrine of the "magnetic" fluid +and many of the erroneous beliefs that commonly were bound up with it. + +In 1841 James Braid, a surgeon of Manchester, rediscovered independently +Bertrand's physiological and psychological explanations of the facts, +carried them further, and placed "hypnotism," as he named the study, on +a sound basis. Braid showed that subjects in "magnetic" sleep, far from +being in a profoundly insensitive condition, are often abnormally +susceptible to impressions on the senses, and showed that many of the +peculiarities of their behaviour were due to suggestions, made verbally +or otherwise, but unintentionally, by the operator or by onlookers. + +It seems, on looking back on the history of hypnotism, that at this time +it was in a fair way to secure general recognition as a most interesting +subject of psychological study and a valuable addition to the resources +of the physician. But it was destined once more to be denied its rights +by official science and to fall back into disrepute. This was due to the +coincidence about the year 1848 of two events of some importance, +namely--the discovery of the anaesthetic properties of chloroform and +the sudden rise of modern spiritualism. The former afforded a very +convenient substitute for the most obvious practical application of +hypnotism, the production of anaesthesia during surgical operations; the +latter involved it once more in a mass of fraud and superstition, and, +for the popular mind, drove it back to the region of the marvellous, the +supernatural and the dangerous, made it, in fact, once more a branch of +the black art. + +From this time onward there took place a gradual differentiation of the +"animal magnetism" of the 18th century into two diverging branches, +hypnotism and spiritualism, two branches which, however, are not yet +entirely separated and, perhaps, never will be. At the same time the +original system of "animal magnetism" has lived on in an enfeebled +condition and is now very nearly, though not quite, extinct. + +In the development of hypnotism since the time of Braid we may +distinguish three lines, the physiological, the psychological and the +pathological. The last may be dismissed in a few words. Its principal +representative was J. M. Charcot, who taught at the Salpêtrière in Paris +that hypnosis is essentially a symptom of a morbid condition of hysteria +or hystero-epilepsy. This doctrine, which, owing to the great repute +enjoyed by Charcot, has done much to retard the application of +hypnotism, is now completely discredited. The workers of the +physiological party attached special importance to the fixation of the +eyes, or to other forms of long continued and monotonous, or violent, +sensory stimulation in the induction of hypnosis. They believed that by +acting on the senses in these ways they induced a peculiar condition of +the nervous system, which consisted in the temporary abolition of the +cerebral functions and the consequent reduction of the subject to +machine-like unconscious automatism. The leading exponent of this view +was R. Heidenhain, professor of physiology at Breslau, whose +experimental investigations played a large part in convincing the +scientific world of the genuineness of the leading symptoms of hypnosis. +The purely psychological doctrine of hypnosis puts aside all physical +and physiological influences and effects as of but little or no +importance, and seeks a psychological explanation of the induction of +hypnosis and of all the phenomena. This dates from 1884, when H. +Bernheim, professor of medicine at Nancy, published his work _De la +Suggestion_ (republished in 1887 with a second part on the therapeutics +of hypnotism). Bernheim was led to the study of hypnotism by A. A. +Liébeault, who for twenty years had used it very largely and +successfully in his general practice among the poor of Nancy. Liébeault +rediscovered independently, and Bernheim made known to the world the +truths, twice previously discovered and twice lost sight of, that +expectation is a most important factor in the induction of hypnosis, +that increased suggestibility is its essential symptom, and that in +general the operator works upon his patient by mental influences. +Although they went too far in the direction of ignoring the peculiarity +of the state of the brain in hypnosis and the predisposing effect of +monotonous sensory stimulation, and in seeking to identify hypnosis with +normal sleep, the views of the Nancy investigators have prevailed, and +are now in the main generally accepted. Their methods of verbal +suggestion have been adopted by leading physicians in almost all +civilized countries and have been proved to be efficacious in the relief +of many disorders; and as a method of psychological investigation +hypnotism has proved, especially in the hands of the late Ed. Gurney, of +Dr Pierre Janet and of other investigators, capable of throwing much +light on the constitution of the mind, has opened up a number of +problems of the deepest interest, and has done more than any other of +the many branches of modern psychology to show the limitations and +comparative barrenness of the old psychology that relied on +introspection alone and figured as a department of general philosophy. +In England, "always the last to enter into the general movement of the +European mind," the prejudice, incredulity and ignorant +misrepresentation with which hypnotism has everywhere been received have +resisted its progress more stubbornly than elsewhere; but even in +England its reality and its value as a therapeutic agent have at last +been officially recognized. In 1892, just fifty years after Braid +clearly demonstrated the facts and published explanations of them almost +identical with those now accepted, a committee of the British Medical +Association reported favourably upon hypnotism after a searching +investigation; it is now regularly employed by a number of physicians of +high standing, and the formation in 1907 of "The Medical Society for the +Study of Suggestive Therapeutics" shows that the footing it has gained +is likely to be made good. + +_Induction of Hypnosis._--It has now been abundantly proved that +hypnosis can be induced in the great majority of normal persons, +provided that they willingly submit themselves to the process. Several +of the most experienced operators have succeeded in hypnotizing more +than 90% of the cases they have attempted, and most of them are agreed +that failure to induce hypnosis in any case is due either to lack of +skill and tact on the part of the operator, or to some unfavourable +mental condition of the subject. It has often been said that some races +or peoples are by nature more readily hypnotizable than others; of the +French people especially this has been maintained. But there is no +sufficient ground for this statement. The differences that undoubtedly +obtain between populations of different regions in respect to the ease +or difficulty with which a large proportion of all persons can be +hypnotized are sufficiently explained by the differences of the attitude +of the public towards hypnotism; in France, e.g., and especially in +Nancy, hypnotism has been made known to the public chiefly as a +recognized auxiliary to the better known methods of medical treatment, +whereas in England the medical profession has allowed the public to make +acquaintance with hypnotism through the medium of disgusting +stage-performances whose only object was to raise a laugh, and has, with +few exceptions, joined in the general chorus of condemnation and +mistrust. Hence in France patients submit themselves with confidence and +goodwill to hypnotic treatment, whereas in England it is still necessary +in most cases to remove an ill-based prejudice before the treatment can +be undertaken with hope of success. For the confidence and goodwill of +the patient are almost essential to success, and even after hypnosis has +been induced on several occasions a patient may be so influenced by +injudicious friends that he cannot again be hypnotized or, if +hypnotized, is much less amenable to the power of suggestion. Various +methods of hypnotization are current, but most practitioners combine the +methods of Braid and of Bernheim. After asking the patient to resign +himself passively into their hands, and after seating him in a +comfortable arm-chair, they direct him to fix his eyes upon some small +object held generally in such a position that some slight muscular +strain is involved in maintaining the fixation; they then suggest to him +verbally the idea or expectation of sleep and the sensations that +normally accompany the oncoming of sleep, the heaviness of the eyes, the +slackness of the limbs and so forth; and when the eyes show signs of +fatigue, they either close them by gentle pressure or tell the subject +to close them. Many also pass their hands slowly and regularly over the +face, with or without contact. The old magnetizers attached great +importance to such "passes," believing that by them the "magnetic fluid" +was imparted to the patient; but it seems clear that, in so far as they +contribute to induce hypnosis, it is in their character merely of +gentle, monotonous, sensory stimulations. A well-disposed subject soon +falls into a drowsy state and tends to pass into natural sleep; but by +speech, by passes, or by manipulating his limbs the operator keeps in +touch with him, keeps his waning attention open to the impressions he +himself makes. Most subjects then find it difficult or impossible to +open their eyes or to make any other movement which is forbidden or said +to be impossible by the operator, although they may be fully conscious +of all that goes on about them and may have the conviction that if they +did but make an effort they could break the spell. This is a light stage +of hypnosis beyond which some subjects can hardly be induced to pass and +beyond which few pass at the first attempt. But on successive occasions, +or even on the first occasion, a favourable subject passes into deeper +stages of hypnosis. Many attempts have been made to distinguish clearly +marked and constantly occurring stages. But it seems now clear that the +complex of symptoms displayed varies in all cases with the +idiosyncrasies of the subject and with the methods adopted by the +operator. In many subjects a waxy rigidity of the limbs appears +spontaneously or can be induced by suggestion; the limbs then retain for +long periods without fatigue any position given them by the operator. +The most susceptible subjects pass into the stage known as artificial +somnambulism. In this condition they continue to respond to all +suggestions made by the operator, but seem as insensitive to all other +impressions as a person in profound sleep or in coma; and on awaking +from this condition they are usually oblivious of all that they have +heard, said or done during the somnambulistic period. When in this last +condition patients are usually more profoundly influenced by +suggestions, especially post-hypnotic suggestions, than when in the +lighter stages; but the lighter stages suffice for the production of +many therapeutic effects. When a patient is completely hypnotized, his +movements, his senses, his ideas and, to some extent, even the organic +processes over which he has no voluntary control become more or less +completely subject to the suggestions of the operator; and usually he is +responsive to the operator alone (_rapport_) unless he is instructed by +the latter to respond also to the suggestions of other persons. If left +to himself the hypnotized subject will usually awake to his normal state +after a period which is longer in proportion to the depth of hypnosis; +and the deeper stages seem to pass over into normal sleep. The subject +can in almost every case be brought quickly back to the normal state by +the verbal command of the operator. + +_The Principal Effects produced by Suggestion during Hypnosis._--The +subject may not only be rendered incapable of contracting any of the +muscles of the voluntary system, but may also be made to use them with +extraordinarily great or sustained force (though by no means in all +cases). He can with difficulty refrain from performing any action +commanded by the operator, and usually carries out any simple command +without hesitation. Any one of the sense-organs, or any sensory region +such as the skin or deep tissues of one limb may be rendered anaesthetic +by verbal suggestion, aided perhaps by some gentle manipulation of the +part. On this fact depends the surgical application of hypnotism. +Sceptical observers are always inclined to doubt the genuineness of the +anaesthesia produced by a mere word of command, but the number of +surgical operations performed under hypnotic anaesthesia suffices to put +its reality beyond all question. A convincing experiment may, however, +be made on almost any good subject. Anaesthesia of one eye may be +suggested and its reality tested in the following way. Anaesthesia of +the left eye may be suggested, and the subject be instructed to fix his +gaze on a distant point and to give some signal as soon as he sees the +operator's finger in the peripheral field of view. The operator then +brings his finger slowly from behind and to the right forwards towards +the subject's line of sight. The subject signals as soon as it crosses +the normal temporal boundary of the field of view of the right eye. The +operator then brings his finger forward from a point behind and to the +left of the subject's head. The subject allows it to cross the monocular +field of the left eye and signals only when the finger enters the field +of vision of the right eye across its nasal boundary. Since few persons, +other than physiologists or medical men, are aware of the relations of +the boundaries of the monocular and binocular fields of vision, the +success of this experiment affords proof that the finger remains +invisible to the subject during its passage across the monocular field +of the left eye. The abolition of pain, especially of neuralgias, the +pain of rheumatic and other inflammations, which is one of the most +valuable applications of hypnotism, is an effect closely allied to the +production of such anaesthesia. + +It has often been stated that in hypnosis the senses may be rendered +extraordinarily acute or hyperaesthetic, so that impressions too faint +to affect the senses of the normal person may be perceived by the +hypnotized subject; but in view of the fact that most observers are +ignorant of the normal limits of sensitivity and discrimination, all +such statements must be received with caution, until we have more +convincing evidence than has yet been brought forward. + +_Positive and Negative Hallucinations_ are among the most striking +effects of hypnotic suggestion. A good subject may be made to experience +an hallucinatory perception of almost any object, the more easily the +less unusual and out of harmony with the surroundings is the suggested +object. He may, e.g., be given a blank card and asked if he thinks it a +good photograph of himself. He may then assent and describe the +photograph in some detail, and, what is more astonishing, he may pick +out the card as the one bearing the photograph, after it has been mixed +with other similar blank cards. This seems to be due to the part played +by _points de repère_, insignificant details of surface or texture, +which serve as an objective basis around which the hallucinatory image +is constructed by the pictorial imagination of the subject. A negative +hallucination may be induced by telling the subject that a certain +object or person is no longer present, when he ignores in every way that +object or person. This is more puzzling than the positive hallucination +and will be referred to again in discussing the theory of hypnosis. Both +kinds of hallucination tend to be systematically and logically +developed; if, e.g., the subject is told that a certain person is no +longer visible, he may become insensitive to impressions made on any +sense by that person. + +_Delusions_, or false beliefs as to their present situation or past +experiences may be induced in many subjects. On being assured that he is +some other person, or that he is in some strange situation, the subject +may accept the suggestion and adapt his behaviour with great histrionic +skill to the induced delusion. It is probable that many, perhaps all, +subjects are vaguely aware, as we sometimes are in dreams, that the +delusions and hallucinations they experience are of an unreal nature. In +the lighter stages of hypnosis a subject usually remembers the events of +his waking life, but in the deeper stages he is apt, while remembering +the events of previous hypnotic periods, to be incapable of recalling +his normal life; but in this respect, as also in respect to the extent +to which on awaking he remembers the events of the hypnotic period, the +suggestions of the operator usually play a determining part. + +Among the organic changes that have been produced by hypnotic suggestion +are slowing or acceleration of the cardiac and respiratory rhythms; rise +and fall of body-temperature through two or three degrees; local +erythema and even inflammation of the skin with vesication or exudation +of small drops of blood; evacuation of the bowel and vomiting; +modifications of the secretory activity of glands, especially of the +sweat-glands. + +_Post-hypnotic Effects._--Most subjects in whom any appreciable degree +of hypnosis can be induced show some susceptibility to post-hypnotic +suggestion, i.e. they may continue to be influenced, when restored to +the fully waking state, by suggestions made during hypnosis, more +especially if the operator suggests that this shall be the case; as a +rule, the deeper the stage of hypnosis reached, the more effective are +post-hypnotic suggestions. The therapeutic applications of hypnotism +depend in the main upon this post-hypnotic continuance of the working of +suggestions. If a subject is told that on awaking, or on a certain +signal, or after the lapse of a given interval of time from the moment +of awaking, he will perform a certain action, he usually feels some +inclination to carry out the suggestion at the appropriate moment. If he +remembers that the action has been suggested to him he may refuse to +perform it, and if it is one repugnant to his moral nature, or merely +one that would make him appear ridiculous, he may persist in his +refusal. But if the action is of a simple and ordinary nature he will +usually perform it, remarking that he cannot be comfortable till it is +done. If the subject was deeply hypnotized and remembers nothing of the +hypnotic period, he will carry out the post-hypnotic suggestion in +almost every case, no matter how complicated or absurd it may be, so +long as it is not one from which his normal self would be extremely +averse; and he will respond appropriately to the suggested signals, +although he is not conscious of their having been named; he will often +perform the action in a very natural way, and will, if questioned, give +some more or less adequate reason for it. Such actions, determined by +post-hypnotic suggestions of which no conscious memory remains, may be +carried out even after the lapse of many weeks or even months. +Inhibitions of movement, anaesthesia, positive and negative +hallucinations, and delusions may also be made to persist for brief +periods after the termination of hypnosis; and organic effects, such as +the action of the bowels, the oncoming of sleep and the cessation of +pain, may be determined by post-hypnotic suggestion. In short, it may be +said that in a good subject all the kinds of suggestion which will take +effect during hypnosis will also be effective if given as post-hypnotic +suggestions. + +_Theory of the Hypnotic State._--Very many so called theories of +hypnosis have been propounded, but few of them demand serious +consideration. One author ascribes all the symptoms to cerebral anaemia, +another to cerebral congestion, a third to temporary suppression of the +functions of the cerebrum, a fourth to abnormal cerebral excitability, a +fifth to the independent functioning of one hemisphere. Another seeks to +explain all the facts by saying that in hypnosis our normal +consciousness disappears and is replaced by a dream-consciousness; and +yet another by the assumption that every human organism comprises two +mental selves or personalities, a normal one and one which only comes +into activity during sleep and hypnosis. Most of these "theories" would, +even if true, carry us but a little way towards a complete understanding +of the facts. There is, however, one theory or principle of explanation +which is now gradually taking shape under the hands of a number of the +more penetrating workers in this field, and which does seem to render +intelligible many of the principle facts. This is the theory of _mental +dissociation_. + +It is clear that a theory of hypnosis must attempt to give some account +of the peculiar condition of the brain which is undoubtedly present as +an essential feature of the state. It is therefore not enough to say +with Bernheim that hypnosis is a state of abnormally increased +suggestibility produced by suggestion; nor is it enough, though it is +partially true, to say that it is a state of mono-ideism or one of +abnormally great concentration of attention. Any theory must be stated +in terms of physiological psychology, it must take account of both the +psychical and the nervous peculiarities of the hypnotic state; it must +exhibit the physiological condition as in some degree similar to that +obtaining in normal sleep; but principally it must account for that +abnormally great receptivity for ideas, and that abnormally intense and +effective operation of ideas so received, which constitute abnormally +great suggestibility. + +The theory of mental dissociation may be stated in purely mental terms, +or primarily in terms of nervous structure and function, and the latter +mode of statement is probably the more profitable at the present time. +The increased effectiveness of ideas might be due to one of two +conditions: (1) it might be that certain tracts of the brain or the +whole brain were in a condition of abnormally great excitability; or (2) +an idea might operate more effectively in the mind and on the body, not +because it, or the underlying brain-process was more intense than +normally, but because it worked out its effects free from the +interference of contrary or irrelevant ideas that might weaken its +force. It is along this second line that the theory of mental +dissociation attempts to explain the increased suggestibility of +hypnosis. To understand the theory we must bear in mind the nature of +mental process in general and of its nervous concomitants. Mental +process consists in the interplay, not merely of ideas, but rather of +complex dispositions which are the more or less enduring conditions of +the rise of ideas to consciousness. Each such disposition seems capable +of remaining inactive or quiescent for long periods, and of being +excited in various degrees, either by impressions made upon the +sense-organs or by the spread of excitement from other dispositions. +When its excitement rises above a certain pitch of intensity, the +corresponding idea rises to the focus of consciousness. These +dispositions are essential factors of all mental process, the essential +conditions of all mental retention. They may be called simply mental +dispositions, their nature being left undefined; but for our present +purpose it is advantageous to regard them as neural dispositions, +complex functional groups of nervous elements or neurones. The neurones +of each such group must be conceived as being so intimately connected +with one another that the excitement of any part of the group at once +spreads through the whole group or disposition, so that it always +functions as a unit. The whole cerebrum must be conceived as consisting +of a great number of such dispositions, inextricably interwoven, but +interconnected in orderly fashion with very various degrees of intimacy; +groups of dispositions are very intimately connected to form neural +systems, so that the excitement of any one member of such a system tends +to spread in succession to all the other members. On the other hand, it +is a peculiarity of the reciprocal relations of all such dispositions +and systems that the excitement of any one to such a degree that the +corresponding idea rises to consciousness prevents or inhibits the +excitement of others, i.e. all of them are in relations of reciprocal +inhibition with one another (see MUSCLE AND NERVE). The excitement of +dispositions associated together to form a system tends towards some end +which, either immediately or remotely, is an action, a bodily movement, +in many cases a movement of the organs of speech only. Now we know from +many exact experiments that the neural dispositions act and react upon +one another to some extent, even when they are excited only in so feeble +a degree that the corresponding ideas do not rise to consciousness. In +the normal state of the brain, then, when any idea is present to +consciousness, the corresponding neural disposition is in a state of +dominant excitement, but the intensity of that excitement is moderated, +depressed or partially inhibited by the sub-excitement of many rival or +competing dispositions of other systems with which it is connected. +Suppose now that all the nervous connexions between the multitudinous +dispositions of the cerebrum are by some means rendered less effective, +that the association-paths are partially blocked or functionally +depressed; the result will be that, while the most intimate connexions, +those between dispositions of any one system remain functional or +permeable, the weaker less intimate connexions, those between +dispositions belonging to different systems will be practically +abolished for the time being; each system of dispositions will then +function more or less as an isolated system, and its activity will no +longer be subject to the depressing or inhibiting influence of other +systems; therefore each system, on being excited in any way, will tend +to its end with more than normal force, being freed from all +interferences; that is to say, each idea or system of ideas will tend to +work itself out and to realize itself in action immediately, without +suffering the opposition of antagonistic ideas which, in the normal +state of the brain, might altogether prevent its realization in action. + +The theory of mental dissociation assumes that the abnormal state of the +brain that obtains during hypnosis is of this kind, a temporary +functional depression of all, or of many of the associations or nervous +links between the neural dispositions; that is, it regards hypnosis as a +state of _relative dissociation_. The lighter the stage of hypnosis the +slighter is the degree of dissociation, the deeper the stage the more +nearly complete is the dissociation. + +It is not essential that the theory should explain in what change this +stage of dissociation consists, but a view compatible with all that we +know of the functions of the central nervous system may be suggested. +The connexions between neural dispositions involve synapses or +cell-junctions, and these seem to be the places of variable resistance +which demarcate the dispositions and systems; and there is good reason +to think that their resistances vary with the state of the neurones +which they connect, being lowered when these are excited and raised when +their excitement ebbs. Now, in the waking state, the varied stimuli, +which constantly rain upon all the sense-organs, maintain the whole +cerebrum in a state of sub-excitement, keep all the cerebral neurones +partially charged with free nervous energy. When the subject lies down +to sleep or submits himself to the hypnotizer he arrests as far as +possible the flow of his thoughts, and the sensory stimuli are +diminished in number and intensity. Under these conditions the general +cerebral activity tends to subside, the free energy with which the +cerebral neurones are charged ebbs away, and the synaptic resistances +rise proportionally; then the effect of sensory impressions tends to be +confined to the lower nervous level, and the brain tends to come to +rest. If this takes place the condition of normal sleep is realized. But +in inducing hypnosis the operator, by means of his words and +manipulations, keeps one system of ideas and the corresponding neural +system in activity, namely, the ideas connected with himself; thus he +keeps open one channel of entry to the brain and mind, and through this +one open channel he can introduce whatever ideas he pleases; and the +ideas so introduced then operate with abnormally great effect because +they work in a free field, unchecked by rival ideas and tendencies. + +This theory of relative dissociation has two great merits: in the first +place it goes far towards enabling us to understand in some degree most +of the phenomena of hypnosis; secondly, we have good evidence that +dissociation really occurs in deep hypnosis and in some allied states. +Any one may readily work out for himself the application of the theory +to the explanation of the power of the operator's suggestions to control +movement, to induce anaesthesia, hallucinations and delusions, and to +exert on the organic processes an influence greater than can be exerted +by mental processes in the normal state of the brain. But the positive +evidence of the occurrence of dissociation is a matter of great +psychological interest and its nature must be briefly indicated. The +phenomena of automatic speech and writing afford the best evidence of +cerebral dissociation. Many persons can, while in an apparently normal +or but very slightly abnormal condition, produce automatic writing, i.e. +intelligibly written sentences, in some cases long connected passages, +of whose import they have no knowledge, their self-conscious +intelligence being continuously directed to some other task. The +carrying out of post-hypnotic suggestions affords in many cases similar +evidence. Thus a subject may be told that after waking he will perform +some action when a given signal, such as a cough, is repeated for the +fifth time. In the post-hypnotic state he remains unaware of his +instructions, is not conscious of noting the signals, and yet carries +out the suggestion at the fifth signal, thereby proving that the signals +have been in some sense noted and counted. Many interesting varieties of +this experiment have been made, some of much greater complexity; but all +agreeing in indicating that the suggested action is prepared for and +determined by cerebral processes that do not affect the consciousness of +the subject, but seem to occur as a system of processes detached from +the main stream of cerebral activity; that is to say, they imply the +operation of relatively dissociated neural systems. + +Many authorities go further than this; they argue that, since actions of +the kind described are determined by processes which involve operations, +such as counting, that we are accustomed to regard as distinctly mental +in character and that normally involve conscious activity, we must +believe that in these cases also consciousness or psychical activity is +involved, but that it remains as a separate system or stream of +consciousness concurrent with the normal or personal consciousness. + +In recent years the study of various abnormal mental states, especially +the investigations by French physicians of severe forms of hysteria, +have brought to light many facts which seem to justify this assumption +of a secondary stream of consciousness, a co- or sub-consciousness +coexistent with the personal consciousness; although, from the nature of +the case, an absolute proof of such co-consciousness can hardly be +obtained. The co-consciousness seems to vary in degree of complexity and +coherence from a mere succession of fragmentary sensations to an +organized stream of mental activity, which may rival in all respects the +primary consciousness; and in cases of the latter type it is usual to +speak of the presence of a secondary personality. The co-consciousness +seems in the simpler cases, e.g. in cases of hysterical or hypnotic +anaesthesia, to consist of elements split off from the normal primary +consciousness, which remains correspondingly poorer; and the assumption +is usually made that such a stream of co-consciousness is the psychical +correlate of groups and systems of neurones dissociated from the main +mass of cerebral neurones. If, in spite of serious objections, we +entertain this conception, we find that it helps us to give some account +of various hypnotic phenomena that otherwise remain quite inexplicable; +some such conception seems to be required more particularly by the facts +of negative hallucination and the execution of post-hypnotic suggestions +involving such operations as counting and exact discrimination without +primary consciousness. + +_Supernormal Hypnotic Phenomena._--The facts hitherto considered, +strange and perplexing as many of them are, do not seem to demand for +their explanation any principles of action fundamentally different from +those operative in the normal human mind. But much of the interest that +has centred in hypnotism in recent years has been due to the fact that +some of its manifestations seem to go beyond all such principles of +explanation, and to suggest the reality of modes of influence and action +that science has not hitherto recognized. Of these by far the best +attested are the post-hypnotic unconscious reckoning of time and +telepathy or "thought-transference" (for the latter see TELEPATHY). The +post-hypnotic reckoning and noting of the lapse of time seems in some +instances to have been carried out, in the absence of all extraneous +aids and with complete unconsciousness on the part of the normal +personality, with such extreme precision that the achievement cannot be +accounted for by any intensification of any faculty that we at present +recognize or understand. Thus, Dr Milne Bramwell has reported the case +of a patient who, when commanded in hypnosis to perform some simple +action after the lapse of many thousands of minutes, would carry out the +suggestion punctually to the minute, without any means of knowing the +exact time of day at which the suggestion was given or the time of day +at the moment its performance fell due; more recently a similar case, +even more striking in some respects, has been carefully observed and +described by Dr T. W. Mitchell. Other reported phenomena, such as +telaesthesia or clairvoyance, and telekinesia, are hardly sufficiently +well attested to demand serious consideration in this place. + +_Medical Applications of Hypnotism._--The study and practice of +hypnotism is not yet, and probably never will be, regarded as a normal +part of the work of the general practitioner. Its successful application +demands so much time, tact, and special experience, that it will +probably remain, as it is now, and as it is perhaps desirable that it +should remain, a specialized branch of medical practice. In England it +is only in recent years that it has been possible for a medical man to +apply it in his practice without incurring professional odium and some +risk of loss of reputation. That, in certain classes of cases, it may +effect a cure or bring relief when all other modes of treatment are of +no avail is now rapidly becoming recognized; but it is less generally +recognized that it may be used with great advantage as a supplement to +other modes of treatment in relieving symptoms that are accentuated by +nervous irritability or mental disturbance. A third wide field of +usefulness lies before it in the cure of undesirable habits of many +kinds. Under the first heading may be put insomnia, neuralgia, +neurasthenia, hysteria in almost all its many forms; under the second, +inflammations such as that of chronic rheumatism, contractures and +paralyses resulting from gross lesion of the brain, epilepsy, dyspepsia, +menstrual irregularities, sea-sickness; under the third, inebriety, the +morphia and other drug habits, nail-biting, _enuresis nocturna_, +masturbation, constipation, facial and other twitchings. In pronounced +mental diseases hypnotism seems to be almost useless; for in general +terms it may be said that it can be applied most effectively where the +brain, the instrument through which it works, is sound and vigorous. The +widespread prejudice against the use of hypnotism is no doubt largely +due to the marvellous and (to most minds) mysterious character of the +effects producible by its means; and this prejudice may be expected to +diminish as our insight into the mode of its operation deepens. The more +purely bodily results achieved by hypnotic suggestion become in some +degree intelligible if we regard it as a powerful means of diverting +nervous energy from one channel or organ to others, so as to give +physiological rest to an overworked organ or tissue, or so as to lead to +the atrophy of one nervous habit and the replacement of it by a more +desirable habit. And in the cure of those disorders which involve a +large mental element the essential part played by it is to drive out +some habitually recurrent idea and to replace it by some idea, +expectation or conviction of healthy tendency. + +It seems clear that the various systems of "mind-curing" in the hands of +persons lacking all medical training, which are now so frequently the +cause of distressing and needless disasters, owe their rapid spread to +the fact that the medical profession has hitherto neglected to attach +sufficient importance to the mental factor in the causation and cure of +disease; and it seems clear, too, that a more general and more +intelligent appreciation of the possibilities of hypnotic treatment +would constitute the best means at the disposal of the profession for +combating this growing evil. + +_The Dangers of Hypnotism._--Much has been written on this head of late +years, and some of the enthusiastic advocates of hypnotic treatment have +done harm to their cause by ignoring or denying in a too thoroughgoing +manner the possibility of undesirable results of the spread of the +knowledge and practice of hypnotism. Like all powerful agencies, +chloroform or morphia, dynamite or strong electric currents, hypnotic +suggestion can only be safely used by those who have special knowledge +and experience, and, like them, it is liable to abuse. There is little +doubt that, if a subject is repeatedly hypnotized and made to entertain +all kinds of absurd delusions and to carry out very frequently +post-hypnotic suggestions, he may be liable to some ill-defined harm; +also, that an unprincipled hypnotizer might secure an undue influence +over a naturally weak subject. + +But there is no ground for the belief that hypnotic treatment, applied +with good intentions and reasonable care and judgment, does or can +produce deleterious effects, such as weakening of the will or liability +to fall spontaneously into hypnosis. All physicians of large experience +in hypnotic practice are in agreement in respect to this point. But some +difference of opinion exists as to the possibility of deliberately +inducing a subject to commit improper or criminal actions during +hypnosis or by post-hypnotic suggestion. There is, however, no doubt +that subjects retain even in deep hypnosis a very considerable power of +resistance to any suggestion that is repugnant to their moral nature; +and it has been shown that, on some cases in which a subject in hypnosis +is made to perform some ostensibly criminal action, such as firing an +unloaded pistol at a bystander or putting poison into a cup for him to +drink, he is aware, however obscurely, of the unreal nature of the +situation. Nevertheless it must be admitted that a person lacking in +moral sentiments might be induced to commit actions from which in the +normal state he would abstain, if only from fear of punishment; and it +is probable that a skilful and evil-intentioned operator could in some +cases so deceive a well-disposed subject as to lead him into +wrong-doing. The proper precaution against such dangers is legislative +regulation of the practice of hypnotism such as is already enforced in +some countries. + + BIBLIOGRAPHY.--The literature of hypnotism has increased in volume at + a rapid rate during recent years. Of recent writings the following may + be mentioned as among the most important:--_Treatment by Hypnotism and + Suggestion_ by C. Lloyd Tuckey, M.D. (5th ed., London, 1907); + _Hypnotism, its History, Practice and Theory_, by J. Milne Bramwell, + M.B. (2nd ed., London, 1906); _Hypnotism_, by Albert Moll (5th ed., + London, 1901). All these three books give good general accounts of + hypnotism, the first being the most strictly medical, the last the + most general in its treatment. See also _Hypnotism: or Suggestion in + Psycho-Therapy_, by August Forel (translated from the 5th German ed. + by G. H. W. Armit, London, 1906); a number of papers by Ed. Gurney, + and by Ed. Gurney and F. W. H. Myers in _Proc. of the Soc. for + Psychical Research_, especially "The Stages of Hypnotism," in vol. + ii.; also some more recent papers in the same journal by other hands; + chapter on Hypnotism in _Human Personality and its Survival of bodily + Death_, by F. W. H. Myers (London, 1903); _The Psychology of + Suggestion_, by Boris Sidis, Ph.D. (New York, 1898); "Zur Psychologie + der Suggestion," by Prof. Th. Lipp, and other papers in the + _Zeitschrift für Hypnotismus_. Of special historical interest are the + following:--_Étude sur le zoomagnétisme_, par A. A. Liébeault (Paris, + 1883); _Hypnotisme, suggestion, psycho-thérapie_, par Prof. Bernheim + (Paris, 1891); _Braid on Hypnotism_ (a new issue of James Braid's + _Neurypnology_), edited by A. E. Waite (London, 1899); _Traité du + somnambulisme_, by A. Bertrand (Paris, 1826). A full bibliography is + appended to Dr Milne Bramwell's _Hypnotism_. (W. McD.) + + + + +HYPOCAUST (Gr. [Greek: hypokauston: hypo], beneath, and [Greek: kauein], +to burn), the term given to the chamber formed under the floors of the +Roman baths, through which the hot air from the furnace passed, +sometimes to a single flue, as in the case of the _tepidarium_, but in +the _calidarium_ and sweating-room to a series of flues placed side by +side forming the lining of the walls. The floor of the hot-air chamber +consisted of tiles, 2 ft. square, laid on a bed of concrete; on this a +series of dwarf piers 2 ft. high were built of 8-in. square tiles placed +about 16 in. apart, which carried the floor of the hall or room; this +floor was formed of a bed of concrete covered with layers of pounded +bricks and marble cement, on which the marble pavement in slabs or +tesserae was laid. In colder countries, as for instance in Germany and +England, the living rooms were all heated in a similar way, and round +Trèves (Trier) both systems have been found in two or three Roman +villas, with the one flue for the ordinary rooms and several wall flues +for the hot baths. In England these hypocausts are found in every Roman +settlement, and the chief interest in these is centred in the +magnificent mosaic pavements with which the principal rooms were laid. +Many of the pavements found in London and elsewhere have been preserved +in the British or the Guildhall museums; and in some of the provincial +towns, such as Leicester and Lincoln, they remain _in situ_ many feet +below the present level of the town. + + + + +HYPOCHONDRIASIS (synonyms--"the spleen," "the vapours"), a medical term +(from [Greek: to hypochondrion, ta hypochondria], the soft part of the +body immediately under the [Greek: chondros] or cartilage of the +breast-bone) given by the ancients, and indeed by physicians down to the +time of William Cullen, to diseases or derangements of one or more of +the abdominal viscera. Cullen (_Clinical Lectures,_ 1777) classified it +amongst nervous diseases, and Jean Pierre Falret (1794-1870) more fully +described it as a morbid condition of the nervous system characterized +by depression of feeling and false beliefs as to an impaired state of +the health. The subjects of hypochondriasis are for the most part +members of families in which hereditary predisposition to degradation of +the nervous system is strong, or those who have suffered from morbid +influences affecting this system during the earlier years of life. It +may be dependent on depressing disease affecting the general system, but +under such circumstances it is generally so complicated with the +symptoms of hysteria as to render differentiation difficult (see +HYSTERIA). Hypochondriasis is often handed down from one generation to +another in its individual form, but it is also not unfrequently to be +met with in an individual as the sole manifestation in him of a family +tendency to insanity. In its most common form it is manifested by simple +false belief as to the state of the health, the intellect being +otherwise unaffected. We may instance the "vapourish" woman or the +"splenetic" as terms society has applied to its milder manifestations. +Such persons are constantly asserting a weak state of health although no +palpable cause can be discovered. In its more definite phases pain or +uneasy sensations are referred by the patient to some particular region, +generally the abdomen, the heart or the head. That these are subjective +is apparent from the fact that the general health is good: all the +functions of the various systems are duly performed; the patient eats +and sleeps well; and, when any circumstance temporarily overrides the +false belief, he is happy and comfortable. No appeal to the reason is of +any avail, and the hypochondriac idea so dominates his existence as to +render him unable to perform the ordinary duties of life. In its most +aggravated form hypochondriasis amounts to actual insanity, delusions +arising as to the existence of living creatures in the intestines or +brain, or to the effect that the body is materially changed; e.g. into +glass, wood, &c. The symptoms of this condition may be remittent; they +may even disappear for years, and only return on the advent of some +exciting cause. Suicide is occasionally committed in order to escape +from the constant misery. Recovery can only be looked for by placing the +patient under such morally hygienic conditions as may help to turn his +mind to other matters. (See also NEUROPATHOLOGY.) + + + + +HYPOCRISY, pretence, or false assumption of a high character, especially +in regard to religious belief or practice. The Greek [Greek: +hypokrisis], from which the word is derived through the Old French, +meant primarily the acting of a part on the stage, from [Greek: +hypokrinesthai], to give an answer, to speak dialogue, play a part on +the stage, hence to practice dissimulation. + + + + +HYPOSTASIS, in theology, a term frequently occurring in the Trinitarian +controversies of the 4th and 5th centuries. According to Irenaeus (i. 5, +4) it was introduced into theology by Gnostic writers, and in earliest +ecclesiastical usage appears, as among the Stoics, to have been +synonymous with [Greek: ousia]. Thus Dionysius of Rome (cf. Routh, _Rel. +Sacr._ iii. 373) condemns the attempt to sever the Godhead into three +separate _hypostases_ and three deities, and the Nicene Creed in the +anathemas speaks of [Greek: ex heteras hypostaseôs ê ousias]. +Alongside, however, of this persistent interchange there was a desire to +distinguish between the terms, and to confine [Greek: hypostasis] to the +Divine _persons_. This tendency arose in Alexandria, and its progress +may be seen in comparing the early and later writings of Athanasius. +That writer, in view of the Arian trouble, felt that it was better to +speak of [Greek: ousia] as "the common undifferentiated substance of +Deity," and [Greek: hypostasis] as "Deity existing in a personal mode, +the substance of Deity with certain special properties" ([Greek: ousia +meta tinôn idiômatôn]). At the council of Alexandria in 362 the phrase +[Greek: treis hypostaseis] was permitted, and the work of this council +was supplemented by Basil, Gregory of Nazianzus and Gregory of Nyssa in +the formula [Greek: mia ousia, treis hypostaseis] or [Greek: mia ousia +en trisin hypostasesin]. + + The results arrived at by these Cappadocian fathers were stated in a + later age by John of Damascus (_De orth. fid._ iii. 6), quoted in R. + L. Ottley, _The Doctrine of the Incarnation_, ii. 257. + + + + +HYPOSTYLE, in architecture, the term applied to a hall, the flat ceiling +of which is supported by columns, as in the Hall of Columns at Karnak. +In this case the columns flanking the central avenue are of greater +height than those of the side aisles, and this admits of openings in the +wall above the smaller columns, through which light is admitted over the +aisle roof, through clerestory windows. + + + + +HYPOSULPHITE OF SODA, the name originally given to the substance known +in chemistry as sodium thiosulphate, Na2S2O3; the earlier name is still +commonly used, especially by photographers, who employ this chemical as +a fixer. In systematic chemistry, sodium hyposulphite is a salt of +hyposulphurous acid, to which Schutzenberger gave the formula H2SO2, but +which Bernthsen showed to be H2S2O4. (See SULPHUR.) + + + + +HYPOTHEC (Lat. _hypotheca_, Gr. [Greek: hypothêkê]), in Roman law, the +most advanced form of the contract of pledge. A specific thing may be +given absolutely to a creditor on the understanding that it is to be +given back when the creditor's debt is paid; or the property in the +thing may be assigned to the creditor while the debtor is allowed to +remain in possession, the creditor as owner being able to take +possession if his debt is not discharged. Here we have the kind of +security known as pledge and mortgage respectively. In the _hypotheca_, +the property does not pass to the creditor, nor does he get possession, +but he acquires a preferential right to have his debt paid out of the +hypothecated property; that is, he can sell it and pay himself out of +the proceeds, or in default of a purchaser he can become the owner +himself. The name and the principle have passed into the law of +Scotland, which distinguishes between conventional hypothecs, as +_bottomry_ and _respondentia_, and tacit hypothecs established by law. +Of the latter the most important is the landlord's hypothec for rent +(corresponding to distress in the law of England), which extends over +the produce of the land and the cattle and sheep fed on it, and over +stock and horses used in husbandry. The law of agricultural hypothec +long caused much discontent in Scotland; its operation was restricted by +the Hypothec Amendment (Scotland) Act 1867, and finally by the Hypothec +Abolition (Scotland) Act 1880 it was enacted that the "landlord's right +of hypothec for the rent of land, including the rent of any buildings +thereon, exceeding two acres in extent, let for agriculture or pasture, +shall cease and determine." By the same act and by the Agricultural +Holdings (Scotland) Act 1883 other rights and remedies for rent, where +the right of hypothec had ceased, were given to the landlord. + + + + +HYPOTHESIS (from Gr. [Greek: hypotithenai], to put under; cf. Lat. +_suppositio_, from _sub-ponere_), in ordinary language, an explanation, +supposition or assumption, which is put forward in the absence of +ascertained facts or causes. Both in ordinary life and in the +acquisition of scientific knowledge hypothesis is all-important. A +detective's work consists largely in forming and testing hypothesis. If +an astronomer is confronted by some phenomenon which has no obvious +explanation he may postulate some set of conditions which from his +general knowledge of the subject would or might give rise to the +phenomenon in question; he then tests his hypothesis until he discovers +whether it does or does not conflict with the facts. An example of this +process is that of the discovery of the planet Neptune: certain +perturbations of the orbit of Uranus had been observed, and it was seen +that these could be explained on the hypothesis of the existence of a +then unknown planet, and this hypothesis was verified by actual +observation. The progress of inductive knowledge is by the formation of +successive hypotheses, and it frequently happens that the demolition of +one or even many hypotheses is the direct road to a new and accurate +hypothesis, i.e. to fresh knowledge. A hypothesis may, therefore, turn +out to be entirely wrong, yet it may be of the greatest practical use. + +The recognition of the importance of hypotheses has led to various +attempts at drawing up exact rules for their formation, but logicians +are generally agreed that only very elementary principles can be laid +down. Thus a hypothesis must contain nothing which is at variance with +known facts or principles: it should not postulate conditions which +cannot be verified empirically. J. S. Mill (_Logic_ III. xiv. 4) laid +down the principle that a hypothesis is not "genuinely scientific" if it +is "destined always to remain a hypothesis": it must "be of such a +nature as to be either proved or disproved by comparison with observed +facts": in the same spirit Bacon said that in searching for causes in +nature "Deum semper excipimus." Mill's principle, though sound in the +abstract, has, except in a few cases, little practical value in +determining the admissibility of hypotheses, and in practice any rule +which tends to discourage hypothesis is in general undesirable. The most +satisfactory check on hypothesis is expert knowledge in the particular +field of research by which rigorous tests may be applied. This test is +roughly of two kinds, first by the ultimate principles or +presuppositions on which a particular branch of knowledge rests, and +second by the comparison of correlative facts. Useful light is shed on +this distinction by Lotze, who contrasts (_Logic_, § 273) _postulates_ +("absolutely necessary assumptions without which the content of the +observation with which we are dealing would contradict the laws of our +thought") with _hypotheses_, which he defines as conjectures, which seek +"to fill up the postulate thus abstractly stated by specifying the +concrete causes, forces or processes, out of which the given phenomenon +really arose in this particular case, while in other cases maybe the +same postulate is to be satisfied by utterly different though equivalent +combinations of forces or active elements." Thus a hypothesis may be +ruled out by principles or postulates without any reference to the +concrete facts which belong to that division of the subject to explain +which the hypothesis is formulated. A true hypothesis, therefore, seeks +not merely to connect or colligate two separate facts, but to do this in +the light of and subject to certain fundamental principles. Various +attempts have been made to classify hypotheses and to distinguish +"hypothesis" from a "theory" or a mere "conjecture": none of these have +any great practical importance, the differences being only in degree, +not in kind. + +The adjective "hypothetical" is used, in the same sense, both loosely in +contradistinction to "real" or "actual," and technically in the phrases +"hypothetical judgment" and "hypothetical syllogism." (See LOGIC and +SYLLOGISM.) + + See Naville, _La Logique de l'hypothèse_ (1880), and textbooks of + logic, e.g. those of Jevons, Bosanquet, Joseph; Liebmann, _Der Klimax + d. Theorien_. + + + + +HYPOTRACHELIUM (Gr. [Greek: hypotrachêlion], the lower part of the neck, +[Greek: trachêlos]), in classical architecture, the space between the +annulet of the echinus and the upper bed of the shafts, including, +according to C. R. Cockerell, the three grooves or sinkings found in +some of the older examples, as in the temple of Neptune at Paestum and +the temple of Aphaea at Aegina; there being only one groove in the +Parthenon, the Theseum and later examples. In the temple of Ceres and +the so-called Basilica at Paestum the hypotrachelium consists of a +concave sinking carved with vertical lines suggestive of leaves, the +tops of which project forward. A similar decoration is found in the +capital of the columns flanking the tomb of Agamemnon at Mycenae, but +here the hypotrachelium projects forward with a cavetto moulding, and is +carved with triple leaves like the buds of a rose. In the Roman Doric +Order the term was sometimes applied to that which is generally known as +the "necking," the space between the fillet and the annulet. + + + + +HYPSOMETER (Gr. [Greek: hypsos], height, [Greek: metron], a measure), an +instrument for measuring heights which employs the principles that the +boiling-point of a liquid is lowered by diminishing the pressure, and +that the barometric pressure varies with the height of the point of +observation. The instrument consists of a cylindrical vessel in which +the liquid, usually water, is boiled, surmounted by a jacketed column, +in the outer partitions of which the vapour circulates, while in the +central one a thermometer is placed. To deduce the height of the station +from the observed boiling-point, it is necessary to know the relation +existing between the boiling-point and pressure, and also between the +pressure and height of the atmosphere. + + + + +HYRACOIDEA, a suborder of ungulate mammals represented at the present +day only by the Syrian hyrax (_Procavia syriaca_), the "coney" of the +Bible, and its numerous African relatives, all of which may be included +in the single genus _Procavia_ (or _Hyrax_), and consequently in the +family _Procaviidae_. These creatures have no proper English name, and +are generally known as hyraxes, from the scientific term (_Hyrax_) by +which they were for many years designated--a term which has +unfortunately had to give place to the earlier _Procavia_. In size these +animals may be compared roughly to rabbits and hares; and they have +rodent-like habits, hunching up their backs after the fashion of some +foreign members of the hare-family, more especially the Liu-Kiu rabbit. +In the matter of nomenclature these animals have been singularly +unfortunate. In the title "hyrax" they have, for instance, usurped the +Greek name for the shrew-mouse; while in the Bible they have been given +the old English name for the rabbit. Perhaps rock-rabbit would be the +best name. At the Cape they are known to the Dutch as dass (badger), +which has been anglicized into "dassie." + +[Illustration: FIG. 1.--The Cape Hyrax (_Procavia capensis_).] + + As regards the recent forms, the dentition in the fully adult animal + consists only of incisors and cheek-teeth, the formula being _i._ ½, + _c._ 0/0, _p._ 4/4 _m._ 3/3. There is, however, a minute upper canine + developed at first, which is early shed; and in extinct forms this + tooth was functional and molar-like. The upper incisors have + persistent pulps, and are curved longitudinally, forming a semicircle + as in rodents; they are, however, not flattened from before backwards + as in that order, but prismatic, with an antero-external, an + antero-internal and a posterior surface, the first two only being + covered with enamel; their tips are consequently not chisel-shaped, + but sharp-pointed. They are preceded by functional, rooted milk-teeth. + The lower incisors have long tapering roots, but not of persistent + growth; and are straight, directed somewhat forwards, with awl-shaped, + tri-lobed crowns. Behind the incisors is a considerable gap, followed + by the cheek-teeth, which are all contiguous, and formed almost + exactly on the pattern of some of the perissodactyle ungulates. The + milk-dentition includes three pairs of incisors and one of canines in + each jaw. The hyoid arch is unlike that of any known mammal. The + dorsal and lumbar vertebrae are very numerous, 28 to 30, of which 21 + or 22 bear ribs. The tail is extremely short. There are no clavicles. + In the fore foot, the three middle toes are subequally developed, the + fifth is present, but smaller, and the first is rudimentary, although, + in one species at least, all its normal bones are present. The + terminal phalanges of the four outer digits are small, somewhat + conical and flattened in form. The carpus has a distinct os centrale. + There is a slight ridge on the femur in the place of a third + trochanter. The fibula is complete, thickest at its upper end, where + it generally unites with the tibia. The articulation between the tibia + and astragalus is more complex than in other mammals, the end of the + malleolus entering into it. The hind-foot is very like that of a + rhinoceros, having three well-developed toes. There is no trace of a + first toe, and the fifth meta-tarsal is represented by a small nodule. + The terminal phalange of the inner (or second) digit is deeply cleft, + and has a peculiar long curved claw, the others having short broad + nails. The stomach is formed upon much the same principle as that of + the horse or rhinoceros, but is more elongated transversely and + divided by a constriction into two cavities--a large left _cul de + sac_, lined by a very dense white epithelium, and a right pyloric + cavity, with a thick, soft, vascular lining. The intestinal canal is + long, and has, in addition to the ordinary short, but capacious and + sacculated caecum at the commencement of the colon, lower down, a pair + of large, conical, pointed caeca. The liver is much subdivided, and + there is no gall-bladder. The brain resembles that of typical + ungulates far more than that of rodents. The testes are permanently + abdominal. The ureters open into the fundus of the bladder as in some + Rodents. The female has six teats, of which four are inguinal and two + axillary, and the placenta is zonary and deciduous. There is a gland + on the back. + + [Illustration: FIG. 2.--Skull and Dentition of Tree-Hyrax (_Procavia + dorsalis_).] + + The more typical members of the genus are terrestrial in their habits, + and their cheek-teeth have nearly the same pattern as in rhinoceroses; + while the interval between the upper incisors is less than the width + of the teeth; and the lower incisors are only slightly notched at the + cutting edge. Vertebrae: C. 7, D. 22, L. 8, S. 6, C. 6. Of this form + the earliest known species, _P. capensis_, is the type; but there are + many other species, as _P. syriaca_, and _P. brucei_ from Syria and + eastern Africa. They inhabit mountainous and rocky regions, and live + on the ground. In a second section the molar teeth have the same + pattern as in _Palaeotherium_ (except that the third lower molar has + but two lobes); the interval between the upper incisors exceeds the + width of the teeth; and the lower incisors have distinctly tri-lobed + crowns. Vertebrae: C. 7, D. 21, L. 7, S. 5, C. 10. The members of this + section frequent the trunks and large branches of trees, sleeping in + holes. There are several species from Western and South Africa, as _P. + arboreus_ and _P. dorsalis_. The members of both groups appear to have + a power like that possessed by geckos of clinging to vertical surfaces + of rocks and trees by the soles of their feet. + + _Extinct Hyracoids._--For many years extinct representatives of the + Hyracoidea were unknown, partly owing to the fact that certain fossils + were not recognized as really belonging to that group. The longest + known of these was originally named _Leptodon graecus_, but, on + account of the preoccupation of the generic title, the designation has + been changed to _Pliohyrax graecus_. This animal, whose remains occur + in the Lower Pliocene of both Attica and Samos, was about the size of + a donkey, and possessed three pairs of upper incisor teeth, of which + the innermost were large and trihedral, recalling those of the + existing genus. On the other hand, the two outer pairs of incisors + were in contact with one another and with the canines, so as to form + on each side a series continuous with the cheek-teeth. + + The next representatives of the group occur in the Upper Eocene beds + of the Fayum district of Egypt, where the genera _Saghatherium_ and + _Megalohyrax_ occur. These are regarded as representing a distinct + family, the _Saghatheriidae_, characterized by the possession of the + full series of twenty-two teeth in the upper jaw, among which the + first pair of incisors was modified to form trihedral rootless tusks, + while the two remaining pairs were separated from one another and from + the teeth in front by gaps. The canine was like a premolar, and in + contact with the first tooth of that series; and the cheek-teeth were + short-crowned, with the premolar simpler than the molars, and a third + lobe to the last lower tooth of the latter series. The members of + this genus were small or medium-sized ungulates with single-rooted + incisors. On the other hand, the representatives of the contemporary + genus _Megalohyrax_ were approximately as large as _Pliohyrax_, and in + some instances had double roots to the second and third incisors. + + It is now possible to define the suborder Hyracoidea as including + ungulates with a centrale in the carpus, plantigrade feet, in which + the first and fifth toes are reduced in greater or less degree, and + clavicles and a foramen in the lower end of the humerus are absent. + The femur has a small third trochanter, the radius and ulna and tibia + and fibula are respectively separate, at least in the young, and the + fibula articulates with the astragalus. The earlier forms had the full + series of 44 teeth, with the premolars simpler than the molars; but in + the later types the canines and some of the incisors disappear, and at + least the hinder premolars become molar-like. In all cases the first + upper incisors are large and rootless. + + That the group originated in Africa there can be no reasonable doubt; + and it is remarkable that so early as the Upper Eocene the types in + existence differed comparatively little in structure from the modern + forms. In fact the hyraxes were then almost as distinct from other + mammals as they are at the present day. + + See also C. W. Andrews, _Descriptive Catalogue of the Tertiary + Vertebrata of the Fayum_, British Museum (1906). (R. L.*) + + + + +HYRCANIA. (1) An ancient district of Asia, south of the Caspian Sea, and +bounded on the E. by the river Oxus, called _Virkana_, or "Wolf's Land," +in Old Persian. It was a wide and indefinite tract. Its chief city is +called Tape by Strabo, Zadracarta by Arrian (probably the modern +Astarabad). The latter is evidently the same as Carta, mentioned by +Strabo as an important city. Little is known of the history of the +country. Xenophon says it was subdued by the Assyrians; Curtius that +6000 Hyrcanians were in the army of Darius III. (2) Two towns named +Hyrcania are mentioned, one in Hyrcania, the other in Lydia. The latter +is said to have derived its name from a colony of Hyrcanians, +transported thither by the Persians. + + + + +HYRCANUS ([Greek: Hykanos]), a Greek surname, of unknown origin, borne +by several Jews of the Maccabaean period. + +JOHN HYRCANUS I., high priest of the Jews from 135 to 105 B.C., was the +youngest son of Simon Maccabaeus. In 137 B.C. he, along with his brother +Judas, commanded the force which repelled the invasion of Judaea led by +Cendebeus, the general of Antiochus VII. _Sidetes_. On the assassination +of his father and two elder brothers by Ptolemy, governor of Jericho, +his brother-in-law, in February 135, he succeeded to the high priesthood +and the supreme authority in Judaea. While still engaged in the struggle +with Ptolemy, he was attacked by Antiochus with a large army (134), and +compelled to shut himself up in Jerusalem; after a severe siege peace +was at last secured only on condition of a Jewish disarmament, and the +payment of an indemnity and an annual tribute, for which hostages were +taken. In 129 he accompanied Antiochus as a vassal prince on his +ill-fated Parthian expedition; returning, however, to Judaea before +winter, he escaped the final disaster. By the judicious mission of an +embassy to Rome he now obtained confirmation of the alliance which his +father had previously made with the growing western power; at the same +time he availed himself of the weakened state of the Syrian monarchy +under Demetrius II. to overrun Samaria, and also to invade Idumaea, +which he completely subdued, compelling its inhabitants to receive +circumcision and accept the Jewish faith. After a long period of rest he +directed his arms against the town of Samaria, which, in spite of the +intervention of Antiochus, his sons Antigonus and Aristobulus ultimately +took, and by his orders razed to the ground (c. 100 B.C.). He died in +105, and was succeeded by Aristobulus, the eldest of his five sons. The +external policy of Hyrcanus was marked by considerable energy and tact, +and, aided as it was by favouring circumstances, was so successful as to +leave the Jewish nation in a position of independence and of influence +such as it had not known since the days of Solomon. During its later +years his reign was much disturbed, however, by the contentions for +ascendancy which arose between the Pharisees and Sadducees, the two +rival sects or parties which then for the first time (under those names +at least) came into prominence. Josephus has related the curious +circumstances under which he ultimately transferred his personal support +from the former to the latter. + +JOHN HYRCANUS II., high priest from 78 to 40 B.C., was the eldest son of +Alexander Jannaeus by his wife Alexandra, and was thus a grandson of the +preceding. When his father died in 78, he was by his mother forthwith +appointed high priest, and on her death in 69 he claimed the succession +to the supreme civil authority also; but, after a brief and troubled +reign of three months, he was compelled to abdicate both kingly and +priestly dignities in favour of his more energetic and ambitious younger +brother Aristobulus II. In 63 it suited the policy of Pompey that he +should be restored to the high priesthood, with some semblance of +supreme command, but of much of this semblance even he was soon again +deprived by the arrangement of the pro-consul Gabinius, according to +which Palestine was in 57 B.C. divided into five separate circles +([Greek: synodoi, synedria]). For services rendered to Caesar after the +battle of Pharsalia, he was again rewarded with the sovereignty ([Greek: +prostasia tou ethnous], Jos. _Ant._ xx. 10) in 47 B.C., Antipater of +Idumaea, however, being at the same time made procurator of Judaea. In +41 B.C. he was practically superseded by Antony's appointment of Herod +and Phasael to be tetrarchs of Judaea; and in the following year he was +taken prisoner by the Parthians, deprived of his ears that he might be +permanently disqualified for priestly office, and carried to Babylon. He +was permitted in 33 B.C. to return to Jerusalem, where on a charge of +treasonable correspondence with Malchus, king of Arabia, he was put to +death in 30 B.C. + + See Josephus (_Ant._ xiii. 8-10; xiv. 5-13; _Bell. Jud._ i. 2; i. + 8-13). Also MACCABEES, _History_. (J. H. A. H.) + + + + +HYSSOP (_Hyssopus officinalis_), a garden herb belonging to the natural +order _Labiatae_, formerly cultivated for use in domestic medicine. It +is a small perennial plant about 2 ft. high, with slender, quadrangular, +woody stems; narrowly elliptical, pointed, entire, dotted leaves, about +1 in. long and 1/3 in. wide, growing in pairs on the stem; and long +terminal, erect, half-whorled, leafy spikes of small violet-blue +flowers, which are in blossom from June to September. Varieties of the +plant occur in gardens with red and white flowers, also one having +variegated leaves. The leaves have a warm, aromatic, bitter taste, and +are believed to owe their properties to a volatile oil which is present +in the proportion of ¼ to ½%. Hyssop is a native of the south of Europe, +its range extending eastward to central Asia. A strong tea made of the +leaves, and sweetened with honey, was formerly used in pulmonary and +catarrhal affections, and externally as an application to bruises and +indolent swellings. + +The hedge hyssop (_Gratiola officinalis_) belongs to the natural order +_Scrophulariaceae_, and is a native of marshy lands in the south of +Europe, whence it was introduced into Britain more than 300 years ago. +Like _Hyssopus officinalis_, it has smooth opposite entire leaves, but +the stems are cylindrical, the leaves twice the size, and the flowers +solitary in the axils of the leaves and having a yellowish-red veined +tube and bluish-white limb, while the capsules are oval and many-seeded. +The herb has a bitter, nauseous taste, but is almost odourless. In small +quantities it acts as a purgative, diuretic and emetic when taken +internally. It was formerly official in the Edinburgh Pharmacopoeia, +being esteemed as a remedy for dropsy. It is said to have formed the +basis of a celebrated nostrum for gout, called _Eau médicinale_, and in +former times was called _Gratia Dei_. When growing in abundance, as it +does in some damp pastures in Switzerland, it becomes dangerous to +cattle. G. _peruviana_ is known to possess similar properties. + + The hyssop (_'ezob_) of Scripture (Ex. xii. 22; Lev. xiv. 4, 6; Numb. + xix. 6, 18; 1 Kings v. 13 (iv. 33); Ps. li. 9 (7); John xix. 29), a + wall-growing plant adapted for sprinkling purposes, has long been the + subject of learned disputation, the only point on which all have + agreed being that it is not to be identified with the _Hyssopus + officinalis_, which is not a native of Palestine. No fewer than + eighteen plants have been supposed by various authors to answer the + conditions, and Celsius has devoted more than forty pages to the + discussion of their several claims. By Tristram (_Oxford Bible for + Teachers_, 1880) and others the caper plant (_Capparis spinosa_) is + supposed to be meant; but, apart from other difficulties, this + identification is open to the objection that the caper seems to be, at + least in one passage (Eccl. xii. 5), otherwise designated + (_'abiy-yônah_). Thenius (on 1 Kings v. 13) suggests _Orthotrichum + saxatile_. The most probable opinion would seem to be that found in + Maimonides and many later writers, according to which the Hebrew + _'ezob_ is to be identified with the Arabic _sa'atar_, now understood + to be _Satureja Thymus_, a plant of very frequent occurrence in Syria + and Palestine, with which _Thymus Serpyllum_, or wild thyme, and + _Satureja Thymbra_ are closely allied. Its smell, taste and medicinal + properties are similar to those of _H. officinalis_. In Morocco the + _sa'atar_ of the Arabs is _Origanum compactum_; and it appears + probable that several plants of the genera _Thymus_, _Origanum_ and + others nearly allied in form and habit, and found in similar + localities, were used under the name of hyssop. + + + + +HYSTASPES (the Greek form of the Persian _Vishtaspa_). (1) A +semi-legendary king (_kava_), praised by Zoroaster as his protector and +a true believer, son of Aurvataspa (Lohrasp). The later tradition and +the Shahname of Firdousi makes him (in the modern form Kai Gushtasp) +king of Iran. As Zoroaster probably preached his religion in eastern +Iran, Vishtaspa must have been a dynast in Bactria or Sogdiana. The +Zoroastrian religion was already dominant in Media in the time of the +Assyrian king Sargon (c. 715 B.C.), and had been propagated here +probably in much earlier times (cf. PERSIA); the time of Zoroaster and +Vishtaspa may therefore be put at c. 1000 B.C. (2) A Persian, father of +Darius I., under whose reign he was governor of Parthia, as Darius +himself mentions in the Behistun inscription (2. 65). By Ammianus +Marcellinus, xxiii. 6. 32, and by many modern authors he has been +identified with the protector of Zoroaster, which is equally impossible +for chronological and historical reasons, and from the evidence of the +development of Zoroastrianism itself (see PERSIA: _Ancient History_). + (Ed. M.) + + + + +HYSTERESIS (Gr. [Greek: hysterêsis], from [Greek: hysterein], to lag +behind), a term added to the vocabulary of physical science by J. A. +Ewing, who defines it as follows: When there are two qualities M and N +such that cyclic variations of N cause cyclic variations of M, then if +the changes of M lag behind those of N, we may say that there is +hysteresis in the relation of M to N (_Phil. Trans._, 1885, 176, p. +524). The phenomenon is best known in connexion with magnetism. If an +iron bar is subjected to a magnetic force which is first gradually +increased to a maximum and then gradually diminished, the resulting +magnetization of the bar for any given value of the magnetic force will +be greater when the force is decreasing than when it is increasing; the +iron always tends to retain the magnetic condition which it has +previously acquired, and changes of its magnetization consequently lag +behind changes of the magnetic force. Thus there is hysteresis in the +relation of magnetization to magnetic force. In consequence of +hysteresis the process of magnetizing a piece of iron to a certain +intensity and then restoring it to its original condition, or of +effecting a double reversal of its magnetization, involves the +expenditure of energy, which is dissipated as heat in the iron. +Electrical generators and transformers often contain pieces of iron the +magnetization of which is reversed many times in a second, and in order +to economize power and to avoid undue heating it is essential that +hysteresis should in such cases be as small as possible. Iron and mild +steels showing remarkably little hysteresis are now specially +manufactured for use in the construction of electrical machinery. (See +MAGNETISM.) + + + + +HYSTERIA, a term applied to an affection which may manifest itself by a +variety of symptoms, and which depends upon a disordered condition of +the highest nervous centres. It is characterized by psychical +peculiarities, while in addition there is often derangement of the +functions subserved by the lower cerebral and spinal centres. +Histological examination of the nervous system has failed to disclose +associated structural alterations. + +By the ancients and by modern physicians down to the time of Sydenham +the symptoms of hysteria were supposed to be directly due to +disturbances of the uterus (Gr. [Greek: hystera], whence the name). This +view is now universally recognized to be erroneous. The term +"functional" is often used by English neurologists as synonymous with +hysterical, a nomenclature which is tentatively advantageous since it is +at least non-committal. P. J. Möbius has defined hysteria as "a state in +which ideas control the body and produce morbid changes in its +functions." P. Janet, who has done much to popularize the psychical +origin of the affection, holds that there is "a limitation of the field +of consciousness" comparable to the contraction of the visual fields met +with in the disease. The hysterical subject, according to this view, is +incapable of taking into the field of consciousness all the impressions +of which the normal individual is conscious. Strong momentary +impressions are no longer controlled so efficiently because of the +defective simultaneous impressions of previous memories. Hence the +readiness with which the impulse of the moment is obeyed, the loss of +emotional control and the increased susceptibility to external +suggestion, which are so characteristic. A secondary subconscious mental +state is engendered by the relegation of less prominent impressions to a +lower sphere. The dual personality which is typically exemplified in +somnambulism and in the hypnotic state is thus induced. The explanation +of hysterical symptoms which are independent of the will, and of the +existence of which the individual may be unaware, is to be found in a +relative preponderance of this secondary subconscious state as compared +with the primary conscious personality. An elaboration of this theory +affords an explanation of hysterical symptoms dependent upon a "fixed +idea." The following definition of hysteria has recently been advanced +by J. F. F. Babinski: "Hysteria is a psychical condition manifesting +itself principally by signs that may be termed primary, and in an +accessory sense others that we may call secondary. The characteristic of +the primary signs is that they may be exactly reproduced in certain +subjects by suggestion and dispelled by persuasion. The characteristic +of the secondary signs is that they are closely related to the primary +phenomena." + +The causes of hysteria may be divided into (a) the predisposing, such as +hereditary predisposition to nervous disease, sex, age and national +idiosyncrasy; and (b) the immediate, such as mental and physical +exhaustion, fright and other emotional influences, pregnancy, the +puerperal condition, diseases of the uterus and its appendages, and the +depressing influence of injury or general disease. Perhaps, taken over +all, hereditary predisposition to nerve-instability may be asserted as +the most prolific cause. There is frequently direct inheritance, and +cases of epilepsy and insanity or other form of nervous disease are +rarely wanting when the family history is carefully enquired into. As +regards age, the condition is apt to appear at the evolution periods of +life--puberty, pregnancy and the climacteric--without any further +assignable cause except that first spoken of. It is rare in young +children, but very frequent in girls between the ages of fifteen and +twenty-five, while it sometimes manifests itself in women at the +menopause. It is much more common in the female than in the male--in the +proportion of 20 to 1. Certain races are more liable to the disease than +others; thus the Latin races are much more prone to hysteria than are +those who come of a Teutonic stock, and in more aggravated and complex +forms. In England it has been asserted that an undue proportion of cases +occur among Jews. Occupation, or be it rather said want of occupation, +is a prolific cause. This is noticeable more especially in the higher +classes of society. + +An hysterical attack may occur as an immediate sequel to an epileptic +fit. If the patient suffers only from _petit mal_ (see EPILEPSY), +unaccompanied by true epileptic fits, the significance of the hysterical +seizure, which is really a post-epileptic phenomenon, may remain +unrecognized. + +It is convenient to group the very varied symptoms of hysteria into +paroxysmal and chronic. The popular term "hysterics" is applied to an +explosion of emotionalism, generally the result of mental excitement, on +which convulsive fits may supervene. The characters of these vary, and +may closely resemble epilepsy. The hysterical fit is generally preceded +by an aura or warning. This sometimes takes the form of a sensation as +of a lump in the throat (_globus hystericus_). The patient may fall, but +very rarely is injured in so doing. The eyes are often tightly closed, +the body and limbs become rigid, and the back may become so arched that +the patient rests on her heels and head (_opisthotonos_). This stage is +usually followed by violent struggling movements. There is no loss of +consciousness. The attack may last for half-an-hour or even longer. +Hysterical fits in their fully-developed form are rarely seen in +England, though common in France. In the chronic condition we find an +extraordinary complexity of symptoms, both physical and mental. The +physical symptoms are extremely diverse. There may be a paralysis of one +or more limbs associated with rigidity, which may persist for weeks, +months or years. In some cases, the patient is unable to walk; in others +there are peculiarities of the gait quite unlike anything met with in +organic disease. Perversions of sensation are usually present; a common +instance is the sensation of a nail being driven through the vertex of +the head (_clavus hystericus_). The region of the spine is a very +frequent seat of hysterical pain. Loss of sensation (_anaesthesia_), of +which the patient may be unaware, is of common occurrence. Very often +this sensory loss is limited exactly to one-half of the body, including +the leg, arm and face on that side (_hemianaesthesia_). Sensation to +touch, pain, heat and cold, and electrical stimuli may have completely +disappeared in the anaesthetic region. In other cases, the anaesthesia +is relative or it may be partial, certain forms of sensation remaining +intact. Anaesthesia is almost always accompanied by an inability to +recognize the exact position of the affected limb when the eyes are +closed. When hemianaesthesia is present, sight, hearing, taste and smell +are usually impaired on that side of the body. Often there is loss of +voice (hysterical aphonia). It is to such cases of hysterical paralysis +and sensory disturbance that the wonderful cures effected by quacks and +charlatans may be referred. The mental symptoms have not the same +tendency to pass away suddenly. They may be spoken of as +inter-paroxysmal and paroxysmal. The chief characteristics of the former +are extreme emotionalism combined with obstructiveness, a desire to be +an object of interest and a constant craving for sympathy which is often +procured at an immense sacrifice of personal comfort. Obstructiveness is +the invariable symptom. Hysteria may pass into absolute insanity. + +The treatment of hysteria demands great tact and firmness on the part of +the physician. The affection is a definite entity and has to be clearly +distinguished from malingering, with which it is so often erroneously +regarded as synonymous. Drugs are of little value. The moral treatment +is all-important. In severe cases, removal from home surroundings and +isolation, either in a hospital ward or nursing home, are essential, in +order that full benefit may be derived from psychotherapeutic measures. + + BIBLIOGRAPHY.--Charcot, _Leçons sur les maladies du système nerveuse_ + (1877); S. Weir Mitchell, _Lectures on Diseases of the Nervous System + especially in Women_ (1885); Buzzard, _Simulation of Hysteria by + Organic Nervous Disease_ (1891); Pitres, _Leçons cliniques sur + l'hystérie et l'hypnotisme_ (1891); Richer, _Études cliniques sur la + grande hystérie_ (1891); Gilles de la Tourette, _Traité clinique et + thérapeutique de l'hystérie_ (1891); Bastian, _Hysterical or + Functional Paralysis_ (1893); Ormerod, Art. "Hysteria," in Clifford + Allbutt's _System of Medicine_ (1899); Camus and Pagnez, _Isolement et + Psychotherapie_ (1904). (J. B. T.; E. Bra.) + + + + +HYSTERON-PROTERON (Gr. [Greek: hysteron], latter, and [Greek: proteron], +former), a figure of speech, in which the order of words or phrases is +inverted, and that which should logically or naturally come last is put +first, to secure emphasis for the principal idea; the classical example +is Virgil's "_moriamur et in media arma ruamus,_" "let us die and charge +into the thick of the fight" (Aen. ii. 358). The term is also applied to +any inversion in order of events, arguments, &c. + + + + +HYTHE, a market town and watering-place, one of the Cinque Ports, and a +municipal and parliamentary borough of Kent, England, 67 m. S.E. by E. +of London on a branch of the South Eastern & Chatham railway. Pop. +(1901) 5557. It is beautifully situated at the foot of a steep hill near +the eastern extremity of Romney Marsh, about half a mile from the sea, +and consists principally of one long street running parallel with the +shore, with which it is connected by a straight avenue of wych elms. On +account of its fine situation and picturesque and interesting +neighbourhood, it is a favourite watering-place. A sea-wall and parade +extend eastward to Sandgate, a distance of 3 m. There is communication +with Sandgate by means of a tramway along the front. On the slope of the +hill above the town stands the fine church of St Leonard, partly Late +Norman, with a very beautiful Early English chancel. The tower was +rebuilt about 1750. In a vault under the chancel there is a collection +of human skulls and bones supposed to be the remains of men killed in a +battle near Hythe in 456. Lionel Lukin (1742-1834), inventor of the +life-boat, is buried in the churchyard. Hythe possesses a guildhall +founded in 1794 and two hospitals, that of St Bartholomew founded by +Haimo, bishop of Rochester, in 1336, and that of St John (rebuilt in +1802), of still greater antiquity but unknown date, founded originally +for the reception of lepers. A government school of musketry, in which +instructors for the army are trained, was established in 1854, and has +been extended since, and the Shorncliffe military camp is within 2½ m. +of the town. + +Lympne, which is now 3 m. inland, is thought to have been the original +harbour which gave Hythe a place among the Cinque Ports. The course of +the ancient estuary may be distinctly traced from here along the road to +Hythe, the sea-sand lying on the surface and colouring the soil. Here +are remains of a Roman fortress, and excavations have brought to light +many remains of the Roman _Portus Lemanis_. Large portions of the +fortress walls are standing. At the south-west corner is one of the +circular towers which occurred along the line of wall. The site is now +occupied by the fine old castellated mansion of Studfall castle, +formerly a residence of the archdeacons of Canterbury. The name denotes +a fallen place, and is not infrequently thus applied to ancient remains. +The church at Lympne is Early English, with a Norman tower built by +Archbishop Lanfranc, and Roman material may be traced in the walls. A +short distance east is Shipway or Shepway Cross, where some of the great +assemblies relating to the Cinque Ports were held. A mile north from +Hythe is Saltwood Castle, of very ancient origin, but rebuilt in the +time of Richard II. The castle was granted to the see of Canterbury in +1026, but escheated to the crown in the time of Henry II., when the +murder of Thomas à Beckett is said to have been concerted here, and +having been restored to the archbishops by King John remained a +residence of theirs until the time of Henry VIII. It was restored as a +residence in 1882. About 2 m. N.W. of Saltwood are remains of the +fortified 14th-century manor-house of Westenhanger. It is quadrangular +and surrounded by a moat, and of the nine towers (alternately square and +round) by which the walls were defended, three remain. + +The parliamentary borough of Hythe, which includes Folkestone, Sandgate +and a number of neighbouring villages, returns one member. The town is +governed by a mayor, 4 aldermen and 12 councillors. Area 2617 acres. + +Hythe (Heda, Heya, Hethe, Hithe, _i.e._ landing-place) was known as a +port in Saxon times, and was granted by Halfden, a Saxon thegn, to +Christ Church, Canterbury. In the Domesday Survey the borough is entered +among the archbishop's lands as appurtenant to his manor of Saltwood, +and the bailiff of the town was appointed by the archbishop. Hythe was +evidently a Cinque Port before the Conquest, as King John in 1205 +confirmed the liberties, viz. freedom from toll, the right to be +impleaded only at the Shepway court, &c., which the townsmen had under +Edward the Confessor. The liberties of the Cinque Ports were confirmed +in Magna Carta and later by Edward I. in a general charter, which was +confirmed, often with additions, by subsequent kings down to James II. +John's charter to Hythe was confirmed by Henry IV., Henry V. and Henry +VI. These charters were granted to the Cinque Ports in return for the +fifty-seven ships which they supplied for the royal service, of which +five were contributed by Hythe. The ports were first represented in the +parliament of 1365, to which they each sent four members. + +Hythe was governed by twelve jurats until 1574, when it was incorporated +by Elizabeth under the title of the mayor, jurats and commonalty of +Hythe; a fair for the sale of fish, &c., was also granted, to be held on +the feast of St Peter and St Paul. As the sea gradually retreated from +Hythe and the harbour became choked up with sand, the town suffered the +fate of other places near it, and lost its old importance. + + + + +I the ninth letter of the English and Latin alphabet, the tenth in the +Greek and Phoenician, because in these the symbol Teth (the Greek +[theta]) preceded it. Teth was not included in the Latin alphabet +because that language had no sound corresponding to the Greek [theta], +but the symbol was metamorphosed and utilized as the numeral C = 100, +which took this form through the influence of the initial letter of the +Latin _centum_. The name of I in the Phoenician alphabet was _Yod_. +Though in form it seems the simplest of letters it was originally much +more complex. In Phoenician it takes the form [symbol], which is found +also in the earliest Syriac and Palestinian inscriptions with little +modification. Ultimately in Hebrew it became reduced to a very small +symbol, whence comes its use as a term of contempt for things of no +importance as in "not one _jot_ or tittle" (Matthew v. 18). The name +passed from Phoenician to Greek, and thence to the Latin of the vulgate +as _iota_, and from the Latin the English word is derived. Amongst the +Greeks of Asia it appears only as the simple upright I, but in some of +the oldest alphabets elsewhere, as Crete, Thera, Attica, Achaia and its +colonies in lower Italy, it takes the form [symbol] or S, while at +Corinth and Corcyra it appears first in a form closely resembling the +later Greek _sigma_ [Sigma]. It had originally no cross-stroke at top +and bottom. I being not _i_ but _z_. The Phoenician alphabet having no +vowel symbols, the value of _yod_ was that of the English _y_. In Greek, +where the consonant sound had disappeared or been converted into _h_, I +is regularly used as a vowel. Occasionally, as in Pamphylian, it is used +dialectically as a glide between _i_ and another vowel, as in the proper +name [Greek: Damatriius]. In Latin I was used alike for both vowel and +consonant, as in _iugum_ (yoke). The sound represented by it was +approximately that still assigned to _i_ on the continent. Neither Greek +nor Latin made any distinction in writing between short and long _i_, +though in the Latin of the Empire the long sound was occasionally +represented by a longer form of the symbol I. The dot over the _i_ +begins in the 5th or 6th century A.D. In pronunciation the English short +_i_ is a more open sound than that of most languages, and does not +correspond to the Greek and Latin sound. Nor are the English short and +long _i_ of the same quality. The short _i_ in Sweet's terminology is a +high-front-wide vowel, the long _i_, in English often spelt _ee_ in +words like _seed_, is diphthonged, beginning like the short vowel but +becoming higher as it proceeds. The Latin short _i_, however, in final +syllables was open and ultimately became _e_, e.g. in the neuter of +_i_-stems as _utile_ from _utili-s_. Medially both the short and the +long sounds are very common in syllables which were originally +unaccented, because in such positions many other sounds passed into _i_: +_officio_ but _facio_, _redimo_ but _emo_, _quidlibet_ but _lubet_ +(_libet_ is later); _collido_ but _laedo_, _fido_ from an older _feido_, +_istis_ (dative plural) from an earlier _istois_. (P. Gi.) + + + + +IAMBIC, the term employed in prosody to denote a succession of verses, +each consisting of a foot or metre called an iambus ([Greek: iambos]), +formed of two syllables, of which the first is short and the second long +(u --). After the dactylic hexameter, the iambic trimeter was the most +popular metre of ancient Greece. Archilochus is said to have been the +inventor of this iambic verse, the [Greek: trimetros] consisting of +three iambic fed. In the Greek tragedians an iambic line is formed of +six feet arranged in obedience to the following scheme:-- + + u -- | u -- | u -- | u -- | u -- | u -- | + u u u | u u u | u u u | u u u | u u u | | + -- -- | | -- -- | | -- -- | | + -- u u | | -- u u | | | | + u u -- | | | | | | + +Much of the beauty of the verse depends on the caesura, which is usually +In the middle of the third foot, and far less frequently in the middle +of the fourth. The English language runs more naturally in the iambic +metre than in any other. The normal blank verse in English is founded +upon an iambic basis, and Milton's line-- + + And swims | or sinks | or wades | or creeps | or flies | -- + +exhibits it in its primitive form. The ordinary alexandrine of French +literature is a hexapod iambic, but in all questions of quantity in +modern prosody great care has to be exercised to recollect that all +ascriptions of classic names to modern forms of rhymed or blank verse +are merely approximate. The octosyllabic, or four-foot iambic metre, has +found great favour in English verse founded on old romances. +Decasyllabic iambic lines rhyming together form an "heroic" metre. + + + + +IAMBLICHUS (d. c. A.D. 330), the chief representative of Syrian +Neoplatonism, is only imperfectly known to us in the events of his life +and the details of his creed. We learn, however, from Suidas, and from +his biographer Eunapius, that he was born at Chalcis in Coele-Syria, the +scion of a rich and illustrious family, that he studied under Anatolius +and afterwards under Porphyry, the pupil of Plotinus, that he himself +gathered together a large number of disciples of different nations with +whom he lived on terms of genial friendship, that he wrote "various +philosophical books," and that he died during the reign of +Constantine,--according to Fabricius, before A.D. 333. His residence +(probably) at his native town of Chalcis was varied by a yearly visit +with his pupils to the baths of Gadara. Of the books referred to by +Suidas only a fraction has been preserved. His commentaries on Plato and +Aristotle, and works on the Chaldaean theology and on the soul, are +lost. For our knowledge of his system we are indebted partly to the +fragments of these writings preserved by Stobaeus and others, and to the +notices of his successors, especially Proclus, partly to his five extant +books, the sections of a great work on the Pythagorean philosophy. +Besides these, Proclus (412-485) seems to have ascribed to him[1] the +authorship of the celebrated book _On the Egyptian Mysteries_ +(so-called), and although its differences in style and in some points of +doctrine from the writings just mentioned make it improbable that the +work was by Iamblichus himself, it certainly emanated from his school, +and in its systematic attempt to give a speculative justification of the +polytheistic cultus of the day, marks the turning-point in the history +of thought at which Iamblichus stood. + +As a speculative theory Neoplatonism (q.v.) had received its highest +development from Plotinus. The modifications introduced by Iamblichus +were the elaboration in greater detail of its formal divisions, the more +systematic application of the Pythagorean number-symbolism, and chiefly, +under the influence of Oriental systems, the thorough-going mythic +interpretation of what the previous philosophy had still regarded as +notional. It is on the last account, probably, that Iamblichus was +looked upon with such extravagant veneration. As a philosopher he had +learning indeed, but little originality. His aim was to give a +philosophical rendering of the popular religion. By his contemporaries +he was accredited with miraculous powers (which he, however, +disclaimed), and by his followers in the decline of Greek philosophy, +and his admirers on its revival in the 15th and 16th centuries, his name +was scarcely mentioned without the epithet "divine" or "most divine," +while, not content with the more modest eulogy of Eunapius that he was +inferior to Porphyry only in style, the emperor Julian regarded him as +not even second to Plato, and said that he would give all the gold of +Lydia for one epistle of Iamblichus. + +Theoretically, the philosophy of Plotinus was an attempt to harmonize +the principles of the various Greek schools. At the head of his system +he placed the transcendent incommunicable one ([Greek: hen amethekton]), +whose first-begotten is intellect ([Greek: nous]), from which proceeds +soul ([Greek: psychê]), which in turn gives birth to [Greek: physis], +the realm of nature. Immediately after the absolute one, Iamblichus +introduced a second superexistent unity to stand between it and the many +as the producer of intellect, and made the three succeeding moments of +the development (intellect, soul and nature) undergo various +modifications. He speaks of them as intellectual ([Greek: theoi +noeroi]), supramundane ([Greek: hyperkosmioi]), and mundane gods +([Greek: egkosmioi]). The first of these--which Plotinus represented +under the three stages of (objective) being ([Greek: on]), (subjective) +life ([Greek: zôê]), and (realized) intellect ([Greek: nous])--is +distinguished by him into spheres of intelligible gods ([Greek: theoi +noêtoi]) and of intellectual gods ([Greek: theoi noeroi]), each +subdivided into triads, the latter sphere being the place of ideas, the +former of the archetypes of these ideas. Between these two worlds, at +once separating and uniting them, some scholars think there was inserted +by Iamblichus, as afterwards by Proclus, a third sphere partaking of the +nature of both ([Greek: theoi noêtoi kai noeroi]). But this supposition +depends on a merely conjectural emendation of the text. We read, +however, that "in the intellectual hebdomad he assigned the third rank +among the fathers to the Demiurge." The Demiurge, Zeus, or +world-creating potency, is thus identified with the perfected [Greek: +nous], the intellectual triad being increased to a hebdomad, probably +(as Zeller supposes) through the subdivision of its first two members. +As in Plotinus [Greek: nous] produced nature by mediation of [Greek: +psychê], so here the intelligible gods are followed by a triad of +psychic gods. The first of these is incommunicable and supramundane, +while the other two seem to be mundane though rational. In the third +class, or mundane gods ([Greek: theoi egkosmioi]), there is a still +greater wealth of divinities, of various local position, function, and +rank. We read of gods, angels, demons and heroes, of twelve heavenly +gods whose number is increased to thirty-six or three hundred and sixty, +and of seventy-two other gods proceeding from them, of twenty-one chiefs +([Greek: hegemones]) and forty-two nature-gods ([Greek: theoi +genesiourgoi]), besides guardian divinities, of particular individuals +and nations. The world is thus peopled by a crowd of superhuman beings +influencing natural events, possessing and communicating knowledge of +the future, and not inaccessible to prayers and offerings. + +The whole of this complex theory is ruled by a mathematical formulism of +triad, hebdomad, &c., while the first principle is identified with the +monad, [Greek: nous] with the dyad, and [Greek: psychê] with the triad, +symbolic meanings being also assigned to the other numbers. "The +theorems of mathematics," he says, "apply absolutely to all things," +from things divine to original matter ([Greek: hylê]). But though he +thus subjects all things to number, he holds elsewhere that numbers are +independent existences, and occupy a middle place between the limited +and unlimited. + +Another difficulty of the system is the account given of nature. It is +said to be "bound by the indissoluble chains of necessity which men call +fate," as distinguished from divine things which are not subject to +fate. Yet, being itself the result of higher powers becoming corporeal, +a continual stream of elevating influence flows from them to it, +interfering with its necessary laws and turning to good ends the +imperfect and evil. Of evil no satisfactory account is given; it is said +to have been generated accidentally. + +In his doctrine of man Iamblichus retains for the soul the middle place +between intellect and nature which it occupies in the universal order. +He rejects the passionless and purely intellectual character ascribed to +the human soul by Plotinus, distinguishing it sharply both from those +above and those below it. He maintains that it moves between the higher +and lower spheres, that it descends by a necessary law (not solely for +trial or punishment) into the body, and, passing perhaps from one human +body to another, returns again to the supersensible. This return is +effected by the virtuous activities which the soul performs through its +own power of free will, and by the assistance of the gods. These virtues +were classified by Porphyry as political, purifying ([Greek: +kathartikai]), theoretical, and paradigmatic; and to these Iamblichus +adds a fifth class of priestly virtues ([Greek: hieratikai aretai]), in +which the divinest part of the soul raises itself above intellect to +absolute being. + +Iamblichus does not seem ever to have attained to that ecstatic +communion with and absorption in deity which was the aim of earlier +Neoplatonism, and which Plotinus enjoyed four times in his life, +Porphyry once. Indeed his tendency was not so much to raise man to God +as to bring the gods down to men--a tendency shown still more plainly in +the "Answer of Abamon the master to Porphyry's letter to Anebo and +solutions of the doubts therein expressed," afterwards entitled the +_Liber de mysteriis_, and ascribed to Iamblichus. + +In answer to questions raised and doubts expressed by Porphyry, the +writer of this treatise appeals to the innate idea all men have of the +gods as testifying to the existence of divinities countless in number +and various in rank (to the correct arrangement of which he, like +Iamblichus, attaches the greatest importance). He holds with the latter +that above all principles of being and intelligence stands the absolute +one, from whom the first god and king spontaneously proceeds; while +after these follow the ethereal, empyrean, and heavenly gods, and the +various orders of archangels, angels, demons, and heroes distinguished +in nature, power, and activity, and in greater profusion than even the +imagination of Iamblichus had conceived. He says that all the gods are +good (though he in another place admits the existence of evil demons who +must be propitiated), and traces the source of evil to matter; rebuts +the objection that their answering prayer implies passivity on the part +of gods or demons; defends divination, soothsaying, and theurgic +practices as manifestations of the divine activity; describes the +appearances of the different sorts of divinities; discusses the various +kinds of sacrifice, which he says must be suitable to the different +natures of the gods, material and immaterial, and to the double +condition of the sacrificer as bound to the body or free from it +(differing thus in his psychology from Iamblichus); and, in conclusion, +states that the only way to happiness is through knowledge of and union +with the gods, and that theurgic practices alone prepare the mind for +this union--again going beyond his master, who held assiduous +contemplation of divine things to be sufficient. It is the passionless +nature of the soul which permits it to be thus united to divine +beings,--knowledge of this mystic union and of the worship associated +with it having been derived from the Egyptian priests, who learnt it +from Hermes. + +On one point only does the author of the _De mysteriis_ seem not to go +so far as Iamblichus in thus making philosophy subservient to +priestcraft. He condemns as folly and impiety the worship of images of +the gods, though his master held that these _simulacra_ were filled with +divine power, whether made by the hand of man or (as he believed) fallen +from heaven. But images could easily be dispensed with from the point of +view of the writer, who not only held that all things were full of gods +([Greek: panta plêrê theôn], as Thales said), but thought that each man +had a special divinity of his own--an [Greek: idios daimôn]--as his +guard and companion. + + The following are the extant works of Iamblichus: (1) _On the + Pythagorean_ (_Life_ [Greek: Peri tou Pythagorikou biou]), ed. T. + Kiessling (1815), A. Nauck (St Petersburg, 1884); for a discussion of + the authorities used see E. Rohde in _Rheinisches Museum_, xxvi., + xxvii. (1871, 1872); Eng. trans. by Thomas Taylor (1818), (2) The + _Exhortation to Philosophy_ ([Greek: Logos protreptikos eis + philosophian]), ed. T. Kiessling (1813); H. Piselli (1888). (3) The + treatise _On the General Science of Mathematics_ ([Greek: Peri tês + koinês mathêmatkês epistêmês]), ed. J. G. Friis (Copenhagen, 1790), N. + Festa (Leipzig, 1891). (4) The book _On the Arithmetic of Nicomachus_ + ([Greek: Peri tês Nikomachou arithmêtikês eisagôgês]), along with + fragments on fate ([Greek: Peri heimarmenês]) and prayer ([Greek: Peri + euchês]), ed. S. Tennulius (1688), the _Arithmetic_ by H. Pistelli + (1894). (5) The _Theological Principles of Arithmetic_ ([Greek: + Theologoumena tês arithmêtikês])--the seventh book of the series--by + F. Ast (Leipzig, 1817). Two lost books, treating of the physical and + ethical signification of numbers, stood fifth and sixth, while books + on music, geometry and astronomy followed. The emperor Julian had a + great admiration for Iamblichus, whom he considered "intellectually + not inferior to Plato"; but the _Letters to Iamblicus the Philosopher_ + which bear his name are now generally considered spurious. + + The so-called _Liber de mysteriis_ was first edited, with Latin + translation and notes, by T. Gale (Oxford, 1678), and more recently by + C. Parthey (Berlin, 1857); Eng. trans. by Thomas Taylor (1821). + + There is a monograph on Iamblichus by G. E. Hebenstreit (_De + Iamblichi, philosophi Syri, doctrina_, Leipzig, 1764), and one of the + _De myst._ by Harless (_Das Buch v. d. ägypt. Myst._, Munich, 1858). + The best accounts of Iamblichus are those of Zeller, _Phil. d. + Griechen_, iii. 2, pp. 613 sq., 2nd ed.; E. Vacherot, _Hist. de + l'école d'Alexandrie_ (1846), ii. 57 sq.; J. Simon, _Hist. de l'école + d'Alexandrie_ (1845); A. E. Chaignet, _Histoire de la psychologie des + Grecs_ (Paris, 1893) v. 67-108; T. Whittaker, _The Neo-Platonists_ + (Cambridge, 1901). (W. R. So.) + + +FOOTNOTE: + + [1] Besides the anonymous testimony prefixed to an ancient MS. of + Proclus, _De Myst._ viii. 3 seems to be quoted by the latter as + Iamblichus's. Cf. Meiners. "Judicium de libro qui de Myst. Aeg. + inscribitur," in _Comment. Soc. Reg. Sci. Gott._, vol. iv., 1781, p. + 77. + + + + +IAMBLICHUS, of Syria, the earliest of the Greek romance writers, +flourished in the 2nd century A.D. He was the author of [Greek: +Babylôniaka], the loves of Rhodanes and Sinonis, of which an epitome is +preserved in Photius (cod. 94). Garmus, a legendary king of Babylon, +forces Sinonis to marry him and throws Rhodanes into prison. The lovers +manage to escape, and after many singular adventures, in which magic +plays a considerable part, Garmus is overthrown by Rhodanes, who becomes +king of Babylon. According to Suidas, Iamblichus was a freedman, and a +scholiast's note on Photius further informs us that he was a native +Syrian (not descended from Greek settlers); that he borrowed the +material for his romance from a love story told him by his Babylonian +tutor, and that he subsequently applied himself with great success to +the study of Greek. A MS. of the original in the library of the Escorial +is said to have been destroyed by fire in 1670. Only a few fragments +have been preserved, in addition to Photius's epitome. + + See _Scriptores erotici_, ed. A. Hirschig (1856) and R. Hercher + (1858); A. Mai, _Scriptorum veterum nova collectio_, ii.; E. Rohde, + _Der griechische Roman_ (1900). + + + + +IANNINA (i.e. "the city of St John"; Gr. _Ioannina_; Turk _Yaniá_; also +written Janina, Jannina, and, according to its Albanian pronunciation, +Yanina), the capital of the vilayet of Iannina, Albania, European +Turkey. Pop. (1905) about 22,000. The largest ethnical groups in the +population are the Albanian and Greek; the purest form of colloquial +Greek is spoken here among the wealthy and highly educated merchant +families. The position of Iannina is strikingly picturesque. At the foot +of the grey limestone mass of Mount Mitzekeli (1500 ft.), which forms +part of the fine range of hills running north from the Gulf of Arta, +there lies a valley (the _Hellopia_ of antiquity) partly occupied by a +lake; and the city is built on the slopes of a slight eminence, +stretching down to the western shore. It has greatly declined from the +state of barbaric prosperity which it enjoyed from 1788 to 1822, when it +was the seat of Ali Pasha (q.v.), and was estimated to have from 30,000 +to 50,000 inhabitants. The fortress--Demir Kule or Iron Castle, which, +like the principal seraglio, was built on a promontory jutting into the +lake--is now in ruins. But the city is the seat of a Greek archbishop, +and still possesses many mosques and churches, besides synagogues, a +Greek college (gymnasium), a library and a hospital. Sayades (opposite +Corfu) and Arta are the places through which it receives its imports. +The rich gold and silver embroidery for which the city has long been +famous is still one of the notable articles in its bazaar; but the +commercial importance of Iannina has notably declined since the cession +of Arta and Thessaly to Greece in 1881. Iannina had previously been one +of the chief centres of the Thessalian grain trade; it now exports +little except cheese, hides, bitumen and sheepskins to the annual value +of about £120,000; the imports, which supply only the local demand for +provisions, textile goods, hardware, &c., are worth about double that +sum. + +The lake of Iannina (perhaps to be identified with the Pambotus or +Pambotis of antiquity) is 6 m. long, and has an area of 24 sq.m., with +an extreme depth of less than 35 ft. In time of flood it is united with +the smaller lake of Labchistas to the north. There are no affluents of +any considerable size, and the only outlets are underground passages or +_katavothra_ extending for many miles through the calcareous rocks. + +The theory supported by W. M. Leake (_Northern Greece_, London, 1835) +that the citadel of Iannina is to be identified with Dodona, is now +generally abandoned in favour of the claims of a more southern site. As +Anna Comnena, in describing the capture of the town ([Greek: ta +Ioannina]) by Bohemond in 1082, speaks of the walls as being +dilapidated, it may be supposed that the place existed before the 11th +century. It is mentioned from time to time in the Byzantine annals, and +on the establishment of the lordship of Epirus by Michael Angelus +Comnenus Ducas, it became his capital. In the middle ages it was +successively attacked by Serbs, Macedonians and Albanians; but it was in +possession of the successors of Michael when the forces of the Sultan +Murad appeared before it in 1430 (cf. Hahn, _Alban. Studien_, Jena +[1854], pp. 319-322). Since 1431 it has continued under Turkish rule. + + Descriptions of Iannina will be found in Holland's _Travels_ (1815); + Hughes, _Travels in Greece_, &c. (1830); H. F. Tozer, _Researches in + the Highlands of Turkey_ (London, 1869). See also ALBANIA and the + authorities there cited. + + + + +IAPETUS, in Greek mythology, son of Uranus and Gaea, one of the Titans, +father of Atlas, Prometheus, Epimetheus and Menoetius, the +personifications of certain human qualities (Hesiod, _Theog._ 507). As a +punishment for having revolted against Zeus, he was imprisoned in +Tartarus (Homer, _Iliad_, viii. 479) or underneath the island of Inarime +off the coast of Campania (Silius Italicus xii. 148). Hyginus makes him +the son of Tartarus and Gaea, and one of the giants. Iapetus was +considered the original ancestor of the human race, as the father of +Prometheus and grandfather of Deucalion. The name is probably identical +with Japhet (Japheth), and the son of Noah in the Greek legend of the +flood becomes the ancestor of (Noah) Deucalion. Iapetus as the +representative of an obsolete order of things is described as warring +against the new order under Zeus, and is naturally relegated to +Tartarus. + + See F. G. Welcker, _Griechische Götterlehre_, i. (1857); C. H. + Völcker, _Die Mythologie des Iapetischen Geschlechtes_ (1824); M. + Mayer, _Giganten und Titanen_ (1887). + + + + +IAPYDES, or IAPODES, one of the three chief peoples of Roman Illyria. +They occupied the interior of the country on the north between the Arsia +(Arsa) and Tedanius (perhaps the Zermanja), which separated them from +the Liburnians. Their territory formed part of the modern Croatia. They +are described by Strabo as a mixed race of Celts and Illyrians, who used +Celtic weapons, tattooed themselves, and lived chiefly on spelt and +millet. They were a warlike race, addicted to plundering expeditions. In +129 B.C. C. Sempronius Tuditanus celebrated a triumph over them, and in +34 B.C. they were finally crushed by Augustus. They appear to have had a +_foedus_ with Rome, but subsequently rebelled. + + See Strabo iv. 207, vii. 313-315; Dio Cassius xlix. 35; Appian, + _Illyrica_, 10, 14, 16; Livy, _Epit._ lix. 131; Tibullus iv. 1. 108; + Cicero, _Pro Balbo_, 14. + + + + +IATROCHEMISTRY (coined from Gr. [Greek: iatros], a physician, and +"chemistry"), a stage in the history of chemistry, during which the +object of this science was held to be "not to make gold but to prepare +medicines." This doctrine dominated chemical thought during the 16th +century, its foremost supporters being Paracelsus, van Helmont and de la +Boë Sylvius. But it gave way to the new definition formulated by Boyle, +viz. that the proper domain of chemistry was "to determine the +composition of substances." (See CHEMISTRY: I. _History_; MEDICINE.) + + + + +IAZYGES, a tribe of Sarmatians first heard of on the Maeotis, where they +were among the allies of Mithradates the Great. Moving westward across +Scythia, and hence called Metanastae, they were on the lower Danube by +the time of Ovid, and about A.D. 50 occupied the plains east of the +Theiss. Here, under the general name of Sarmatae, they were a perpetual +trouble to the Roman province of Dacia. They were divided into freemen +and serfs (_Sarmatae Limigantes_), the latter of whom had a different +manner of life and were probably an older settled population enslaved by +nomad masters. They rose against them in A.D. 334, but were repressed by +foreign aid. Nothing is heard of Iazyges or Sarmatae after the Hunnish +invasions. Graves at Keszthely and elsewhere in the Theiss valley, shown +by their contents to belong to nomads of the first centuries A.D., are +referred to the Iazyges. (E. H. M.) + + + + +IBADAN, a town of British West Africa, in Yorubaland, Southern Nigeria, +123 m. by rail N.E. of Lagos, and about 50 m. N.E. of Abeokuta. Pop. +1910 estimated at 150,000. The town occupies the slope of a hill, and +stretches into the valley through which the river Ona flows. It is +enclosed by mud walls, which have a circuit of 18 m., and is encompassed +by cultivated land 5 or 6 m. in breadth. The native houses are all low, +thatched structures, enclosing a square court, and the only break in the +mud wall is the door. There are numerous mosques, _orishas_ +(idol-houses) and open spaces shaded with trees. There are a few +buildings in the European style. Most of the inhabitants are engaged in +agriculture; but a great variety of handicrafts is also carried on. +Ibadan is the capital of one of the Yoruba states and enjoys a large +measure of autonomy. Nominally the state is subject to the _alafin_ +(ruler) of Oyo; but it is virtually independent. The administration is +in the hands of two chiefs, a civil and a military, the _bale_ and the +_balogun_; these together form the highest court of appeal. There is +also an _iyaloda_ or mother of the town, to whom are submitted all the +disputes of the women. Ibadan long had a feud with Abeokuta, but on the +establishment of the British protectorate the intertribal wars were +stopped. In 1862 the people of Ibadan destroyed Ijaya, a neighbouring +town of 60,000 inhabitants. A British resident and a detachment of Hausa +troops are stationed at Ibadan. + + See also YORUBAS, ABEOKUTA and LAGOS. + + + + +IBAGUÉ, or SAN BONIFACIO DE IBAGUÉ, a city of Colombia, and capital of +the department of Tolima, about 60 m. W. of Bogotá and 18 m. N.W. of the +Nevado de Tolima. Pop. (1900, estimate) 13,000. Ibagué is built on a +beautiful plain between the Chipalo and Combeima, small affluents of the +Cuello, a western tributary of the Magdalena. Its elevation, 4300 ft. +above the sea, gives it a mild, subtropical climate. The plain and the +neighbouring valleys produce cacao, tobacco, rice and sugar-cane. There +are two thermal springs in the vicinity, and undeveloped mines of +sulphur and silver. The city has an endowed college. It is an important +commercial centre, being on the road which crosses the Quindio pass, or +_paramo_, into the Cauca valley. Ibagué was founded in 1550 and was the +capital of the republic for a short time in 1854. + + + + +IBARRA, a city of Ecuador and capital of the province of Imbabura, about +50 m. N.N.E. of Quito, on a small fertile plain at the northern foot of +Imbabura volcano, 7300 ft. above sea-level. Pop. (1900, estimate) 5000. +It stands on the left bank of the Tahuando, a small stream whose waters +flow north and west to the Pacific through the Mira, and is separated +from the higher plateau of Quito by an elevated transverse ridge of +which the Imbabura and Mojanda volcanoes form a part. The surrounding +country is mountainous, the valleys being very fertile. Ibarra itself +has a mild, humid climate, and is set in the midst of orchards and +gardens. It is the see of a bishop and has a large number of churches +and convents, and many substantial residences. Ibarra has manufactures +of cotton and woollen fabrics, hats, sandals (_alpargates_), sacks and +rope from _cabulla_ fibre, laces, sugar and various kinds of distilled +spirits and cordials made from the sugar-cane grown in the vicinity. +Mules are bred for the Colombian markets of Pasto and Popayan. Ibarra +was founded in 1597 by Alvaro de Ibarra, the president of Quito. It has +suffered from the eruptions of Imbabura, and more severely from +earthquakes, that of 1859 causing great damage to its public buildings, +and the greater one of the 16th of August 1868 almost completely +destroyed the town and killed a large number of its inhabitants. The +village of Carranqui, 1¼ m. from Ibarra, is the birthplace of Atahualpa, +the Inca sovereign executed by Pizarro, and close by is the small lake +called Yaguarcocha where the army of Huaynacapac, the father of +Atahualpa, inflicted a bloody defeat on the Carranquis. Another +aboriginal battle-field is that of Hatuntaqui, near Ibarra, where +Huaynacapac won a decisive victory and added the greater part of Ecuador +to his realm. The whole region is full of _tolas_, or Indian burial +mounds. + + + + +IBERIANS (Iberi, [Greek: Ibêres]), an ancient people inhabiting parts of +the Spanish peninsula. Their ethnic affinities are not known, and our +knowledge of their history is comparatively slight. It is almost +impossible to make any statement in regard to them which will meet with +general agreement. At the same time, the general lines of Iberian +controversy are clear enough The principal sources of information about +the Iberians are (1) historical, (2) numismatic, (3) linguistic, (4) +anthropological. + +1. _Historical._--The name seems to have been applied by the earlier +Greek navigators to the peoples who inhabited the eastern coast of +Spain; probably it originally meant those who dwelt by the river Iberus +(mod. _Ebro_). It is possible (Boudard, _Études sur l'alphabet ibérien_ +(Paris, 1852) that the river-name itself represents the Basque phrase +_ibay-erri_ "the country of the river." On the other hand, even in older +Greek usage (as in Thuc. vi. 1) the term Iberia is said to have embraced +the country as far east as the Rhone (see Herodorus of Heraclea, _Fragm. +Hist. Gr._ ii. 34), and by the time of Strabo it was the common Greek +name for the Spanish peninsula. Iberians thus meant sometimes the +population of the peninsula in general and sometimes, it would appear, +the peoples of some definite race ([Greek: genos]) which formed one +element in that population. Of the tribal distribution of this race, of +its linguistic, social and political characteristics, and of the history +of its relation to the other peoples of Spain, we have only the most +general, fragmentary and contradictory accounts. On the whole, the +historical evidence indicates that in Spain, when it first became known +to the Greeks and Romans there existed many separate and variously +civilized tribes connected by at least apparent identity of race, and by +similarity (but not identity) of language, and sufficiently +distinguished by their general characteristics from Phoenicians, Romans +and Celts. The statement of Diodorus Siculus that the mingling of these +Iberians with the immigrant Celts gave rise to the Celtiberians is in +itself probable. Varro and Dionysius Afer proposed to identify the +Iberians of Spain with the Iberians of the Caucasus, the one regarding +the eastern, and other the western, settlements as the earlier. + +2. _Numismatic._--Knowledge of ancient Iberian language and history is +mainly derived from a variety of coins, found widely distributed in the +peninsula,[1] and also in the neighbourhood of Narbonne. They are +inscribed in an alphabet which has many points of similarity with the +western Greek alphabets, and some with the Punic alphabet; but which +seems to retain a few characters from an older script akin to those of +Minoan Crete and Roman Libya.[2] The same Iberian alphabet is found also +rarely in inscriptions. The coinage began before the Roman conquest was +completed; the monetary system resembles that of the Roman republic, +with values analogous to _denarii_ and _quinarii_. The coin inscriptions +usually give only the name of the town, e.g. PLPLIS (Bilbilis), KLAQRIQS +(Calagurris), SEQBRICS (Segobriga), TMANIAV (Dumania). The types show +late Greek and perhaps also late Punic influence, but approximate later +to Roman models. The commonest reverse type, a charging horseman, +reappears on the Roman coins of Bilbilis, Osca, Segobriga and other +places. Another common type is one man leading two horses or brandishing +a sword or a bow. The obverse has usually a male head, sometimes +inscribed with what appears to be a native name. + +3. _Linguistic._--The survival of the non-Aryan language among the +Basques around the west Pyrenees has suggested the attempt to interpret +by its means a large class of similar-sounding place-names of ancient +Spain, some of which are authenticated by their occurrence on the +inscribed coins, and to link it with other traces of non-Aryan speech +round the shores of the Western Mediterranean and on the Atlantic +seaboard of Europe. This phase of Iberian theory opens with K. W. +Humboldt (_Prüfung der Untersuchungen über die Urbewohner Hispaniens +vermittelst der waskischen Sprache_, Berlin, 1821), who contended that +there existed once a single great Iberian people, speaking a distinct +language of their own; that an essentially "Iberian" population was to +be found in Sicily, Sardinia and Corsica, in southern France, and even +in the British Isles; and that the Basques of the present day were +remnants of this race, which had elsewhere been expelled or absorbed. +This last was the central and the seminal idea of the work, and it has +been the point round which the battle of scholarship has mainly raged. +The principal evidence which Humboldt adduced in its support was the +possibility of explaining a vast number of the ancient topographical +names of Spain, and of other asserted Iberian districts, by the forms +and significations of Basque. In reply, Graslin (_De l'Ibérie_, Paris, +1839), maintained that the name Iberia was nothing but a Greek misnomer +of Spain, and that there was no proof that the Basque people had ever +occupied a wider area than at present; and Bladé (_Origine des Basques_, +Paris, 1869) took the same line of argument, holding that Iberia is a +purely geographical term, that there was no proper Iberian race, that +the Basques were always shut in by alien races, that their affinity is +still to seek, and that the whole Basque-Iberian theory is a figment. +His main contention has met with some acceptance,[3] but the great +current of ethnographical speculation still flows in the direction +indicated by Humboldt. + +4. _Anthropological._--Humboldt's "Iberian theory" depended partly on +linguistic comparisons, but partly on his observation of widespread +similarity of physical type among the population of south-western +Europe. Since his time the anthropological researches of Broca, Thurnam +and Davis, Huxley, Busk, Beddoe, Virchow, Tubino and others have proved +the existence in Europe, from Neolithic times, of a race, small of +stature, with long or oval skulls, and accustomed to bury their dead in +tombs. Their remains have been found in Belgium and France, in Britain, +Germany and Denmark, as well as in Spain; and they bear a close +resemblance to a type which is common among the Basques as well as all +over the Iberian peninsula. This Neolithic race has consequently been +nicknamed "Iberians," and it is now common to speak of the "Iberian" +ancestry of the people of Britain, recognizing the racial +characteristics of "Iberians" in the "small swarthy Welshman," the +"small dark Highlander," and the "Black Celts to the west of the +Shannon," as well as in the typical inhabitants of Aquitania and +Brittany.[4] Later investigators went further. M. d'Arbois de +Jubainville, for example (_Les Premiers habitants de l'Europe_, Paris, +1877), maintained that besides possessing Spain, Gaul, Italy and the +British Isles, "Iberian" peoples penetrated into the Balkan peninsula, +and occupied a part of northern Africa, Corsica and Sardinia; and it is +now generally accepted that a race with fairly uniform characteristics +was at one time in possession of the south of France (or at least of +Aquitania), the whole of Spain from the Pyrenees to the straits, the +Canary Islands (the Guanches) a part of northern Africa and Corsica. +Whether this type is more conveniently designated by the word _Iberian_, +or by some other name ("Eur-african," "Mediterranean," &c.) is a matter +of comparative indifference, provided that there is no misunderstanding +as to the steps by which the term _Iberian_ attained its meaning in +modern anthropology. + + AUTHORITIES.--K. W. von Humboldt, "Über die cantabrische oder + baskische Sprache" in Adelung, _Mithridates_ iv. (1817), and _Prüfung + d. Untersuchungen ü. die Urbewohner Hispaniens vermittelst der + waskischen Sprache_ (Berlin, 1821); L. F. Graslin, _De l'Ibérie_ + (Paris, 1838); T. B. G. M. Bory de St Vincent, _Essai géologique sur + le genre humain_ (1838); G. Lagneau, "Sur l'ethnologie des peuples + ibériens," in _Bull. soc. anthrop._ (1867), pp. 146-161; J. F. Bladé, + _Études sur l'origine des Basques_ (Paris, 1869), _Défense des + études_, &c. (Paris, 1870); Phillips, _Die Einwanderung der Iberer in + die pyren. Halbinsel_ (Vienna, 1870), _Über das iberische Alphabet_ + (Vienna, 1870); W. Boyd Dawkins, "The Northern Range of the Basques," + in _Fortnightly Rev._ N.S. xvi. 323-337 (1874); W. T. van Eys, "La + Langue ibérienne et la langue basque," in _Revue de linguistique_, pp. + 3-15 (1874); W. Webster, "The Basque and the Kelt," in _Journ. + Anthrop. Inst._ v. 5-29 (1875); F. M. Tubino, _Los Aborigines ibericos + o los Berberos en la peninsula_ (Madrid, 1876); A. Luchaire, _Les + Origines linguistiques de l'Aquitaine_ (Paris, 1877); W. Boyd Dawkins, + _Early Man in Britain_ (London, 1880); A. Castaing, "Les Origines des + Aquitains," _Mém. Soc. Eth._ N.S. 1, pp. 183-328 (1884); G. C. C. + Gerland, "Die Basken und die Iberer" in Gröber, _Grundriss d. roman. + Philologie_, 1, pp. 313-334 (1888); M. H. d'Arbois de Jubainville, + _Les Premiers habitants de l'Europe_ (1889-1894); J. F. Bladé, _Les + Vascons avant leur établissement en Novempopulanie_, Agen. (1891); W. + Webster, "The Celt-iberians," _Academy_ xl. 268-269 (and consequent + correspondence) (1891); J. Rhys, "The Inscriptions and Language of the + Northern Picts," _Proc. Soc. Ant. Scot._ xxvi. 263-351 (1892); F. + Fita, "El Vascuence en las inscripciones ógmicas," _Bol. Real. Acad. + Hist. Madrid_ (June 1893), xxii. 579-587; G. v. d. Gabelentz, + "Baskisch u. Berberisch," _Sitz. k. preuss. Akad. Wiss._ 593-613 + (Berlin, 1893), _Die Verwandtschaft der Baskischen mit der + Berber-Sprache Nordafrikas nachgewiesen_ (Braunschweig, 1894); M. H. + d'Arbois de Jubainville, "Les Celtes en Espagne," _Rev. celtique_, + xiv. 357-395 (1894); G. Buschan, "Über die iberische Rasse," + _Ausland_, lxvi. 342-344 (1894); F. Olóriz y Aguilera, _Distribucion + geografica del indice cefalico en España_ (Madrid, 1894), "La Talla + humana en España" in _Discursos R. Acad. Medicina_ xxxvi. 389 (Madrid, + 1896); R. Collignon, "La Race basque," _L'Anthropologie_, v. 276-287 + (1894); T. de Aranzadi, "Le Peuple basque, résumé" _Bull. soc. + d'anth._ 510-520 (1894), "Consideraciones acerca de la raza basca" + _Euskel-Erria_ xxxv. 33, 65, 97, 129 (1896); H. Schuchhardt, + _Baskische Studien_, i. "Über die Entstehung der Bezugsformen des + baskischen Zeitworts"; _Denkschriften der K. Akad. der Wiss._, + Phil.-Hist., Classe, Bd. 42, Abh. 3. (Wien, 1893); Ph. Salmon, _Rev. + mens. Éc. d'anthr._ v. 155-181, 214-220 (1895); R. Collignon, "Anthr. + du S.-O. de la France," _Mém. Soc. Anthr._ § 3. 1. 4. p. 1-129 (1895), + _Ann. de géogr._ v. 156-166 (1896), and with J. Deniker, "Les Maures + de Sénégal," _L'Anthr._ vii. 57-69 (1897); G. Hervé, _Rev. mens. Éc. + d'anthr._ vi. 97-109 (1896); G. Sergi, _Africa: Anthropologia della + stirpe Camitica_ (Turin, 1897), _Arii ed Italici_ (1898); L. de Hoyos + Sainz, "L'Anthropologie et la préhistorique en Espagne et en Portugal + en 1897," _L'Anthropologie_, ix. 37-51 (1898); J. Deniker (see + Collignon) "Les Races de l'Europe," _L'Anthropologie_, ix. 113-133 + (1898); M. Gèze, "De quelques rapports entre les langues berbère et + basque," _Mém. soc. arch. du Midi de la France_, xiii. See also the + works quoted in the footnotes; and the bibliography under BASQUES. + (J. L. M.) + + +FOOTNOTES: + + [1] For the prehistoric civilization of the peninsula as a whole see + SPAIN. + + [2] P. A. Boudard's _Études sur l'alphabet ibérien_ (Paris, 1852). + and _Numismatique ibérienne_ (Béziers, 1859); Aloiss Heiss, _Notes + sur les monnaies celtibériennes_ (Paris, 1865), and _Description + générale des monnaies antiques de l'Espagne_ (Paris, 1870); Phillips, + _Über das iberische Alphabet_ (Vienna, 1870), _Die Einwanderung der + Iberer in die pyren. Halbinsel_ (Vienna, 1870); W. M. Flinders + Petrie, _Journ. Anthr. Inst._ xxix. (1899) 204, and above all E. + Hübner, _Monumenta linguae Ibericae_. + + [3] W. van Eys, for example, "La Langue ibérienne et la langue + basque," in _Revue de linguistique_, goes against Humboldt; but + Prince Napoleon and to a considerable extent A. Luchaire maintain the + justice of his method and the value of many of his results. See + Luchaire, _Les Origines linguistiques de l'Aquitaine_ (Paris, 1877). + + [4] Compare the interesting résumé of the whole question in Boyd + Dawkins's _Early Man in Britain_ (London, 1880). + + + + +IBEX, one of the names of the Alpine wild goat, otherwise known as the +steinbok and bouquetin, and scientifically as _Capra ibex_. Formerly the +ibex was common on the mountain-ranges of Germany, Switzerland and +Tirol, but is now confined to the Alps which separate Valais from +Piedmont, and to the lofty peaks of Savoy, where its existence is mainly +due to game-laws. The ibex is a handsome animal, measuring about 4½ ft. +in length and standing about 40 in. at the shoulder. The skin is covered +in summer with a short fur of an ashy-grey colour, and in winter with +much longer yellowish-brown hair concealing a dense fur beneath. The +horns of the male rise from the crest of the skull, and after bending +gradually backwards terminate in smooth tips; the front surface of the +remainder carrying bold transverse ridges or knots. About 1 yd. is the +maximum recorded length of ibex-horns. The fact that the fore-legs are +somewhat shorter than those behind enables the ibex to ascend mountain +slopes with more facility than it can descend, while its hoofs are as +hard as steel, rough underneath and when walking over a flat surface +capable of being spread out. These, together with its powerful sinews, +enable it to take prodigious leaps, to balance itself on the smallest +foothold and to scale almost perpendicular rocks. Ibex live habitually +at a greater height than chamois or any other Alpine mammals, their +vertical limit being the line of perpetual snow. There they rest in +sunny nooks during the day, descending at night to the highest woods to +graze. Ibex are gregarious, feeding in herds of ten to fifteen +individuals; but the old males generally live apart from, and usually at +greater elevations than, the females and young. They utter a sharp +whistling sound not unlike that of the chamois, but when greatly +irritated or frightened make a peculiar snorting noise. The period of +gestation in the female is ninety days, after which she +produces--usually at the end of June--a single young one which is able +at once to follow its mother. Kids when caught young and fed on goat's +milk can be readily tamed; and in the 16th century young tamed ibex were +frequently driven to the mountains along with the goats, in whose +company they would afterwards return. Even wild ibex have been known to +stray among the herds of goats, although they shun the society of +chamois. Its flesh is said to resemble mutton, but has a flavour of +game. + +[Illustration: The Ibex (_Capra ibex_).] + +By naturalists the name "ibex" has been extended to embrace all the +kindred species of wild goats, while by sportsmen it is used in a still +more elastic sense, to include not only the true wild goat (known in +India as the Sind ibex) but even the short-horned _Hemitragus hylocrius_ +of the Nilgiris. Dealing only with species zoologically known as ibex, +the one nearest akin to the European kind is the Asiatic or Siberian +ibex (_Capra sibirica_), which, with several local phases, extends from +the northern side of Kashmir over an enormous area in Central Asia. +These ibex, especially the race from the Thian Shan, are incomparably +finer than the European species, their bold knotted horns sometimes +attaining a length of close on 60 in. The Arabian, or Nubian, ibex (_C. +nubiana_) is characterized by the more slender type of horn, in which +the front edge is much narrower; while the Simien ibex (_C. vali_) of +Central Abyssinia is a very large and dark-coloured animal, with the +horns black instead of brownish, and bearing only slightly marked front +ridges. The Caucasian ibex (_C. caucasica_), or tur, is a wholly +fox-coloured animal, in which the horns are still flatter in front, and +thus depart yet further from the ibex type. In the Spanish ibex (_C. +pyrenaica_) the horns are flattened, with ill-defined knobs, and a +spiral twist. (See GOAT.) (W. H. F.; R. L.*) + + + + +IBIS, one of the sacred birds of the ancient Egyptians. James Bruce +identified this bird with the _Abu-Hannes_ or "Father John" of the +Abyssinians, and in 1790 it received from Latham (_Index +ornithologicus_, p. 706) the name of _Tantalus aethiopicus_. This +determination was placed beyond question by Cuvier (_Ann. du Muséum_, +iv. 116-135) and Savigny (_Hist. nat. et mythol. de l'ibis_) in 1805. +They, however, removed it from the Linnaean genus _Tantalus_ and, +Lacépède having some years before founded a genus _Ibis_, it was +transferred thither, and is now generally known as _I. aethiopica_, +though some speak of it as _I. religiosa_. No attempt can here be made +to treat the ibis from a mythological or antiquarian point of view. +Savigny's memoir contains a great deal of matter on the subject. +Wilkinson (_Ancient Egyptians_, ser. 2, vol. ii. pp. 217-224) added some +of the results of later research, and Renouf in his _Hibbert Lectures_ +explains the origin of the myth. + +The ibis is chiefly an inhabitant of the Nile basin from Dongola +southward, as well as of Kordofan and Sennar; whence about midsummer it +moves northwards to Egypt.[1] In Lower Egypt it bears the name of +_Abu-mengel_, or "father of the sickle," from the form of its bill, but +it does not stay long in that country, disappearing when the Nile has +subsided. Hence most travellers have failed to meet with it there[2] +(since their acquaintance with the birds of Egypt is limited to those +which frequent the country in winter), and writers have denied generally +to this species a place in its modern fauna (cf. Shelley, _Birds of +Egypt_, p. 261). However, in 1864, von Heuglin (_Journ. für +Ornithologie_, 1865, p. 100) saw a young bird which had been shot in the +Delta, and E. C. Taylor (_Ibis_, 1878, p. 372) saw an adult which had +been killed near Lake Menzal in 1877. The story told to Herodotus of its +destroying snakes is, according to Savigny, devoid of truth, but Cuvier +states that he discovered partly digested remains of a snake in the +stomach of a mummied ibis. + +The ibis is somewhat larger than a curlew, _Numenius arquata_, which +bird it resembles, with a much stouter bill and stouter legs. The head +and greater part of the neck are bare and black. The plumage is white, +except the primaries, which are black, and a black plume, formed by the +secondaries, tertials and lower scapulars, and richly glossed with +bronze, blue and green, which curves gracefully over the hind-quarters. +The bill and feet are also black. The young lack the ornamental plume, +and in them the head and neck are clothed with short black feathers, +while the bill is yellow. The nest is placed in bushes or high trees, +the bird generally building in companies, and in the middle of August +von Heuglin (_Orn. Nord-Ost-Afrikas_, p. 1138) found that it had from +two to four young or much incubated eggs.[3] These are of a dingy white, +splashed, spotted and speckled with reddish-brown. + +Congeneric with the typical ibis are two or three other species, the _I. +melanocephala_ of India, the _I. molucca_ or _I. strictipennis_, of +Australia, and the _I. bernieri_ of Madagascar, all of which closely +resemble _I. aethiopica_; while many other forms not very far removed +from it, though placed by authors in distinct genera,[4] are known. +Among these are several beautiful species such as the Japanese +_Geronticus nippon_, the _Lophotibis cristata_ of Madagascar, and the +scarlet ibis,[5] _Eudocimus ruber_, of America. The glossy ibis, +_Plegadis falcinellus_, found throughout the West Indies, Central and +the south-eastern part of North America, as well as in many parts of +Europe (whence it not unfrequently strays to the British Islands), +Africa, Asia and Australia. This bird, believed to be the second kind of +ibis spoken of by Herodotus, is rather smaller than the sacred ibis, and +mostly of a dark chestnut colour with brilliant green and purple +reflections on the upper parts, exhibiting, however, when young none of +the rufous hue. This species lays eggs of a deep sea-green colour, +having wholly the character of heron's eggs, and it often breeds in +company with herons, while the eggs of all other ibises whose eggs are +known resemble those of the sacred ibis. Though ibises resemble the +curlews externally, there is no affinity between them. The _Ibididae_ +are more nearly related to the storks, _Ciconiidae_, and still more to +the spoonbills, _Plataleidae_, with which latter many systematists +consider them to form one group, the _Hemiglottides_ of Nitzsch. +Together these groups form the sub-order _Ciconiae_ of the order +_Ciconiiformes_. The true ibises are also to be clearly separated from +the wood-ibises, _Tantalidae_, of which there are four or five species, +by several not unimportant structural characters. Fossil remains of a +true ibis, _I. pagana_, have been found in considerable numbers in the +middle Tertiary beds of France.[6] (A. N.) + + +FOOTNOTES: + + [1] It has been said to occur occasionally in Europe (Greece and + southern Russia). + + [2] E. C. Taylor remarked (_Ibis_, 1859, p. 51), that the buff-backed + heron, _Ardea bubulcus_, was made by the tourists' dragomans to do + duty for the "sacred ibis," and this seems to be no novel practice, + since by it, or something like it, Hasselqvist was misled, and + through him Linnaeus. + + [3] The ibis has more than once nested in the gardens of the + Zoological Society in London, and even reared its young there. + + [4] For some account of these may be consulted Dr Reichenow's paper + in _Journ. für Ornithologie_ (1877), pp. 143-156; Elliot's in _Proc. + Zool. Society_ (1877), pp. 477-510; and that of Oustalet in _Nouv. + Arch. du Muséum_, ser. 2, vols. i. pp. 167-184. + + [5] It is a popular error--especially among painters--that this bird + was the sacred ibis of the Egyptians. + + [6] The name "_Ibis_" was selected as the title of an ornithological + magazine, frequently referred to in this and other articles, which + made its first appearance in 1859. + + + + +IBLIS, or EBLIS, in Moslem mythology the counterpart of the Christian +and Jewish devil. He figures oftener in the Koran under the name +Shaitan, Iblis being mentioned 11 times, whereas Shaitan appears in 87 +passages. He is chief of the spirits of evil, and his personality is +adapted to that of his Jewish prototype. Iblis rebelled against Allah +and was expelled from Paradise. The Koranic legend is that his fall was +a punishment for his refusal to worship Adam. Condemned to death he was +afterwards respited till the judgment day (Koran vii. 13). + + See Gustav Weil, _The Bible, the Koran and the Talmud_ (London, 1846). + + + + +IBN 'ABD RABBIHI [Abu 'Umar Ahmad ibn Mahommed ibn 'Abd Rabbihi] +(860-940), Arabian poet, was born in Cordova and descended from a freed +slave of Hisham, the second Spanish Omayyad caliph. He enjoyed a great +reputation for learning and eloquence. No diwan of his is extant, but +many selections from his poems are given in the _Yatimat ud-Dahr_, i. +412-436 (Damascus, 1887). More widely known than his poetry is his great +anthology, the _'Iqd ul-Farid_ ("The Precious Necklace"), a work divided +into twenty-five sections, the thirteenth being named the middle jewel +of the necklace, the chapters on either side of this being named after +other jewels. It is an _adab_ book (see ARABIA: _Literature_, section +"Belles Lettres") resembling Ibn Qutaiba's _'Uyun ul-Akhbar_, from which +it borrows largely. It has been printed, several times in Cairo (1876, +1886, &c.). (G. W. T.) + + + + +IBN 'ARABI [Muhyiuddin Abu 'Abdallah ibn ul-'Arabi] (1165-1240), Moslem +theologian and mystic, was born in Murcia and educated in Seville. When +thirty-eight he travelled in Egypt, Arabia, Bagdad, Mosul and Asia +Minor, after which he lived in Damascus for the rest of his life. In law +he was a Zahirite, in theology a mystic of the extreme order, though +professing orthodox Ash'arite theology and combating in many points the +Indo-Persian mysticism (pantheism). He claims to have had conversations +with all the prophets past and future, and reports conversations with +God himself. Of his numerous works about 150 still exist. The most +extensive is the twelve-volume _Futuhat ul-Makkiyat_ ("Meccan +Revelations"), a general encyclopaedia of Sufic beliefs and doctrines. +Numerous extracts from this work are contained in Sha'rani's (d. 1565) +manual of Sufic dogma (_Yawaqit_) published several times in Cairo. A +short account of these works is given in A. von Kremer's _Geschichte der +herrschenden Ideen des Islams_, pp. 102-109 (Leipzig, 1868). Another +characteristic and more accessible work of Ibn 'Arabi is the _Fusus +ul-Hikam_, on the nature and importance of the twenty-seven chief +prophets, written in 1230 (ed. Bulaq, 1837) and with the _Commentary_ +(Cairo, 1891) of Qashani (d. 1350); cf. analysis by M. Schreiner in +_Journal of German Oriental Society_, lii. 516-525. + + Of some 289 works said to have been written by Ibn 'Arabi 150 are + mentioned in C. Brockelmann's _Gesch. der arabischen Litteratur_, vol. + i. (Weimar, 1898), pp. 441-448. See also R. A. Nicholson, _A Literary + History of the Arabs_, pp. 399-404 (London, 1907). (G. W. T.) + + + + +IBN ATHIR, the family name of three brothers, all famous in Arabian +literature, born at Jazirat ibn 'Umar in Kurdistan. The eldest brother, +known as MAJD UD-DIN (1149-1210), was long in the service of the amir of +Mosul, and was an earnest student of tradition and language. His +dictionary of traditions (_Kitab un-Nihaya_) was published at Cairo +(1893), and his dictionary of family names (_Kitab ul-Murassa'_) has +been edited by Seybold (Weimar, 1896). The youngest brother, known as +DIYA UD-DIN (1163-1239), served Saladin from 1191 on, then his son, +al-Malik ul-Afdal, and was afterwards in Egypt, Samosata, Aleppo, Mosul +and Bagdad. He was one of the most famous aesthetic and stylistic +critics in Arabian literature. His _Kitab ul-Mathal_, published in Bulaq +in 1865 (cf. _Journal of the German Oriental Society_, xxxv. 148, and +Goldziher's _Abhandlungen_, i. 161 sqq.), contains some very +independent criticism of ancient and modern Arabic verse. Some of his +letters have been published by D. S. Margoliouth "On the Royal +Correspondence of Diya ed-Din el-Jazari" in the _Actes du dixième +congrès international des orientalistes_, sect. 3, pp. 7-21. + +The brother best known by the simple name of Ibn Athir was ABU-L-HASAN +'IZZUDDIN MAHOMMED IBN UL-ATHIR (1160-1234), who devoted himself to the +study of history and tradition. At the age of twenty-one he settled with +his father in Mosul and continued his studies there. In the service of +the amir for many years, he visited Bagdad and Jerusalem and later +Aleppo and Damascus. He died in Mosul. His great history, the _Kamil_, +extends to the year 1231; it has been edited by C. J. Tornberg, _Ibn +al-Athiri Chronicon quod perfectissimum inscribitur_ (14 vols., Leiden, +1851-1876), and has been published in 12 vols. in Cairo (1873 and 1886). +The first part of this work up to A.H. 310 (A.D. 923) is an abbreviation +of the work of Tabari (q.v.) with additions. Ibn Athir also wrote a +history of the Atabegs of Mosul, published in the _Recueil des +historiens des croisades_ (vol. ii., Paris); a work (_Usd ul-Ghaba_), +giving an account of 7500 companions of Mahomet (5 vols., Cairo, 1863), +and a compendium (the _Lubab_) of Sam'ani's _Kitab ul-Ansab_ (cf. F. +Wüstenfeld's _Specimen el-Lobabi_, Göttingen, 1835). (G. W. T.) + + + + +IBN BATUTA, i.e. ABU ABDULLAH MAHOMMED, surnamed IBN BATUTA (1304-1378), +the greatest of Moslem travellers, was born at Tangier in 1304. He +entered on his travels at twenty-one (1325) and closed them in 1355. He +began by traversing the coast of the Mediterranean from Tangier to +Alexandria, finding time to marry two wives on the road. After some stay +at Cairo, then probably the greatest city in the world (excluding +China), and an unsuccessful attempt to reach Mecca from Aidhab on the +west coast of the Red Sea, he visited Palestine, Aleppo and Damascus. He +then made the pilgrimage to Mecca and Medina, and visited the shrine of +Ali at Mashhad-Ali, travelling thence to Basra, and across the mountains +of Khuzistan to Isfahan, thence to Shiraz and back to Kufa and Bagdad. +After an excursion to Mosul and Diarbekr, he made the _haj_ a second +time, staying at Mecca three years. He next sailed down the Red Sea to +Aden (then a place of great trade), the singular position of which he +describes, noticing its dependence for water-supply upon the great +cisterns restored in modern times. He continued his voyage down the +African coast, visiting, among other places, Mombasa and Quiloa (Kilwa). +Returning north he passed by the chief cities of Oman to New Ormuz +(Hurmuz), which had about 15 years before, c. 1315, been transferred to +its famous island-site from the mainland (Old Ormuz). After visiting +other parts of the gulf he crossed the breadth of Arabia to Mecca, +making the _haj_ for the third time. Crossing the Red Sea, he made a +journey of great hardship to Syene, and thence along the Nile to Cairo. +After this, travelling through Syria, he made a circuit among the petty +Turkish states into which Asia Minor was divided after the fall of the +kingdom of Rum (Iconium). He now crossed the Black Sea to Kaffa, then +mainly occupied by the Genoese, and apparently the first Christian city +he had seen, for he was much perturbed by the bell-ringing. He next +travelled into Kipchak (the Mongol khanate of Russia), and joined the +camp of the reigning khan Mahommed Uzbeg, from whom the great and +heterogeneous _Uzbeg_ race is perhaps named. Among other places in this +empire he travelled to Bolghar (54° 54´ N.) in order to witness the +shortness of the summer night, and desired to continue his travels north +into the "Land of Darkness" (in the extreme north of Russia), of which +wonderful things were told, but was obliged to forego this. Returning to +the khan's camp he joined the cortège of one of the Khatuns, who was a +Greek princess by birth (probably illegitimate) and in her train +travelled to Constantinople, where he had an interview with the emperor +Andronikos III. the Younger (1328-1341). He tells how, as he passed the +city gates, he heard the guards muttering _Sarakinu_. Returning to the +court of Uzbeg, at Sarai on the Volga, he crossed the steppes to +Khwarizm and Bokhara; thence through Khorasan and Kabul, and over the +Hindu Kush (to which he gives that name, its first occurrence). He +reached the Indus, on his own statement, in September, 1333. This +closes the first part of his narrative. + +From Sind, which he traversed to the sea and back again, he proceeded to +Multan, and eventually, on the invitation of Mahommed Tughlak, the +reigning sovereign, to Delhi. Mahommed was a singular character, full of +pretence at least to many accomplishments and virtues, the founder of +public charities, and a profuse patron of scholars, but a parricide, a +fratricide, and as madly capricious, bloodthirsty and unjust as +Caligula. "No day did his palace gate fail to witness the elevation of +some abject to affluence and the torture and murder of some living +soul." He appointed the traveller to be kazi of Delhi, with a present of +12,000 silver dinars (rupees), and an annual salary of the same amount, +besides an assignment of village lands. In the sultan's service Ibn +Batuta remained eight years; but his good fortune stimulated his natural +extravagance, and his debts soon amounted to four or five times his +salary. At last he fell into disfavour and retired from court, only to +be summoned again on a congenial duty. The emperor of China, last of the +Mongol dynasty, had sent a mission to Delhi, and the Moor was to +accompany the return embassy (1342). The party travelled through central +India to Cambay and thence sailed to Calicut, classed by the traveller +with the neighbouring Kaulam (Quilon), Alexandria, Sudak in the Crimea, +and Zayton (Amoy harbour) in China, as one of the greatest trading +havens in the world--an interesting enumeration from one who had seen +them all. The mission party was to embark in Chinese junks (the word +used) and smaller vessels, but that carrying the other envoys and the +presents, which started before Ibn Batuta was ready, was wrecked +totally; the vessel that he had engaged went off with his property, and +he was left on the beach of Calicut. Not daring to return to Delhi, he +remained about Honore and other cities of the western coast, taking part +in various adventures, among others the capture of Sindabur (Goa), and +visiting the Maldive Islands, where he became kazi, and married four +wives, and of which he has left the best medieval account, hardly +surpassed by any modern. In August 1344 he left the Maldives for Ceylon; +here he made the pilgrimage to the "Footmark of our Father Adam." Thence +he betook himself to Maabar (the Coromandel coast), where he joined a +Mussulman adventurer, residing at Madura, who had made himself master of +much of that region. After once more visiting Malabar, Canara and the +Maldives, he departed for Bengal, a voyage of forty-three days, landing +at Sadkawan (Chittagong). In Bengal he visited the famous Moslem saint +Shaykh Jalaluddin, whose shrine (_Shah Jalal_ at Silhet) is still +maintained. Returning to the delta, he took ship at Sunarganw (near +Dacca) on a junk bound for Java (i.e. _Java Minor_ of Marco Polo, or +Sumatra). Touching the coast of Arakan or Burma, he reached Sumatra in +forty days, and was provided with a junk for China by Malik al Dhahir, a +zealous disciple of Islam, which had recently spread among the states on +the northern coast of that island. Calling (apparently) at Cambodia on +his way, Ibn Batuta reached China at Zayton (Amoy harbour), famous from +Marco Polo; he also visited Sin Kalan or Canton, and professes to have +been in Khansa (_Kinsay_ of Marco Polo, i.e. Hangchau), and Khanbalik +(_Cambaluc_ or Peking). The truth of his visit to these two cities, and +especially to the last, has been questioned. The traveller's history, +not least in China, singularly illustrates the free masonry of Islam, +and its power of carrying a Moslem doctor over the known world of Asia +and Africa. On his way home he saw the great bird _Rukh_ (evidently, +from his description, an island lifted by refraction); revisited +Sumatra, Malabar, Oman, Persia, Bagdad, and crossed the great desert to +Palmyra and Damascus, where he got his first news of home, and heard of +his father's death fifteen years before. Diverging to Hamath and Aleppo, +on his return to Damascus, he found the Black Death raging, so that two +thousand four hundred died in one day. Revisiting Jerusalem and Cairo he +made the _haj_ a fourth time, and finally reappeared at Fez (visiting +Sardinia _en route_) on the 8th of November 1349, after twenty-four +years' absence. Morocco, he felt, was, after all, the best of countries. +"The _dirhems_ of the West are but little; but then you get more for +them." After going home to Tangier, Ibn Batuta crossed into Spain and +made the round of Andalusia, including Gibraltar, which had just then +stood a siege from the "Roman tyrant Adfunus" (Alphonso XI. of Castile, +1312-1350). In 1352 the restless man started for Central Africa, passing +by the oases of the Sahara (where the houses were built of rock-salt, as +Herodotus tells, and roofed with camel skins) to Timbuktu and Gogo on +the Niger, a river which he calls the Nile, believing it to flow down +into Egypt, an opinion maintained by some up to the date of Lander's +discovery. Being then recalled by his own king, he returned to Fez +(early in 1354) via Takadda, Haggar and Tuat. Thus ended his +twenty-eight years' wanderings which in their main lines alone exceeded +75,000 m. By royal order he dictated his narrative to Mahommed Ibn +Juzai, who concludes the work, 13th of December 1355 (A.D.) with the +declaration: "This Shaykh is the traveller of our age; and he who should +call him the traveller of the whole body of Islam would not exceed the +truth." Ibn Batuta died in 1378, aged seventy-three. + + Ibn Batuta's travels have only been known in Europe during the 19th + century; at first merely by Arabic abridgments in the Gotha and + Cambridge libraries. Notices or extracts had been published by Seetzen + (c. 1808), Kosegarten (1818), Apetz (1819), and Burckhardt (1819), + when in 1829 Dr S. Lee published for the Oriental Translation Fund a + version from the abridged MSS. at Cambridge, which attracted much + interest. The French capture of Constantina afforded MSS. of the + complete work, one of them the autograph of Ibn Juzai. And from these, + after versions of fragments by various French scholars, was derived at + last (1858-1859) the standard edition and translation of the whole by + M. Défrémery and Dr Sanguinetti, in 4 vols. See also Sir Henry Yule, + Cathay, ii. 397-526; C. Raymond Beazley, _Dawn of Modern Geography_, + iii. 535-538. Though there are some singular chronological + difficulties in the narrative, and a good many cursory inaccuracies + and exaggerations, there is no part of it except, perhaps, certain + portions of the journeys in north China, which is open to doubt. The + accounts of the Maldive Islands, and of the Negro countries on the + Niger, are replete with interesting and accurate particulars. The + former agrees surprisingly with that given by the only other foreign + resident we know of, Pyrard de la Val, two hundred and fifty years + later. Ibn Batuta's statements and anecdotes regarding the showy + virtues and solid vices of Sultan Muhammad Tughlak are in entire + agreement with Indian historians, and add many fresh details. + (H. Y.; C. R. B.) + + + + +IBN DURAID [Abu Bakr Mahommed ibn ul-Hasan ibn Duraid ul-Azdi] +(837-934), Arabian poet and philologist, was born at Basra of south +Arabian stock. At his native place he was trained under various +teachers, but fled in 871 to Oman at the time Basra was attacked by the +negroes, known as the Zanj, under Muhallabi. After living twelve years +in Oman he went to Persia, and, under the protection of the governor, +'Abdallah ibn Mahommed ibn Mikal, and his son, Isma'il, wrote his chief +works. In 920 he went to Bagdad, where he received a pension from the +caliph Moqtadir. + + The _Maqsura_, a poem in praise of Ibn Mikal and his son, has been + edited by A. Haitsma (1773) E. Scheidius (1786) and N. Boyesen (1828). + Various commentaries on the poem exist in MS. (cf. C. Brockelmann, + _Gesch. der ar. Lit._, i. 211 ff., Weimar, 1898), The _Jamhara + fi-l-Lugha_ is a large dictionary written in Persian but not printed. + Another work is the _Kitab ul-Ishtiqaq_ ("Book of Etymology"), edited + by F. Wüstenfeld (Göttingen, 1854); it was written in opposition to + the anti-Arabian party to show the etymological connexion of the + Arabian tribal names. (G. W. T.) + + + + +IBN FARADI [Abu-l-Walid 'Abdallah ibn ul-Faradi] (962-1012), Arabian +historian, was born at Cordova and studied law and tradition. In 992 he +made the pilgrimage and proceeded to Egypt and Kairawan, studying in +these places. After his return in 1009 he became cadi in Valencia, and +was killed at Cordova when the Berbers took the city. + + His chief work is the _History of the Learned Men of Andalusia_, + edited by F. Codera (Madrid, 1891-1892). He wrote also a history of + the poets of Andalusia. (G. W. T.) + + + + +IBN FARID [Abu-l-Qasim 'Umar ibn ul-Farid] (1181-1235), Arabian poet, +was born in Cairo, lived for some time in Mecca and died in Cairo. His +poetry is entirely Sufic, and he was esteemed the greatest mystic poet +of the Arabs. Some of his poems are said to have been written in +ecstasies. His diwan has been published with commentary at Beirut, 1887, +&c.; with the commentaries of Burini (d. 1615) and 'Abdul-Ghani (d. +1730) at Marseilles, 1853, and at Cairo; and with the commentary of +Rushayyid Ghalib (19th century) at Cairo, 1893. One of the separate +poems was edited by J. von Hammer Purgstall as _Das arabische hohe Lied +der Liebe_ (Vienna, 1854). + + See R. A. Nicholson, _A Literary History of the Arabs_ (London, 1907), + pp. 394-398. (G. W. T.) + + + + +IBN GABIROL [SOLOMON BEN JUDAH], Jewish poet and philosopher, was born +at Malaga, probably about 1021. The early part of his troublous life was +spent at Saragossa, but few personal details of it are recorded. His +parents died while he was a child and he was under the protection first +of a certain Jekuthiel, who died in 1039, and afterwards of Samuel +ha-Nagid, the well-known patron of learning. His passionate disposition, +however, embittered no doubt by his misfortunes, involved him in +frequent difficulties and led to his quarrelling with Samuel. It is +generally agreed that he died young, although the date is uncertain. Al +Harizi[1] says at the age of twenty-nine, and Moses b. Ezra[2] about +thirty, but Abraham Zaccuto[3] states that he died (at Valencia) in +1070. M. Steinschneider[4] accepts the date 1058. + +His literary activity began early. He is said to have composed poems at +the age of sixteen, and elegies by him are extant on Hai Gaon (died in +1038) and Jekuthiel (died in 1039), each of which was written probably +soon after the death of the person commemorated. About the same time he +also wrote his _'Anaq_, a poem on grammar, of which only 97 lines out of +400 are preserved. Moses ben Ezra says of him that he imitated Moslem +models, and was the first to open to Jewish poets the door of +versification,[5] meaning that he first popularized the use of Arabic +metres in Hebrew. It is as a poet that he has been known to the Jews to +the present day, and admired for the youthful freshness and beauty of +his work, in which he may be compared to the romantic school in France +and England in the early 19th century. Besides his lyrical and satirical +poems, he contributed many of the finest compositions to the liturgy +(some of them with the acrostic "Shelomoh ha-qato"), which are widely +different from the artificial manner of the earlier payyetanim. The best +known of his longer liturgical compositions are the philosophical +_Kether Malkuth_ (for the Day of Atonement) and the _Azharoth_, on the +613 precepts (for _Shebhu'oth_). Owing to his pure biblical style he had +an abiding influence on subsequent liturgical writers. + +Outside the Jewish community he was known as the philosopher Avicebron +(Avencebrol, Avicebrol, &c.) The credit of identifying this name as a +medieval corruption of Ibn Gabirol is due to S. Munk, who showed that +selections made by Shem Tobh Palqera (or Falqera) from the Meqor Hayyim +(the Hebrew translation of an Arabic original) by Ibn Gabirol, +corresponded to the Latin _Fons Vitae_ of Avicebron. The Latin version, +made by Johannes Hispalensis and Gundisalvi about one hundred years +after the author's death, had at once become known among the Schoolmen +of the 12th century and exerted a powerful influence upon them, although +so little was known of the author that it was doubted whether he was a +Christian or a Moslem. The teaching of the _Fons Vitae_ was entirely new +to the country of its origin, and being drawn largely from Neoplatonic +sources could not be expected to find favour with Jewish thinkers. Its +distinctive doctrines are: (1) that all created beings, spiritual or +corporeal, are composed of matter and form, the various species of +matter being but varieties of the universal matter, and similarly all +forms being contained in one universal form; (2) that between the primal +One and the intellect (the [Greek: nous] of Plotinus) there is +interposed the divine Will, which is itself divine and above the +distinction of form and matter, but is the cause of their union in the +being next to itself, the intellect, in which Avicebron holds that the +distinction does exist. The doctrine that there is a material, as well +as a formal, element in all created beings was explicitly adopted from +Avicebron by Duns Scotus (as against the view of Albertus Magnus and +Thomas Aquinas), and perhaps his exaltation of the will above the +intellect is due to the same influence. Avicebron develops his +philosophical system throughout quite independently of his religious +views--a practice wholly foreign to Jewish teachers, and one which could +not be acceptable to them. Indeed, this charge is expressly brought +against him by Abraham ben David of Toledo (died in 1180). It is +doubtless this non-religious attitude which accounts for the small +attention paid to the _Fons Vitae_ by the Jews, as compared with the +wide influence of the philosophy of Maimonides. + +The other important work of Ibn Gabirol is _Islah al-akhlaq_ (the +improvement of character), a popular work in Arabic, translated into +Hebrew (_Tiqqun middoth ha-nephesh_) by Judah ibn Tibbon. It is widely +different in treatment from the _Fons_, being intended as a practical +not a speculative work. + +The collection of moral maxims, compiled in Arabic but best known (in +the Hebrew translation of Judah ibn Tibbon) as _Mibhar ha-peninim_, is +generally ascribed to Ibn Gabirol, though on less certain grounds. + + BIBLIOGRAPHY.--Texts of the liturgical poems are to be found in the + prayer-books: others in Dukes and Edelmann, _Treasures of Oxford_ + (Oxford, 1850); Dukes, _Shire Shelomoh_ (Hanover, 1858); S. Sachs, + _Shir ha-shirim asher li-Shelomoh_ (Paris, 1868, incomplete); Brody, + _Die weltlichen Gedichte des ... Gabirol_ (Berlin, 1897, &c.). + + "Avencebrolis Fons Vitae" (Latin text) in Clemens Bäumker's _Beiträge + zur Gesch. d. Philosophie_, Bd. i. Hefte 2-4 (Münster, 1892); _The + Improvement of the Moral Qualities_ [Arabic and English] ed. by S. S. + Wise (New York, 1901); _A Choice of Pearls_ [Hebrew and English] ed. + by Ascher (London, 1859). + + On the philosophy in general: S. Munk, _Mélanges_ (quoted above); + Guttmann, _Die Philosophie des Sal.-ibn Gabirol_ (Göttingen, 1889); D. + Kaufmann, _Studien über Sal.-ibn Gabirol_ (Budapest, 1899); S. + Horovitz, "Die Psychologie Ibn Gabirols," in the _Jahresbericht des + jüd. theol. Seminars Fränckel'scher Stiftung_ (Breslau, 1900); + Wittmann, "Zur Stellung Avencebrols ..." (in Bäumker's _Beiträge_, Bd. + v. Heft 1, Münster, 1905). (A. Cy.) + + +FOOTNOTES: + + [1] _Jud. Har. Macamæ_, ed. Lagarde (Göttingen, 1883), p. 89, l. 61. + + [2] See the passage quoted by Munk, _Mélanges de philosophie arabe et + juive_ (Paris, 1859), pp. 264 and 517. + + [3] _Liber Juchassin_, ed. Filipowski (London, 1857), p. 217. + + [4] _Hebr. Übersetzungen_ (Berlin, 1893), § 219, note 70; cf. + Kaufmann, _Studien über Sal.-ibn Gabirol_ (Budapest, 1899), p. 79, + note 2. + + [5] See Munk, _op. cit._ pp. 515-516, transl. on pp. 263-264. Metre + had been already used by Dunash. + + + + +IBN HAUKAL, strictly IBN HAUQAL, a 10th century Arabian geographer. +Nothing is known of his life. His work on geography, written in 977, is +only a revision and extension of the _Masalik ul-Mamalik_ of +al-Istakhri, who wrote in 951. This itself was a revised edition of the +_Kitab ul-Ashkal_ or _Suwar ul-Aqalim_ of Abu Zaid ul-Balkhi, who wrote +about 921. Ibn Haukal's work was published by M. J. de Goeje (Leiden, +1873). An anonymous epitome of the book was written in 1233. + + See M. J. de Goeje, "Die Istahri-Balhi Frage," in the _Zeitschrift der + deutschen Morgenländischen Gesellschaft_, xxv. 42 sqq. + + + + +IBN HAZM [Abu Mahommed 'Ali ibn Ahmad ibn Hazm] (994-1064), Moslem +theologian, was born in a suburb of Cordova. He studied history, law and +theology, and became a vizier as his father had been before him, but was +deposed for heresy, and spent the rest of his life quietly in the +country. In legal matters he belonged first to the Shafi'ite school, but +came to adopt the views of the Zahirites, who admitted only the external +sense of the Koran and tradition, disallowing the use of analogy +(_Qiyas_) and _Taqlid_ (appeal to the authority of an imam), and +objecting altogether to the use of individual opinion (_Ra'y_). Every +sentence of the Koran was to be interpreted in a general and universal +sense; the special application to the circumstances of the time it was +written was denied. Every word of the Koran was to be taken in a literal +sense, but that sense was to be learned from other uses in the Koran +itself, not from the meaning in other literature of the time. The +special feature of Ibn Hazm's teaching was that he extended the +application of these principles from the study of law to that of +dogmatic theology. He thus found himself in opposition at one time to +the Mo'tazilites, at another to the Ash'arites. He did not, however, +succeed in forming a school. His chief work is the _Kitab ul-Milal +wan-Nihal_, or "Book of Sects" (published in Cairo, 1899). + + For his teaching cf. I. Goldziher, _Die Zahiriten_, pp. 116-172 + (Leipzig, (1884), and M. Schreiner in the _Journal of the German + Oriental Society_, lii. 464-486. For a list of his other works see C. + Brockelmann's _Geschichte der arabischen Literatur_, vol. i. (Weimar, + 1898), p. 400. (G. W. T.) + + + + + +IBN HISHAM [Abu Mahommed 'Abdulmalik ibn Hisham ibn Ayyub ul-Himyari] +(d. 834), Arabian biographer, studied in Kufa but lived afterwards in +Fostat (old Cairo), where he gained a name as a grammarian and student +of language and history. His chief work is his edition of Ibn Ishaq's +(q.v.) _Life of the Apostle of God_, which has been edited by F. +Wüstenfeld (Göttingen, 1858-1860). An abridged German translation has +been made by G. Weil (Stuttgart, 1864; cf. P. Brönnle, _Die +Commentatoren des Ibn Ishaq und ihre Scholien_, Halle, 1895). Ibn Hisham +is said to have written a work explaining the difficult words which +occur in poems on the life of the Apostle, and another on the +genealogies of the Himyarites and their princes. (G. W. T.) + + + + +IBN ISHAQ [Mahommed ibn Ishaq Abu 'Abdallah] (d. 768), Arabic historian, +lived in Medina, where he interested himself to such an extent in the +details of the Prophet's life that he was attacked by those to whom his +work seemed to have a rationalistic tendency. He consequently left +Medina in 733, and went to Alexandria, then to Kufa and Hira, and +finally to Bagdad, where the caliph Mansur provided him with the means +of writing his great work. This was the _Life of the Apostle of God_, +which is now lost and is known to us only in the recension of Ibn Hisham +(q.v.). The work has been attacked by Arabian writers (as in the +_Fihrist_) as untrustworthy, and it seems clear that he introduced +forged verses (cf. _Journal of the German Oriental Society_, xiv. 288 +sqq.). It remains, however, one of the most important works of the age. + (G. W. T.) + + + + +IBN JUBAIR [Abu-l Husain Mahommed ibn Ahmad ibn Jubair] (1145-1217), +Arabian geographer, was born in Valencia. At Granada he studied the +Koran, tradition, law and literature, and later became secretary to the +Mohad governor of that city. During this time he composed many poems. In +1183 he left the court and travelled to Alexandria, Jerusalem, Medina, +Mecca, Damascus, Mosul and Bagdad, returning in 1185 by way of Sicily. + + The _Travels of Ibn Jubair_ were edited by W. Wright (Leiden, 1852); + and a new edition of this text, revised by M. J. de Goeje, was + published by the Gibb Trustees (London, 1907). The part relating to + Sicily was published, with French translation and notes, by M. Amari + in the _Journal asiatique_ (1845-1846) and a French translation alone + of the same part by G. Crolla in _Museon_, vi. 123-132. (G. W. T.) + + + + +IBN KHALDUN [Abu Zaid ibn Mahommed ibn Mahommed ibn Khaldun] +(1332-1406), Arabic historian, was born at Tunis. He studied the various +branches of Arabic learning with great success. In 1352 he obtained +employment under the Marinid sultan Abu Inan (Faris I.) at Fez. In the +beginning of 1356, his integrity having been suspected, he was thrown +into prison until the death of Abu Inan in 1358, when the vizier +al-Hasan ibn Omar set him at liberty and reinstated him in his rank and +offices. He here continued to render great service to Abu Salem (Ibrahim +III.), Abu Inan's successor, but, having offended the prime minister, he +obtained permission to emigrate to Spain, where, at Granada, he was +received with great cordiality by Ibn al Ahmar, who had been greatly +indebted to his good offices when an exile at the court of Abu Salem. +The favours he received from the sovereign excited the jealousy of the +vizier, and he was driven back to Africa (1364), where he was received +with great cordiality by the sultan of Bougie, Abu Abdallah, who had +been formerly his companion in prison. On the fall of Abu Abdallah Ibn +Khaldun raised a large force amongst the desert Arabs, and entered the +service of the sultan of Tlemçen. A few years later he was taken +prisoner by Abdalaziz ('Abd ul 'Aziz), who had defeated the sultan of +Tlemçen and seized the throne. He then entered a monastic establishment, +and occupied himself with scholastic duties, until in 1370 he was sent +for to Tlemçen by the new sultan. After the death of 'Abd ul 'Aziz he +resided at Fez, enjoying the patronage and confidence of the regent. +After some further vicissitudes in 1378 he entered the service of the +sultan of his native town of Tunis, where he devoted himself almost +exclusively to his studies and wrote his history of the Berbers. Having +received permission to make the pilgrimage to Mecca, he reached Cairo, +where he was presented to the sultan, al-Malik udh-Dhahir Barkuk, who +insisted on his remaining there, and in the year 1384 made him grand +cadi of the Malikite rite for Cairo. This office he filled with great +prudence and probity, removing many abuses in the administration of +justice in Egypt. At this time the ship in which his wife and family, +with all his property, were coming to join him, was wrecked, and every +one on board lost. He endeavoured to find consolation in the completion +of his history of the Arabs of Spain. At the same time he was removed +from his office of cadi, which gave him more leisure for his work. Three +years later he made the pilgrimage to Mecca, and on his return lived in +retirement in the Fayum until 1399, when he was again called upon to +resume his functions as cadi. He was removed and reinstated in the +office no fewer than five times. + +In 1400 he was sent to Damascus, in connexion with the expedition +intended to oppose Timur or Tamerlane. When Timur had become master of +the situation, Ibn Khaldun let himself down from the walls of the city +by a rope, and presented himself before the conqueror, who permitted him +to return to Egypt. Ibn Khaldun died on the 16th of March 1406, at the +age of sixty-four. + + The great work by which he is known is a "Universal History," but it + deals more particularly with the history of the Arabs of Spain and + Africa. Its Arabic title is _Kitab ul'Ibar, wa diwan el Mubtada wa'l + Khabar, fi ayyam ul 'Arab wa'l'Ajam wa'l Berber_; that is, "The Book + of Examples and the Collection of Origins and Information respecting + the History of the Arabs, Foreigners and Berbers." It consists of + three books, an introduction and an autobiography. Book i. treats of + the influence of civilization upon man; book ii. of the history of the + Arabs and other peoples from the remotest antiquity until the author's + own times; book iii. of the history of the Berber tribes and of the + kingdoms founded by that race in North Africa. The introduction is an + elaborate treatise on the science of history and the development of + society, and the autobiography contains the history, not only of the + author himself, but of his family and of the dynasties which ruled in + Fez, Tunis and Tlemçen during his lifetime. An edition of the Arabic + text has been printed at Bulaq, (7 vols., 1867) and a part of the work + has been translated by the late Baron McG. de Slane under the title of + _Histoire des Berbères_ (Algiers, 1852-1856); it contains an admirable + account of the author and analysis of his work. Vol. i., the + _Muqaddama_ (preface), was published by M. Quatremère (3 vols., Paris, + 1858), often republished in the East, and a French translation was + made by McG. de Slane (3 vols., Paris, 1862-1868). The parts of the + history referring to the expeditions of the Franks into Moslem lands + were edited by C. J. Tornberg (Upsala, 1840), and the parts treating + of the Banu-l Ahmar kings of Granada were translated into French by M. + Gaudefroy-Demombynes in the _Journal asiatique_, ser. 9, vol. xiii. + The _Autobiography_ of Ibn Khaldun was translated into French by de + Slane in the _Journal asiatique_, ser. 4, vol. iii. For an English + appreciation of the philosophical spirit of Ibn Khaldun see R. Flint's + _History of the Philosophy of History_ (Edinburgh, 1893), pp. 157-170. + (E. H. P.; G. W. T.) + + + + +IBN KHALLIKAN [Abu-l 'Abbas Ahmad ibn Khallikan] (1211-1282), Arabian +biographer, was born at Arbela, the son of a professor reputed to be +ascended from the Barmecides of the court of Harun al-Rashid. When +eighteen he went to Aleppo, where he studied for six years, then to +Damascus, and in 1238 to Alexandria and Cairo. In 1252 he married and +became chief cadi of Syria in Damascus in 1261. Having held this office +for ten years, he was professor in Cairo until 1278, when he again took +office in Damascus for three years. In 1281 he accepted a professorship +in the same city, but died in the following year. + + His great work is the _Kitab Wafayat ul-A'yan_, "The Obituaries of + Eminent Men." It contains in alphabetical order the lives of the most + celebrated persons of Moslem history and literature, except those of + Mahomet, the four caliphs and the companions of Mahomet and their + followers (the _Tabiun_). The work is anecdotal and contains many + brief extracts from the poetry of the writers. It was published by F. + Wüstenfeld (Göttingen, 1835-1843), in part by McG. de Slane (Paris, + 1838-1842), and also in Cairo (1859 and 1882). An English translation + by McG. de Slane was published for the Oriental Translation Fund in 4 + vols. (London, 1842-1871). Thirteen extra biographies from a + manuscript in Amsterdam were published by Pijnappel (Amsterdam, 1845). + A Persian translation exists in manuscript, and various extracts from + the work are known. Several supplements to the book have been written, + the best known being that of Mahommed ibn Shakir (d. 1362), published + at Cairo 1882. A collection of poems by Ibn Khallikan is also extant. + (G. W. T.) + + + + +IBN QUTAIBA, or KOTAIBA [Abu Mahommed ibn Muslim ibn Qutaiba] (828-889), +Arabian writer, was born at Bagdad or Kufa, and was of Iranian descent, +his father belonging to Merv. Having studied tradition and philology he +became cadi in Dinawar and afterwards teacher in Bagdad, where he died. +He was the first representative of the eclectic school of Bagdad +philologists that succeeded the schools of Kufa and Basra (see ARABIA: +_Literature_, section "Grammar"). Although engaged also in theological +polemic (cf. I. Goldziher, _Muhammedanische Studien_, ii. 136, Halle, +1890), his chief works were directed to the training of the ideal +secretary. Of these five may be said to form a series. The _Adab +ul-Katib_ ("Training of the Secretary") contains instruction in writing +and is a compendium of Arabic style. It has been edited by Max Grünert +(Leiden, 1900). The _Kitab ush-Sharab_ is still in manuscript. The +_Kitab ul-Ma'arif_ has been edited by F. Wüstenfeld as the _Handbuch der +Geschichte_[1] (Göttingen, 1850); the _Kitab ush-Shi'r wash-Shu'arai_ +("Book of Poetry and Poets") edited by M. J. de Goeje (Leiden, 1904).[2] +The fifth and most important is the _'Uyun ul-Akhbar_, which deals in +ten books with lordship, war, nobility, character, science and +eloquence, asceticism, friendship, requests, foods and women, with many +illustrations from history, poetry and proverb (ed. C. Brockelmann, +Leiden, 1900 sqq.). + + For other works (which were much quoted by later Arabian writers) see + C. Brockelmann, _Gesch. der arabischen Literatur_, vol. i. (Weimar, + 1898), pp. 120-122. (G. W. T.) + + +FOOTNOTES: + + [1] Summary in E. G. Browne, _A Literary History of Persia_ (London, + 1902), pp. 387 f. + + [2] The preface was translated into German by Theodor Nöldeke in his + _Beiträge_ (Hanover, 1864), pp. 1-51. + + + + +IBN SA'D [Abu 'Abdallah Mahommed ibn Sa'd ibn Mani' uz-Zuhri, often +called Katib ul-Waqidi ("secretary of Waqidi") of Basra] (d. 845), +Arabian biographer, received his training in tradition from Waqidi and +other celebrated teachers. He lived for the most part in Bagdad, and had +the reputation of being both trustworthy and accurate in his writings, +which, in consequence, were much used by later writers. His work, the +_Kitab ul-Tabaqat ul-Kabir_ (15 vols.) contains the lives of Mahomet, +his Companions and Helpers (including those who fought at Badr as a +special class) and of the following generation (the Followers) who +received their traditions from the personal friends of the Prophet. + + This work has been edited under the superintendence of E. Sachau + (Leiden, 1904 sqq.); cf. O. Loth, _Das Classenbuch des Ibn Sa'd_ + (Leipzig, 1869). (G. W. T.) + + + + +IBN TIBBON, a family of Jewish translators, who flourished in Provence +in the 12th and 13th centuries. They all made original contributions to +philosophical and scientific literature, but their permanent fame is +based on their translations. Between them they rendered into Hebrew all +the chief Jewish writings of the middle ages. These Hebrew translations +were, in their turn, rendered into Latin (by Buxtorf and others) and in +this form the works of Jewish authors found their way into the learned +circles of Europe. The chief members of the Ibn Tibbon family were (1) +JUDAH BEN SAUL (1120-1190), who was born in Spain but settled in Lunel. +He translated the works of Bahya, Halevi, Saadiah and the grammatical +treatises of Janah. (2) His son, SAMUEL (1150-1230), translated the +_Guide of the Perplexed_ by Maimonides. He justly termed his father "the +father of the Translators," but Samuel's own method surpassed his +father's in lucidity and fidelity to the original. (3) Son of Samuel, +MOSES (died 1283). He translated into Hebrew a large number of Arabic +books (including the Arabic form of Euclid). The Ibn Tibbon family thus +rendered conspicuous services to European culture, and did much to +further among Jews who did not understand Arabic the study of science +and philosophy. (I. A.) + + + + +IBN TUFAIL, or TOFAIL [Abu Bakr Mahommed ibn 'Abd-ul-Malik ibn Tufail +ul-Qaisi] (d. 1185), Moslem philosopher, was born at Guadix near +Granada. There he received a good training in philosophy and medicine, +and is said to have been a pupil of Avempace (q.v.). He became secretary +to the governor of Granada, and later physician and vizier to the Mohad +caliph, Abu Ya'qub Yusuf. He died at Morocco. + + His chief work is a philosophical romance, in which he describes the + awakening and growth of intellect in a child removed from the + influences of ordinary life. Its Arabic title is _Risalat Hayy ibn + Yaqzan_; it was edited by E. Pococke as _Philosophus autodidactus_ + (Oxford, 1671; 2nd ed., 1700), and with a French translation by L. + Gauthier (Algiers, 1900). An English translation by S. Ockley was + published in 1708 and has been reprinted since. A Spanish translation + by F. Pons Boigues was published at Saragossa (1900). Another work of + Ibn Tufail, the _Kitab Asrar ul-Hikma ul-mashraqiyya_ ("Secrets of + Eastern Science"), was published at Bulaq (1882); cf. S. Munk, + _Mélanges_ (1859), pp. 410 sqq., and T. J. de Boer, _Geschichte der + Philosophie im Islam_ (Stuttgart, 1901), pp. 160 sqq. (also an English + translation). (G. W. T.) + + + + +IBN USAIBI'A [Muwaffaquddin Abu-l-'Abbas Ahmad ibn ul-Qasim ibn Abi +Usaibi'a] (1203-1270), Arabian physician, was born at Damascus, the son +of an oculist, and studied medicine at Damascus and Cairo. In 1236 he +was appointed by Saladin physician to a new hospital in Cairo, but +surrendered the appointment the following year to take up a post given +him by the amir of Damascus in Salkhad near that city. There he lived +and died. He wrote '_Uyun ul-Anba'fi Tabaqat ul-Atibba_' or "Lives of +the Physicians," which in its first edition (1245-1246) was dedicated to +the vizier of Damascus. This he enlarged, though it is uncertain whether +the new edition was made public in the lifetime of the author. + + Edition by A. Müller (Königsberg, 1884). (G. W. T.) + + + + +IBO, a district of British West Africa, on the lower Niger immediately +above the delta, and mainly on the eastern bank of the river. The chief +town, frequently called by the same name (more correctly Abo or Áboh), +lies on a creek which falls into the main stream about 150 m. from its +mouth and contains from 6000 to 8000 inhabitants. The Ibo are a strong +well-built Negro race. Their women are distinguished by their +embonpoint. The language of the Ibo is one of the most widely spoken on +the lower Niger. The Rev. J. F. Schön began its reduction in 1841, and +in 1861 he published a grammar (_Oku Ibo Grammatical Elements_, London, +Church Miss. Soc.). (See NIGERIA.) + + + + +IBRAHIM AL-MAUSILI (742-804), Arabian singer, was born of Persian +parents settled in Kufa. In his early years his parents died and he was +trained by an uncle. Singing, not study, attracted him, and at the age +of twenty-three he fled to Mosul, where he joined a band of wild youths. +After a year he went to Rai (Rei, Rhagae), where he met an ambassador of +the caliph Mansur, who enabled him to come to Basra and take singing +lessons. His fame as a singer spread, and the caliph Mahdi brought him +to the court. There he remained a favourite under Hadi, while Harun +al-Rashid kept him always with him until his death, when he ordered his +son (Ma'mun) to say the prayer over his corpse. Ibrahim, as might be +expected, was no strict Moslem. Two or three times he was knouted and +imprisoned for excess in wine-drinking, but was always taken into favour +again. His powers of song were far beyond anything else known at the +time. Two of his pupils, his son Ishaq and Muhariq, attained celebrity +after him. + + See the Preface to W. Ahlwardt's _Abu Nowas_ (Greifswald, 1861), pp. + 13-18, and the many stories of his life in the _Kitab ul-Aghani_, v. + 2-49. (G. W. T.) + + + + +IBRAHIM PASHA (1789-1848), Egyptian general, is sometimes spoken of as +the adopted son of Mehemet Ali, pasha of Egypt. He is also and more +commonly called his son. He was born in his father's native town, Kavala +in Thrace. During his father's struggle to establish himself in Egypt, +Ibrahim, then sixteen years of age, was sent as a hostage to the Ottoman +capitan pasha (admiral), but when Mehemet Ali was recognized as pasha, +and had defeated the English expedition under General A. M. Fraser, he +was allowed to return to Egypt. When Mehemet Ali went to Arabia to +prosecute the war against the Wahhabis in 1813, Ibrahim was left in +command in Upper Egypt. He continued the war with the broken power of +the Mamelukes, whom he suppressed. In 1816 he succeeded his brother +Tusun in command of the Egyptian forces in Arabia. Mehemet Ali had +already begun to introduce European discipline into his army, and +Ibrahim had probably received some training, but his first campaign was +conducted more in the old Asiatic style than his later operations. The +campaign lasted two years, and terminated in the destruction of the +Wahhabis as a political power. Ibrahim landed at Yembo, the port of +Medina, on the 30th of September 1816. The holy cities had been +recovered from the Wahhabis, and Ibrahim's task was to follow them into +the desert of Nejd and destroy their fortresses. Such training as the +Egyptian troops had received, and their artillery, gave them a marked +superiority in the open field. But the difficulty of crossing the desert +to the Wahhabi stronghold of Deraiya, some 400 m. east of Medina, and +the courage of their opponents, made the conquest a very arduous one. +Ibrahim displayed great energy and tenacity, sharing all the hardships +of his army, and never allowing himself to be discouraged by failure. By +the end of September 1818 he had forced the Wahhabi leader to surrender, +and had taken Deraiya, which he ruined. On the 11th of December 1819 he +made a triumphal entry into Cairo. After his return he gave effective +support to the Frenchman, Colonel Sève (Suleiman Pasha), who was +employed to drill the army on the European model. Ibrahim set an example +by submitting to be drilled as a recruit. When in 1824 Mehemet Ali was +appointed governor of the Morea by the sultan, who desired his help +against the insurgent Greeks, he sent Ibrahim with a squadron and an +army of 17,000 men. The expedition sailed on the 10th of July 1824, but +was for some months unable to do more than come and go between Rhodes +and Crete. The fear of the Greek fire ships stopped his way to the +Morea. When the Greek sailors mutinied from want of pay, he was able to +land at Modon on the 26th of February 1825. He remained in the Morea +till the capitulation of the 1st of October 1828 was forced on him by +the intervention of the Western powers. Ibrahim's operations in the +Morea were energetic and ferocious. He easily defeated the Greeks in the +open field, and though the siege of Missolonghi proved costly to his own +troops and to the Turks who operated with him, he brought it to a +successful termination on the 24th of April 1826. The Greek guerrilla +bands harassed his army, and in revenge he desolated the country and +sent thousands of the inhabitants into slavery in Egypt. These measures +of repression aroused great indignation in Europe, and led first to the +intervention of the English, French and Russian squadrons (see NAVARINO, +BATTLE OF), and then to the landing of a French expeditionary force. By +the terms of the capitulation of the 1st of October 1828, Ibrahim +evacuated the country. It is fairly certain that the Turkish government, +jealous of his power, had laid a plot to prevent him and his troops from +returning to Egypt. English officers who saw him at Navarino describe +him as short, grossly fat and deeply marked with smallpox. His obesity +did not cause any abatement of activity when next he took the field. In +1831, his father's quarrel with the Porte having become flagrant, +Ibrahim was sent to conquer Syria. He carried out his task with truly +remarkable energy. He took Acre after a severe siege on the 27th of May +1832, occupied Damascus, defeated a Turkish army at Homs on the 8th of +July, defeated another Turkish army at Beilan on the 29th of July, +invaded Asia Minor, and finally routed the grand vizier at Konia on the +21st of December. The convention of Kutaiah on the 6th of May left Syria +for a time in the hands of Mehemet Ali. Ibrahim was undoubtedly helped +by Colonel Sève and the European officers in his army, but his +intelligent docility to their advice, as well as his personal hardihood +and energy, compare most favourably with the sloth, ignorance and +arrogant conceit of the Turkish generals opposed to him. He is entitled +to full credit for the diplomatic judgment and tact he showed in +securing the support of the inhabitants, whom he protected and whose +rivalries he utilized. After the campaign of 1832 and 1833 Ibrahim +remained as governor in Syria. He might perhaps have administered +successfully, but the exactions he was compelled to enforce by his +father soon ruined the popularity of his government and provoked +revolts. In 1838 the Porte felt strong enough to renew the struggle, and +war broke out once more. Ibrahim won his last victory for his father at +Nezib on the 24th of June 1839. But Great Britain and Austria intervened +to preserve the integrity of Turkey. Their squadrons cut his +communications by sea with Egypt, a general revolt isolated him in +Syria, and he was finally compelled to evacuate the country in February +1841. Ibrahim spent the rest of his life in peace, but his health was +ruined. In 1846 he paid a visit to western Europe, where he was received +with some respect and a great deal of curiosity. When his father became +imbecile in 1848 he held the regency till his own death on the 10th of +November 1848. + + See Edouard Gouin, _L'Égypte au XIX^e siècle_ (Paris, 1847); Aimé + Vingtrinier, _Soliman-Pasha_ (_Colonel Sève_) (Paris, 1886). A great + deal of unpublished material of the highest interest with regard to + Ibrahim's personality and his system in Syria is preserved in the + British Foreign Office archives; for references to these see + _Cambridge Mod. Hist._ x. 852, bibliography to chap. xvii. + + + + +IBSEN, HENRIK (1828-1906), Norwegian dramatic and lyric poet, eldest son +of Knud Henriksen Ibsen, a merchant, and of his wife Marichen Cornelia +Altenburg, was born at Skien on the 20th of March 1828. For five +generations the family had consisted on the father's side of a blending +of the Danish, German and Scottish races, with no intermixture of pure +Norwegian. In 1836 Knud Ibsen became insolvent, and the family withdrew, +in great poverty, to a cottage in the outskirts of the town. After brief +schooling at Skien, Ibsen was, towards the close of 1843, apprenticed to +an apothecary in Grimstad; here he remained through seven dreary years +of drudgery, which set their mark upon his spirit. In 1847, in his +nineteenth year, he began to write poetry. He made a gloomy and almost +sinister impression upon persons who met him at this time, and one of +his associates of those days has recorded that Ibsen "walked about +Grimstad like a mystery sealed with seven seals." He had continued, by +assiduous reading, his self-education, and in 1850 he contrived to come +up as a student to Christiania. In the same year he published his first +work, the blank-verse tragedy of _Catilina_, under the pseudonym +Brynjolf Bjarme. A second drama, _The Viking's Barrow_, was acted (but +not printed) a few months later; Ibsen was at this time entirely under +the influence of the Danish poet Oehlenschläger. During the next year or +two he made a very precarious livelihood in Christiania as a journalist, +but in November 1851 he had the good fortune to be appointed +"stage-poet" at the little theatre of Bergen, with a small but regular +salary. He was practically manager at this house, and he also received a +travelling stipend. In 1852, therefore, he went for five months to study +the stage, to Copenhagen and to Dresden. Among many dramatic experiments +which Ibsen made in Bergen, the most considerable and most satisfactory +is the saga-drama of _Mistress Inger at Östraat_, which was produced in +1855; and printed at Christiania in 1857; here are already perceptible +some qualities of his mature character. Much less significant, although +at the time more successful, is _The Feast at Solhaug_, a tragedy +produced in Bergen in 1856; here for a moment Ibsen abandoned his own +nascent manner for an imitation of the popular romantic dramatist of +Denmark, Henrik Hertz. It is noticeable that Ibsen, by far the most +original of modern writers for the stage, was remarkably slow in +discovering the true bent of his genius. His next dramatic work was the +romantic tragedy of _Olaf Liljekrans_, performed in 1857, but unprinted +until 1898. This was the last play Ibsen wrote in Bergen. In the summer +of the former year his five years' appointment came to an end, and he +returned to Christiania. Almost immediately he began the composition of +a work which showed an extraordinary advance on all that he had written +before, the beautiful saga-drama of _The Warriors in Helgeland_, in +which he threw off completely the influence of the Danish romantic +tragedians, and took his material directly from the ancient Icelandic +sources. This play marks an epoch in the development of Norwegian +literature. It was received by the managers, both in Christiania and +Copenhagen, with contemptuous disapproval, and in the autumn of 1857 +Ibsen could not contrive to produce it even at the new theatre of which +he was now the manager. _The Warriors_ was printed at Christiania in +1858, but was not acted anywhere until 1861. During these years Ibsen +suffered many reverses and humiliations, but he persisted in his own +line in art. Some of his finest short poems, among others the admirable +seafaring romance, _Terje Vigen_, belong to the year 1860. The +annoyances which Ibsen suffered, and the retrograde and ignorant +conditions which he felt around him in Norway, developed the ironic +qualities in his genius, and he became an acid satirist. The brilliant +rhymed drama, _Love's Comedy_, a masterpiece of lyric wit and incisive +vivacity, was published in 1862. This was a protest against the +conventionality which deadens the beauty of all the formal relations +between men and women, and against the pettiness, the publicity, and the +prosiness of betrothed and married life among the middle classes in +Norway; it showed how society murders the poetry of love. For some time +past Ibsen had been meditating another saga-drama in prose, and in 1864 +this appeared, _Kongsemnerne_ (The Pretenders). These works, however, +now so universally admired, contained an element of strangeness which +was not welcome when they were new. Ibsen's position in Christiania grew +more and more disagreeable, and he had positive misfortunes which added +to his embarrassment. In 1862 his theatre became bankrupt, and he was +glad to accept the poorly-paid post of "aesthetic adviser" at the other +house. An attempt to obtain a poet's pension (_digtergage_) was +unsuccessful; the Storthing, which had just voted one to Björnson, +refused to do the same for Ibsen. His cup was full of disillusion and +bitterness, and in April 1864 he started, by Berlin and Trieste, +ultimately to settle in Rome. His anger and scorn gave point to the +satirical arrows which he shot back to his thankless fatherland from +Italy in the splendid poem of _Brand_, published in Copenhagen in 1866, +a fierce attack on the Laodicean state of religious and moral sentiment +in the Norway of that day; the central figure, the stern priest Brand, +who attempts to live like Christ and is snubbed and hounded away by his +latitudinarian companions, is one of the finest conceptions of a modern +poet. Ibsen had scarcely closed _Brand_ before he started a third +lyrico-dramatic satire. _Peer Gynt_ (1867), which remains, in a +technical sense, the most highly finished of all his metrical works. In +_Brand_ the hero had denounced certain weaknesses which Ibsen saw in the +Norwegian character, but these and other faults are personified in the +hero of _Peer Gynt_; or rather, in this figure the poet pictured, in a +type, the Norwegian nation in all the egotism, vacillation, and +lukewarmness which he believed to be characteristic of it. Ibsen, +however, acted better than he preached, and he soon forgot his +abstraction in the portrait of Peer Gynt as a human individual. In this +magnificent work modern Norwegian literature first rises to a level with +the finest European poetry of the century. In 1869 Ibsen wrote the +earliest of his prose dramas, the political comedy, _The Young Men's +League_, in which for the first time he exercised his extraordinary gift +for perfectly natural and yet pregnant dialogue. Ibsen was in Egypt, in +October 1869, when his comedy was put on the stage in Christiania, amid +violent expressions of hostility; on hearing the news, he wrote his +brilliant little poem of defiance, called _At Port Saïd_. By this time, +however, he had become a successful author; _Brand_ sold largely, and +has continued to be the most popular of Ibsen's writings. In 1866, +moreover, the Storthing had been persuaded to vote him a "poet's +pension," and there was now an end of Ibsen's long struggle with +poverty. In 1868 he left Rome, and settled in Dresden until 1874, when +he returned to Norway. But after a short visit he went back to Germany, +and lived first at Dresden, afterwards at Munich, and did not finally +settle in Christiania until 1891. His shorter lyrical poems were +collected in 1871, and in that year his name and certain of his writings +were for the first time mentioned to the English public. At this time he +was revising his old works, which were out of print, and which he would +not resign again to the reading world until he had subjected them to +what in some instances (for example, _Mistress Inger at Östraat_) +amounted to practical recomposition. In 1873 he published a double +drama, each part of which was of unusual bulk, the whole forming the +tragedy of _Emperor and Galilean_; this, Ibsen's latest historical play, +has for subject the unsuccessful struggle of Julian the Apostate to hold +the world against the rising tide of Christianity. The work is of an +experimental kind, and takes its place between the early poetry and the +later prose of the author. Compared with the series of plays which Ibsen +had already inaugurated with _The Young Men's League_, _Emperor and +Galilean_ preserves a colour of idealism and even of mysticism which was +for many years to be absent from Ibsen's writings, but to reappear in +his old age with _The Master-builder_. There is some foundation for the +charge that Ibsen has made his romantic Greek emperor needlessly +squalid, and that he has robbed him, at last, too roughly of all that +made him a sympathetic exponent of Hellenism. Ibsen was now greatly +occupied by the political spectacle of Germany at war first in Denmark, +then in France, and he believed that all things were conspiring to start +a new epoch of individualism. He was therefore deeply disgusted by the +Paris commune, and disappointed by the conservative reaction which +succeeded it. This disillusion in political matters had a very direct +influence upon Ibsen's literary work. It persuaded him that nothing +could be expected in the way of reform from democracies, from large +blind masses of men moved capriciously in any direction, but that the +sole hope for the future must lie in the study of personality, in the +development of individual character. He set himself to diagnose the +conditions of society, which he had convinced himself lay sick unto +death. Hitherto Ibsen had usually employed rhymed verse for his dramatic +compositions, or, in the case of his saga-plays, a studied and +artificial prose. Now, in spite of the surprising achievements of his +poetry, he determined to abandon versification, and to write only in the +language of everyday conversation. In the first drama of this his new +period, _The Pillars of Society_ (1877), he dealt with the problem of +hypocrisy in a small commercial centre of industry, and he drew in the +Bernick family a marvellous picture of social egotism in a prosperous +seaport town. There was a certain similarity between this piece and _A +Doll's House_ (1879), although the latter was much the more successful +in awakening curiosity. Indeed, no production of Ibsen's has been so +widely discussed as this, which is nevertheless not the most coherently +conceived of his plays. Here also, social hypocrisy, was the object of +the playwright's satire, but this time mainly in relation to marriage. +In _A Doll's House_ Ibsen first developed his views with regard to the +individualism of woman. In his previous writings he had depicted woman +as a devoted and willing sacrifice to man; here he begins to explain +that she has no less a duty to herself, and must keep alive her own +conception of honour and of responsibility. The conclusion of _A Doll's +House_ was violently and continuously discussed through the length and +breadth of Europe, and to the situation of Nora Helmer is probably due +more than to anything else the long tradition that Ibsen is "immoral." +He braved convention still more audaciously in _Ghosts_ (1881), perhaps +the most powerful of the series of plays in which Ibsen diagnoses the +diseases of modern society. It was received in Norway with a tumult of +ill-will, and the author was attacked no less venomously than he had +been twenty years before. Ibsen was astonished and indignant at the +reception given to _Ghosts_, and at the insolent indifferentism of the +majority to all ideas of social reform. He wrote, more as a pamphlet +than as a play, what is yet one of the most effective of his comedies, +_An Enemy of the People_ (1882). Dr Stockmann, the hero of that piece, +discovers that the drainage system of the bathing-station on which the +little town depends is faulty, and the water impure and dangerous. He +supposes that the corporation will be grateful to have these +deficiencies pointed out; on the contrary, they hound him out of their +midst as an "enemy of the people." In this play occurs Ibsen's famous +and typical saying, "a minority may be right--a majority is always +wrong." This polemical comedy seemed at first to be somewhat weakened by +the personal indignation which runs through it, but it has held the +stage. Ibsen's next drama, _The Wild Duck_ (1884), was written in +singular contrast with the zest and fire which had inspired _An Enemy of +the People_. Here he is squalid and pessimistic to a degree elsewhere +unparalleled in his writings; it is not quite certain that he is not +here guilty of a touch of parody of himself. The main figure of the play +is an unhealthy, unlucky enthusiast, who goes about making hopeless +mischief by exposing weak places in the sordid subterfuges of others. +This drama contains a figure, Hjálmar Ekdal, who claims the bad +pre-eminence of being the meanest scoundrel in all drama. _The Wild +Duck_ is the darkest, the least relieved, of Ibsen's studies of social +life, and his object in composing it is not obvious. With _Rosmersholm_ +(1886) he rose to the height of his genius again; this is a mournful, +but neither a pessimistic nor a cynical play. The fates which hang round +the contrasted lives of Rosmer and Rebecca, the weak-willed scrupulous +man and the strong-willed unshrinking woman, the old culture and the +new, the sickly conscience and the robust one, create a splendid +dramatic antithesis. Ibsen then began to compose a series of dramas, of +a more and more symbolical and poetic character; the earliest of these +was the mystical _The Lady from the Sea_ (1888). At Christmas 1890 he +brought out _Hedda Gabler_; two years later _The Master-builder_ +(_Bygmester Solnaes_), in which many critics see the highest attainment +of his genius; at the close of 1894 _Little Eyolf_; in 1896 _John +Gabriel Borkman_; and in 1900 _When We Dead Awaken_. On the occasion of +his seventieth birthday (1898) Ibsen was the recipient of the highest +honours from his own country and of congratulations and gifts from all +parts of the world. A colossal bronze statue of him was erected outside +the new National Theatre, Christiania, in September 1899. In 1901 his +health began to decline, and he was ordered by the physician to abandon +every species of mental effort. The evil advanced, and he became +unconscious of the passage of events. After lingering in this sad +condition he died, without suffering, on the 23rd of May 1906, and was +accorded a public funeral, with the highest national honours. + +No recent writer belonging to the smaller countries of Europe has had so +widely spread a fame as that of Ibsen, and although the value of his +dramatic work is still contested, it has received the compliment of +vivacious discussion in every part of the world. There would, perhaps, +have been less violence in this discussion if it had been perceived that +the author does not pose as a moral teacher, but as an imaginative +investigator. He often and with much heat insisted that he was not +called upon as a poet to suggest a remedy for the diseases of society, +but to diagnose them. In this he was diametrically opposed to Tolstoi, +who admitted that he wrote his books for the healing of the nations. If +the subjects which Ibsen treats, or some of them, are open to +controversy, we are at least on firm ground in doing homage to the +splendour of his art as a playwright. He reintroduced into modern +dramatic literature something of the velocity and inevitability of Greek +tragic intrigue. It is very rarely that any technical fault can be found +with the architecture of his plots, and his dialogue is the most +lifelike that the modern stage has seen. His long apprenticeship to the +theatre was of immense service to him in this respect. In every country, +though least perhaps in England, the influence of Ibsen has been marked +in the theatrical productions of the younger school. Even in England, on +the rare occasions when his dramas are acted, they awaken great interest +among intelligent playgoers. + + The editions of Ibsen's works are numerous, but the final text is + included in the _Samlede Vaerker_, with a bibliography by J. B. + Halvorsen, published in Copenhagen, in 10 vols. (1898-1902). They have + been translated into the principal European languages, and into + Japanese. The study of Ibsen in English was begun by Mr Gosse in 1872, + and continued by Mr William Archer, whose version of Ibsen's prose + dramas appeared in 5 vols. (1890, 1891; new and revised edition, + 1906). Other translators have been Mr C. Herford, Mr R. A. + Streatfield, Miss Frances Lord and Mr Adie. His _Correspondence_ was + edited, in 2 vols., under the supervision of his son, Sigurd Ibsen, in + 1904 (Eng. trans., 1905). Critical studies on the writings and + position of Ibsen are innumerable, and only those which were + influential in guiding opinion, during the early part of his career, + in the various countries, can be mentioned here: Georg Brandes + _Ästhetiske Studier_ (Copenhagen, 1868); Les Quesnel, _Poésie + scandinave_ (Paris 1874); Valfrid Valsenius, _Henrik Ibsen_ + (Helsingfors, 1879); Edmund Gosse, _Studies in Northern Literature_ + (London, 1879); L. Passarge, _Henrik Ibsen_ (Leipzig, 1883); G. + Brandes, _Björnson och Ibsen_ (Stockholm, 1882); Henrik Jaeger, + _Henrik Ibsen 1828-1888_ (Copenhagen, 1888; Eng. trans., 1890); T. + Terwey, _Henrik Ibsen_ (Amsterdam, 1882); G. Bernard Shaw, _The + Quintessence of Ibsen_ (London, 1892). In France Count Moritz Prozor + carried on an ardent propaganda in favour of Ibsen from 1885, and + Jules Lemaître's articles in his _Les Contemporains_ and _Impressions + de théâtre_ did much to encourage discussion. W. Archer forwarded the + cause in England from 1878 onwards. In Germany Ibsen began to be known + in 1866, when John Grieg, P. F. Siebold and Adolf Strodtmann + successively drew attention to his early dramas; but his real + popularity among the Germans dates from 1880. (E. G.) + + + + +IBYCUS, of Rhegium in Italy, Greek lyric poet, contemporary of Anacreon, +flourished in the 6th century B.C. Notwithstanding his good position at +home, he lived a wandering life, and spent a considerable time at the +court of Polycrates, tyrant of Samos. The story of his death is thus +related: While in the neighbourhood of Corinth, the poet was mortally +wounded by robbers. As he lay dying he saw a flock of cranes flying +overhead, and called upon them to avenge his death. The murderers betook +themselves to Corinth, and soon after, while sitting in the theatre, saw +the cranes hovering above. One of them, either in alarm or jest, +ejaculated, "Behold the avengers of Ibycus," and thus gave the clue to +the detection of the crime (Plutarch, _De Garrulitate_, xiv.). The +phrase, "the cranes of Ibycus," passed into a proverb among the Greeks +for the discovery of crime through divine intervention. According to +Suidas, Ibycus wrote seven books of lyrics, to some extent mythical and +heroic, but mainly erotic (Cicero, _Tusc. Disp._ iv. 33), celebrating +the charms of beautiful youths and girls. F. G. Welcker suggests that +they were sung by choruses of boys at the "beauty competitions" held at +Lesbos. Although the metre and dialect are Dorian, the poems breathe the +spirit of Aeolian melic poetry. + + The best editions of the fragments are by F. W. Schneidewin (1833) and + Bergk, _Poëtae lyrici Graeci_. + + + + +ICA (YCA, or ECCA), a city of southern Peru and the capital of a +department of the same name, 170 m. S.S.E. of Lima, and 46 m. by rail +S.E. of Pisco; its port on the Pacific coast. Pop. (1906, official +estimate) 6000. It lies in a valley of the foothills of the Cordillera +Occidental, which is watered by the Rio de Ica, is made highly fertile +by irrigation, and is filled with vineyards and cotton fields; between +this valley and the coast is a desert. The original town was founded in +1563, 4 m. E. of its present site, but it was destroyed by the +earthquake of 1571, and again by that of 1664, after which the present +town was laid out near the ruins. In 1882 a Chilean marauding expedition +inflicted great damage to private property in the town and vicinity. +These repeated disasters give the place a partially ruined appearance, +but it has considerable commercial and industrial prosperity. It has a +large cotton factory and there are some smaller industries. Wine-making +is one of the principal industries of the valley, and much brandy, +called _pisco_, is exported from Pisco. A new industry is that of drying +the fruits for which this region is celebrated. Ica is the seat of a +national college. + +The department of ICA lies between the Western Cordillera and the +Pacific coast, and extends from the department of Lima S.E. to that of +Arequipa. Pop. (1906, official estimate) 68,220; area 8721 sq. m. Ica is +in the rainless region of Peru, and the greater part of its surface is +barren. It is crossed by the rivers Pisco, Ica and Grande, whose +tributaries drain the western slope of the Cordillera, and whose valleys +are fertile and highly cultivated. The valley of the Nasca, a tributary +of the Grande, is celebrated for an extensive irrigating system +constructed by the natives before the discovery of America. The +principal products of the department are cotton, grapes, wine, spirits, +sugar and fruit. These are two good ports on the northern coast, Tambo +de Mora and Pisco, the latter being connected with the capital by a +railway across the desert, 46 m. long. + + + + +ICE (a word common to Teutonic languages; cf. Ger. _Eis_), the solid +crystalline form which water assumes when exposed to a sufficiently low +temperature. It is a colourless crystalline substance, assuming forms +belonging to the hexagonal system, and distinguished by a well-marked +habit of twinning, which occasions the beautiful "ice flowers" displayed +by hoar-frost. It is frequently precipitated as hoar-frost, snow or +hail; and in the glaciers and snows of lofty mountain systems or of +regions of high latitude it exists on a gigantic scale, being +especially characteristic of the seas and lands around the poles. In +various regions, especially in France and Italy, great quantities of ice +form in caves, which, in virtue of their depth below the earth's +surface, their height above the sea-level, or their exposure to suitable +winds, or to two or more of these conditions in combination, are +unaffected by ordinary climatic changes, so that the mean annual +temperature is sufficiently low to ensure the permanency of the ice. The +temperature at which water freezes, and also at which ice melts, is so +readily determined that it is employed as one of the standard +temperatures in the graduation of ordinary thermometer scales, this +temperature being the zero of the Centigrade and Réaumur scales, and 32° +of the Fahrenheit (see THERMOMETRY). In the act of freezing, water, +though its temperature remains unchanged, undergoes a remarkable +expansion so that ice at 0° C. is less dense than water--a fact +demonstrated by its power of floating. The sub-aqueous retention of +"ground-ice" or "anchor-ice," which forms in certain circumstances at +the bottom of streams or pools in which there are many eddies, is due to +the cohesion between it and the stones or rocks which compose the bed of +the streams or pools. As water expands on freezing, so conversely ice +contracts on melting; and the ice-cold water thus formed continues to +contract when heated until it has reached its point of maximum density, +the temperature at which this occurs being about 39° Fahr, or 4° C. +Above this point water continuously expands, and at no temperature is it +less dense than ice as is shown by the following table:-- + + Density of ice at 0°C. = .9175 + " water at 0°C. = .99988 + " " 4°C. = 1.00000 + " " 10°C. = .99976 + " " 100°C. = .95866 + +Under the influence of heat, ice itself behaves as most solids do, +contracting when cooled, expanding when heated. According to Plücker, +the coefficient of cubical dilatation at moderately low temperatures is +0.0001585. From a series of elaborate experiments, Person deduced 0.505 +as the specific heat of ice, or about half that of water. + +Though no rise of temperature accompanies the melting of ice, there is +yet a definite quantity of heat absorbed, namely, about 80 calories per +gram; this is called the latent heat of fusion of water (see FUSION). +The same amount of heat is evolved when water becomes ice. That ice can +be melted by increase of pressure was first pointed out by James Thomson +in 1849. He showed that, since water expands on freezing, the laws of +thermodynamics require that its freezing-point must be lowered by +increase of pressure; and he calculated that for every additional +atmosphere of pressure the freezing-point of water was lowered by +0.0075°. This result was verified by his brother, Sir William Thomson +(Lord Kelvin), in 1850. The Thomsons and H. L. F. Helmholtz successfully +applied this behaviour of ice under pressure to the explanation of many +properties of the substance. When two blocks of ice at 0° C. are pressed +together or even simply laid in contact, they gradually unite along +their touching surfaces till they form one block. This "regelation" is +due to the increased pressure at the various points of contact causing +the ice there to melt and cool. The water so formed tends to escape, +thus relieving the pressure for an instant, refreezing and returning to +the original temperature. This succession of melting and freezing, with +their accompanying thermal effects, goes on until the two blocks are +cemented into one. + +Ice forms over fresh water if the temperature of the air has been for a +sufficient time at or below the freezing-point; but not until the whole +mass of water has been cooled down to its point of maximum density, so +that the subsequent cooling of the surface can give rise to no +convection currents, is freezing possible. Sea-water, in the most +favourable circumstances, does not freeze till its temperature is +reduced to about -2° C.; and the ice, when formed, is found to have +rejected four-fifths of the salt which was originally present. In the +upper provinces of India water is made to freeze during cold clear +nights by leaving it overnight in porous vessels, or in bottles which +are enwrapped in moistened cloth. The water then freezes in virtue of +the cold produced by its own evaporation or by the drying of the +moistened wrapper. In Bengal the natives resort to a still more +elaborate forcing of the conditions. Pits are dug about 2 ft. deep and +filled three-quarters full with dry straw, on which are set flat porous +pans containing the water to be frozen. Exposed overnight to a cool dry +gentle wind from the north-west, the water evaporates at the expense of +its own heat, and the consequent cooling takes place with sufficient +rapidity to overbalance the slow influx of heat from above through the +cooled dense air or from below through the badly conducting straw. + + See WATER, and for the manufacture of ice see REFRIGERATING. + + + + +ICEBERG (from ice and _Berg_, Ger. for hill, mountain), a floating mass +of ice broken from the end of a glacier or from an ice-sheet. The word +is sometimes, but rarely, applied to the arch of an Arctic glacier +viewed from the sea. It is more commonly used to describe huge floating +masses of ice that drift from polar regions into navigable waters. They +are occasionally encountered far beyond the polar regions, rising into +beautiful forms with breakers roaring into their caves and streams of +water pouring from their pinnacles in the warmer air. When, however, +they rest in comparatively warm water, melting takes place most rapidly +at the base and they frequently overturn. Only one-ninth of the mass of +ice is seen above water. When a glacier descends to the sea, as in +Alaska, and "advances into water, the depth of which approaches its +thickness, the ends are broken off and the detached masses float away as +icebergs. Many of the bergs are overturned, or at least tilted, as they +set sail. If this does not happen at once it is likely to occur later as +the result of the wave-cutting and melting which disturb their +equilibrium" (T. C. Chamberlin and R. D. Salisbury, _Geology: Processes +and their Results_, 1905). These bergs carry a load of débris from the +glacier and gradually strew their load upon the sea floor. They do not +travel far before losing all stony and earthy débris, but glacial +material found in dredgings shows that icebergs occasionally carry their +load far from land. The structure of the iceberg varies with its origin +and is always that of the glacier or ice-sheet from which it was broken. +The breaking off of the ice-sheet from a Greenland glacier is called +locally the "calving" of the glacier. The constantly renewed material +from which the icebergs are formed is brought down by the motion of the +glacier. The ice-sheet cracks at the end, and masses break off, owing to +the upward pressure of the water upon the lighter ice which is pushed +into it. This is accomplished with considerable violence. The +disintegration of an Arctic ice-sheet is a simpler matter, as the ice is +already floating. + + + + +ICELAND (Dan. _Island_), an island in the North Atlantic Ocean, +belonging to Denmark. Its extreme northerly point is touched by the +Arctic Circle; it lies between 13° 22´ and 24° 35´ W., and between 63° +12´ and 66° 33´ N., and has an area of 40,437 sq. m. Its length is 298 +m. and its breadth 194 m., the shape being a rough oval, broken at the +north-west, where a peninsula, diversified by a great number of fjords, +projects from the main portion of the island. The total length of the +coast-line is about 3730 m., of which approximately one-third belongs to +the north-western peninsula. Iceland is a plateau or tableland, built up +of volcanic rocks of older and younger formation, and pierced on all +sides by fjords and valleys. Compared with the tableland, the lowlands +have a relatively small area, namely, one-fourteenth of the whole; but +these lowlands are almost the only parts of the island which are +inhabited. In consequence of the rigour of its climate, the central +tableland is absolutely uninhabitable. At the outside, not more than +one-fourth of the area of Iceland is inhabited; the rest consists of +elevated deserts, lava streams and glaciers. The north-west peninsula is +separated from the main mass of the island by the bays Hunaflói and +Breiðifjörðr, so that there are really two tablelands, a larger and a +smaller. The isthmus which connects the two is only 4¼ m. across, but +has an altitude of 748 ft. The mean elevation of the north-west +peninsula is 2000 ft. The fjords and glens which cut into it are shut in +by precipitous walls of basalt, which plainly shows that they have been +formed by erosion through the mass of the plateau. The surface of this +tableland is also bare and desolate, being covered with gravel and +fragments of rock. Here and there are large straggling snowfields, the +largest being Glámu and Drangajökull,[1] on the culminating points of +the plateau. The only inhabited districts are the shores of the fjords, +where grass grows capable of supporting sheep; but a large proportion of +the population gain their livelihood by fishing. The other and larger +tableland, which constitutes the substantial part of Iceland, reaches +its culminating point in the south-east, in the gigantic snowfield of +Vatnajökull, which covers 3300 sq. m. The axis of highest elevation of +Iceland stretches from north-west to south-east, from the head of +Hvammsfjörðr to Hornafjörðr, and from this water-parting the rivers +descend on both sides. The crest of the water-parting is crowned by a +chain of snow-capped mountains, separated by broad patches of lower +ground. They are really a chain of minor plateaus which rise 4500 to +6250 ft. above sea-level and 2000 to 3000 ft. above the tableland +itself. In the extreme east is Vatnajökull, which is separated from +Tungnafellsjökull by Vonarskard (3300 ft.). Between Tungnafellsjökull +and Hofsjökull lies the broad depression of Sprengisandr (2130 ft.). +Continuing north-west, between Hofsjökull and the next snow-capped +mountain, Langjökull, lies Kjölur (2000 ft.); and between Langjökull and +Eiriksjökull, Flosaskard (2630 ft.). To the north of the _jöklar_ last +mentioned there are a number of lakes, all well stocked with fish. +Numerous valleys or glens penetrate into the tableland, especially on +the north and east, and between them long mountain spurs, sections of +the tableland which have resisted the action of erosion, thrust +themselves towards the sea. Of these the most considerable is the mass +crowned by Mýrdalsjökull, which stretches towards the south. The +interior of the tableland consists for the most part of barren, +grassless deserts, the surface being covered by gravel, loose fragments +of rock, lava, driftsand, volcanic ashes and glacial detritus. + +Save the lower parts of the larger glens, there are no lowlands on the +north and east. The south coast is flat next the sea; but immediately +underneath Vatnajökull there is a strip of gravel and sand, brought down +and deposited by the glacial streams. The largest low-lying plain of +Iceland, lying between Mýrdalsjökull and Reykjanes, has an area of about +1550 sq. m. In its lowest parts this plain barely keeps above sea-level, +but it rises gradually towards the interior, terminating in a +ramification of valleys. Its maximum altitude is attained at 381 ft. +near Geysir. On the west of Mount Hekla this plain connects by a regular +slope directly with the tableland, to the great injury of its inhabited +districts, which are thus exposed to the clouds of pumice dust and +driftsand that cover large areas of the interior. Nevertheless the +greater part of this lowland plain produces good grass, and is +relatively well inhabited. The plain is drained by three +rivers--Markarfljót, Thjórsá and Oelfusá--all of large volume, and +numerous smaller streams. Towards the west there exist a number of warm +springs. There is another lowland plain around the head of Faxaflói, +nearly 400 sq. m. in extent. As a rule the surface of this second plain +is very marshy. Several dales or glens penetrate the central tableland; +the eastern part of this lowland is called Borgarfjörðr, the western +part Mýrar. + +The great bays on the west of the island (Faxaflói and Breiðifjörðr),[2] +as well as the many bays on the north, which are separated from one +another by rocky promontories, appear to owe their origin to subsidences +of the surface; whereas the fjords of the north-west peninsula, which +make excellent harbours, and those of the east coast seem to be the +result chiefly of erosion. + +[Illustration: Map of Iceland.] + +_Glaciers_.--An area of 5170 sq. m. is covered with snowfields and +glaciers. This extraordinary development of ice and snow is due to the +raw, moist climate, the large rainfall and the low summer temperature. +The snow-line varies greatly in different parts of the island, its range +being from 1300 to 4250 ft. It is highest on the tableland, on the north +side of Vatnajökull, and lowest on the north-west peninsula, to the +south of North Cape. Without exception the great _névés_ of Iceland +belong to the interior tableland. They consist of slightly rounded domes +or billowy snowfields of vast thickness. In external appearance they +bear a closer resemblance to the glaciers of the Polar regions than to +those of the Alps. The largest snowfields are Vatnajökull (3280 sq. m.), +Hofsjökull (520) Langjökull (500) and Mýrdalsjökull (390). The glaciers +which stream off from these snowfields are often of vast extent, e.g. +the largest glacier of Vatnajökull has an area of 150 to 200 sq. m., but +the greater number are small. Altogether, more than 120 glaciers are +known in Iceland. It is on the south side of Vatnajökull that they +descend lowest; the lower end of Breidamerkurjökull was in the year 1894 +only 30 ft. above sea-level. The glaciers of the north-west peninsula +also descend nearly to sea-level. The great number of streams of large +volume is due to the moist climate and the abundance of glaciers, and +the milky white or yellowish-brown colour of their waters (whence the +common name Hvítá, white) is due to the glacial clays. The majority of +them change their courses very often, and vary greatly in volume; +frequently they are impetuous torrents, forming numerous waterfalls. +Iceland also possesses a great number of lakes, the largest being +Thingvallavatn[3] and Thorisvatn, each about 27 sq. m. in area. Mývatn, +in the north, is well known from the natural beauty of its surroundings. +Above its surface tower a great number of volcanoes and several craters, +and its waters are alive with water-fowl, a multitude of ducks of +various species breeding on its islands. The lakes of Iceland owe their +origin to different causes, some being due to glacial erosion, others to +volcanic subsidence. Mývatn fills a depression between lava streams, and +has a depth of not more than 8¾ ft. The group of lakes called Fiskivötn +(or Veidivötn), which lie in a desolate region to the west of +Vatnajökull, consist for the most part of crater lakes. The groups of +lakes which lie north-west from Langjökull occupy basins formed between +ridges of glacial gravel; and in the valleys numerous lakes are found +at the backs of the old moraines. + +_Volcanoes_.--Iceland is one of the most volcanic regions of the earth; +volcanic activity has gone on continuously from the formation of the +island in the Tertiary period down to the present time. So far as is +known, there have in historic times been eruptions from twenty-five +volcanic vents. Altogether 107 volcanoes are known to exist in Iceland, +with thousands of craters, great and small. The lava-streams which have +flowed from them since the Glacial epoch now cover an area of 4650 sq. +m. They are grouped in dense masses round the volcanoes from which they +have flowed, the bulk of the lava dating from outbreaks which occurred +in prehistoric times. The largest volume of lava which has issued at one +outflow within historic times is the stream which came from the craters +of Laki at Skaptá. This belongs to the year 1783, and covers an area of +218 sq. m., and amounts to a volume represented by a cube each of whose +sides measures 7½ m. The largest unbroken lava-field in Iceland is +Odaðahraun (Lava of Evil Deeds), upon the tableland north from +Vatnajökull (2000 to 4000 ft. above sea-level). It is the accretion of +countless eruptions from over twenty volcanoes, and covers an area of +1300 sq.m. (or, including all its ramifications and minor detached +streams, 1700 sq. m.), and its volume would fill a cube measuring 13.4 +m. in every direction. As regards their superficies, the lava-streams +differ greatly. Sometimes they are very uneven and jagged (_apalhraun_), +consisting of blocks of lava loosely flung together in the utmost +confusion. The great lava-fields, however, are composed of vast sheets +of lava, ruptured and riven in divers ways (_helluhraun_). The smooth +surface of the viscous billowy lava is further diversified by long +twisted "ropes," curving backwards and forwards up and down the +undulations. Moreover, there are gigantic fissures, running for several +miles, caused by subsidences of the underlying sections. The best-known +fissure of this character is Almannagjá at Thingvellir. On the occasion +of outbreaks the fine ashes are scattered over a large portion of the +island, and sometimes carried far across the Atlantic. After the +eruption of Katla in 1625 the ashes were blown as far as Bergen in +Norway, and when Askja was in eruption in 1875 a rain of ashes fell on +the west coast of Norway 11 hours 40 minutes, and at Stockholm 15 hours, +afterwards. The volcanic ash frequently proves extremely harmful, +destroying the pastures so that the sheep and cattle die of hunger and +disease. The outbreak of Laki in 1783 occasioned the loss of 11,500 +cattle, 28,000 horses and 190,500 sheep--that is to say, 53% of the +cattle in the island, 77% of the horses and 82% of the sheep. After that +the island was visited by a famine, which destroyed 9500 people, or +one-fifth of the total population. + +The Icelandic volcanoes may be divided into three classes: (1) +cone-shaped, like Vesuvius, built up of alternate layers of ashes, +scoriae and lava; (2) cupola-shaped, with an easy slope and a vast +crater opening at the top--these shield-shaped cupolas are composed +entirely of layers of lava, and their inclination is seldom steeper than +7°-8°; (3) chains of craters running close alongside a fissure in the +ground. For the most part the individual craters are low, generally not +exceeding 300 to 500 ft. These crater chains are both very common and +often very long. The chain of Laki, which was formed in 1783, extends 20 +m., and embraces about one hundred separate craters. Sometimes, however, +the lava-streams are vomited straight out of gigantic fissures in the +earth without any crater being formed. Many of the Icelandic volcanoes +during their periods of quiescence are covered with snow and ice. Then +when an outbreak occurs the snow and ice melt, and in that way they +sometimes give rise to serious catastrophes (_jökulhlaup_), through +large areas being suddenly inundated by great floods of water, which +bear masses of ice floating on their surface. Katla caused very serious +destruction in this way by converting several cultivated districts into +barren wastes. In the same way in the year 1362 Oeræfajökull, the +loftiest mountain in Iceland (6424 ft.), swept forty farms, together +with their inhabitants and live stock, bodily into the ocean. The +best-known volcano is Hekla (5108 ft.), which was in eruption eighteen +times within the historic period down to 1845. Katla during the same +period was active thirteen times down to 1860. The largest volcano is +Askja, situated in the middle of the lava-field of Odaðahraun. Its +crater measures 34 sq. m. in area. At Mývatn there are several +volcanoes, which were particularly active in the years 1724-1730. On +several occasions there have been volcanic outbreaks under the sea +outside the peninsula of Reykjanes, islands appearing and afterwards +disappearing again. The crater chain of Laki has only been in eruption +once in historic times, namely, the violent and disastrous outbreak of +1783. Iceland, however, possesses no constantly active volcano. There +are often long intervals between the successive outbreaks, and many of +the volcanoes (and this is especially true of the chains of craters) +have only vented themselves in a solitary outburst. + +Earthquakes are frequent, especially in the districts which are +peculiarly volcanic. Historical evidence goes to show that they are +closely associated with three naturally defined regions: (1) the region +between Skjálfandi and Axarfjörðr in the north, where violent earth +tremblings are extremely common; (2) at Faxaflói, where minor vibrations +are frequent; (3) the southern lowlands, between Reykjanes and +Mýrdalsjökull, have frequently been devastated by violent earthquake +shocks, with great loss of property and life, e.g. on the 14th-16th of +August 1784, when 92 farmsteads were totally destroyed, and 372 +farmsteads and 11 churches were seriously damaged; and again in August +and September 1896, when another terrible earthquake destroyed 161 +farmsteads and damaged 155 others. Hot springs are found in every part +of Iceland, both singly and in groups; they are particularly numerous in +the western portion of the southern lowlands, where amongst others is +the famous Geyser (q.v.). Sulphur springs and boiling mud lakes are also +general in the volcanic districts; and in places there are carbonic acid +springs, these more especially on the peninsula of Snæfellsnes, north of +Faxaflói. + + _Geology_.--Iceland is built up almost entirely of volcanic rocks, + none of them older, however, than the middle of the Tertiary period. + The earlier flows were probably contemporaneous with those of + Greenland, the Færoes, the western islands of Scotland and the + north-east of Ireland. The principal varieties are basalt and + palagonitic breccias, the former covering two-thirds of the entire + area, the latter the remaining one-third. Compared with these two + systems, all other formations have an insignificant development. The + palagonitic breccias, which stretch in an irregular belt across the + island, are younger than the basalt. In the north-west, north and east + the coasts are formed of basalt, and rise in steep, gloomy walls of + rock to altitudes of 3000 ft. and more above sea-level. Deposits of + clay, with remains of plants of the Tertiary period, lignite and + tree-trunks pressed flat, which the Icelanders call _surtarbrandur_, + occur in places in the heart of the basalt formation. These + fossiliferous strata are developed in greatest thickness in the + north-west peninsula. Indeed, in some few places well-marked + impressions of leaves and fruit have been discovered, proving that in + Tertiary times Iceland possessed extensive forests, and its annual + mean temperature must have been at least 48° Fahr., whereas the + present mean is 35.6°. The palagonitic breccias, which attain their + greatest development in the south of the island and on the tableland, + consist of reddish, brown or yellowish rocks, tuffs and breccias, + belonging to several different groups or divisions, the youngest of + which seems to be of a date subsequent to the Glacial epoch. All over + Iceland, in both the basalt and breccia formations, there occur small + intrusive beds and dikes of liparite, and as this rock is of a lighter + colour than the basalt, it is visible from a distance. In the + south-east of the island, in the parish of Lón, there exist a few + mountains of gabbro, a rock which does not occur in any other part of + Iceland. Near Húsavik in the north there have been found marine + deposits containing a number of marine shells; they belong to the Red + Crag division of the Pliocene. In the middle of Iceland, where the + geological foundation is tuff and breccias, large areas are buried + under ancient outflows of lava, which bear evidences of glacial + scratching. These lava streams, which are of a doleritic character, + flowed before the Glacial age, or during its continuance, out of lava + cones with gigantic crater openings, such as may be seen at the + present day. During the Glacial epoch the whole of Iceland was covered + by a vast sheet of inland ice, except for a few small isolated peaks + rising along its outer margins. This ice-cap had on the tableland a + thickness of 2300 to 2600 ft. Rocks scored by glacial ice and showing + plain indications of striation, together with thousands of erratic + blocks, are found scattered all over Iceland. Signs of elevation + subsequent to the Glacial epoch are common all round the island, + especially on the north-west peninsula. There are found strikingly + developed marine terraces of gravel, shore lines and surf beaches + marked on the solid rock. In several places there are traces of + shells; and sometimes skeletal remains of whales and walruses, as well + as ancient driftwood, have been discovered at tolerable distances from + the present coast. The ancient shore-lines occur at two different + altitudes. Along the higher, 230 to 266 ft. above the existing + sea-level, shells have been found which are characteristic of high + Arctic latitudes and no longer exist in Iceland; whereas on the lower + shore-line, 100 to 130 ft., the shells belong to species which occur + amongst the coast fauna of the present day. + + The geysers and other hot springs are due to the same causes as the + active volcanoes, and the earthquakes are probably manifestations of + the same forces. A feature of special interest to geologists in the + present conditions of the island is the great power of the wind both + as a transporting and denuding agent. The rock sculpture is often very + similar to that of a tropical desert.[4] + +_Climate_.--Considering its high latitude and situation, Iceland has a +relatively mild climate. The meteorological conditions vary greatly, +however, in different parts of the island. In the south and east the +weather is generally changeable, stormy and moist; whilst on the north +the rainfall is less. The climate of the interior tableland approximates +to the continental type and is often extremely cold. The mean annual +temperature is 37.2° F. in Stykkishólmr on Breiðifjörðr, 38.5° at +Eyrarbakki in the south of Iceland, 41° at Vestmannæyjar, 36° at +Akureyri in the north, 36.7° on Berufjörðr in the east, and 30.6° at +Mödrudalr on the central tableland. The range is great not only from +year to year, but also from month to month. For instance, at +Stykkishólmr the highest annual mean for March was 39.7°, and the lowest +8°, during a period of thirty-eight years. Iceland lies contiguous to +that part of the north Atlantic in which the shifting areas of low +pressure prevail, so that storms are frequent and the barometer is +seldom firm. The barometric pressure at sea-level in the south-west of +Iceland during the period 1878-1900 varied between 30.8 and 27.1 in. The +climate of the coasts is relatively mild in summer, but tolerably cold +in winter. The winter means of the north and east coasts average 31.7° +and 31.3° F. respectively; the summer means, 42.8° and 44.6°; and the +means of the year, 33.1° and 35.6°. The winter means of the south and +west coasts average 32° and 31.7° respectively; the summer means, 48.2° +and 50°; the annual means, 37.4° and 39.2°. The rainfall on the south +and east coasts is considerable, e.g. at Vestmannæyjar, 49.4 in. in the +year; at Berufjörðr, 43.6 in. On the west coast it is less, e.g. 24.3 +in. at Stykkishólmr; but least of all on the north coast, being only +14.6 in. on the island of Grimsey, which lies off that coast. Mist is +commonly prevalent on the east coast; at Berufjörðr there is mist on no +fewer than 212 days in the year. The south and west coasts are washed by +the Gulf Stream, and the north coast by an Arctic current, which +frequently brings with it a quantity of drift-ice, and thus exercises a +considerable effect upon the climate of the island; sometimes it blocks +the north coast in the summer months. On the whole, during the 19th +century, the north coast was free from ice on an average of one year in +every four or five. The clearness of the atmosphere has been frequently +remarked. Thunderstorms occur mostly in winter. + + _Flora_.--The vegetation presents the characteristics of an Arctic + European type, and is tolerably uniform throughout the island, the + differences even on the tableland being slight. At present 435 species + of phanerogams and vascular cryptogams are known; the lower orders + have been little investigated. The grasses are of the greatest + importance to the inhabitants, for upon them they are dependent for + the keep of their live stock. Heather covers large tracts, and also + affords pasture for sheep. The development of forest trees is + insignificant. Birch woods exist in a good many places, especially in + the warmer valleys; but the trees are very short, scarcely attaining + more than 3 to 10 ft. in height. In a few places, however, they reach + 13 to 20 ft. and occasionally more. A few mountain ash or rowan trees + (_Sorbus aucuparia_) are found singly here and there, and attain to 30 + ft. in height. Willows are also pretty general, the highest in growth + being _Salix phyllicifolia_, 7 to 10 ft. The wild flora of Iceland is + small and delicate, with bright bloom, the heaths being especially + admired. Wild crowberries and bilberries are the only fruit found in + the island. + + _Fauna_.--The Icelandic fauna is of a sub-Arctic type. But while the + species are few, the individuals are often numerous. The land mammals + are very poorly represented; and it is doubtful whether any species is + indigenous. The polar bear is an occasional visitant, being brought to + the coast by the Greenland drift-ice. Foxes are common, both the white + and the blue occurring; mice and the brown rat have been introduced, + though one variety of mouse is possibly indigenous. Reindeer were + introduced in 1770. The marine mammalia are numerous. The walrus is + now seldom seen, although in prehistoric times it was common. There + are numerous species of seals; and the seas abound in whales. Of birds + there are over 100 species, more than one-half being aquatic. In the + interior the whistling swan is common, and numerous varieties of ducks + are found in the lakes. The eider duck, which breeds on the islands of + Breiðifjörðr, is a source of livelihood to the inhabitants, as are + also the many kinds of sea-fowl which breed on the sea-cliffs. Iceland + possesses neither reptiles nor batrachians. The fish fauna is abundant + in individuals, some sixty-eight species being found off the coasts. + The cod fisheries are amongst the most important in the world. Large + quantities of herring, plaice and halibut are also taken. Many of the + rivers abound in salmon, and trout are plentiful in the lakes and + streams. + +_Population and Towns_.--The census of 1890 gave a total population of +70,927, and this number had increased by 1901 to 78,489. The increase +during the 19th century was 27,000, while at least 15,600 Icelanders +emigrated to America, chiefly to Manitoba, from 1872 to the close of the +century. The largest town is Reykjavik on Faxaflói, with 6700 +inhabitants, the capital of the island, and the place of residence of +the governor-general and the bishop. Here the Althing meets; and here, +further, are the principal public institutions of the island (library, +schools, &c.). The town possesses a statue to Thorvaldsen, the famous +sculptor, who was of Icelandic descent. The remaining towns include +Isafjörðr (pop. 1000) on the north-west peninsula, Akureyri (1000) on +the north and Seydisfjörðr (800) in the east. + +_Industries_.--The principal occupation of the Icelanders is +cattle-breeding, and more particularly sheep-breeding, although the +fishing industries have come rapidly to the front in modern times. In +1850, 82% of the population were dependent upon cattle-breeding and 7% +upon fishing; in 1890 the numbers were 64% and 18% respectively. The +culture of grain is not practised in Iceland; all bread-stuffs are +imported. In ancient times barley was grown in some places, but it never +paid for the cost of cultivation. Cattle-breeding has declined in +importance, while the number of sheep has increased. Formerly gardening +was of no importance, but considerable progress has been made in this +branch in modern times, as also in the cultivation of potatoes and +turnips. Fruit-trees will not thrive; but black and red currants and +rhubarb are grown, the last-named doing excellently. Iceland possesses +four agricultural schools, one agricultural society, and small +agricultural associations in nearly every district. The fisheries give +employment to about 12,000 people. For the most part the fishing is +carried on from open boats, notwithstanding the dangers of so stormy a +coast. But larger decked vessels have come into increasing use. In +summer the waters are visited by a great number of foreign fishermen, +inclusive of about 300 fishing-boats from French ports, as well as by +fishing-boats from the Færoes and Norway, and steam trawlers from +England. Excellent profit is made in certain parts of the island from +the herring fishery; this is especially the case on the east coast. +There are marine insurance societies and a school of navigation at +Reykjavik. The export of fish and fish products has greatly increased. +In 1849 to 1855 the annual average exported was 1480 tons; whereas at +the close of the century (in 1899) it amounted to 11,339 tons and 68,079 +barrels of oil, valued at £276,596. + +_Commerce_.--From the first colonization of the island down to the 14th +century the trade was in the hands of native Icelanders and Norsemen; in +the 15th century it was chiefly in the hands of the English, in the 16th +of Germans from the Hanse towns. From 1602 to 1786 commerce was a +monopoly of the Danish government; in the latter year it was declared +free to all Danish subjects and in 1854 free to all nations. Since 1874, +when Iceland obtained her own administration, commerce has increased +considerably. Thus the total value of the imports and exports together +in 1849 did not exceed £170,000; while in 1891-1895 the imports averaged +£356,000 and the exports £340,000. In 1902 imports were valued at +£596,193 and exports at £511,083. Trade is almost entirely with Denmark, +the United Kingdom, and Norway and Sweden, in this order according to +value. The principal native products exported are live sheep, horses, +salt meat, wool and hides, to which must be added the fish +products--cod, train-oil, herring and salmon--eiderdown and woollen +wares. The spinning, weaving and knitting of wool is a widespread +industry, and the native tweed (_vaðmal_) is the principal material for +the clothing of the inhabitants. The imports consist principally of +cereals and flour, coffee, sugar, ale, wines and spirits, tobacco, +manufactured wares, iron and metal wares, timber, salt, coal, &c. The +money, weights and measures in use are the same as in Denmark. The +Islands Bank in Reykjavik (1904) is authorized to issue bank-notes up to +£133,900 in total value. + +_Communications_.--All land journeys are made on horseback, and in the +remoter parts all goods have to be transported by the same means. +Throughout the greater part of the island there exist no proper roads +even in the inhabited districts, but only bridle-paths, and in the +uninhabited districts not even these. Nevertheless much has been done to +improve such paths as there are, and several miles of driving roads have +been made, more particularly in the south. Since 1888 many bridges have +been built; previous to that year there was none. The larger rivers have +been spanned by iron swing-bridges, and the Blanda is crossed by a fixed +iron bridge. Postal connexion is maintained with Denmark by steamers, +which sail from Copenhagen and call at Leith. Besides, steamers go round +the island, touching at nearly every port. + +_Religion_.--The Icelanders are Lutherans. For ecclesiastical purposes +the island is divided into 20 deaneries and 142 parishes, and the +affairs of each ecclesiastical parish are administered by a parish +council, and in each deanery by a district (_hjerað_) council. When a +living falls vacant, the governor-general of the island, after +consultation with the bishop, selects three candidates, and from these +the congregation chooses one, the election being subsequently confirmed +by the governor-general. In the case of certain livings, however, the +election requires confirmation by the crown. In 1847 a theological +seminary was founded at Reykjavik, and there the majority of the +Icelandic ministry are educated; some, however, are graduates of the +university of Copenhagen. + +_Health_.--The public health has greatly improved in modern times; the +death-rate of young children has especially diminished. This improvement +is due to greater cleanliness, better dwellings, better nourishment, and +the increase in the number of doctors. There are now doctors in all +parts of the country, whereas formerly there were hardly any in the +island. There is a modern asylum for leprosy at Laugarnes near +Reykjavik, and a medical school at Reykjavik, opened in 1876. The +general sanitary affairs of the island are under the control of a chief +surgeon (national physician) who lives in Reykjavik, and has +superintendence over the doctors and the medical school. + +_Government_.--According to the constitution granted to Iceland in 1874, +the king of Denmark shares the legislative power with the Althing, an +assembly of 36 members, 30 of whom are elected by household suffrage, +and 6 nominated by the king. The Althing meets every second year, and +sits in two divisions, the upper and the lower. The upper division +consists of the 6 members nominated by the king and 6 elected by the +representatives of the people out of their own body. The lower division +consists of the remaining 24 representative members. The minister for +Iceland, who resided in Copenhagen until 1903, when his office was +transferred to Reykjavik, is responsible to the king and the Althing for +the maintenance of the constitution, and he submits to the king for +confirmation the legislative measures proposed by the Althing. The king +appoints a governor-general (_landshöfðingi_) who is resident in the +island and carries on the government on the responsibility of the +minister. Formerly Iceland was divided into four quarters, the east, the +south, the west and north. Now the north and the east are united under +one governor, and the south and the west under another. The island is +further divided into 18 _sýslur_ (counties), and these again into 169 +hreppur (rapes) or poor-law districts. Responsible to the governors are +the sheriffs (_sýslumenn_), who act as tax gatherers, notaries public +and judges of first instance; the sheriff has in every _hreppur_ an +assistant, called _hreppstjóri_. In every _hreppur_ there is also a +representative committee, who administer the poor laws, and look after +the general concerns of the _hreppur_. These committees are controlled +by the committees of the _sýslur_ (county boards), and these again are +under the control of the _amtsráð_ (quarter board), consisting of three +members. From the sheriff courts appeals lie to the superior court at +Reykjavik, consisting of three judges. Appeals may be taken in all +criminal cases and most civil cases to the supreme court at Copenhagen. + +Iceland has her own budget, the Althing having, by the constitution of +1874, the right to vote its own supplies. As the Althing only meets +every other year, the budget is passed for two years at once. The total +income and expenditure are each about £70,000 per financial period. +There is a national reserve fund of about £60,000, but no public debt; +nor is there any contribution for either military or naval purposes. +Iceland has her own customs service, but the only import duties levied +are upon spirits, tobacco, coffee and sugar, and in each case the duties +are fairly low. + +_Education_.--Education is pretty widespread amongst the people. In the +towns and fishing villages there are a few elementary schools, but often +the children are instructed at home; in some places by peripatetic +teachers. It is incumbent upon the clergy to see that all children are +taught reading, writing and arithmetic. The people are great readers; +considering the number of the inhabitants, books and periodicals have a +very extensive circulation. Eighteen newspapers are issued (once and +twice a week), besides several journals, and Iceland has always been +distinguished for her native literature. At Reykjavik there are a Latin +school, a medical school and a theological school; at Mödruvellir and +Hafnarfjörðr, modern high schools (_Realschulen_); and in addition to +these there are four agricultural schools, a school of navigation, and +three girls' schools. The national library at Reykjavik contains some +40,000 volumes and 3000 MSS. At the same place there is also a valuable +archaeological collection. Amongst the learned societies are the +Icelandic Literary Society (_Bokmentafjelag_), the society of the +Friends of the People, and the Archaeological Society of Reykjavik. + + AUTHORITIES.--Among numerous works of Dr Thorvald Thoroddsen, see + _Geschichte der Islands Geographie_ (Leipzig, 1898); and the following + articles in _Geografisk Tidskrift_ (Copenhagen): "Om Islands + geografiske og geologiske Undersögelse" (1893); "Islandske Fjorde og + Bugter" (1901); "Geog. og geol. Unders. ved den sydlige Del af + Faxaflói paa Island" (1903); "Lavaörkener og Vulkaner paa Islands + Höjland" (1905). See also C. S. Forbes, _Iceland_ (London, 1860); S. + Baring-Gould, _Iceland, its Scenes and Sagas_ (London, 1863); Sir R. + F. Burton, _Ultima Thule_ (Edinburgh, 1875); W. T. McCormick, _A Ride + across Iceland_ (London, 1892); J. Coles, Summer Travelling in Iceland + (London, 1882); H. J. Johnston Lavis, "Notes on the Geography, + Geology, Agriculture and Economics of Iceland," _Scott. Geog. Mag._ + xi. (1895); W. Bisiker, _Across Iceland_ (London, 1902); J. Hann, "Die + Anomalien der Witterung auf Island in dem Zeitraume 1851-1900, &c.," + _Sitzungsberichte, Vienna Acad. Sci._ (1904); P. Hermann, _Island in + Vergangenheit und Gegenwart_ (Leipzig, 1907). Also _Geografisk + Tidskrift_, and the _Geographical Journal_ (London), _passim_. + (Th. T.) + + +HISTORY + +Shortly after the discovery of Iceland by the Scandinavian, c. 850 (it +had long been inhabited by a small colony of Irish Culdees), a stream of +immigration set in towards it, which lasted for sixty years, and +resulted in the establishment of some 4000 homesteads. In this +immigration three distinct streams can be traced. (1) About 870-890 four +great noblemen from Norway, Ingolf, Ketil Hæng, Skalla-Grim and Thorolf, +settled with their dependants in the south-west of the new found land. +(2) In 890-900 there came from the western Islands Queen Aud, widow of +Olaf the White, king of Dublin, preceded and followed by a number of her +kinsmen and relations (many like herself being Christians), Helgi +Biolan, Biorn the Eastern, Helgi the Lean, Ketil the Foolish, &c., who +settled the best land in the island (west, north-west and north), and +founded families who long swayed its destinies. There also came from the +Western Islands a fellowship of vikings seeking a free home in the +north. They had colonized the west in the viking times; they had "fought +at Hafursfirth," helping their stay-at-home kinsmen against the +centralization of the great head-king, who, when he had crushed +opposition in Norway, followed up his victory by compelling them to flee +or bow to his rule. Such were Ingimund the Old, Geirmund Hellskin, Thord +Beardie (who had wed St. Edmund's granddaughter,) Audun Shackle, +Bryniulf the Old, Uni, to whom Harold promised the earldom of the new +land if he could make the settlers acknowledge him as king (a hopeless +project), and others by whom the north-west, north and east were almost +completely "claimed." (3) In 900-930 a few more incomers direct from +Norway completed the settlement of the south, north-east and south-east. +Among them were Earl Hrollaug (half-brother of Hrolf Ganger and of the +first earl of Orkney), Hialti, Hrafnkell Frey's priest, and the sons of +Asbiorn. Fully three-quarters of the land was settled from the west, and +among these immigrants there was no small proportion of Irish blood. In +1100 there were 4500 franklins, i.e. about 50,000 souls. + +_Table of Icelandic Literature and History._ + + +------------+-----------------------------------------------------------------+ + | | I. _The Commonwealth. 400 years._ | + | Heroic | | | + | Age. | | | + | | | | + | 870- 930 |Poetry of Western Islands. |Settlement by colonists from Western | + | | | Isles and Norway. | + | 930- 980 |Early Icelandic poets, |Constitution worked out--Events of | + | | chiefly abroad. | earlier sagas take place. | + | 980-1030 |Icelandic poets abroad. |Christianity comes in--Events of | + +------------+ | later sagas take place. | + | Saga | | | + | Telling. | | | + | | | | + | 1030-1100 |_First era of phonetic |Peace--Ecclesiastical organization. | + | | change._ | | + +------------+ | | + | The | | | + | Literary | | | + | Age. | | | + | | | | + | 1100-1150 |ARI and his school-- | | + | | THORODD--Vernacular | | + | | writing begins. | | + | 1150-1220 |SAGA-WRITERS--Second |First civil wars--1208-22--Rise of | + | | generation of historians.| Sturlungs. | + | 1220-1248 |SNORRI and his |Second civil wars, 1226-58--Fall | + | | school--Biographers. | of Great Houses. | + | 1248-1284 |STURLA--_Second era of |Change of law, 1271--Submission to | + | | phonetic change._ | Norwegian kings. | + +------------+ | | + | | II. _Medievalism. 250 years._ | + | | | | + |Continental | | | + | Influence | | | + | chiefly | | | + | Norse. | | | + | | | | + | 1284-1320 |Collecting and editing-- |Foreign influence through Norway. | + | | Foreign romances. | | + | 1320-1390 |Annalists--Copyists--New |Great eruptions, 1362 and | + | | Medieval poetry begins. | 1389--Epidemics--Danish rule, 1380.| + | 1390-1413 |Death of old |Epidemics--Norse trade--Close of | + | | traditions, &c. | intercourse with Norway. | + +------------+ | | + | Dark Age. | | | + | | | | + | 1413-1530 |Only Medieval poetry |Isolation from | + | | flourishes. | Continent--English trade. | + +------------+ | | + | | III. _Reformation--Absolute Rule--Decay. 320 years._ | + | | | | + |Reformation.| | | + | | | | + | 1530-1575 |ODD--Printing--_Third era |Religious struggle--New | + | | of phonetic change._ | organization--Hanse trade | + +------------+ | | + |Renaissance.| | | + | | | | + | 1575-1640 |First antiquarians. |Danish monopoly--Pirates' ravages. | + | 1640-1700 |HALLGRIM--Paper copies | | + | | taken. | | + +------------+ | | + | Gradual | | | + | Decay. | | | + | | | | + | 1700-1730 |JON VIDALIN--Arni |I D / Smallpox kills one-third | + | | Magnusson--MSS. taken |n e | population, 1707. | + | | abroad. |c c | Great famine, 10,000 die, | + | 1730-1768 |Eggert Olafsson. |r a | 1759--Sheep plague, | + | | |e y < 1762--Eruption, 1765 | + | 1768-1800 |Finn Jonsson--Icelandic |a . | Great eruption, 1783. | + | | scholars abroad. |s | Beginnings of recovery-- | + | 1800-1850 |Rationalistic |i | Travellers make known island| + | | movement--European |n | to Europe--Free constitution| + | | influences first felt. |g \ in Denmark, 1848. | + +------------+ | | + | | IV. _Modern Iceland._ | + | | | | + |Recovery of | | | + | Iceland. | | | + | | | | + | 1850-1874 |Modern thought and |Increasing wealth and population-- | + | | learning--Icelandic | Free trade, 1854--Jon Sigurdsson | + | | scholars abroad | and home rule struggle. | + | 1874 | |Home rule granted. | + +------------+---------------------------+-------------------------------------+ + + + Organization. + +The unit of Icelandic politics was the homestead with its franklin-owner +(_buendi_), its primal organization the hundred-moot (_thing_), its tie +the goðorð (godar) or chieftainship. The chief who had led a band of +kinsmen and dependants to the new land, taken a "claim" there, and +parcelled it out among them, naturally became their leader, presiding as +priest at the temple feasts and sacrifices of heathen times, acting as +speaker of their moot, and as their representative towards the +neighbouring chiefs. He was not a feudal lord nor a local sheriff, for +any franklin could change his goðorð when he would, and the rights of +"judgment by peers" were in full use; moreover, the office could be +bequeathed, sold, divided or pledged by the possessor; still the goði +had considerable power as long as the commonwealth lasted. + +Disputes between neighbouring chiefs and their clients, and uncertainty +as to the law, brought about the _Constitution of Ulfliot_ (c. 930), +which appointed a central moot for the whole island, the Althing, and a +speaker to speak a single "law" (principally that followed by the +Gula-moot in Norway); the _Reforms of Thord Gellir_ (964), settling a +fixed number of moots and chieftaincies, dividing the island into four +quarters (thus characterized by Ari: north, thickest settled, most +famous; east, first completely settled; south, best land and greatest +chiefs; west, remarkable for noble families), to each of which a +head-court, the "quarter-court," was assigned; and the _Innovations of +Skapti_ (ascribed in the saga to Nial) _the Law-Speaker_ (d. 1030), who +set up a "fifth court" as the ultimate tribunal in criminal matters, and +strengthened the community against the chiefs. But here constitutional +growth ceased: the law-making body made few and unimportant +modifications of custom; the courts were still too weak for the chiefs +who misused and defied them; the speaker's power was not sufficiently +supported to enable him to be any more than a highly respected lord +chief justice, whereas he ought to have become a justiza if anarchy was +to be avoided; even the ecclesiastical innovations, while they secured +peace for a time, provoked in the end the struggles which put an end to +the commonwealth. + +Christianity was introduced c. 1000. Tithes were established in 1096, +and an ecclesiastical code made c. 1125. The first disputes about the +jurisdiction of the clergy were moved by Gudmund in the 13th century, +bringing on a civil war, while the questions of patronage and rights +over glebe and mortmainland occupied Bishop Arni and his adversaries +fifty years afterwards, when the land was under Norwegian viceroys and +Norwegian law. For the civil wars broke down the great houses who had +monopolized the chieftaincies; and after violent struggles (in which the +Sturlungs of the first generation perished at Orlygstad, 1238, and +Reykiaholt, 1241, while of the second generation Thord Kakali was called +away by the king in 1250, and Thorgils Skardi slain in 1258) the +submission of the island to Norway quarter after quarter, took place in +1262-1264, under Gizur's auspices, and the old Common Law was replaced +by the New Norse Code "Ironside" in 1271. + +The political life and law of the old days is abundantly illustrated in +the sagas (especially Eyrbyggia, Hamsa-Thori, Reykdæla, Hrafnkell, and +Niala), the two collections of law-scrolls (_Codex Regius_, c. 1235, and +_Stadarhol's Book_, c. 1271), the Libellus, the Liberfragments, and the +Landnamabók of Ari, and the Diplomatarium. K. Maurer has made the +subject his own in his _Beiträge, Island, Grágás_, &c. + +The medieval Icelandic church had two bishoprics, Skalholt (S., W., and +E.) 1056, and Holar (N.) 1106, and about 175 parishes (two-thirds of +which belonged to the southern bishopric). They belonged to the +metropolitan see of Bremen, then to Lund, lastly to Nidaros, 1237. There +were several religious foundations: Thingore (founded 1133), Thwera +(1155), Hitardale (c. 1166), Kirkby Nunnery (1184), Stad Nunnery (1296), +and Saurby (c. 1200) were Benedictine, while Ver (1168), Flatey after +Holyfell (1172), Videy (1226), Madderfield Priory (1296), and Skrid +Priory (14th century) were Augustinian. The bishops, elected by the +people at the Althing till 1237, enjoyed considerable power; two, +Thorlak of Skalholt and John of Holar, were publicly voted saints at the +Althing, and one, Gudmund, received the title of "Good" by decree of the +bishop and chapter. Full details as to ecclesiastical history will be +found in the _Biskupasögur_ (edited by Dr Vigfusson). + + + Mode of life. + +Iceland was not agricultural but pastoral, depending upon flocks Mode of +and herds for subsistence, for, though rye and other grain would grow in +favoured localities, the hay, self-sown, was the only regular crop. In +some districts the fisheries and fowling were of importance, but +nine-tenths of the population lived by their sheep and cattle. Life on +each homestead was regularly portioned out: out door occupations--fishing, +shepherding, fowling, and the hay-making and fuel-gathering--occupying the +summer; while indoor business--weaving, tool-making, &c.--filled up the +long winter. The year was broken by the spring feasts and moots, the great +Althing meeting at midsummer, the marriage and arval gatherings after the +summer, and the long yule feasts at midwinter. There were but two degrees +of men, free and unfree, though only the franklins had any political +power; and, from the nature of the life, social intercourse was +unrestrained and unfettered; goði and thrall lived the same lives, ate the +same food, spoke the same tongue, and differed little in clothing or +habits. The thrall had a house of his own and was rather villein or serf +than slave, having rights and a legal price by law. During the heathen +days many great chiefs passed part of their lives in Norway at the king's +court, but after the establishment of Christianity in Iceland they kept +more at home, visiting the continent, however, for purposes of state, +suits with clergy, &c. Trade was from the first almost entirely in foreign +(Norse) hands. + +The introduction of a church system brought little change. The great +families put their members into orders, and so continued to enjoy the +profits of the land which they had given to the church; the priests +married and otherwise behaved like the franklins around them in everyday +matters, farming, trading, going to law like laymen. + + + Effects of the Union. + +Life in the commonwealth was turbulent and anarchic, but free and +varied; it produced men of mark, and fostered bravery, adventure and +progress. But on the union with Norway all this ceased, and there was +left but a low dead level of poor peasant proprietors careless of all +save how to live by as little labour as possible, and pay as few taxes +as they could to their foreign rulers. The island received a foreign +governor (_Earl_, _Hirdstjori_ or _Stiptamtsmadr_ as he was successively +called), and was parcelled out into counties (_sýslur_), administered by +sheriffs (_sýslumadr_) appointed by the king. A royal court took the +place of the Althing courts; the local business of the local things was +carried out by the (_hreppstjóri_) bailiff, a subordinate of the +sheriff; and the goðorð, things, quarter-courts, trial by jury, &c., +were swept away by these innovations. The power of the crown was +increased by the confiscation of the great Sturlung estates, which were +underleased to farmers, while the early falling off of the Norse trade +threatened to deprive the island of the means of existence; for the +great epidemics and eruptions of the 14th century had gravely attacked +its pastoral wealth and ruined much of its pasture and fishery. + +The union of the Three Crowns transferred the practical rule of Iceland +to Denmark in 1280, and the old Treaty of Union, by which the island had +reserved its essential rights, was disregarded by the absolute Danish +monarchs; but, though new taxation was imposed, it was rather their +careless neglect than their too active interference that damaged +Iceland's interests. But for an English trade, which sprang up out of +the half-smuggling, half-buccaneering enterprise of the Bristol +merchants, the island would have fared badly, for during the whole of +the 15th century their trade with England, exporting sulphur, eiderdown +(of which the English taught them the value), wool, and salt stock-fish, +and importing as before wood, iron, honey, wine, grain and flax goods, +was their only link with the outer world. This period of Iceland's +existence is eventless: she had got peace but with few of its blessings; +all spirit seemed to have died with the commonwealth; even shepherding +and such agriculture as there had been sank to a lower stage; wagons, +ploughs and carts went out of use and knowledge; architecture in timber +became a lost art, and the fine carved and painted halls of the heathen +days were replaced by turf-walled barns half sunk in the earth; the +large decked luggers of the old days gave way to small undecked +fishing-boats. + + + The Reformation. + +The Reformation in Iceland wakened men's minds, but it left their +circumstances little changed. Though the fires of martyrdom were never +lighted in Iceland, the story of the easily accepted Reformation is not +altogether a pleasant one. When it was accomplished, the little knot of +able men who came to the front did much in preserving the records of the +past, while Odd and Hallgrim exhibit the noblest impulses of their time. +While there was this revolution in religion a social and political +revolution never came to Iceland. The Hanse trade replaced the English +for the worse; and the Danish monopoly which succeeded it when the +Danish kings began to act again with vigour was still less profitable. +The glebes and hospital lands were a fresh power in the hands of the +crown, and the subservient Lutheran clergy became the most powerful +class in the island, while the system of under-leasing at rackrent and +short lease with unsecured tenant right extended over at least a quarter +of the better land. + + + Decadence. + +A new plague, that of the English, Gascon and Algerine pirates, marked +the close of the 16th century and opening of the 17th, causing +widespread panic and some devastation in 1579, 1613-1616 and 1627. +Nothing points more to the helplessness of the natives' condition than +their powerlessness against these foes. But the 18th century is the most +gloomy in Iceland's annals. Smallpox, famine, sheep disease, and the +eruptions of 1765 and 1783 follow each other in terrible succession. +Against such visitations, which reduced the population by about a +fourth, little could be done. The few literary men, whose work was done +and whose books were published abroad, were only concerned with the +past, and Jon Vidalin is the one man of mark, beside Eggert Olafsson, +who worked and wrote for his own generation.[5] + + + Modern times. + +Gradually the ideas which were agitating Europe spread through +Scandinavia into Iceland, and its claims were more respectfully listened +to. The continental system, which, by its leading to the blockade of +Denmark, threatened to starve Iceland, was neutralized by special action +of the British government. Trade and fishery grew a little brisker, and +at length the turn came. + +The rationalistic movement, headed by Magnus Stephenson, a patriotic, +narrow-minded lawyer, did little good as far as church reform went, but +was accompanied by a more successful effort to educate the people. A +Useful Knowledge Society was formed and did some honest work. Newspapers +and periodicals were published, and the very stir which the +ecclesiastical disputes encouraged did good. When free trade came, and +when the free constitution of Denmark had produced its legitimate +effects, the endeavours of a few patriots such as Jon Sigurdsson were +able to push on the next generation a step further. Questions of a +modern political complexion arose; the cattle export controversy and the +great home rule struggle began. After thirty years' agitation home rule +was conceded in 1874 (see above, _Government_). (F. Y. P.) + + +ANCIENT LITERATURE + +_Poetry._--Iceland has always borne a high renown for song, but has +never produced a poet of the highest order, the qualities which in other +lands were most sought for and admired in poetry being in Iceland +lavished on the saga, a prose epic, while Icelandic poetry is to be +rated very high for the one quality which its authors have ever aimed +at--melody of sound. To these generalizations there are few exceptions, +though Icelandic literature includes a group of poems which possess +qualities of high imagination, deep pathos, fresh love of nature, +passionate dramatic power, and noble simplicity of language which +Icelandic poetry lacks. The solution is that these poems do not belong +to Iceland at all. They are the poetry of the "Western Islands." + +It was among the Scandinavian colonists of the British coasts that in +the first generations after the colonization of Iceland therefrom a +magnificent school of poetry arose, to which we owe works that for power +and beauty can be paralleled in no Teutonic language till centuries +after their date. To this school, which is totally distinct from the +Icelandic, ran its own course apart and perished before the 13th +century, the following works belong (of their authors we have scarcely a +name or two; their dates can be rarely exactly fixed, but they lie +between the beginning of the 9th and the end of the 10th centuries), +classified into groups:-- + + (a) The _Helgi_ trilogy (last third lost save a few verses, but + preserved in prose in _Hromund Gripsson's Saga_), the _Raising of + Anganty_ and _Death of Hialmar_ (in _Hervarar Saga_), the fragments of + a _Volsung Lay_ (_Volsungakiraða_) (part interpolated in earlier + poems, part underlying the prose in _Volsunga Saga_), all by one poet, + to whom Dr Vigfusson would also ascribe _Völuspá_, _Vegtamskviða_, + _Þrymskviða_, _Grötta Song_ and _Völundarkviða_. + + (b) The Dramatic Poems:--_Flyting of Loki_, the _För Skirnis_, the + _Harbarðslioð_ and several fragments, all one man's work, to whose + school belong, probably, the _Lay_ underlying the story of Ivar's + death in _Skioldunga Saga_. + + (c) The Didactic Poetry:--_Grímnismál_, _Vafpruðnismál_, _Alvíssmal_, + &c. + + (d) The Genealogical and Mythological Poems:--_Hyndluljoð_ written for + one of the Haurda-Kari family, so famous in the Orkneys; _Ynglingatal_ + and _Haustlong_, by Thiodolf of Hvin; _Rig's Thul_, &c. + + (e) The Dirges and Battle Songs--such as that on Hafur-firth Battle + _Hrafnsmal_, by Thiodolf of Hvin or Thorbjörn Hornklofi, shortly after + 870; Eirik's Dirge (_Eíríksmál_) between 950 and 969; the _Dart-Lay on + Clontarf Battle_ (1014); _Bíarka-mal_ (fragments of which we have, and + paraphrase of more is found in _Hrolf Kraki's Saga_ and in Saxo). + + There are also fragments of poems in _Half's Saga_, _Asmund + Kappa-Bana's Saga_, in the Latin verses of Saxo, and the Shield Lays + (_Ragnarsdrapa_) by Bragi, &c., of this school, which closes with the + _Sun-Song_, a powerful Christian Dantesque poem, recalling some of the + early compositions of the Irish Church, and with the 12th-century _Lay + of Ragnar_, _Lay of Starkad_, _The Proverb Song_ (_Havamal_) and + _Krakumal_, to which we may add those singular Gloss-poems, the + _Þulur_, which also belong to the Western Isles. + + To Greenland, Iceland's farthest colony, founded in the 10th century, + we owe the two _Lays of Atli_, and probably _Hymiskvtiða_, which, + though of a weirder, harsher cast, yet belong to the Western Isles + school and not to Iceland. + +In form all these poems belong to two or three classes:--_kviða_, an +epic "cantilena"; _tál_, a genealogical poem; _drapa_, songs of praise, +&c., written in modifications of the old Teutonic metre which we know in +Beowulf; _galdr_ and _lokkr_, spell and charm songs in a more lyric +measure; and _mál_, a dialogue poem, and _liod_, a lay, in elegiac +measure suited to the subject. + +The characteristics of this Western school are no doubt the result of +the contact of Scandinavian colonists of the viking-tide, living lives +of the wildest adventure, with an imaginative and civilized race, that +exercised upon them a very strong and lasting influence (the effects of +which were also felt in Iceland, but in a different way). The frequent +intermarriages which mingled the best families of either race are +sufficient proof of the close communion of Northmen and Celts in the 9th +and 10th centuries, while there are in the poems themselves traces of +Celtic mythology, language and manners.[6] + +When one turns to the early poetry of the Scandinavian continent, +preserved in the rune-staves on the memorial stones of Sweden, Norway +and Denmark, in the didactic _Havamal_, the _Great Volsung Lay_ (i.e. +Sigurd II., Fafnis's Lay, Sigrdrifa's Lay) and _Hamdismal_, all +continental, and all entirely consonant to the remains of Old English +poetry in metre, feeling and treatment, one can see that it is with this +school that the Icelandic "makers" are in sympathy, and that from it +their verse naturally descends. While shrewdness, plain +straightforwardness, and a certain stern way of looking at life are +common to both, the Icelandic school adds a complexity of structure and +ornament, an elaborate mythological and enigmatical phraseology, and a +regularity of rhyme, assonance, luxuriance, quantity and +syllabification, which it caught from the Latin and Celtic poets, and +adapted with exquisite ingenuity to its own main object, that of +securing the greatest possible beauty of sound. + +The first generations of Icelandic poets resemble in many ways the later +troubadours; the books of the kings and the sagas are full of their +strange lives. Men of good birth (nearly always, too, of Celtic blood on +one side at least), they leave Iceland young and attach themselves to +the kings and earls of the north, living in their courts as their +henchmen, sharing their adventures in weal and woe, praising their +victories, and hymning their deaths if they did not fall by their +sides--men of quick passion, unhappy in their loves, jealous of rival +poets and of their own fame, ever ready to answer criticism with a +satire or with a sword-thrust, but clinging through all to their art, in +which they attained most marvellous skill. + +Such men were Egil, the foe of Eirik Bloodaxe and the friend of +Æthelstan; Kormak, the hot-headed champion; Eyvind, King Haakon's poet, +called Skaldaspillir, because he copied in his dirge over that king the +older and finer _Eíríksmál_; Gunnlaug, who sang at Æthelred's court, and +fell at the hands of a brother bard, Hrafn; Hallfred, Olaf Tryggvason's +poet, who lies in Iona by the side of Macbeth; Sighvat, Saint Olafs +henchman, most prolific of all his comrades; Thormod, Coalbrow's poet, +who died singing after Sticklestad battle; Ref, Ottar the Black, Arnor +the earls' poet, and, of those whose poetry was almost confined to +Iceland, Gretti, Biorn the Hitdale champion, and the two model Icelandic +masters, Einar Skulason and Markus the Lawman, both of the 12th century. + +It is impossible to do more here than mention the names of the most +famous of the long roll of poets which are noted in the works of Snorri +and in the two _Skalda-tal_. They range from the rough and noble pathos +of Egil, the mystic obscurity of Kormak, the pride and grief of +Hallfred, and the marvellous, fluency of Sighvat, to the florid +intricacy of Einar and Markus. + +The art of poetry stood to the Icelanders in lieu of music; scarcely any +prominent man but knew how to turn a mocking or laudatory stanza, and +down to the fall of the commonwealth the accomplishment was in high +request. In the literary age the chief poets belong to the great +Sturlung family, Snorri and his two nephews, Sturla and Olaf, the White +Poet, being the most famous "makers" of their day. Indeed, it is in +Snorri's _Edda_, a poetic grammar of a very perfect kind, that the best +examples of the whole of northern poetry are to be found. The last part, +_Hattatal_, a treatise on metre, was written for Earl Skuli about 1222, +in imitation of Earl Rognvald and Hall's _Hattalykill_ (_Clavis +metrica_) of 1150. The second part, _Skaldskapar-mal_, a gradus of +synonyms and epithets, which contains over 240 quotations from 65 poets, +and 10 anonymous lays--a treasury of verse--was composed c. 1230. The +first part, an exquisite sketch of northern mythology, _Gylfa-ginning_, +was probably prefixed to the whole later. There is some of Sturla's +poetry in his _Islendinga Saga_, and verses of Snorri occur in the +_Grammatical Treatise_ on figures of speech, &c., of Olaf, which +contains about one hundred and forty quotations from various authors, +and was written about 1250. + +Besides those sources, the _Kings' Lives of Snorri_ and later authors +contain a great deal of verse by Icelandic poets. King Harold +Sigurdsson, who fell at Stamford Bridge 1066, was both a good critic and +composed himself. Many tales are told of him and his poet visitors and +henchmen. The Icelandic sagas also comprise much verse which is partly +genuine, partly the work of the 12th and 13th century editors. Thus +there are genuine pieces in _Nial's Saga_ (chaps. 34, 78, 103, 126, +146), in _Eyrbyggia_, _Laxdæla_, _Egil's Saga_ (part only), _Grettla_ +(two and a half stanzas, cf. _Landnamabók_), _Biorn's Saga_, _Gunnlaug's +Saga_, _Havard's Saga_, _Kormak's Saga_, _Viga-Glum's Saga_, _Erik the +Red's Saga_ and _Fostbrædra Saga_. In _Nial's_, _Gisli's_ and +_Droplaug's Sons' Sagas_ there is good verse of a later poet, and in +many sagas worthless rubbish foisted in as ornamental. + +To these may be added two or three works of a semi-literary kind, +composed by learned men, not by heroes and warriors. Such are +_Konunga-tál_, _Hugsvinnsmál_ (a paraphrase of Cato's Distichs), +_Merlin's Prophecy_ (paraphrased from Geoffrey of Monmouth by Gunnlaug +the monk), _Jomsvikinga-drapa_ (by Bishop Ketil), and the +_Islendinga-drapa_, which has preserved brief notices of several lost +sagas concerning Icelandic worthies, with which _Gudmundar-drapa_, +though of the 14th century, may be also placed. + +Just as the change of law gave the death-blow to an already perishing +commonwealth, so the rush of medieval influence, which followed the +union with Norway, completed a process which had been in force since the +end of the 11th century, when it overthrew the old Icelandic poetry in +favour of the rimur. + +The introduction of the _danz_, ballads (or _fornkvædi_, as they are now +called) for singing, with a burden, usually relating to a love-tale, +which were immensely popular with the people and performed by whole +companies at weddings, yule feasts and the like, had relegated the +regular Icelandic poetry to more serious events or to the more +cultivated of the chiefs. But these "jigs," as the Elizabethans would +have called them, dissatisfied the popular ear in one way: they were, +like old English ballads, which they closely resembled, in rhyme, but +void of alliteration, and accordingly they were modified and replaced by +the "rimur," the staple literary product of the 15th century. These were +rhymed but also alliterative, in regular form, with prologue or +_mansong_ (often the prettiest part of the whole), main portion telling +the tale (mostly derived in early days from the French romances of the +Carlovingian, Arthurian or Alexandrian cycles, or from the mythic or +skrök-sögur), and epilogue. Their chief value to us lies in their having +preserved versions of several French poems now lost, and in their +evidence as to the feelings and bent of Icelanders in the "Dark Age" of +the island's history. The ring and melody which they all possess is +their chief beauty. + +Of the earliest, _Olafsrima_, by Einar Gilsson (c. 1350), and the best, +the Aristophanic _Skída-rima_ (c. 1430), by Einar Fostri, the names may +be given. Rimur on sacred subjects was called "diktur"; of these, on the +legends of the saints' lives, many remain. The most notable of its class +is the _Lilia_ of Eystein Asgrimsson, a monk of Holyfell (c. 1350), a +most "sweet sounding song." Later the poems of the famous Jon Arason (b. +1484), last Catholic bishop of Holar (c. 1530), _Liomr_ ("gleam") and +_Píslargrátr_ ("passion-tears"), deserve mention. Arason is also +celebrated as having introduced printing into Iceland. + +Taste has sunk since the old days; but still this rimur poetry is +popular and genuine. Moreover, the very prosaic and artificial verse of +Sturla and the last of the old school deserved the oblivion which came +over them, as a casual perusal of the stanzas scattered through +_Islendinga_ will prove. It is interesting to notice that a certain +number of _kenningar_ (poetical paraphrases) have survived from the old +school even to the present day, though the mass of them have happily +perished. The change in the _phonesis_ of the language is well +illustrated by the new metres as compared with the old Icelandic +_drott-kvædi_ in its varied forms. Most of the older rimur and diktur +are as yet unprinted. Many of the _fornkvædi_ are printed in a volume of +the old _Nordiske Litteralur-Samfund_. + +The effects of the Reformation was deeply felt in Icelandic literature, +both prose and verse. The name of Hallgrim Petursson, whose +_Passion-hymns_, "the flower of all Icelandic poetry," have been the +most popular composition in the language, is foremost of all writers +since the second change of faith. The gentle sweetness of thought, and +the exquisite harmony of wording in his poems, more than justify the +popular verdict. His _Hymns_ were finished in 1660 and published in +1666, two great Protestant poets thus being contemporaries. A collection +of Reformation hymns, adapted, many of them, from the German, the +_Holar-book_, had preceded them in 1619. There was a good deal of +verse-writing of a secular kind, far inferior in every way, during this +period. In spite of the many physical distresses that weighed upon the +island, ballads (_fornkvædi_) were still written, ceasing about 1750, +rimur composed, and more elaborate compositions published. + +The most notable names are those of the improvisatore Stephen the +Blind; Thorlak Gudbrandsson, author of _Ulfar-Rímur_, d. 1707; John +Magnusson, who wrote _Hristafla_, a didactic poem; Stefan Olafsson, +composer of psalms, rimur, &c., d. 1688; Gunnar Pálsson, the author of +_Gunnarslag_, often printed with the Eddic poems, c. 1791; and Eggert +Olafsson, traveller, naturalist and patriot, whose untimely death in +1768 was a great loss to his country. His _Bunadar-balkr_, a Georgic +written, like Tusser's _Points_, with a practical view of raising the +state of agriculture, has always been much prized. Paul Vidalin's +ditties are very naïve and clever. + +Of later poets, down to more recent times, perhaps the best was Sigurd +of Broadfirth, many of whose prettiest poems were composed in Greenland +like those of Jon Biarnisson before him, c. 1750; John Thorlaksson's +translation of Milton's great epic into Eddic verse is praiseworthy in +intention, but, as may be imagined, falls far short of its aim. He also +turned Pope's _Essay on Man_ and Klopstock's _Messiah_ into Icelandic. +Benedikt Gröndal tried the same experiment with Homer in his _Ilion's +Kvædi_, c. 1825. There is a fine prose translation of the _Odyssey_ by +Sweinbjörn Egillson, the lexicographer, both faithful and poetic in high +degree. + +_Sagas._--The real strength of ancient Icelandic literature is shown in +its most indigenous growth, the "Saga" (see also SAGA). This is, in its +purest form, the life of a hero, composed in regular form, governed by +fixed rules, and intended for oral recitation. It bears the strongest +likeness to the epic in all save its unversified form; in both are +found, as fixed essentials, simplicity of plot, chronological order of +events, set phrases used even in describing the restless play of emotion +or the changeful fortunes of a fight or a storm, while in both the +absence of digression, comment or intrusion of the narrator's person is +invariably maintained. The saga grew up in the quieter days which +followed the change of faith (1002), when the deeds of the great +families' heroes were still cherished by their descendants, and the +exploits of the great kings of Norway and Denmark handed down with +reverence. Telling of stories was a recognized form of entertainment at +all feasts and gatherings, and it was the necessity of the reciter which +gradually worked them into a regular form, by which the memory was +relieved and the artistic features of the story allowed to be more +carefully elaborated. That this form was so perfect must be attributed +to Irish influence, without which indeed there would have been a saga, +but not the same saga. It is to the west that the best sagas belong; it +is to the west that nearly every classic writer whose name we know +belongs; and it is precisely in the west that the admixture of Irish +blood is greatest. In comparing the Irish tales with the saga, there +will be felt deep divergencies in matter, style and taste, the richness +of one contrasting with the chastened simplicity of the other; the one's +half-comic, half-earnest bombast is wholly unlike the other's grim +humour; the marvellous, so unearthly in the one, is almost credible in +the other; but in both are the keen grasp of character, the biting +phrase, the love of action and the delight in blood which almost assumes +the garb of a religious passion. + +When the saga had been fixed by a generation or two of oral reciters, it +was written down; and this stereotyped the form, so that afterwards when +literary works were composed by learned men (such as Abbot Karl's +_Swerri's Saga_ and Sturla's _Islendinga_) the same style was adopted. + + + Icelandic sagas. + +Taking first the sagas relating to Icelanders, of which some thirty-five +or forty remain out of thrice that number, they were first written down +between 1140 and 1220, in the generation which succeeded Ari and felt +the impulse his books had given to writing, on separate scrolls, no +doubt mainly for the reciter's convenience; they then went through the +different phases which such popular compositions have to pass in all +lands--editing and compounding (1220-1260), padding and amplifying +(1260-1300), and finally collection in large MSS. (14th century). Sagas +exist showing all these phases, some primitive and rough, some refined +and beautified, some diluted and weakened, according as their copyists +have been faithful, artistic or foolish; for the first generation of +MSS. have all perished. We have also complex sagas put together in the +13th century out of the scrolls relating to a given locality, such a +group as still exists untouched in _Vapnfirdinga_ being fused into such +a saga as _Niala_ or _Laxdæla_. Of the authors nothing is known; we can +only guess that some belong to the Sturlung school. According to subject +they fall into two classes, those relating to the older generation +before Christianity and those telling of St Olaf's contemporaries; only +two fall into a third generation. + +Beginning with the sagas of the west, most perfect in style and form, +the earliest in subject is that of _Gold-Thori_ (c. 930), whose +adventurous career it relates; _Hensa-Þorissaga_ tells of the burning of +Blund-Ketil, a noble chief, an event which led to Thord Gelli's reforms +next year (c. 964); _Gislasaga_ (960-980) tells of the career and death +of that ill-fated outlaw; it is beautifully written, and the verses by +the editor (13th century) are good and appropriate; _Hord's Saga_ (980) +is the life of a band of outlaws on Whalesfirth, and especially of their +leader Hord. Of later subject are the sagas of _Havard_ and his revenge +for his son, murdered by a neighbouring chief (997-1002); of the +_Heiðarirgasaga_ (990-1014), a typical tale of a great blood feud, +written in the most primitive prose; of Gunnlaug and Hrafn +(_Gunnlaugssaga Ormstungu_, 980-1008), the rival poets and their +ill-starred love. The verse in this saga is important and interesting. +To the west also belong the three great complex sagas _Egla_, +_Eyrbyggia_ and _Laxdæla_. The first (870-980), after noticing the +migration of the father and grandfather of the hero poet Egil, and the +origin of the feud between them and the kings of Norway, treats fully of +Egil's career, his enmity with Eirik Bloodaxe, his service with +Æthelstan, and finally, after many adventures abroad, of his latter days +in Iceland at Borg, illustrating very clearly what manner of men those +great settlers and their descendants were, and the feelings of pride and +freedom which led them to Iceland. The style is that of Snorri, who had +himself dwelt at Borg. _Eyrbyggia_ (890-1031) is the saga of politics, +the most loosely woven of all the compound stories. It includes a mass +of information on the law, religion, traditions, &c., of the heathen +days in Iceland, and the lives of Eric, the real discoverer of +Greenland, Biorn of Broadwick, a famous chief, and Snorri, the greatest +statesman of his day. Dr Vigfusson would ascribe its editing and +completion to Sturla the Lawman, c. 1250. _Laxdæla_ (910-1026) is the +saga of Romance. Its heroine Gudrun is the most famous of all Icelandic +ladies. Her love for Kiartan the poet, and his career abroad, his +betrayal by his friend Bolli, the sad death of Kiartan at his hands, the +revenge taken for him on Bolli, whose slayers are themselves afterwards +put to death, and the end of Gudrun, who becomes an anchorite after her +stormy life, make up the pith of the story. The contrast of the +characters, the rich style and fine dialogue which are so remarkable in +this saga, have much in common with the best works of the Sturlung +school. + +Of the north there are the sagas of _Kormak_ (930-960), most primitive +of all, a tale of a wild poet's love and feuds, containing many notices +of the heathen times; of _Vatzdælasaga_ (890-980), relating to the +settlement and the chief family in Waterdale; of _Hallfred_ the poet +(996-1014), narrating his fortune at King Olafs court, his love affairs +in Iceland, and finally his death and burial at Iona; of _Reyk-dæla_ +(990), which preserves the lives of Askell and his son Viga-Skuti; of +_Svarf-dæla_ (980-990), a cruel, coarse story of the old days, with some +good scenes in it, unfortunately imperfect, chapters 1-10 being forged; +of _Viga-Glum_ (970-990), a fine story of a heathen hero, brave, crafty +and cruel. To the north also belong the sagas of _Gretti_ the Strong +(1010-1031), the life and death of the most famous of Icelandic outlaws, +the real story of whose career is mixed up with the mythical adventures +of Beowulf, here put down to Gretti, and with late romantic episodes and +fabulous folk-tales (Dr Vigfusson would ascribe the best parts of this +saga to Sturla; its last editor, whose additions would be better away, +must have touched it up about 1300), and the stories of the +_Ljosvetningasaga_ (1009-1060). Gudmund the Mighty and his family and +neighbours are the heroes of these tales, which form a little cycle. +The _Banda-manna saga_ (1050-1060), the only comedy among the sagas, is +also a northern tale; it relates the struggles of a plebeian who gets a +chieftancy against the old families of the neighbourhood, whom he +successfully outwits; _Öl-kofra þattr_ is a later imitation of it in the +same humorous strain. The sagas of the north are rougher and coarser +than those of the west, but have a good deal of individual character. + +Of tales relating to the east there survive the Weapon-firth cycle--the +tales of _Thorstein the White_ (c. 900), of _Thorstein the Staffsmitten_ +(c. 985), of _Gunnar Thidrand's Bane_ (1000-1008) and of the +_Weapon-firth Men_ (975-990), all relating to the family of Hof and +their friends and kin for several generations--and the story of +_Hrafnkell Frey's Priest_ (c. 960), the most idyllic of sagas and best +of the eastern tales. Of later times there are _Droplaug's Sons' Saga_ +(997-1007), written probably about 1110, and preserved in the uncouth +style of the original (a brother's revenge for his brother's death is +the substance of it; _Brandkrossa Þattr_ is an appendix to it), and the +tales of _Thorstein Hall of Side's Son_ (c. 1014) and his brother +_Thidrandi_ (c. 996), which belong to the cycle of _Hall o' Side's +Saga_, unhappily lost; they are weird tales of bloodshed and magic, with +idyllic and pathetic episodes. + +The sagas of the south are either lost or absorbed in that of _Nial_ +(970-1014), a long and complex story into which are woven the tales of +_Gunnar Nial_, and parts of others, as _Brian Boroimhe_, _Hall o' Side_, +&c. It is, whether we look at style, contents or legal and historical +weight, the foremost of all sagas. It deals especially with law, and +contains the pith and the moral of all early Icelandic history. Its hero +Nial, type of the good lawyer, is contrasted with its villain Mord, the +ensample of cunning, chicane, and legal wrong doing; and a great part of +the saga is taken up with the three cases and suits of the divorce, the +death of Hoskuld and the burning of Nial, which are given with great +minuteness. The number and variety of its dramatis personae give it the +liveliest interest throughout. The women Hallgerda, Bergthora and +Ragnhild are as sharply contrasted as the men Gunnar, Skarphedin, Flosi +and Kari. The pathos of such tragedies as the death of Gunnar and +Hoskuld and the burning is interrupted by the humour of the Althing +scenes and the intellectual interest of the legal proceedings. The plot +dealing first with the life and death of Gunnar, type of the chivalry of +his day, then with the burning of Nial by Flosi, and how it came about, +and lastly with Kari's revenge on the burners, is the ideal saga-plot. +The author must have been of the east, a good lawyer and genealogist, +and have composed it about 1250, to judge from internal evidence. It has +been overworked by a later editor, c. 1300, who inserted many spurious +verses. + + + Of Greenland and North America. + +Relating partly to Iceland, but mostly to Greenland and Vinland (N. +America), are the _Floamannasaga_ (985-990), a good story of the +adventures of Thorgils and of the struggles of shipwrecked colonists in +Greenland, a graphic and terrible picture; and _Eirikssaga rauða_ +(990-1000), two versions, one northern (Flatey-book), one western, the +better (in _Hawk's Book_, and AM. 557), the story of the discovery of +Greenland and Vinland (America) by the Icelanders at the end of the 9th +century. Later is the _Fostbrædrasaga_ (1015-1030), a very interesting +story, told in a quaint romantic style, of Thorgeir, the reckless +henchman of King Olaf, and how his death was revenged in Greenland by +his sworn brother the true-hearted Thormod Coalbrow's poet, who +afterward dies at Sticklestad. The tale of _Einar Sookisson_ (c. 1125) +may also be noticed. The lost saga of _Poet Helgi_, of which only +fragments remain, was also laid in Greenland. + +Besides complete sagas there are embedded in the _Heimskringla_ numerous +small _Þættir_ or episodes, small tales of Icelanders' adventures, often +relating to poets and their lives at the kings' courts; one or two of +these seem to be fragments of sagas now lost. Among the more notable are +those of _Orm Storolfsson_, _Ogmund Dijtt_, _Halldor Snorrason_, +_Thorstein Oxfoot_, _Hromund Halt_, _Thorwald Tasaldi_, _Svadi_ and +_Arnor Herlingar-nef_, _Audunn of Westfirth_, _Sneglu-Halli_, _Hrafn of +Hrutfiord_, _Hreidar Heimski_, _Gisli Illugison_, _Ivar_ the poet, +_Gull-Æsu Thord_, _Einar Skulason_ the poet, _Mani_ the poet, &c. + +The forged Icelandic sagas appear as early as the 13th century. They are +very poor, and either worked up on hints given in genuine stories or +altogether apocryphal. + +_History._--About the year of the battle of Hastings was born Ari Froði +Thorgilsson (1067-1148), one of the blood of Queen Aud, who founded the +famous historical school of Iceland, and himself produced its greatest +monument in a work which can be compared for value with the English +Domesday Book. Nearly all that we know of the heathen commonwealth may +be traced to the collections of Ari. It was he too that fixed the style +in which history should be composed in Iceland. It was he that secured +and put into order the vast mass of fragmentary tradition that was +already dying out in his day. And perhaps it is the highest praise of +all to him that he wrote in his own "Danish tongue," and so ensured the +use of that tongue by the cultured of after generations. Ari's great +works are _Konungabók_, or _The Book of Kings_, relating the history of +the kings of Norway from the rise of the Yngling dynasty down to the +death of Harald Sigurdsson in the year of his own birth. This book he +composed from the dictation of old men such as Odd Kolsson, from the +genealogical poems, and from the various dirges, battle-songs and +eulogia of the poets. It is most probable that he also compiled shorter +_Kings' Books_ relating to Denmark and perhaps to England. The +_Konungabók_ is preserved under the _Heimskringla_ of Snorri Sturloson, +parts of it almost as they came from Ari's hands, for example _Ynglinga_ +and _Harald Fairhair's Saga_, and the prefaces stating the plan and +critical foundations of the work, parts of it only used as a framework +for the magnificent superstructure of the lives of the two Olafs, and of +Harald Hardrada and his nephew Magnus the Good. The best text of Ari's +_Konungabók_ (_Ynglinga_, and the sagas down to but not including Olaf +Tryggvason's) is that of _Frisbók_. + +The _Book of Settlements_ (_Landnamabók_) is a wonderful performance, +both in its scheme and carrying out. It is divided into five parts, the +first of which contains a brief account of the discovery of the island; +the other four, one by one taking a quarter of the land, describe the +name, pedigree and history of each settler in geographical order, notice +the most important facts in the history of his descendants, the names of +their homesteads, their courts and temples, thus including mention of +4000 persons, one-third of whom are women, and 2000 places. The mass of +information contained in so small a space, the clearness and accuracy of +the details, the immense amount of life which is breathed into the +whole, astonish the reader, when he reflects that this colossal task was +accomplished by one man, for his collaborator Kolsegg merely filled up +his plan with regard to part of the east coast, a district with which +Ari in his western home at Stad was little familiar. _Landnamabók_ has +reached us in two complete editions, one edited by Sturla, who brought +down the genealogies to his own grandfather and grandmother, Sturla and +Gudny, and one by Hawk, who traces the pedigrees still later to himself. + +Ari also wrote a _Book of Icelanders_ (_Islendingabók_, c. 1127), which +has perished as a whole, but fragments of it are embedded in many sagas +and _Kings' Lives_; it seems to have been a complete epitome of his +earlier works, together with an account of the constitutional history, +ecclesiastical and civil, of Iceland. An abridgment of the latter part +of it, the little _Libellus Islandorum_ (to which the title of the +bigger _Liber--Islendingabók_--is often given), was made by the +historian for his friends Bishops Ketil and Thorlak, for whom he wrote +the _Liber_ (c. 1137). This charming little book is, with the much later +collections of laws, our sole authority for the Icelandic constitution +of the commonwealth, but, "much as it tells, the lost _Liber_ would have +been of still greater importance." _Kristni-Saga_, the story of the +christening of Iceland, is also a work of Ari's, "overlaid" by a later +editor, but often preserving Ari's very words. This saga, together with +several scattered tales of early Christians in Iceland before the change +of faith (1002), may have made up a section of the lost _Liber_. Of the +author of these works little is known. He lived in quiet days a quiet +life; but he shows himself in his works, as Snorri describes him, "a man +wise, of good memory and a speaker of the truth." If Thucydides is +justly accounted the first political historian, Ari may be fitly styled +the first of scientific historians. + +A famous contemporary and friend of Ari is Sæmund (1056-1131), a great +churchman, whose learning so impressed his age that he got the +reputation of a magician. He was the friend of Bishop John, the founder +of the great Odd-Verjar family, and the author of a _Book of Kings_ from +Harald Fairhair to Magnus the Good, in which he seems to have fixed the +exact chronology of each reign. It is most probable that he wrote in +Latin. The idea that he had anything to do with the poetic _Edda_ in +general, or the _Sun's Song_ in particular, is unfounded. + +The flame which Ari had kindled was fed by his successors in the 12th +century. Eirik Oddsson (c. 1150) wrote the lives of Sigurd Evil-deacon +and the sons of Harold Gille, in his _Hryggiar-Stykki_ (Sheldrake), of +which parts remain in the MSS. collections of _Kings' Lives_, +_Morkin-skinna_, &c. Karl Jonsson, abbot of Thingore, the Benedictine +minister, wrote (c. 1184) _Sverrissaga_ from the lips of that great +king, a fine racy biography, with a style and spirit of its own. +_Böglunga-Sögur_ tell the story of the civil wars which followed +Sverri's death. They are probably by a contemporary. + +The Latin _Lives of St Olaf_, Odd's in Latin (c. 1175), compiled from +original authorities, and the _Legendary Life_, by another monk whose +name is lost, are of the medieval Latin school of Sæmund to which +Gunnlaug belonged. + +Snorri Sturlason (q.v.) was known to his contemporaries as a statesman +and poet; to us he is above all an historian. Snorri (1179-1241) wrote +the _Lives of the Kings_ (_Heimskringla_), from Olaf Tryggvason to +Sigurd the Crusader inclusive; and we have them substantially as they +came from his hand in the _Great King Olaf's Saga_; _St Olaf's Saga_, as +in _Heimskringla_ and the Stockholm MS.; and the succeeding _Kings' +Lives_, as in Hulda and Hrokkinskinna, in which, however, a few episodes +have been inserted. + +These works were indebted for their facts to Ari's labours, and to sagas +written since Ari's death; but the style and treatment of them are +Snorri's own. The fine Thucydidean speeches, the dramatic power of +grasping character, and the pathos and poetry that run through the +stories, along with a humour such as is shown in the _Edda_, and a +varied grace of style that never flags or palls, make Snorri one of the +greatest of historians. + +Here it should be noticed that _Heimskringla_ and its class of MSS. +(_Eirspennil_, _Jofraskinna_, _Gullinskinna_, _Fris-bok_ and _Kringla_) +do not give the full text of Snorri's works. They are abridgments made +in Norway by Icelanders for their Norwegian patrons, the _Life of St +Olaf_ alone being preserved intact, for the great interest of the +Norwegians lay in him, but all the other _Kings' Lives_ being more or +less mutilated, so that they cannot be trusted for historic purposes; +nor do they give a fair idea of Snorri's style. + +_Agrip_ is a 12th-century compendium of the _Kings' Lives_ from Harald +Fairhair to Sverri, by a scholastic writer of the school of Sæmund. As +the only Icelandic abridgment of Norwegian history taken not from Snorri +but sources now lost, it is of worth. Its real title is _Konunga-tal_. + +_Noregs Konunga-tal_, now called _Fagrskinna_, is a Norse compendium of +the _Kings' Lives_ from Halfdan the Black to Sverri's accession, +probably written for King Haakon, to whom it was read on his death-bed. +It is an original work, and contains much not found elsewhere. As +non-Icelandic it is only noticed here for completeness. + +Styrmi Karason, a contemporary of Snorri's, dying in 1245, was a +distinguished churchman (lawman twice) and scholar. He wrote a _Life of +St Olaf_, now lost; his authority is cited. He also copied out +_Landnamabók_ and _Sverri's Life_ from his MSS., of which surviving +copies were taken. + +Sturla, Snorri's nephew, wrote the _Hakonssaga_ and _Magnussaga_ at the +request of King Magnus, finishing the first c. 1265, the latter c. +1280. King Haakon's Life is preserved in full; of the other only +fragments remain. These are the last of the series of historic works +which Ari's labours began, from which the history of Norway for 500 +years must be gathered. + +A few books relating the history of other Scandinavian realms will +complete this survey. In _Skioldunga-bok_ was told the history of the +early kings of Denmark, perhaps derived from Ari's collections, and +running parallel to _Ynglinga_. The earlier part of it has perished save +a fragment _Sogu-brot_, and citations and paraphrases in Saxo, and the +mythical _Ragnar Lodbrok's_ and _Gongu-Hrolf's Sagas_; the latter part, +_Lives of Harold Bluetooth and the Kings down to Sveyn II._, is still in +existence and known as _Skioldunga_. + +The _Knutssaga_ is of later origin and separate authorships, parallel to +Snorri's _Heimskringla_, but earlier in date. The _Lives of King +Valdemar and his Son_, written c. 1185, by a contemporary of Abbot +Karl's, are the last of this series. The whole were edited and compiled +into one book, often quoted as _Skioldunga_, by a 13th-century editor, +possibly Olaf, the White Poet, Sturla's brother, guest and friend of +King Valdemar II. _Jomsvikinga Saga_, the history of the pirates of Jom, +down to Knut the Great's days, also relates to Danish history. + +The complex work now known as _Orkneyinga_ is made up of the _Earls' +Saga_, lives of the first great earls, Turf-Einar, Thorfinn, &c.; the +_Life of St Magnus_, founded partly on Abbot Robert's Latin life of him +(c. 1150) an Orkney work, partly on Norse or Icelandic biographies; a +_Mirade-book_ of the same saint; the _Lives of Earl Rognwald and Sveyn_, +the last of the vikings, and a few episodes such as the _Burning of +Bishop Adam_. A scholastic sketch of the rise of the Scandinavian +empire, the _Foundation of Norway_, dating c. 1120, is prefixed to the +whole. + +_Færeyinga_ tells the tale of the conversion of the Færeys or Faroes, +and the lives of its chiefs Sigmund and Leif, composed in the 13th +century from their separate sagas by an Icelander of the Sturlung +school. + +_Biographies._--The saga has already been shown in two forms, its +original epic shape and its later development applied to the lives of +Norwegian and Danish kings and earls, as heroic but deeper and broader +subjects than before. In the 13th century it is put to a third use, to +tell the plain story of men's lives for their contemporaries, after +satisfying which demand it dies away for ever. + +These biographies are more literary and medieval and less poetic than +the Icelandic sagas and king's lives; their simplicity, truth, realism +and purity of style are the same. They run in two parallel streams, some +being concerned with chiefs and champions, some with bishops. The former +are mostly found embedded in the complex mass of stories known as +_Sturlunga_, from which Dr Vigfusson has extricated them, and for the +first time set them in order. Among them are the sagas of _Thorgils and +Haflidi_ (1118-1121), the feud and peacemaking of two great chiefs, +contemporaries of Ari; of _Sturla_ (1150-1183), the founder of the great +Sturlung family, down to the settlement of his great lawsuit by Jon +Loptsson, who thereupon took his son Snorri the historian to +fosterage,--a humorous story but with traces of the decadence about it, +and glimpses of the evil days that were to come; of the +_Önundar-brennusaga_ (1185-1200), a tale of feud and fire-raising in the +north of the island, the hero of which, Gudmund Dyri, goes at last into +a cloister; of _Hrafn Sveinbiornsson_ (1190-1213), the noblest Icelander +of his day, warrior, leech, seaman, craftsman, poet and chief, whose +life at home, travels and pilgrimages abroad (Hrafn was one of the first +to visit Becket's shrine), and death at the hands of a foe whom he had +twice spared, are recounted by a loving friend in pious memory of his +virtues, c. 1220; of _Áron Hiorleifsson_ (1200-1255), a man whose +strength, courage and adventures befit rather a henchman of Olaf +Tryggvason than one of King Haakon's thanes (the beginning of the feuds +that rise round Bishop Gudmund are told here), of the _Svinefell-men_ +(1248-1252), a pitiful story of a family feud in the far east of +Iceland. + +But the most important works of this class are the _Islendinga Saga_ and +_Thorgils Saga_ of Lawman Sturla. Sturla and his brother Olaf were the +sons of Thord Sturlason and his mistress Thora. Sturla was born and +brought up in prosperous times, but his manhood was passed in the midst +of strife, in which his family fell one by one, and he himself, though a +peaceful man who cared little for politics, was more than once forced to +fly for his life. While in refuge with King Magnus, in Norway, he wrote +his two sagas of that king and his father. After his first stay in +Norway he came back in 1271, with the new Norse law-book, and served a +second time as lawman. The _Islendinga_ must have been the work of his +later years, composed at Fairey in Broadfirth, where he died, 30th July +1284, aged about seventy years. The saga of _Thorgils Skardi_ +(1252-1261) seems to have been the first of his works on Icelandic +contemporary history; it deals with the life of his own nephew, +especially his career in Iceland from 1252 to 1258. The second part of +_Islendinga_ (1242-1262), which relates to the second part of the civil +war, telling of the careers of Thord Kakali, Kolbein the Young, Earl +Gizur and Hrafn Oddsson. The end is imperfect, there being a blank of +some years before the fragmentary ending to which an editor has affixed +a notice of the author's death. The first part of _Islendinga_ +(1202-1242) tells of the beginning and first part of the civil wars, the +lives of Snorri and Sighvat, Sturla's uncles, of his cousin and namesake +Sturla Sighvatsson, of Bishop Gudmund, and Thorwald Gizursson,--the fall +of the Sturlungs, and with them the last hopes of the great houses to +maintain the commonwealth, being the climax of the story. + +Sturla's power lies in his faithfulness to nature, minute observance of +detail and purity of style. The great extent of his subject, and the +difficulty of dealing with it in the saga form, are most skilfully +overcome; nor does he allow prejudice or favour to stand in the way of +the truth. He ranks below Ari in value and below Snorri in power; but no +one else can dispute his place in the first rank of Icelandic writers. + +Of the ecclesiastical biographers, an anonymous Skalholt clerk is the +best. He wrote _Hungrvaka_, lives of the first five bishops of Skalholt, +and biographies of his patron Bishop Paul (_Pálssaga_) and also of St +Thorlak (_Thorlakssaga_). They are full of interesting notices of social +and church life. Thorlak was a learned man, and had studied at Paris and +Lincoln, which he left in 1161. These lives cover the years 1056-1193. +The life of St John, a great reformer, a contemporary of Thorodd, whom +he employed to build a church for him, is by another author (1052-1121). +The life of Gudmund (_Gudmundar Saga Goda_), as priest, recounts the +early life of this Icelandic Becket till his election as bishop +(1160-1202); his after career must be sought out in _Islendinga_. It is +written by a friend and contemporary. A later life by Arngrim, abbot of +Thingore, written c. 1350, as evidence of his subject's sanctity, tells +a good deal about Icelandic life, &c. The lives of Bishops Arni and +Lawrence bring down our knowledge of Icelandic history into the 14th +century. The former work, _Arna Saga Biskups_, is imperfect; it is the +record of the struggles of church and state over patronage rights and +glebes, written c. 1315; it now covers only the years 1269-1291; a great +many documents are given in it, after the modern fashion. The latter, +_Laurentius Saga Biskups_, by his disciple, priest Einar Haflidason, is +a charming biography of a good and pious man, whose chequered career in +Norway and Iceland is picturesquely told (1324-1331). It is the last of +the sagas. _Bishop Jon's Table-Talk_ (1325-1339) is also worth noticing; +it contains many popular stories which the good bishop, who had studied +at Bologna and Paris, was wont to tell to his friends. + +_Annals._--The _Annals_ are now almost the sole material for Icelandic +history; they had begun earlier, but after 1331 they got fuller and +richer, till they end in 1430. The best are _Annales Regii_, ending +1306, _Einar Haflidason's Annals_, known as "Lawman's Annals," reaching +to 1392, and preserved with others in _Flatey-book_, and the _New +Annals_, last of all. The _Diplomatarium Islandicum_, edited by Jon +Sigurdsson, contains what remains of deeds, inventories, letters, &c., +from the old days, completing our scanty material for this dark period +of the island's history. + +_Literature of Foreign Origin._--After the union with Norway and change +of law genuine tradition died out with the great houses. The ordinary +medieval literature reached Iceland through Norway, and every one began +to put it into a vernacular dress, so neglecting their own classics that +but for a few collectors like Lawman Hauk they would have perished +entirely. + +The Norwegian kings, Haakon Haakonson (c. 1225), and Haakon V. (c. +1305), employed Icelanders at their courts in translating the French +romances of the Alexander, Arthur and Charlemagne cycles. Some forty or +fifty of these _Riddara-Sögur_ (Romances of Chivalry) remain. They +reached Iceland and were eagerly read, many Rimur being founded on them. +Norse versions of _Mary of Brittany's Lays_, the stories of _Brutus_ and +of _Troy_, and part of the _Pharsalia_ translated are also found. The +_Speculum Regale_, with its interesting geographical and social +information, is also Norse, written c. 1240, by a Halogalander. The +computistic and arithmetical treatises of Stiorn-Odd, Biarni the +Number-skilled (d. 1173), and Hauk Erlendsson the Lawman (d. 1334), and +the geography of Ivar Bardsson, a Norwegian (c. 1340), are of course of +foreign origin. A few tracts on geography, &c., in Hauk's book, and a +_Guide to the Holy Land_, by Nicholas, abbot of Thwera (d. 1158), +complete the list of scientific works. + +The stories which contain the last lees of the old mythology and +pre-history seem to be also non-Icelandic, but amplified by Icelandic +editors, who probably got the plots from the Western Islands. _Völsunga +Saga_ and _Hervarar Saga_ contain quotations and paraphrases of lays by +the Helgi poet, and _Half's_, _Ragnar's_ and _Asmund Kappabana's Sagas_ +all have bits of Western poetry in them. _Hrolf Kraki's Saga_ +paraphrases part of _Biarkamal_; _Hromund Gripsson's_ gives the story of +Helgi and Kara (the lost third of the Helgi trilogy); _Gautrek's Arrow +Odd's_, _Frithiof's Sagas_, &c., contain shreds of true tradition amidst +a mass of later fictitious matter of no worth. With the _Riddara-Sögur_ +they enjoyed great popularity in the 15th century, and gave matter for +many Rimur. _Thidrek's Saga_, a late version of the Völsung story, is of +Norse composition (c. 1230), from North German sources. + +The medieval religious literature of Western Europe also influenced +Iceland, and the _Homilies_ (like the _Laws_) were, according to +Thorodd, the earliest books written in the vernacular, antedating even +Ari's histories. The lives of the _Virgin_, the _Apostles_ and the +_Saints_ fill many MSS. (edited in four large volumes by Professor +Unger), and are the works of many authors, chiefly of the 13th and 14th +centuries; amongst them are the lives of _SS. Edward the Confessor_, +_Oswald of Northumbria_, _Dunstan_ and _Thomas of Canterbury_. Of the +authors we know Priest Berg Gunsteinsson (d. 1211); Kygri-Biorn, +bishop-elect (d. 1237); Bishop Brand (d. 1264); Abbot Runolf (d. 1307); +Bishop Lawrence's son Arni (c. 1330); Abbot Berg (c. 1340), &c. A +paraphrase of the historical books of the Bible was made by Bishop Brand +(d. 1264), called _Gydinga Sögur_. About 1310 King Haakon V. ordered a +commentary on the Bible to be made, which was completed down to Exodus +xix. To this Brand's work was afterwards affixed, and the whole is known +as _Stiorn_. The Norse version of the famous _Barlaam and Josaphat_, +made for Prince Haakon (c. 1240), must not be forgotten. + +_Post-classical Literature._--The post-classical literature falls +chiefly under three heads--religious, literary and scientific. Under the +first comes foremost the noble translation of the New Testament by Odd +Gottskalksson, son of the bishop of Hólar. Brought up in Norway, he +travelled in Denmark and Germany, and took upon him the new faith before +he returned to Iceland, where he became secretary to Bishop Ogmund of +Skalholt. Here he began by translating the Gospel of Matthew into his +mother-tongue in secret. Having finished the remainder of the New +Testament at his own house at Olves, he took it to Denmark, where it was +printed at Roskild in 1540. Odd afterwards translated the Psalms, and +several devotional works of the day, Corvinus's _Epistles_, &c. He was +made lawman of the north and west, and died from a fall in the Laxa in +Kios, June 1556. Three years after his death the first press was set up +in Iceland by John Matthewson, at Breidabolstad, in Hunafloe, and a +_Gospel and Epistle Book_, according to Odd's version, issued from it +in 1562. In 1584 Bishop Gudbrand, who had brought over a splendid fount +of type from Denmark in 1575 (which he completed with his own hands), +printed a translation of the whole Bible at Hólar, incorporating Odd's +versions and some books (Proverbs and the Son of Sirach, 1580) +translated by Bishop Gizar, but supplying most of the Old Testament +himself. This fine volume was the basis of every Bible issued for +Iceland till 1826, when it was replaced by a bad modern version. For +beauty of language and faithful simplicity of style the finer parts of +this version, especially the New Testament, have never been surpassed. + +The most notable theological work Iceland ever produced is the +_Postill-Book_ of Bishop John Vidalin (1666-1720), whose bold homely +style and stirring eloquence made "John's Book," as it is lovingly +called, a favourite in every household, till in the 19th century it was +replaced for the worse by the more sentimental and polished Danish +tracts and sermons. Theological literature is very popular, and many +works on this subject, chiefly translations, will be found in the lists +of Icelandic bibliographers. + +The first modern scientific work is the _Iter per patriam_ of Eggert +Olafsson and Biarni Paulsson, which gives an account of the physical +peculiarities--fauna, flora, &c.--of the island as far as could be done +at the date of its appearance, 1772. The island was first made known to +"the world" by this book and by the sketch of Unno von Troil, a Swede, +who accompanied Sir Joseph Banks to Iceland in 1772, and afterwards +wrote a series of "letters" on the land and its literature, &c. This +tour was the forerunner of an endless series of "travels," of which +those of Sir W. J. Hooker, Sir G. S. Mackenzie (1810), Ebenezer +Henderson (1818), Joseph Paul Gaimard (1838-1843), Paijkull (1867) and, +lastly, that of Sir Richard Burton, an excellent account of the land and +people, crammed with information of every kind (1875), are the best. + +Iceland is emphatically a land of proverbs, while of folk-tales, those +other keys to the people's heart, there is plentiful store. Early work +in this direction was done by Jon Gudmundsson, Olaf the Old and John +Olafsson in the 17th century, who all put traditions on paper, and their +labours were completed by the magnificent collection of Jon Arnason +(1862-1864), who was inspired by the example of the Grimms. Many tales +are but weak echoes of the sagas; many were family legends, many are old +fairy tales in a garb suited to their new northern home; but, besides +all these, there are a number of traditions and superstitions of +indigenous origin. + +The Renaissance of Iceland dates from the beginning of the 17th century, +when a school of antiquaries arose. Arngrim Jonsson's _Brevis +Commentarius_ (1593), and _Crymogaea_ (1609), were the first-fruits of +this movement, of which Bishops Odd, Thorlak and Bryniulf (worthy +parallels to Parker and Laud) were the wise and earnest supporters. The +first (d. 1630) collected much material for church history. The second +(d. 1656) saved _Sturlunga_ and the _Bishops' Lives_, encouraged John +Egilsson to write his _New Hungerwaker_, lives of the bishops of the +Dark Ages and Reformation, and helped Biorn of Skardsa (d. 1655), a bold +and patriotic antiquary (whose _Annals_ continue Einar's), in his +researches. The last (d. 1675) collected a fine library of MSS., and +employed the famous copyist John Erlendsson, to whom and the bishop's +brother, John Gizurarsson (d. 1648), we are indebted for transcripts of +many lost MSS. + +Torfaeus (1636-1719) and Bartholin, a Dane (d. 1690), roused the taste +for northern literature in Europe, a taste which has never since +flagged; and soon after them Arni Magnusson (1663-1730) transferred all +that remained of vellum and good paper MSS. in Iceland to Denmark, and +laid the foundations of the famous library and bequest, for which all +Icelandic students are so much beholden. For over forty years Arni stuck +to his task, rescuing every scrap he could lay hands on from the risks +of the Icelandic climate and carelessness, and when he died only one +good MSS. remained in the island. Besides his magnificent collection, +there are a few MSS. of great value at Upsala, at Stockholm, and in the +old royal collection at Copenhagen. Those in the university library in +the latter city perished in the fire of 1728. Sagas were printed at +Upsala and Copenhagen in the 17th century, and the Arna-Magnaean fund +has been working since 1772. In that year appeared also the first volume +of Bishop Finn Jonsson's _Historia Ecclesiastica Islandiae_, a work of +high value and much erudition, containing not only ecclesiastical but +civil and literary history, illustrated by a well-chosen mass of +documents, 870-1740. It has been continued by Bishop P. Peterson to +modern times, 1740-1840. The results, however, of modern observers and +scholars must be sought for in the periodicals, _Safn_, _Felagsrit_, _Ny +Felagsrit_ and others. John Espolin's _Arbækr_ is very good up to its +date, 1821. + + A brilliant sketch of Icelandic classic literature is given by Dr + Gudbrandr Vigfusson in the Prolegomena to _Sturlunga Saga_ (Oxford, + 1879). It replaces much earlier work, especially the _Sciagraphia_ of + Halfdan Einarsson (1777), and the _Saga-Bibliotek_ of Müller. The + numerous editions of the classics by the Icelandic societies, the + Danish Société des Antiquités, Nordiske Litteratur Samfund, and the + new Gammel Nordisk Litteratur Samfund, the splendid Norwegian editions + of Unger, the labours of the Icelanders Sigurdsson and Gislason, and + of those foreign scholars in Scandinavia and Germany who have thrown + themselves into the work of illustrating, publishing and editing the + sagas and poems (men like P. A. Munch, S. Bugge, F. W. Bergmann, Th. + Möbius and K. von Maurer, to name only a few), can only be referred to + here. See also Finnur Jónsson, _Den Oldnorske og Oldislanske + Litteraturs Historie_ (Copenhagen, 1893-1900); R. B. Anderson's + translation (Chicago, 1884) of Winkel Horn's _History of the + Literature of the Scandinavian North_; and W. Morris and E. + Magnusson's _Saga Library_. (F. Y. P.) + + +RECENT LITERATURE + +The recent literature of Iceland has been in a more flourishing state +than ever before since the 13th century. Lyrical poetry is by far the +largest and the most interesting portion of it. The great influence of +Jónas Hallgrímsson (1807-1845) is still felt, and his school was the +reigning one up to the end of the 19th century, although then a change +seemed to be in sight. The most successful poet of this school is +Steingrímr Thorsteinsson (b. 1830). He is specially famous for his +splendid descriptions of scenery (_The Song of Gilsbakki_), his +love-songs and his sarcastic epigrams. As a translator he has enriched +the literature with _The Arabian Nights_, _Sakuntala_, _King Lear_ and +several other masterpieces of foreign literature. Equal in fame is +Matthías Jochumsson (b. 1835), who, following another of Jónas +Hallgrímsson's many ways, has successfully revived the old metres of the +classical Icelandic poets, whom he resembles in his majestic, but +sometimes too gorgeous, language. He is as an artist inferior to +Steingrímr Thorsteinsson, but surpasses him in bold flight of +imagination. He has successfully treated subjects from Icelandic history +_Grettisljóð_, a series of poems about the famous outlaw Grettir. His +chief fault is a certain carelessness in writing; he can never write a +bad poem, but rarely a poem absolutely flawless. He has translated +Tegnér's _Frithiofs Saga_, several plays of Shakespeare and some other +foreign masterpieces. The great religious poet of Iceland, Hallgrímr +Pétursson, has found a worthy successor in Valdemar Briem (b. 1848), +whose _Songs of the Bible_ are deservedly popular. He is like Matthías +Jochumsson in the copious flow of his rhetoric; some of his poems are +perfect both as regards form and contents, but he sometimes neglects the +latter while polishing the former. An interesting position is occupied +by Benedict Gröndal (b. 1826), whose travesties of the old romantic +stories,[7] and his Aristophanic drama _Gandreiðin_ ("The Magic Ride") +about contemporary events, are among the best satirical and humorous +productions of Icelandic literature. + +Influenced by Jónas Hallgrímsson with regard to language and poetic +diction, but keeping unbroken the traditions of Icelandic medieval +poetry maintained by Sigurðr Breiðfjörð (1798-1846), is another school +of poets, very unlike the first. In the middle of the 19th century this +school was best represented by Hjálmar Jónsson from Bóla (1796-1875), a +poor farmer with little education, but endowed with great poetical +talents, and the author of satirical verses not inferior to those of +Juvenal both in force and coarseness. In the last decades of the 19th +century this school produced two poets of a very high order, both +distinctly original and Icelandic. One is Páll Olafsson (b. 1827). His +songs are mostly written in the medieval quatrains (_ferskeytla_), and +are generally of a humorous and satirical character; his convivial songs +are known by heart by every modern Icelander; and although some of the +poets of the present day are more admired, there is none who is more +loved by the people. The other is Þorsteinn Erlingsson (b. 1858). His +exquisite satirical songs, in an easy and elegant but still manly and +splendid language, have raised much discussion. Of his poems may be +mentioned _The Oath_, a series of most beautiful ballads, with a +tragical love-story of the 17th century as their base, but with many and +happy satirical allusions to modern life; _Jörundr_, a long poem about +the convict king, the Danish pirate Jörgensen, who nearly succeeded in +making himself the master of Iceland, and _The Fate of the Gods_ and +_The Men of the West_ (the Americans), two poems which, with their +anti-clerical and half-socialistic tendencies, have caused strong +protests from orthodox Lutheran clergy. Near to this school, but still +standing apart, is Grímur Thomsen (b. 1820). + +In the beginning of the 'eighties a new school arose--having its origin +in the colony of Icelandic students at the University of Copenhagen. +They had all attended the lectures of Georg Brandes, the great reformer +of Scandinavian literature, and, influenced by his literary theories, +they chose their models in the realistic school. This school is very +dissimilar from the half-romantic school of Jónas Hallgrímsson; it is +nearer the national Icelandic school represented by Páll Olafsson and +Þorsteinn Erlingsson, but differs from those writers by introducing +foreign elements hitherto unknown in Icelandic literature, +and--especially in the case of the prose-writers--by imitating closely +the style and manner of some of the great Norwegian novelists. Their +influence brought the Icelandic literature into new roads, and it is +interesting to see how the tough Icelandic element gradually assimilates +the foreign. Of the lyrical poets, Hannes Hafsteinn (b. 1861) is by far +the most important. In his splendid ballad, _The Death of Skarphedinn_, +and in his beautiful series of songs describing a voyage through some of +the most picturesque parts of Iceland, he is entirely original; but in +his love-songs, beautiful as many of them are, a strong foreign +influence can be observed. Among the innovations of this poet we may +note a predilection for new metres, sometimes adopted from foreign +languages, sometimes invented by himself, a thing practised rarely and +generally with small success by the Icelandic poets. + +No Icelandic novelist has as yet equalled Jón Thóroddsen (1819-1868). +The influence of the realistic school has of late been predominant. The +most distinguished writer of that school has been Gestur Pálsson +(1852-1891), whose short stories with their sharp and biting satire have +produced many imitations in Iceland. The best are _A Home of Love_ and +_Captain Sigurd_. Jónas Jónasson (b. 1856), a clergyman of northern +Iceland, has, in a series of novels and short stories, given accurate, +but somewhat dry, descriptions of the more gloomy sides of Icelandic +country life. His best novel is _Randiðr from Hvassafell_, an historical +novel of the middle ages. Besides these we may mention Torfhildur Hólm, +one of the few women who have distinguished themselves in Icelandic +literature. Her novels are mostly historical. The last decade of the +19th century saw the establishment of a permanent theatre at Reykjavik. +The poet Matthías Jochumsson has written several dramas, but their chief +merits are lyrical. The most successful of Icelandic dramatists as yet +is Indrði Einarsson, whose plays, chiefly historical, in spite of +excessive rhetoric, are very interesting and possess a true dramatic +spirit. + +In geography and geology Þorvaldr Thoroddsen has acquired a European +fame for his researches and travels in Iceland, especially in the +rarely-visited interior. Of his numerous writings in Icelandic, Danish +and German, the _History of Icelandic Geography_ is a monumental +work. In history Páll Melsteð's (b. 1812) chief work, the large _History +of the World_, belongs to this period, and its pure style has had a +beneficial influence upon modern Icelandic prose. + +Of the younger historians we may mention Þorkell Bjarnason (_History of +the Reformation in Iceland_). Jón Þorkelsson (b. 1822), inspector of the +archives of Iceland, has rendered great services to the study of +Icelandic history and literature by his editions of the _Diplomatarium +Islandicum_ and _Obituarium Islandicum_, and by his _Icelandic Poetry in +the 15th and 16th Century_, written in Danish, an indispensable work for +any student of that period. A leading position among Icelandic +lexicographers is occupied by Jón Þorkelsson, formerly head of the Latin +school at Reykjavik, whose _Supplement til islandske Ordbøger_, an +Icelandic-Danish vocabulary (three separate collections), has hardly +been equalled in learning and accuracy. Other distinguished philologists +are his successor as head of the Latin school, Bjôrn Magnússon Olsen +(_Researches on Sturlunga_, _Ari the Wise_, _The Runes in the Old +Icelandic Literature_--the last two works in Danish); Finnur Jónsson, +professor at the University of Copenhagen (_History of the Old Norwegian +and Icelandic Literature_, in Danish, and excellent editions of many old +Icelandic classical works); and Valtýr Guðmundsson, lecturer at the +University of Copenhagen (several works on the old architecture of +Scandinavia) and editor of the influential Icelandic literary and +political review, _Eimreiðin_ ("The Locomotive"). + + See J. C. Poestion, _Islandische Dichter der Neuzeit_ (Leipzig, 1897); + C. Küchler, _Geschichte der isländischen Dichtung der Neuzeit_ + (Leipzig, 1896); Ph. Schweitzer, _Island; Land und Leute_ (Leipzig, + 1885); Alexander Baumgartner, _Island und die Faroer_ (Freiburg im + Breisgau, 1889). (S. Bl.) + + +FOOTNOTES: + + [1] _Jökull_, plural _jöklar_, Icel. snowfield, glacier. + + [2] _Flói_, bay; _fjörðr_, fjord. + + [3] _Vatn_, lake. + + [4] See Th. Thoroddsen, "Explorations in Iceland during the years + 1881-1898," _Geographical Journal_, vol. xiii. (1899), pp. 251-274, + 480-513, with map. + + [5] For the periods succeeding the union, Danish state papers and the + _History_ of Finn Jonsson are the best authority. + + [6] Many of these poems were Englished in prose by the translator of + Mallet, by B. Thorpe in his _Sæmund's Edda_, and two or three by + Messrs Morris and Magnussen, as appendices to their translation of + _Volsunga Saga_. Earlier translations in verse are those in Dryden's + _Miscellany_ (vol. vi), A. Cottle's _Edda_, Mathias's _Translations_, + and W. Herbert's _Old Icelandic Poetry_. Gray's versions of + _Darradar-liod_ and _Vegtamskviða_ are well known. + + [7] E.g. "The Battle of the Plains of Death," a burlesque on the + battle of Solferino. + + + + +ICELAND MOSS, a lichen (_Cetraria islandica_) whose erect or ascending +foliaceous habit gives it something of the appearance of a moss, whence +probably the name. It is often of a pale chestnut colour, but varies +considerably, being sometimes almost entirely greyish white; and grows +to a height of from 3 to 4 in., the branches being channelled or rolled +into tubes, which terminate in flattened lobes with fringed edges. It +grows abundantly in the mountainous regions of northern countries, and +it is specially characteristic of the lava slopes and plains of the west +and north of Iceland. It is found on the mountains of north Wales, north +England, Scotland and south-west Ireland. As met with in commerce it is +a light-grey harsh cartilaginous body, almost destitute of colour, and +having a slightly bitter taste. It contains about 70% of lichenin or +lichen-starch, a body isomeric with common starch, but wanting any +appearance of structure. It also yields a peculiar modification of +chlorophyll, called thallochlor, fumaric acid, licheno-stearic acid and +cetraric acid, to which last it owes its bitter taste. It forms a +nutritious and easily digested amylaceous food, being used in place of +starch in some preparations of cocoa. It is not, however, in great +request, and even in Iceland it is only habitually resorted to in +seasons of scarcity. Cetraric acid or cetrarin, a white +micro-crystalline powder with a bitter taste, is readily soluble in +alcohol, and slightly soluble in water and ether. It has been +recommended for medicinal use, in doses of 2 to 4 grains, as a bitter +tonic and aperient. + + + + +ICE-PLANT, the popular name for _Mesembryanthemum crystallinum_, a hardy +annual most effective for rockwork. It is a low-growing spreading +herbaceous plant with the fleshy stem and leaves covered with large +glittering papillae which give it the appearance of being coated with +ice. It is a dry-country plant, a native of Greece and other parts of +the Mediterranean region, the Canary Islands, South Africa and +California. _Mesembryanthemum_ is a large genus (containing about 300 +species) of erect or prostrate fleshy herbs or low shrubs, mostly +natives of South Africa, and rarely hardy in the British Isles where +they are mostly grown as greenhouse plants. They bear conspicuous white, +yellow or red flowers with many petals inserted in the calyx-tube. The +thick fleshy leaves are very variable in shape, and often have spiny +rigid hairs on the margin. They are essentially sun-loving plants. The +best-known member of the genus is _M. cordifolium, var. variegatum_, +with heart-shaped green and silvery leaves and bright rosy-purple +flowers. It is extensively used for edging flower-beds and borders +during the summer months. + + + + +ICE-YACHTING, the sport of sailing and racing ice-boats. It is practised +in Great Britain, Norway and Sweden, to some extent, and is very popular +in Holland and on the Gulf of Finland, but its highest development is in +the United States and Canada. The Dutch ice-yacht is a flat-bottomed +boat resting crossways upon a planking about three feet wide and sixteen +long, to which are affixed four steel runners, one each at bow, stern +and each end of the planking. The rudder is a fifth runner fixed to a +tiller. Heavy mainsails and jibs are generally used and the boat is +built more for safety than for speed. The ice-boat of the Gulf of +Finland is a V-shaped frame with a heavy plank running from bow to +stern, in which the mast is stepped. The stern or steering runner is +worked by a tiller or wheel. The sail is a large lug and the boom and +gaff are attached to the mast by travellers. The passengers sit upon +planks or rope netting. The Russian boats are faster than the Dutch. + +In 1790 ice-yachting was in vogue on the Hudson river, its headquarters +being at Poughkeepsie, New York. The type was a square box on three +runners, the two forward ones being nailed to the box and the third +acting as a rudder operated by a tiller. The sail was a flatheaded +sprit. This primitive style generally obtained until 1853, when +triangular frames with "boxes" for the crew aft and jib and mainsail rig +were introduced. A heavy, hard-riding type soon developed, with short +gaffs, low sails, large jibs and booms extending far over the stern. It +was over-canvassed and the mast was stepped directly over the +runner-plank, bringing the centre of sail-balance so far aft that the +boats were apt to run away, and the over-canvassing frequently caused +the windward runner to swing up into the air to a dangerous height. The +largest and fastest example of this type, which prevailed until 1879, +was Commodore J. A. Roosevelt's first "Icicle," which measured 69 ft. +over all and carried 1070 sq. ft. of canvas. In 1879 Mr H. Relyea built +the "Robert Scott," which had a single backbone and wire guy-ropes, and +it became the model for all Hudson river ice-yachts. Masts were now +stepped farther forward, jibs were shortened, booms cut down, and the +centre of sail-balance was brought more inboard and higher up, causing +the centres of effort and resistance to come more in harmony. The +shallow steering-box became elliptical. In 1881 occurred the first race +for the American Challenge Pennant, which represents the championship of +the Hudson river, the clubs competing including the Hudson river, North +Shrewsbury, Orange lake, Newburgh and Carthage Ice-Yacht Clubs. The +races are usually sailed five times round a triangle of which each leg +measures one mile, at least two of the legs being to windward. +Ice-yachts are divided into four classes, carrying respectively 600 sq. +ft. of canvas or more, between 450 and 600, between 300 and 450, and +less than 300 sq. ft. Ice-yachting is very popular on the Great Lakes, +both in the United States and Canada, the Kingston (Ontario) Club having +a fleet of over 25 sail. Other important centres of the sport are Lakes +Minnetonka and White Bear in Minnesota, Lakes Winnebago and Pepin in +Wisconsin, Bar Harbor lake in Maine, the St Lawrence river, Quinte Bay +and Lake Champlain. + +A modern ice-yacht is made of a single-piece backbone the entire length +of the boat, and a runner-plank upon which it rests at right angles, the +two forming a kite-shaped frame. The best woods for these pieces are +basswood, butternut and pine. They are cut from the log in such a way +that the heart of the timber expands, giving the planks a permanent +curve, which, in the finished boat, is turned upward. The two forward +runners, usually made of soft cast iron and about 2 ft. 7 in. long and +2½ in. high, are set into oak frames a little over 5 ft. long and 5 in. +high. The runners have a cutting edge of 90%, though a V-shaped edge is +often preferred for racing. The rudder is a runner about 3 ft. 7 in. +long, worked by a tiller, sometimes made very long, 7½ ft. not being +uncommon. This enables the helmsman to lie in the box at full length and +steer with his feet, leaving his hands free to tend the sheet. Masts and +spars are generally made hollow for racing-yachts and the rigging is +pliable steel wire. The sails are of 10-oz. duck for a boat carrying 400 +sq. ft. of canvas. They have very high peaks, short hoists and long +booms. The mainsail and jib rig is general, but a double-masted lateen +rig has been found advantageous. The foremost ice-yacht builder of +America is G. E. Buckhout of Poughkeepsie. + +An ice-yacht about 40 ft. in length will carry 6 or 7 passengers or +crew, who are distributed in such a manner as to preserve the balance of +the boat. In a good breeze the crew lie out on the windward side of the +runner-plank to balance the boat and reduce the pressure on the leeward +runner. A course of 20 m. with many turns has been sailed on the Hudson +in less than 48 minutes, the record for a measured mile with flying +start being at the rate of about 72 m. an hour. In a high wind, however, +ice-yachts often move at the rate of 85 and even 90 m. an hour. + +Several of the laws of ice navigation seem marvellous to the +uninitiated. Commodore Irving Grinnell, who has made a scientific study +of the sport, says: "The two marked peculiarities of ice-yachting which +cause it to differ materially from yachting on the sea are: (1) Sailing +faster than the wind. (2) Sheets flat aft under all circumstances." Mr +H. A. Buck, in the "Badminton Library," _Skating, Curling, Tobogganing_, +&c., thus explains these paradoxes. An ice-boat sails faster than the +wind because she invariably sails at some angle to it. The momentum is +increased by every puff of wind striking the sails obliquely, until it +is finally equalled by the increase of friction engendered. Thus the +continued bursts of wind against the sails cause a greater accumulation +of speed in the ice-yacht than is possessed by the wind itself. When the +boat sails directly before the wind she is, like a balloon, at its +mercy, and thus does not sail faster than the wind. The ice-yacht always +sails with its sheets flat aft, because the greater speed of the boat +changes the angle at which the wind strikes the sail from that at which +it would strike if the yacht were stationary to such a degree that, in +whatever direction the yacht is sailing, the result is always the same +as if the yacht were close-hauled to the wind. It follows that the yacht +is actually overhauling the wind, and her canvas shivers as if in the +wind's eye. When eased off her momentum becomes less and less until it +drops to the velocity of the wind, when she can readily be stopped by +being spun round and brought head to the wind. The latter method is one +way of "coming to," instead of luffing up in the usual way from a beam +wind. In beating to windward an ice-boat is handled like a water yacht, +though she points more closely. + +On the bays near New York a peculiar kind of ice-boat has developed, +called _scooter_, which may be described as a toboggan with a sail. A +typical scooter is about 15 ft. long with an extreme beam of 5 ft., +perfectly oval in form and flat. It has mainsail and jib carried on a +mast 9 or 10 ft. long and set well aft, and is provided with two long +parallel metal runners. There is no rudder, the scooter being steered +entirely by trimming the sails, particularly the jib. As the craft is +flat and buoyant it sails well in water, and can thus be used on very +thin ice without danger. A speed of 50 m. an hour has been attained by a +scooter (see _Outing_ for March 1905). + + See _Ice Sports_, in the "Isthmian Library"; _Skating, Curling, + Tobogganing, &c._ in the "Badminton Library." + + + + +I-CH'ANG (YI-CH'ANG, anciently known as _Yi-ling_), a town of China in +the province of Hu-peh, one of the four ports opened to foreign trade by +treaty in 1877. It is situated in 30° 42´ N. and (approximately) 111° +20´ E., on the Yangtsze-Kiang, 1000 m. from Shanghai. Built on the left +bank of the river where it escapes from the ravines and gorges which for +350 m. have imprisoned its channel, I-ch'ang is exposed to considerable +risk of floods; in 1870 the waters rose 20 ft. in one day, and the town +had many of its houses and about half of its wall swept away. The first +English vessels to ascend the river as far as I-ch'ang were those of +Admiral Sir James Hope's expedition in 1861. All cargo to or from +Szech'uen is here transhipped from steamer to junk, or _vice versâ_. +About 10 m. above I-ch'ang the famed scenery of the Yangtsze gorges +begins. Through these the great river runs in a series of rapids, which +make navigation by vessels of any size extremely difficult. A very large +trade, nevertheless, is carried on by this route between Chungk'ing and +I-ch'ang. As a local centre of distribution this port is of no great +consequence, the transhipment trade with Szech'uen being almost its sole +business. The population is estimated at 35,000. The number of foreign +residents is very small, trade being carried on by Chinese agents. +Before the anti-opium campaign of 1906 (see CHINA) opium was much grown. +The trade of the port amounted in 1899 to £531,229, and in 1904 to +£424,442, the principal import being cotton yarn and the principal +export opium. + + + + +ICHNEUMON (Gr. [Greek: ichneumôn], from [Greek: ichneuein], to track +out), the common name of the North African representative of a number of +small weasel-shaped mammals belonging to the carnivorous family +_Viverridae_; the Indian representatives of the group being known as +mongooses. A large number of species of the type genus are known, and +range over southern Asia and all Africa, the typical _Herpestes +ichneumon_ also occurring in the south of Spain. The latter is an +inhabitant of Egypt and the north of Africa, where it is known to +foreign residents as "Pharaoh's rat." It is covered with long harsh fur +of a tawny-grey colour, darker on the head and along the middle of the +back, its legs reddish and its feet and tail black. It lives largely on +rats and mice, birds and reptiles, and for this reason it is +domesticated. It is, however, fond of poultry and their eggs, and its +depredations among fowls detract from its merits as a vermin-killer. +During the inundations of the Nile it is said to approach the +habitations of man, but at other seasons it keeps to the fields and to +the banks of the river. The Indian mongoose (_H. mungo_) is considerably +smaller than the Egyptian animal, with fur of a pale-grey colour, the +hairs being largely white-ringed, while the cheeks and throat are more +or less reddish. Like the former it is frequently domesticated. It is +especially serviceable in India as a serpent-killer, destroying not only +the eggs and young of these creatures, but killing the most venomous +adult snakes. The fact that it survives those encounters has led to the +belief that it either enjoys immunity from the effects of snake poison, +or that after being bitten it has recourse, as the Hindus maintain, to +the root of a plant as an antidote. It has been found, however, that +when actually bitten it falls a victim to the poison as rapidly as other +mammals, while there is no evidence of its seeking a vegetable antidote. +The truth seems to be that the mongoose, by its exceeding agility and +quickness of eye, avoids the fangs of the snake while fixing its own +teeth in the back of the reptile's neck. Moreover, when excited, the +mongoose erects its long stiff hair, and it must be very difficult for a +snake to drive its fangs through this and the thick skin which all the +members of the genus possess. The mongoose never hesitates to attack a +snake; the moment he sees his enemy, "his whole nature," writes a +spectator of one of those fights, "appears to be changed. His fur stands +on end, and he presents the incarnation of intense rage. The snake +invariably attempts to escape, but, finding it impossible to evade the +rapid onslaught of the mongoose, raises his crest and lashes out +fiercely at his little persecutor, who seems to delight in dodging out +of the way just in time. This goes on until the mongoose sees his +opportunity, when like lightning he rushes in and seizes the snake with +his teeth by the back of the neck close to the head, shaking him as a +terrier does a rat. These tactics are repeated until the snake is +killed." The mongoose is equally dexterous in killing rats and other +four-footed vermin. + +[Illustration: Egyptian Ichneumon (_Herpestes ichneumon_).] + + + + +ICHNEUMON-FLY, a general name applied to parasitic insects of the +section _Ichneumonoidea_ (or _Entomophaga_), order _Hymenoptera_, from +the typical genus _Ichneumon_, belonging to the chief family of that +section--itself fancifully so called after the Egyptian mammal +(_Herpestes_). The species of the families (_Ichneumonidae_, +_Braconidae_, _Evaniidae_, _Proctotrypidae_, and _Chalcididae_) are +often indiscriminately called "Ichneumons," but the "super-family" of +the Ichneumonoidea in the classification of W. H. Ashmead contains only +the _Evaniidae_, the _Stephanidae_, and the large assemblage of insects +usually included in the two families of the _Ichneumonidae_ and the +_Braconidae_, which are respectively equivalent to the _Ichneumones +genuini_ and _I. adsciti_ of older naturalists, chiefly differing in the +former having two recurrent nerves to the anterior wing, whilst the +latter has only one such nerve. The _Ichneumonidae_ proper are one of +the most extensive groups of insects. Gravenhorst described some 1650 +European species, to which considerable subsequent additions have been +made. There are 6 sub-families of the _Ichneumonidae_, viz. the +_Ichneumoninae_, _Cryptinae_, _Agriotypinae_, _Ophioninae_, +_Tryphoninae_ and _Pimplinae_, differing considerably in size and +facies, but united in the common attribute of being, in their earlier +stages, parasitic upon other insects. They have all long narrow bodies; +a small free head with long filiform or setaceous antennae, which are +never elbowed, and have always more than sixteen joints; the abdomen +attached to the thorax at its hinder extremity between the base of the +posterior coxae, and provided in the female with a straight ovipositor +often exserted and very long; and the wings veined, with perfect cells +on the disk of the front pair. Ashmead proposes to separate the +_Agriotypidae_ (which are remarkable for their aquatic habit, being +parasitic on caddis-worms) from the _Ichneumonidae_ on account of their +firm ventral abdominal segments and spined scutellum. He also separates +from the _Braconidae_ the _Alysiidae_ as a distinct family; they have +peculiar mandibles with out-turned tips. + +Their parasitic habits render these flies of great importance in the +economy of nature, as they serve to check any inordinate increase in the +numbers of injurious insects. Without their aid it would in many cases +be impossible for the agriculturist to hold his own against the ravages +of his minute insect foes, whose habits are not sufficiently known to +render artificial checks or destroying agents available. The females of +all the species are constantly on the alert to discover the proper +living food for their own larvae, which are hatched from the eggs they +deposit in or on the eggs, larvae or pupae of other insects of all +orders, chiefly _Lepidoptera_, the caterpillars of butterflies and moths +being specially attacked (as also are spiders). Any one who has watched +insect life during the summer can hardly have failed to notice the busy +way in which the parent ichneumon, a small four-winged fly, with +constantly vibrating antennae, searches for her prey; and the clusters +of minute cocoons round the remains of some cabbage-butterfly +caterpillar must also have been observed by many. This is the work of +_Apanteles_ (or _Microgaster_) _glomeratus_, one of the _Braconidae_, +which in days past was a source of disquietude to naturalists, who +believed that the life of the one defunct larva had _transmigrated_ into +the numerous smaller flies reared from it. Ichneumon-flies which attack +external feeders have a short ovipositor, but those attached to +wood-feeding insects have that organ of great length, for the purpose of +reaching the haunts of their concealed prey. Thus a species from Japan +(_Bracon penetrator_) has its ovipositor nine times the length of the +body; and the large species of _Rhyssa_ and _Ephialtes_, parasitic on +_Sirex_ and large wood-boring beetles in temperate Europe, have very +long instruments (with which when handled they will endeavour to sting, +sometimes penetrating the skin), in order to get at their secreted +victims. A common reddish-coloured species of _Ophion_ (_O. obscurum_), +with a sabre-shaped abdomen, is noteworthy from the fact of its eggs +being attached by stalks outside the body of the caterpillar of the +puss-moth (_Cerura vinula_). Lepidopterists wishing to breed the latter +cut off the eggs of the parasite with scissors. + +The larvae of the ichneumon-flies are white, fleshy, cylindrical, +footless grubs; the majority of them spin silk cocoons before pupating, +often in a mass (sometimes almost geometrically), and sometimes in +layers of different colours and texture. + + AUTHORITIES.--Among the older works on Ichneumonoidea may be specially + mentioned J. L. K. Gravenhorst, _Ichneumonologia Europaea_ (Breslau, + 1829); A. H. Haliday (_Entom. Mag._ i.-v., 1833-1838), and A. Förster + (_Verhandl. Naturhist. Ver. Rheinl. u. Westph._ xix., xxv., 1862, + 1868). Full reference to the systematic literature of the group will + be found in C. G. de Dalla Torre's _Catalogus hymenopterorum_, vols, + iii., iv. (Leipzig, 1898-1902), and a comprehensive summary in W. H. + Ashmead's recent memoir (_Proc. U.S. Nat. Mus._ xxiii., 1901). For the + British species consult C. Morley, _Ichneumons of Great Britain_ + (Plymouth, 1903), and T. A. Marshall (_Trans. Entom. Soc._, + 1885-1899). (G. H. C.) + + + + +ICHNOGRAPHY (Gr. [Greek: ichnos], a trace, and [Greek: graphê], +description), in architecture, a term defined by Vitruvius (i.2) as "the +ground-plan of the work," i.e. the geometrical projection or horizontal +section representing the plan of any building, taken at such a level as +to show the outer walls, with the doorways, windows, fireplaces, &c., +and the correct thickness of the walls; the position of piers, columns +or pilasters, courtyards and other features which constitute the +design. + + + + + + +End of the Project Gutenberg EBook of Encyclopaedia Britannica, 11th +Edition, Volume 14, Slice 2, by Various + +*** END OF THE PROJECT GUTENBERG EBOOK 40370 *** |