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diff --git a/40370.txt b/40370.txt deleted file mode 100644 index b153ba0..0000000 --- a/40370.txt +++ /dev/null @@ -1,21433 +0,0 @@ -The Project Gutenberg EBook of Encyclopaedia Britannica, 11th Edition, -Volume 14, Slice 2, by Various - -This eBook is for the use of anyone anywhere at no cost and with -almost no restrictions whatsoever. You may copy it, give it away or -re-use it under the terms of the Project Gutenberg License included -with this eBook or online at www.gutenberg.org - - -Title: Encyclopaedia Britannica, 11th Edition, Volume 14, Slice 2 - "Hydromechanics" to "Ichnography" - -Author: Various - -Release Date: July 29, 2012 [EBook #40370] - -Language: English - -Character set encoding: ASCII - -*** START OF THIS PROJECT GUTENBERG EBOOK ENCYCLOPAEDIA BRITANNICA *** - - - - -Produced by Marius Masi, Don Kretz and the Online -Distributed Proofreading Team at http://www.pgdp.net - - - - - - - -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 - HYERES IBADAN - HYGIEIA IBAGUE - 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: hydromechanika]), 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 ton ochoumenon], 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'equilibre 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 Edme Mariotte (1620-1684), whose _Traite 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 _Traite 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 resistance des fluides_, was brought to perfection in - his _Opuscules mathematiques_, 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 Abbe Charles Bossut (_Nouvelles Experiences sur la - resistance 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 (_Experiences - 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 (_Traite de la mesure 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 - Ingenieur_, 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 _Beitrage zur Hydrographie - des Konigreiches Bohmen_ (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 S 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 X 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 X 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/cm^2; and one - ton/inch^2, 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]y^3, 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) S 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] a^2 - ----- = (n + 1)------ -------- = - --- dr, (12) - [rho] [rho]0 [theta]0 r^2 - - 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 = (1/2)z^2/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 \ z^2 - ------ - 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] | | x^2 dA - sin [alpha] | | xy dA, (8) - _/_/ _/_/ - _ _ _ _ - / / / / - [=y]hA = -cos [alpha] | | xy dA - sin [alpha] | | y^2 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 = -a^2 cos [alpha], [=y]h = -b^2 sin [alpha], (10) - - where - _ _ _ _ - / / / / - | | x^2 dA = Aa^2, | | y^2 dA = Ab^2, (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 3/4 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 S 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 = --- X 42 X ---- = 2.24 ft.; (2) - 10 9000 - - also - - cot [theta] = 24, [theta] = 2 deg. 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] y^2 dA - = w tan [theta].Ak^2 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 = wAk^2 tan [theta], (5) - - BM = BB1 cot [theta] = Ak^2/V, (6) - - giving the radius of curvature BM of the curve of buoyancy B, in terms - of the displacement V, and Ak^2 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 S 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 - - a^2 - hV/A, b^2 - 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 = (k^2 - 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 Ak^2 - 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]u^2 + m[rho]uv + n[rho]uw) dS, (1) - _/_/ _/_/ - - which by Green's transformation is - _ _ _ - / / / /d([rho]u^2) 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]u^2 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]u^2 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) S 21; for - - d[rho]u d[rho]u^2 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 + (1/2)q^2, (7) - _/ - - q^2 = u^2 + v^2 + w^2, (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 - (1/2)q^2 is replaced by (1/2)q^2/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] = (1/2) -----------, [eta] = (1/2) -----------, [zeta] = (1/2) -----------, (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) S 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 (S 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) S 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 + (1/2)q^2 = 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 d(1/2)q^2 q^2 - ----- ----- + ----- = ----- - --------- = ---, (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 d(1/2)q^2 d(1/2)q^2 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 + q^2/2g = 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, - - q^2/2g = 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 d^2[psi] d^2[psi] - 2[zeta] = -- - -- = -------- + -------- = -[Nabla]^2[psi], suppose, (3) - dx dy dx^2 dy^2 - - 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 a^2/c, and so describe a circle with velocity - - mc/(a^2 - c^2) in the periodic time 2[pi](a^2 - c^2)/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 (1/2)[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] + (1/2)R(x^2 + y^2) = [psi]', (6) - - a constant over the boundary; and [psi]' is the current-function of - the relative motion past the cylinder, but now - - V^2[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 + (1/2)R(x^2 + y^2) 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 + a^2/z), (1) - - so that - - / a^2\ / a^2 \ - [phi] = U ( r + --- ) cos [theta] = U ( 1 + --- ) x, (2) - \ r / \ r^2 / - - / a^2\ / a^2 \ - [psi] = U ( r - --- ) sin [theta] = U ( 1 - --- ) y. - \ r / \ r^2 / - - 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 - - / a^2\ - ( r - --- ) sin [theta] = c, (x^2 + y^2)(y - c) - a^2y = 0 (3) - \ r / - - a cubic curve (C3). - - Over a concentric cylinder, external or internal, of radius r = b, - - / a^2 \ - [psi]' = [psi] + U1y = [U ( 1 - --- ) + U1] y, (4) - \ b^2 / - - and [psi]' is zero if - - U1/U = (a^2 - b^2)/b^2; (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] = Ua^2/z, (6) - - [phi] = U(a^2/r) cos [theta] = Ua^2x/(x^2 + y^2), (7) - - [psi] = -U(a^2/r) sin [theta] = -Ua^2y/(x^2 + y^2), (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] = (1/2)[theta]', (9) - dy / dx x^2 - y^2 - - and the velocity is Ua^2/r^2. - - Along the path of a particle, defined by the C3 of (3), - - y^2 y(y - c) - sin^2 1/2[theta]' = --------- = --------, (10) - x^2 + y^2 a^2 - - d[theta]' 2y - c dy - 1/2 sin [theta]' --------- = ------ --, (11) - ds a^2 ds - - on the radius of curvature is (1/4)a^2/(y - (1/2)c), 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 / a^2\ a^2 + b^2 - --------- = - -- ( 1 + --- ) = ---------, (13) - [phi]1 U1 \ b^2/ a^2 - b^2 - - and this, by S 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 (a^2 + b^2)/(a^2 - b^2) 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 - - a^2 + b^2 dU a^2 + b^2 dU - [pi][rho]b^2 --------- -- = --------- M'--, (14) - a^2 - b^2 dt a^2 - b^2 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, - - a^2 / b^2 \ b^2 / a^2\ - [phi] = U --------- ( --- + r ) cos [theta] - U1--------- ( r + --- ) cos [theta], (15) - b^2 - a^2 \ r / b^2 - a^2 \ r / - - a^2 / b^2 \ b^2 / a^2\ - [psi] = -U --------- ( --- - r ) sin [theta] - U1--------- ( r - --- ) sin [theta]; (16) - b^2 - a^2 \ r / b^2 - a^2 \ r / - - and similarly, with velocity components V and V1 along Oy - - a^2 / b^2 \ b^2 / a^2\ - [phi] = V --------- ( --- + r ) sin [theta] - V1--------- ( r + --- ) sin [theta], (17) - b^2 - a^2 \ r / b^2 - a^2 \ r / - - a^2 / b^2 \ b^2 / a^2\ - [psi] = V --------- ( --- - r ) cos [theta] + V1--------- ( r - --- ) cos [theta], (18) - b^2 - a^2 \ r / b^2 - a^2 \ r / - - and then for the resultant motion - a^2 z a^2 b^2 U + Vi - w = (U^2 + V^2) --------- ------ + --------- ------ - b^2 - a^2 U + Vi b^2 - a^2 z - - a^2 z a^2 b^2 U1 + V1i - -(U1^2 + V1^2) --------- -------- + --------- --------. (19) - b^2 - a^2 U1 + V1i b^2 - a^2 z - - The resultant impulse of the liquid on the cylinder is given by the - component, over r = a (S 36), - _ - / / b^2 + a^2 2b^2 \ - X = | [rho][phi] cos [theta].ad[theta] = [pi][rho]a^2 ( U --------- - U1 --------- ); (20) - _/ \ b^2 - a^2 b^2 - a^2/ - - and over r = b - _ - / / 2a^2 b^2 + a^2 \ - X1 = | [rho][phi] cos [theta].bd[theta] = [pi][rho]b^2 ( U --------- - U1--------- ), (21) - _/ \ b^2 - a^2 b^2 - a^2 / - - 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 2a^2 b^2 - a^2 - X1 = 0, -- = ---------, X = [pi][rho]a^2U ---------. (22) - U b^2 + a^2 b^2 + a^2 - - 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]b^2 - X = -[pi][rho]a^2 U, -- = -------------------------------------, - U [rho](b^2 + a^2) + [sigma](b^2 - a^2) - - U - U1 ([rho] - [sigma])(b^2 - a^2) - ------ = -------------------------------------, (23) - U1 [rho](b^2 + a^2) + [sigma](b^2 - a^2) - - 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) S 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](b^2 - a^2). - - 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]a^2 and [rho]m[pi]b^2, having - resultant [rho]m[pi](b^2 - a^2), 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 - U^2 (2U sin [theta] + m/a)^2 - U^2 - ---------- = ------------------------------, (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]a^2 dU/dt, -[pi][rho]a^2 dV/dt, due to the kinetic - reaction of the liquid; - - (iii.) 0, -[pi]([sigma] - [rho])a^2 g, 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]a^2-- = - [pi][rho]a^2-- - 2[pi][rho]mV, (4) - dt dt - - dV dV - [pi][rho]a^2-- = - [pi][rho]a^2-- + 2[pi][rho]mV - [pi]([sigma] - [rho])a^2g, (5) - dt dt - - or, putting m = a^2[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 - Ua^2 r^(-2) cos 2[theta] + mr^(-1) sin [theta])(Ua^2 r^(-2) sin 2[theta] + mr^(-1) cos [theta]) - + [rho]dy (- U + Ua^2 r^(-2) cos 2[theta] + mr^(-1) sin [theta])(Ua^2 r^(-2) sin 2[theta] - mr^(-1) cos [theta]) - = 2[rho]dymUr^(-1)(cos [theta] - a^2 r^(-2)cos 3[theta]), (8) - - and with y = b tan [theta], r = b sec [theta], this is - - 2[rho]mUd[theta] (1 - a^2 b^(-2) cos 3[theta] cos [theta]), (9) - - and integrating between the limits [theta] = [+-](1/2)[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]) = c^2(ch^2[eta] - cos^2 [xi]) - d([eta] - - = (1/2)c^2(ch 2[eta] - cos 2[xi]) = r1r2 = OD^2, (2) - - if OD is the semi-diameter conjugate to OP, and r1, r2 the focal - distances, - - r1, r2 = c(ch[eta] [+-] cos [xi]); (3) - - r^2 = x^2 + y^2 = c^2(ch^2[eta] - sin^2 [xi]) - - = (1/2)c^2(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) S 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] + (1/2)R(x^2 + y^2) - = [-m sh 2([eta] - [alpha]) + (1/4)Rc^2] cos 2[xi] + (1/4)Rc^2 ch 2[eta], (2) - - which is constant over the ellipse [eta] if - - (1/4)Rc^2 = 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 - - x^2/a^2 + y^2/b^2 = 1, (4) - - [psi]1' = m1(x^2/a^2 + y^2/b^2) (5) - - with - - [nabla]^2[psi]1' = -2R = -2m1(1/a^2 + 1/b^2), - - [psi]1 = m1(x^2/a^2 + y^2/b^2) - (1/2)R(x^2 + y^2) - = -(1/2)R(x^2 - y^2)(a^2 - b^2)/(a^2 + b^2), (6) - - [phi]1 = Rxy(a^2 - b^2)/(a^2 + b^2), - - w1 = [phi]1 +[psi]1i = -(1/2)iR(x + yi)^2(a^2 - b^2)/(a^2 + b^2). - - The velocity of a liquid particle is thus (a^2 - b^2)/(a^2 + b^2) 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 (a^2 - - b^2)^2/(a^2 + b^2)^2 of the solid; and the effective radius of - gyration, solid and liquid, is given by - - k^2 = (1/4)(a^2 + b^2), and (1/4)(a^2 - b^2)^2/(a^2 + b^2). (7) - - For the liquid in the interspace between [alpha] and [eta], - - [phi] m ch 2([eta] - [alpha]) sin 2[xi] - ------ = ---------------------------------------------------- - [phi]1 (1/4)Rc^2 sh 2[eta] sin 2[xi](a^2 - b^2)/(a^2 + b^2) - - = 1/th 2([eta] - [alpha])th 2[eta]; (8) - - and the effective k^2 of the liquid is reduced to - - (1/4)c^2/th 2([eta] - [alpha]) sh 2[eta], (9) - - which becomes (1/4)c^2/sh 2[eta] = 1/8 (a^2 - b^2)/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 + (1/2)Rx^2 and [psi]2 + (1/2)Ry^2 is constant over - the boundary. - - Inside a cylinder - - [phi]1 + [psi]1i = -(1/2)iR(x + yi)^2 a^2/(a^2 + b^2), (10) - - [phi]2 + [psi]2i = (1/2)iR(x + yi)^2 b^2/(a^2 + b^2), (11) - - and for the interspace, the ellipse [alpha] being fixed, and [alpha]1 - revolving with angular velocity R - - [phi]1 + [psi]1i = -1/8 iRc^2 sh 2([eta] - [alpha] - + [xi]i)(ch 2[alpha] + 1)/sh 2([alpha]1 - [alpha]), (12) - - [phi]2 + [psi]2i = 1/8 iRc^2 sh 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 + (1/2)Rx^2 = 1/8 Rc^2(ch 2[alpha]1 + 1), (14) - - [psi]2 + (1/2)Ry^2 = 1/8 Rc^2(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 (1/2)([eta] - [alpha]) sin (1/2)([xi] - [beta]) (18) - - will give motion streaming past the fixed cylinder [eta] = [alpha], - and dividing along [xi] = [beta]; and then - - x^2 - y^2 = c^2 sin [xi] ch [eta], 2xy = c^2 cos [xi] sh [eta]. (19) - - In particular, with sh [alpha] = 1, the cross-section of [eta] = - [alpha] is - - x^4 + 6x^2 y^2 + y^4 = 2c^4, or x^4 + y^4 = c^4 (20) - - when the axes are turned through 45 deg. - - 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 + (1/2)Rx^2 = (1/2)Ra^2, or [psi]1 = 0 when x = [+-]a, - - (iii.) [psi]1 + (1/2)Rx^2 = (1/2)Ra^2, [psi]1 = (1/2)R(a^2 - x^2), when y = [+-] b. - - Expanded in a Fourier series, - - 32 __ cos (2n + 1) (1/2)[pi]x/a - a^2 - x^2 = ------ a^2 \ -------------------------, (1) - [pi]^3 /__ (2n + 1)^3 - - so that - - 16 __ cos (2n + 1) (1/2)[pi]x/a . ch(2n + 1) (1/2)[pi]y/a) - [psi]1 = ----- a^2 \ ----------------------------------------------------, - [pi]^3 /__ (2n + 1)^3 . ch(2n + 1) (1/2)[pi]b/a - - - 16 __ cos (2n + 1) (1/2)[pi]z/a - w1 = [phi]1 + [psi]1i = iR ------ \ ----------------------------------, (2) - [pi]^3 /__ (2n + 1)^3 ch(2n + 1) (1/2)[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^(1/2) cos (1/2)[theta] = a^(1/2), or r + x = 2a, (3) - - the conditions are satisfied by - - [psi]' = Ur sin [theta] - 2Ua^(1/2) r^(1/2) sin (1/2)[theta] - = 2Ur^(1/2) sin (1/2)[theta](r^(1/2) cos (1/2)[theta] - a^(1/2)), (4) - - [psi] = 2Ua^(1/2) r^(1/2) sin (1/2)[theta] = -U[root][2a(r-x)], (5) - - w = -2Ua^(1/2) z^(1/2), (6) - - and the resistance of the liquid is 2[pi][rho]aV^2/2g. - - A relative stream line, along which [psi]' = Uc, is the quartic curve - - (4a^2 y^2 - (y - c)^4 4a^2 y^2 + (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 /d^2[psi] d^2[psi] 1 d[psi]\ 1 - = --- ( -------- + -------- - --- ------ ) = - ---[nabla]^2 [psi], (2) - y \ dx^2 dy^2 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 y^2 dx dy y^2 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 - - d^2 [psi] d^2 [psi] 1 d[psi] - [nabla]^2[psi] = 0, or --------- + --------- - --- ------ = 0. (7) - dx^2 dy^2 y dy - - Changing to polar coordinates, x = r cos[theta], y = r sin[theta], the - equation (2) becomes, with cos[theta] = [mu], - - d^2 [psi] d^2 [psi] - r^2--------- + (1 - [mu]^2) --------- = 2[zeta]r^3 sin [theta], (8) - dr^2 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) + ------- ) y^2-----, (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 (1/2)[theta] - = -(1/2)B0 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] + (1/2)Uy^2 = constant, (12) - y ds ds - - over the surface of the solid; and [psi] must be replaced by [psi]' = - [psi] + (1/2)Uy^2 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] + (1/2)Uy^2 = (1/2)U(r^2 - a^3/r) sin^2 [theta], - [psi] = -(1/2)Ua^3 sin^2 [theta]/r; (13) - - and then - - [phi]' = Ux(1 + (1/2)a^3/r^2), [phi] = (1/2)Ua^3 cos [theta]/r^2, (14) - - d[phi] a^3 d[phi] a^3 - - ------ = U --- cos [theta], - --------- = (1/2)U --- sin [theta], (15) - dr r^3 rd[theta] r^3 - - so that, if the direction of motion makes an angle [psi] with Ox, - - tan ([psi] - [theta]) = (1/2) tan [theta], - tan [psi] = 3 tan [theta]/(2 - tan^2 [theta]), (16) - - Along the path of a liquid particle [psi]' is constant, and putting it - equal to (1/2)Uc^2, - - (r^2 - a^3/r) sin^2 [theta] = c^2, sin^2 [theta] = c^2r/(r^3 - a^3), (17) - - the polar equation; or - - y^2 = c^2 r^3/(r^3 - a^3), r^3 = a^3 y^2/(y^2 - c^2), (18) - - a curve of the 10th degree (C10). - - In the absolute path in space - - cos [psi] = (2 - 3 sin^2 [theta])/[root](4 - sin^2 [theta]), - and sin^3 [theta] = (y^3 - c^2 y)/a^3, (19) - - which leads to no simple relation. - - The velocity past the surface of the sphere is - - 1 d[psi]' / a^3 \ sin^2 [theta] - ------------ ------- = (1/2)U ( 2r + --- ) ------------- = 3/2 U sin [theta], when r = a; (20) - r sin[theta] dr \ r^2 / r sin [theta] - - so that the loss of head is - - (9/4 sin^2 [theta] - 1) U^2/2g, having a maximum 5/4 U^2/2g, (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] = -(1/2)Uy^2 a^4[mu]/r^4, [psi]' = (1/2)Uy^2(1 - a^4[mu]/r^4), (22) - - [phi]' = Ux + [phi], [phi] = -1/3 U(a^4/r^3)P2, P2 = 3/2 [mu]^2 - (1/2), (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 = (1/2)[rho] | | | | ( ------ ) + ( ------ ) + ( ------ ) | dx dy dz, - _/_/_/ |_ \ dx / \ dy / \ dz / _| - _ _ - / / d[phi] - = (1/2)[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 = (1/2)[rho] | | | ( ------ ) + ( ------ ) | dx dy = (1/2)[rho] | | | ( ------ ) + ( ------ ) | dx dy - _/_/ |_ \ dx / \ dy / _| _/_/ |_ \ dx / \ dy / _| - _ _ - / d[phi] / d[phi] - = (1/2)[rho] | [phi] ------ ds = (1/2)[rho] | [psi] ------ ds. (7) - _/ d[nu] _/ d[nu] - - For example, in the equilateral triangle of (8) S 28, referred to - coordinate axes made by the base and height, - - [psi]' = -2R[alpha][beta][gamma]/h = -(1/2)Ry[(h - y)^2 - 3x^2]/h (8) - - [psi] = [psi]' - (1/2)R [(1/3h - y)^2 + x^2] - - = -(1/2)R [(1/2)h^3 + 1/3 h^2 y + h) (x^2 - y^2) - 3x^2 y + y^3] /h (9) - - and over the base y = 0, - - dx/d[nu] = -dx/dy = + (1/2)R(1/3 h^2 - 3x^2)/h, [psi] = -(1/2)R(1/9 h^2 + x^2). (10) - - Integrating over the base, to obtain one-third of the kinetic energy - T, - _ - / h/[root]3 - 1/3 T = (1/2)[rho] | (1/4)R^2(3x^4 - 1/27 h^4) dx/h - _/ -h/[root]3 - - = [rho]R^2 h^4/135[root]3 (11) - - so that the effective k^2 of the liquid filling the triangle is given - by - - k^2 = T/(1/2)[rho]R^2 A = 2h^2/45 - - = 2/5 (radius of the inscribed circle)^2, (12) - - or two-fifths of the k^2 for the solid triangle. - - Again, since - - d[phi]/d[nu] = d[psi]/ds, d[phi]/ds = -d[psi]/d[nu], (13) - _ _ - / / - T = (1/2)[rho] | [phi] d[psi] = -(1/2)[rho] | [psi] d[phi]. (14) - _/ _/ - - With the Stokes' function [psi] for motion symmetrical about an - axis. - _ _ - / d[psi] / - T = (1/2)[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 \ - (1/2) ( -- - -- ) = [zeta], (5) - \ dx dy / - - in the previous notation of S 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 S 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 + (1/2)dq^2, (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]\ d^2 d^2 d^2 - 2( ------ - ------ ) = [nabla]^2u, ... , [nabla]^2 = - ---- - ---- - ----, (10) - \ dy dz / dx^2 dy^2 dz^2 - - which is expressed by - - [nabla]^2(u,v,w) = 2 curl ([xi], [eta], [zeta]), - ([xi], [eta], [zeta]) = (1/2) 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 S25 (1), a first integral of the equations in (5) may be written - _ - / dp d[phi] d[psi] / d[phi] d[psi] \ - | ----- + V + (1/2)q^2 - ------ - 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 S 34 - - p/[rho] + V + (1/2)q'^2 - [f]([psi]') = constant (9) - - becomes transformed into - - p U d[psi] - ----- + V + (1/2)q^2 - --- ------ + (1/2)U^2 - [f]([psi] + (1/2)Uy^2) = constant, (10) - [rho] y dy - - [psi]' = [psi] + (1/4)U^2, (11) - - subject to the condition, from (4) S 34, - - y^(-2)[nabla]^2 [psi]' = -[f]'([psi]'), - y^(-2)[nabla]^2 [psi] = -[f]'([psi] + (1/2)Uy^2). (12) - - Thus, for example, with - - [psi]' = (3/4)Uy^2(r^2 a^(-2) - 1), r^2 = x^2 + y^2, (13) - - for the space inside the sphere r = a, compared with the value of - [psi]' in S 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 a^2 - - so that S 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 | / x^2 \^2 / y^2 \^2 | - ----- + V - ---U | ( --- -1 ) - ( --- - 1/2 ) | = constant; (16) - [rho] 8 |_ \ a^2 / \ a^2 / _| - - 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 - - x^2 y^2 z^2 - --- + --- + --- = 1; (1) - a^2 b^2 c^2 - - 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 - - b^2 - c^2 c^2 - a^2 a^2 - b^2 - [phi] = - [Omega]1 --------- yz - [Omega]2 ---------zx - [Omega]3 ---------xy, (3) - b^2 + c^2 c^2 + a^2 a^2 + b^2 - - 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, - - 2a^2 2a^2 - u' = u + yR - zQ = --------- [Omega]3 y - --------- [Omega]2 z, (4) - a^2 + b^2 c^2 + a^2 - - 2b^2 2b^2 - v' = v + zP - xR = --------- [Omega]1 z - --------- [Omega]3 x, (5) - b^2 + c^2 a^2 + b^2 - - 2c^2 2c^2 - w' = w + xQ - yP = --------- [Omega]2 x - --------- [Omega]1 y, (6) - c^2 + a^2 b^2 + c^2 - - 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 (a^2 + [lambda], b^2 + [lambda], c^2 + [lambda])P - - P^2 = 4(a^2 + [lambda]) (b^2 + [lambda]) (c^2 + [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](Ax^2 + By^2 + Cz^2) - - + (1/2)([alpha]x^2 + [beta]y^2 + [gamma]z^2 + 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 - - 4c^2(c^2 - a^2) / c^2 - a^2 \^2 - [alpha] = ---------------[Omega]2^2 - ( ---------[Omega]2 - [eta] ) - (c^2 + a^2)^2 \ c^2 + a^2 / - - 4b^2(a^2 - b^2) / a^2 - b^2 \^2 - - ---------------[Omega]3^2 - ( ---------[Omega]3 - [zeta] ), (15) - (a^2 + b^2)^2 \ a^2 + b^2 / - - with similar equations for [beta] and [gamma]. - - If we can make - - (4[pi][rho]A + [alpha])x^2 = (4[pi][rho]B + [beta])b^2 - = (4[pi][rho]C + [gamma])c^2, (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] 2c^2 d[eta] 2a^2 - ----- = - ---------[Omega]2 [zeta], ------ = ---------[Omega]1 [zeta], - dt a^2 + c^2 dt a^2 + c^2 - - d[zeta] 2c^2 - ------- = ---------([Omega]2 [xi] - [Omega]2 [eta]) (18) - dt a^2 + c^2 - - d[Omega]1 a^2 + c^2 - --------- = [Omega]2 [zeta] + ---------[eta][zeta], - dt a^2 - c^2 - - d[Omega]2 a^2 + c^2 - --------- = [Omega]1 [zeta] + ---------[xi][zeta]; (19) - dt a^2 - c^2 - - of which three integrals are - - a^2 - [xi]^2 + [eta]^2 = L - ---[zeta]^2, (20) - c^2 - - (a^2 + c^2)^2 - [Omega]1^2 + [Omega]2^2 = M + -------------- [zeta]^2, (21) - 2c^2(a^2 - c^2) - - a^2 + c^2 - [Omega]1 [xi] + [Omega]2 [eta]N = + --------- [zeta]^2; (22) - 4c^2 - and then - - / d[zeta]\ 4c^4 - ( ------- )^2 = -----------([Omega]2[xi] - [Omega]1^2 [eta])^2 - \ dt / (a^2 + c^2) - - 4c^4 - = -------------[([xi]^2 + [eta]^2)([Omega)1^2 + [Omega]2^2) -([Omega]1[xi] + [Omega]2[eta])^2] - (a^2 + c^2)^2 - _ - 4c^4 | / (a^2 + c^2)^2 a^2 (a^2 + c^2)\ - = ------------- | LM - N^2 + ( L--------------- - M --- - N ----------- )[zeta]^2 - (a^2 + c^2)^2 |_ \ 2c^2(a^2 + c^2) c^2 2c^2 / - _ - (a^2 + c^2)(9a^2 - c^2) | - - ----------------------- [zeta]^4 | = Z, (23) - 16c^4(a^2 - c^2) _| - - 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 (a^2 + c^2) - [Omega]2 ------ = -----------[Omega]2 - [Omega]1 --------- = [Omega]^2[zeta] - -----------([Omega]1 [xi] + [Omega]2 [eta])[zeta], (24) - dt dt dt (a^2 - c^2) - - a^2 + c^2 - N + --------- - d[phi] (a^2 + c^2) 4c^2 - ------ = [zeta] - ----------- . ----------------------------, (25) - dt (a^2 - c^2) (a^2 + c^2)^2 - M + ---------------[zeta]^2 - 2c^2(a^2 - c^2) - - a^2 + c^2 - _ _ N + ---------[zeta]^2 - / [zeta]d a^2 + c^2 / 4c^2 [zeta] d[zeta] - [phi] = | ------- - --------- | --------------------------- . --------------, (26) - _/ [root]Z a^2 - c^2 _/ (a^2 + c^2)^2 [root]Z - M + ---------------[zeta]^2 - 2c^2(a^2 - c^2) - - 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] a^2 + c^2 [omega] - ------ = [zeta]- --------- -------[zeta], (30) - dt a^2 - c^2 [Omega] - - d[psi] 2a^2 [Omega] - ------ = - --------- -------[zeta], (31) - dt a^2 + c^2 [omega] - - a^2 + c^2 [omega] 2a^2 [Omega] - 1 - --------- ------- = - --------- -------, (32) - a^2 - c^2 [Omega] a^2 + c^2 [omega] - - / [omega] a^2 + c^2 \^2 (a^2 - c^2)(9a^2 - c^2) - ( ------- - (1/2) --------- ) = -----------------------, (33) - \ [Omega] a^2 - c^2 / 4(a^2 + c^2) - - 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) q^2 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] = (1/2)[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, A^1; 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' - = (1/2)([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' - = (1/2)([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 (1/2)[pi]/n and - [Omega] increases by (1/2)i[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------------ = (1/2) sin^2 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') sin^2 2n[alpha] - - cos 2n[alpha] - cos 2n[theta] - X ----------------------------- - 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^(-(1/2)[pi]s/c), (2) - _ _ - / [oo] / c c - PM = | sin [theta] ds = | e^(-(1/2)[pi]s/c) ds = -------- e^(-(1/2)[pi]s/c) = --------- sin [theta], (3) - _/ s _/ (1/2)[pi] (1/2)[pi] - - so that PT = c/(1/2)[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 = 1/2, the reentrant walls are given of - Borda's mouthpiece, and the coefficient of contraction becomes 1/2. - 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 - - 1/2[pi] ds 2n - e^(1/2[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^((1/2)[pi]^2/c) = tan [theta], ch ((1/2)[pi]s/c) sin 2[theta] = 1, (4) - - sh (1/2)[pi]x/c = cot [theta], sh (1/2)[pi]y/c = tan [theta], - - sh (1/2)[pi]x/c sh (1/2)[pi]y/c = 1, e^((1/2)[pi](x + y)/c) = e^((1/2)[pi]x/c) + e^((1/2)[pi]y/c) + 1. (5) - - With n = (1/2), 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) - cos^2 n[alpha] - - cos^2 n[alpha] sin^2 n[theta] - e^([pi]^2/c) = -------------------------------, (8) - sin^2 n[theta] - sin^2 n[alpha] - - the intrinsic equation, the other free surface A'P'J' being given by - - cos^2 n[alpha] sin^2 n[theta] - e^([pi]^2/c) = -------------------------------. (9) - sin^2 n[alpha] - sin^2 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 = cot^2 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 (1/2)[Omega] = / ------ / -----, sh (1/2)[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] - (1/2)sin^2 [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 (1/2) sin^2 [alpha] u - j cos[theta] - cos[beta] - ----- = -------------------------, ------ = (1/2) sin^2 [alpha]-----------------------------------------------------, - a - a' cos [alpha] - cos [theta] a - a' (cos [alpha] - cos [beta])(cos [alpha] - cos [theta]) - - u - j' cos [theta] - cos [beta]' - ----- = (1/2) sin^2 [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] - (1/2) sin^2 [alpha] ------ - q a - b - - Q [root](a - u.u - a') - sh [Omega] = sh log --- = -------------------- sin [alpha] - q u - b - - Q (u - b) cos [alpha] - (1/2)(a - a') sin^2 [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] - (1/2)(a - a') sin^2 [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. Rethy. - - 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] = (1/2)[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 = (1/2) 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 - - x^2 y^2 z^2 - -------------- + -------------- + -------------- = 1 (3) - a^2 + [lambda] b^2 + [lambda] c^2 + [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) - a^2 + [lambda] b^2 + [lambda] c^2 + [lambda] - - p^2x^2 p^2y^2 p^2z^2 - 1 = ------------------ + ------------------ + ------------------, (6) - (a^2 + [lambda])^2 (b^2 + [lambda])^2 (c^2 + [lambda])^2 - - p^2 = (a^2 + [lambda])l^2 + (b^2 + [lambda])m^2 + (c^2 + [lambda])n^2, (7) - = a^2 l^2 + b^2 m^2 + c^2 n^2 + [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(a^2 + [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(a^2 + [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(a^2 + [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(a^2 + [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](b^2 + [lambda].c^2 + [lambda]). (13) - - Expressed as a differential relation, with the value of U from (11), - _ _ - d | d[psi] | d[alpha] - --------- | [alpha][psi] + 2(a^2 + [lambda])[alpha]--------- | - [psi]--------- = 0, (14) - d[lambda] |_ d[lambda] _| d[lambda] - - d[psi] d / d[psi] \ - 3[alpha]--------- + 2(a^2 + [lambda])-------- ( [alpha]-------- ) = 0, (15) - d[lambda] d[lambda] \ d[lambda]/ - - and integrating - - d[psi] - (a^2 + [lambda])^3/2 [alpha]--------- = a constant, (16) - d[lambda] - - so that we may put - _ - / Md[lambda] - [psi] = | -----------------, (17) - _/ (a^2 + [lambda])P - - P^2 = 4(a^2 + [lambda])(b^2 + [lambda])(c^2 + [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(a^2 + [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 = -2a^2--------- - [psi]0 - d[lambda] - _ - M / [oo] Md[lambda] - = --- - | ----------------- - abc _/ 0 (a^2 + [lambda])P - - M - = --- (1 - A0), (20) - abc - - with the notation - _ - / [oo] abc d[lambda] - A or A_[lambda] = | ----------------- - _/[lambda] (a^2 + [lambda])P - _ - d / [oo] d[lambda] - = -2abc---- | ---------, (21) - da^2 _/ [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] (b^2 + [lambda], c^2 + [lambda])P - - and - - A + B + C = abc/(1/2)P, A0 + B0 + C0 = 1. (28) - - For a sphere - - a = b = c, A0 = B0 = C0 = 1/3, [alpha] = [beta] = [gamma] = 1/2, (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 + (1/2)W' - - 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] (a^2 + [lambda])P - [phi] = Ux ----------------- = Ux -------------------------------------------, (1) - B0 + C0 - B1 - C1 abc / [lambda]1 abcd[lambda] - 1 - ------ - | ----------------- - a1b1c1 _/ 0 (a^2 + [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] = (1/2)Ux -------, (3) - B0 - B1 - - and the Stokes' current function [psi] can be written down - - B - B1 - [psi] = - (1/2)Uy^2 -------; (4) - B0 - B1 - - reducing, when the liquid extends to infinity and B1 = 0, to - A B - [phi] = (1/2)Ux --, [psi] = - (1/2)Uy^2 --; (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]' = (1/2)Ux ( 1 + -- ), [psi]' = (1/2)Uy^2 ( 1 - -- ). (6) - \ B0 / \ B0 / - - Changing the origin from the centre to the focus of a prolate - spheroid, then putting b^2 = pa, [lambda] = [lambda]'a, and proceeding - to the limit where a = [oo], we find for a paraboloid of revolution - - p B p - B = (1/2) -------------, -- = -------------, (7) - p + [lambda]' B0 p + [lambda]' - - y^2 - ------------- = p + [lambda]' - 2x, (8) - p + [lambda]' - - with [lambda]' = 0 over the surface of the paraboloid; and then - - [psi]' = (1/2)U [y^2 - p[root](x^2 + y^2) + px]; (9) - - [psi] = -(1/2)Up [[root](x^2 + y^2) - x]; (10) - - [phi] = -(1/2)Up log [ [root](x^2 + y^2) + x]. (11) - - The relative path of a liquid particle is along a stream line - - [psi]' = (1/2)Uc^2, a constant, (12) - - p^2y^2 - (y^2 - c^2)^2 p^2y^2 - (y^2 - c^2)^2 - x = ----------------------, [root](x^2 + y^2) = ---------------------- (13) - 2p(y^2 - c^2) 2p(y^2 - c^2) - - a C4; while the absolute path of a particle in space will be given by - - dy r - x y^2 - c^2 - -- = - ----- = ---------, (14) - dx y 2py - - y^2 - c^2 = a^2 e^(-x/p). (15) - - 46. Between two concentric spheres, with - - a^2 + [lambda] = r^2, a^2 + [lambda]1 = a1^2, (1) - - A = B = C = a^3/3r^3, - - a^3 a^3 a^3 a^3 - --- + 2 ---- --- + 2 ---- - r^3 a1^3 r^3 a1^3 - [phi] = (1/2)Ux ------------, [psi] = (1/2)Uy^2 ------------; (2) - 1 - a^4/a1^2 1 - a^3/a1^3 - - and the effective inertia of the liquid in the interspace is - - A0 + 2A1 a1^3 + 2a^3 - --------- W' = (1/2) ----------- W'. (3) - 2A0 - 2A1 a1^3 - a^3 - - 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 = a^2/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 y^2 - m-- cos PSx = -m----; (5) - df PS^3 - - and for its image at H the Stokes' function is - - d a^3 y^2 - m-- cos PHx = -m--- ----; (6) - df f^3 PH^3 - - so that for the combination - - / a^3 1 1 \ y^2 / a^3 f^3 \ - [psi] = my^2 ( --- ---- - ---- ) = m--- ( ---- - ---- ), (7) - \ f^3 PH^3 PS^3 / f^3 \ PH^3 PS^3 / - - 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 - - / a1^3 a2^3 a^3 \ - [psi]' = (1/2)Uy^2 ( 1 - ---- - ---- + --- ), (8) - \ r1^3 r2^3 r^3 / - - where a1, a2, a = a1a2/[root](a1^2 + a2^2) 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 - - / a1^2 a2^2 a^2 \ - [psi]' = Uy ( 1 - ---- - ---- + --- ). (9) - \ r1^2 r2^2 r^2 / - - With a2 = [oo], these reduce to - - / a^5 \ x / a^4 \ x - [psi]' = (1/2)Uy^2 ( 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 deg., will require - _ _ - | x a^3 a^4(a - 2x) a^3 a^4(a + 2x) | - [psi]' = (1/2)Uy^2 | --- - ----- + ----------- + ----- - ----------- |, (11) - |_ a 2r1^3 2r1^5 2r2^3 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 deg. 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--------- - \ a^2 + [lambda] b^2 + [lambda] / d[lambda] - R = - --------------------------------------------------------, (2) - 1/(b^2 + [lambda] - 1/(a^2 = [lambda]) - - and that the continuity of the liquid is secured if - - d[chi] - (a^2 + [lambda])^3/2 (b^2 + [lambda])^3/2 (c^2 +[lambda]) (1/2)--------- = constant, (3) - d[lambda] - _ - / [oo] Nd[lambda] N B_[lambda] - A_[lambda] - [chi] = | --------------------------------- = --- . -----------------------; (4) - _/[lambda] (a^2 + [lambda])(b^2 + [lambda])P abc a^2 - b^2 - - and at the surface [lambda] = 0, - - / 1 1 \ N B0 - A0 N 1 - ( --- + --- ) --- --------- - --- ------- - \a^2 b^2/ abc a^2 - b^2 abc a^2 b^2 - R = - -----------------------------------------, (5) - 1/b^2 - 1/a^2 - - N 1/b^2 - 1/a^2 - --- = R --------------------------------, (6) - abc 1 / 1 1 \ B0 - A0 - ------ - ( --- + --- ) --------- - a^2b^2 \a^2 b^2/ a^2 - b^2 - - (a^2 - b^2)^2/(a^2 + b^2) - = R -----------------------------------. - (a^2 - b^2)/(a^2 + b^2) - (B0 - A0) - - The velocity function of the liquid inside the ellipsoid [lambda] = 0 - due to the same angular velocity will be - - [phi]1 = Rxy(a^2 - b^2)/(a^2 + b^2), (7) - - and on the surface outside - - N B0 - A0 - [phi]0 = xy[chi]0 = xy--- ---------, (8) - abc a^2 - b^2 - - so that the ratio of the exterior and interior value of [phi] at the - surface is - - [phi]0 B0 - A0 - ------ = -----------------------------------, (9) - [phi]1 (a^2 - b^2)/(a^2 + b^2) - (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 - - a1^2 - b1^2 abc - (B0 - A0) - (B1 - A1) + ----------- ------ - a1^2 + b1^2 a1b1c1 - ------------------------------------------------------. (11) - a^2 - b^2 a1^2 - b1^2 abc - --------- - ----------- ------ - (B0 - A0) + (B1 - A1) - a^2 + b^2 a1^2 + b1^2 a1b1c1 - - Make c = [oo] for confocal elliptic cylinders; and then - _ - /[oo] ab ab / /b^2 + [lambda] \ - A[lambda] = | -------------------------------------------------------- = --------- ( 1 - / -------------- ), (12) - _/[lambda] (a^2 + [lambda])[root]([4.a^2 + [lambda].b^2 + [lambda]) a^2 - b^2 \ \/ a^2 + [lambda] / - - ab / /a^2 + [lambda] \ - B[lambda] = --------- ( / -------------- - 1 ), C[lambda]= 0; - a^2 - b^2 \ \/ b^2 + [lambda] / - - and then as above in S 31, with - - a = c ch [alpha], b = c sh [alpha], - a1 = [root](a^2 + [lambda]) = c ch [alpha]1, b1 = c sh [alpha]1 (13) - - the ratio in (11) agrees with S 31 (6). - - As before in S 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]/P^3 - _/ [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.) x1^2 + x2^2 + x3^2 = F^2, 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. Kotter, 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 = (1/2)p(x1^2 + x2^2) + (1/2)p'x3^2 - + q(x1y1 + x2y2) + q'x3y3 - + (1/2)r(y1^2 + y2^2) + (1/2)r'y3^2 (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 - --- ( --- ) = (x1^2 + x2^2)(y1^2 + y2^2) - (x1y1 + x2y2)^2 - r^2 \ dt / - - = (x1^2 + x2^2)(y1^2 + y2^2) - (FG - x3y3)^2 - = (x1^2 + x2^2)(y1^2 + y2^2 + y3^2 - G^2) - (Gx3 - Fy3)^2, (4) - - in which - - x1^2 + x2^2 = F^2 - x3^2, x1y1 + x2y2 = FG - x3y3, (5) - - r(y1^2 + y2^2) = 2T - p(x1^2 + x2^2) - p'x3^2 - - 2q(x1y1 + x2y2) - 2q'x3y3 - r'y3^2 - = (p - p')x3^2 + 2(q - q')x3y3 + m1, (6) - - m1 - 2T - pF^2 - 2qFG - r1y3^2 (7) - - so that - - 1 / dx3 \^2 - --- ( --- ) = X3 (8) - r^2 \ 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 x1^2 + x2^2 - - 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 F^2 - x3^2 - - d /x1 + x2i Fy3 - Gx3 - --- log \ / -------- = -(q' - q)x3 - (r' - r)y3 - Fr----------, (13) - dti \/ x1 - x2i F^2 - x3^2 - - 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 sin^2[theta] ------ = --- x1 + --- x2 - dt dy1 dy2 - - = (qx1 + ry1)x1 + (qx2 + ry2)x2 - - = qx1^2 + x2^2) + r (x1y1 + x2y2) - - = gF^2 sin^2 [theta] + r(FG - x3y3), (16) - _ - / FG - x3y3 Fr dx3 - [psi] - qFt = | ---------- --------, (17) - _/ F^2 - x3^2 [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) - - F^2(X^2 + Y^2) = y1^2 + y2^2 + y3^2 - G^2, (21) - - Fy3 - Gx3 + i[root]X3 - F(X + Yi) = --------------------- [epsilon]^[psi]_i. (22) - [root](F^2 - x3^2) - - 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) - G^2 |, (23) - |_ r r _| - - and putting x3 - F = y, - _ - / dy \^2 | p' - p q' - q - ( -- ) = r^2 y^2 | 4 ------ F^2 + 4 ------ FG - G^2 - \ dt / |_ r r - _ - / p' - p q' - q \ p' - p | - + 2 ( 2 ------ F + ------ G ) y + ------ y^2 |, (24) - \ r r / r _| - - so that the stability of this axial movement is secured if - - p' - p q' - q - A = 4 ------F^2 + 4 ------FG - G^2 (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 + Cy^2) - - 1 sh^(-1) [root]A[root](A + 2By + Cy^2) 1 ch^(-1) A + By - = ------- ----------------------------- = ------- -----------------, (26) - [root]A ch^(-1) y[root](B^2 ~ AC) [root]A sh^(-1) y[root](B^2 ~ 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 (1/2)[theta] = x, - - (Nxe[psi]i)^3/2 = (x + 1)[root]X1 + i(x - 1)[root]X2, (27) - - X1 - -- = [+-]ax^4 + 2ax^3 [+-] 3(a + b)x^2 + 2bx [+-] b, (28) - X2 - - N^3 = -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)(V^2/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 u^2 - Wh tan[theta] = N = (c2 - c1) -- --- tan [theta], (6) - c2 g - - c2 - c1 c1 u^2 1 + [alpha] u^2 - 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 Wk1^2. - But if Wk2^2 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', - - Wk2^2 [omega] = M - M', W'k'^2 [omega] = M', (1) - - Wk2^2 + W'k'^2 [omega] = M, (2) - - C2 = Wk2^2 + W'k'^2 = (W + W'[epsilon])k2^2, (3) - - in which we have put k'^2 = [epsilon]k^2, 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)-- u^2 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)-- u^2 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] = (1/2) --p sec [theta], (7) - C2 - - the roots would be imaginary for a value of p smaller than given by - - c1 - C1^2 p^2 - 4(c2 - c1)-- C2u^2 = 0, (8) - c2 - - p^2 c1 C2 - --- = 4 (c2 - c1) -- ----. (9) - u^2 c2 C1^2 - - _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] = (1/2), | Bullet | Bullet [f] = 0, | - | | S.G. 7.2. | S.G. 8. | [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 deg.0'|Infinity|0 deg.0'|Infinity|0 deg.0'|Infinity|0 deg.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 = (1/2) dp/u, (10) - - which is the ratio of the linear velocity of rotation (1/2)dp to u, - the velocity of advance, - - c1 C2d^2 - tan^2 [delta] = [pi]^2/n^2 = d^2p^2/4u^2 = (c2 - c1) -- ----- - c2 C1^2 - - 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 - tan^2 [delta] = ------- = --- ([beta] - [alpha]) ( -- ) / ( -- ), (12) - n^2 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 S 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] ab^2 d[lambda] / [oo] ab^2 d[lambda] - A0 = | ----------------------------------------------------------- = | --------------------------------------, (13) - _/ 0 (a^2 + [lambda])[root][4(a^2 + [lambda])(b^2 + [lambda])^2] _/ 0 2(a^2 + [lambda])^3/2 (b^2 + [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) - (x^2- 1)^3/2 x^2 - 1 - - -x x^2 - 2B0 = ------------ ch^(-1)x + -------, (18) - x^2 - 1)^3/2 x^2 + 1 - - x sh^(-1) [root](x^2-1) x - x^2 A0 + 2B0 = ----------------------- = ------------- log [x + [root](x^2 - 1)]. (19) - [root](x^2-1) [root](x^2-1) - - 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) - - d^2 - Wk1^2 = 1/6 [pi] d^3 x --- (1 - f^5) [sigma], (21) - 10 - - l^2 + d^2 - Wk2^2 = 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 - f^3 [sigma] - - k1^2 1 1 - f^5 k2^2 x^2 + 1 - ---- = --- -------, ----- = -------, (25) - d^2 10 1 - f^3 k1^2 2 - - [rho] x^2 + 1 - tan^2 [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 + -- tan^2 [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] = ----- (x^2 + 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]) (x^2 + 1) sin^2 [theta] cos [theta] - [mu] p - - = nd ([beta] - [alpha]) (x^2 + 1) sin [theta] cos [theta], (4) - - and the length of one turn of the helix - - 2[pi] - ----- (u cos [theta] + v sin [theta] ) = nd(x^2 + 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 S 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 S 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'Q^2 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 cos^2 [theta] F sin^2 [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 - - d^2[theta] / F^2 F^2 \ F[xi] d[mu] - C3---------- = ( --- - --- ) sin [theta] cos [theta] - ----- sin [theta] = F-----, (20) - dt^2 \ c1 c2 / c1 dt - _ _ - d[theta] / | F^2 cos^2 [theta] F^2 sin^2 [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 S 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 _Encyklopadie 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; a^2, b^2, polyps budded from 2; - a^3, 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; a^3, b^3, 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; a^1-d^1, branch formed by similar budding from 1; - a^2-d^2 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 (3^1, - 3^2, 3^3, 3^4; 6^1-6^3), 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. Gunther [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 ("Gehorspangen," _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 oogonia, and grows at the expense of -its sister-cells. No regular follicle is formed, but the oocyte absorbs -nutriment from the remaining oogonia. In _Hydra_ the oocyte is a large -amoeboid cell, which sends out pseudopodia amongst the oogonia and -absorbs nutriment from them. When the oocyte is full grown, the residual -oogonia 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 Herouard (Hydrozoa [2]). - - _Haleremita_ Schaudinn. See F. Schaudinn [50] and Delage and Herouard - (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 - Herouard (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 - Herouard. 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. _Lafoeidae._--Trophosome as in the preceding; gonosome, free - medusae or gonophores, the medusae with large open otocysts. The - hydroid genus _Lafoea_ 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 Herouard (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 mulleri._] - - 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 mulleri_ (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_ -(_Gehorspangen_). 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" -(_Knospenahre_), 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_ ("_Fangfaden_"), 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_ ("_Tastfaden_"), 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. Herouard (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 -Herouard, 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, "Uber die - Entwickelung von Hydra," _Zeitschr. f. wiss. Zool._ lii. (1891), pp. - 169-216, pls. ix.-xii.; 3. "Uber 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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H. - Driesch, "Tektonische Studien an Hydroidpolypen," (1) _Jen. - Zeitschr._, xxiv. (1890), pp. 189-226, 12 figs.; (2) _t.c._ pp. - 657-688, 6 figs.; (3) _ibid._ xxv. (1891), pp. 467-479, 3 figs.; 14. - G. Duplessis, "On _Campanularia volubilis_," _Soc. Vaud. Bull._ 13 - (Lausanne, 1874-1875); 15. J. W. Fewkes, "On _Mnestra_," _Amer. - Natural._, xviii. (1884), pp. 197-198, 3 figs.; 16. S. Goto, - "Dendrocoryne Inaba, Vertreterin einer neuen Familie der - Hydromedusen," _Annot. Zool. Tokyo_, i. (1897), pp. 93-104, pl. vi., - figs. 106-113; 17. "The Craspe dote Medusa _Olindias_ and some of its - Natural Allies," _Mark Anniversary Volume_ (New York, 1903), pp. 1-22, - 3 pls.; 18. H. Grenacher, "Uber die Nesselkapseln von Hydra," _Zool. - Anz._ xviii. (1895), pp. 310-321, 7 figs.; 19. R. T. Gunther, "On the - Structure and Affinities of _Mnestra parasites_ Krohn; with a revision - of the Classification of the _Cladonemidae_," _Mitt. Stat. Neapel_, - xvi. (1903), pp. 35-62, pls. ii. iii.; 20. E. Haeckel, "Das System der - Medusen," _Denkschr. med.-nat.-wiss. Ges._ (Jena, 1879-1881); 21. - "Deep Sea Medusae," in _Reports of the Challenger Expedition_, Zool. - iv. pt. 2 (London, 1882); 22. P. Hallez, "Bougainvillia fruticosa - Allm. est le facies d'eau agitee du Bougainvillia ramosa Van Ben." - _C.-R. Acad. Sci. Paris_, cxl. (1905), pp. 457-459; 23. O. & R. - Hertwig, _Der Organismus der Medusen_ (Jena, 1878), 70 pp., 3 pls.; - 24. _Das Nervensystem und die Sinnesorgane der Medusen_ (Leipzig, - 1878), 186 pp., 10 pls.; 25. S. J. Hickson, "The Medusae of - _Millepora_," _Proc. Roy. Soc._ lxvi. (1899), pp. 6-10, 10 figs.; 26. - T. Hincks, _A History of British Hydroid Zoophytes_ (2 vols., London, - 1868); 27. N. Iwanzov, "Uber den Bau, die Wirkungsweise und die - Entwickelung der Nesselkapseln von Coelenteraten," _Bull. Soc. Imp. - Natural, Moscou_ (1896), pp. 323-355, 4 pls.; 28. C. F. Jickeli, "Der - Bau der Hydroidpolypen," (1) _Morph. Jahrbuch_, viii. (1883), pp. - 373-416, pls. xvi.-xviii.; (2) t.c., pp. 580-680, pls. xxv.-xxviii.; - 29. Albert Lang, "Uber die Knospung bei Hydra und einigen - Hydropolypen," _Zeitschr. f. wiss. Zool._ liv. (1892), pp. 365-384, - pl. xvii.; 30. Arnold Lang, "Gastroblasta Raffaelei. Eine durch eine - Art unvollstandiger Theilung entstehende Medusen-Kolonie," _Jena - Zeitschr._ xix. (1886), pp. 735-762, pls. xx., xxi.; 31. A. Linko, - "Observations sur les meduses de la mer Blanche," _Trav. Soc. Imp. - Nat. St Petersbourg_, xxix. (1899); 32. "Uber den Bau der Augen bei - den Hydromedusen," _Zapiski Imp. Akad. Nauk (Mem. Acad. Imp. Sci.) St - Petersbourg_ (8) x. 3 (1900), 23 pp., 2 pls.; 33. O. Maas, "Die - craspedoten Medusen," in _Ergebn. Plankton Expedition_, ii. (Kiel and - Leipzig, 1893), 107 pp., 8 pls., 3 figs.; 34. "Die Medusen," _Mem. - Mus. Comp. Zool. Harvard_, xxiii. (1897), i.; 35. "On _Hydroctena_," - _Zool. Centralbl._ xi. (1904), pp. 240-243; 36. "Revision des meduses - 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 uber 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, "Beitrage - 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, "Uber 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, "Uber das Verhalten der Keimblatter bei der Knospung der - Colenteraten," _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. Vanhoffen, "Versuch einer - naturlichen Gruppierung der Anthomedusen," _Zool. Anzeiger_, xiv. - (1891), pp. 439-446; 56. C. Viguier, "Etudes sur les animaux - inferieurs 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 Merejk," - _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, "Beitrage 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: hydor], 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 deg. 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 - 1(1/2) 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 1(1/2) - 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 deg. 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 deg. F. it carried 300 - grains in the upper dish. The hydrometer therefore displaced 1000 - grains of distilled water at 60 deg. 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. Baume, 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 deg. R. - (54(1/2) deg. 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 Baume's - hydrometer are given by Nicholson (_Journal of Philosophy_, i. 89) as - follows:-- - - _Baume's Hydrometer for Spirits. Temperature 10 deg. 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 Baume, 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 deg. by Cartier, and 30 deg. on Carrier's scale - corresponded to 32 deg. on Baume'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 deg., 40 deg., 45 deg., 50 deg., 55 deg., 60 deg., - 65 deg. and 70 deg. 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 deg. 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 deg. 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 deg. 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 deg.-100 deg., 80 deg.-120 deg., 100 deg.-140 - deg., 130 deg.-170 deg., 160 deg.-200 deg. The reading gives the - volume of proof spirit equivalent to the volume of liquor; thus the - readings 80 deg. and 120 deg. 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 deg. F., the alcohol having a - specific gravity of 0.7939 at 60 deg. as compared with water at its - maximum density. The specific gravity of proof spirit is 0.93353 at 60 - deg.; 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 1(1/2) 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 deg. - 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 deg. 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 deg. 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 deg. C. instead of 15 deg. C., and taking alcohol of density - .7939 at 15.5 deg. 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 deg. C. - In order to graduate the stem the instrument is first weighed, then - immersed in distilled water at 4 deg. 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, _Traite d'areometrie_, Paris, 1842). - - Dr Bories 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 Bories 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 Bories, - 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 3(1/2) in. in length. This is divided into ten equal parts, each - of which is subdivided into five. As in Bories'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 deg. F. and 62 deg. - 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 deg. F. | 62 deg. 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, S 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 deg. 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 deg. 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 deg. 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 Grafenberg 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 Ortel 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 Grafenberg, 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 Grafenberg 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 -Grafenberg. - -Ernst Brand (1826-1897) of Berlin, Raljen and Theodor von Jurgensen 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 deg. to 212 deg. or higher, but mainly used at 150 deg. 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, _Traite d'hydrotherapie_ (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, Francois 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: hydor], 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: hydor], 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 deg. -C., and boiling at 58 deg. 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. Herouard, _Traite de zoologie concrete_, ii. part 2, - _Les Coelenteres_ (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. - - - - -HYERES, 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. Hyeres is celebrated (as is also -its fashionable suburb, Costebelle, nearer the seashore) as a winter -health resort. The town proper is situated about 2(1/2) 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 chateau, 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 Hyeres, 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 Iles -d'Hyeres. - -The town of Hyeres 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 Provencal 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 -chateau 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. Lentheric, _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 antiquites_, with full references to authorities; and E. Thramer - in Roscher's _Lexikon der Mythologie_, with a special section on the - modern theories of Hygieia. - - - - -HYGIENE (Fr. _hygiene_, 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 Rouge 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 Golenischeff 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 ed. p. 236; W. M. F. Petrie, _Hyksos and Israelite - Cities_, p. 67; Golenischeff 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. Turk in _Breslauer Philologische Abhandlungen_, vii. (1895); W. - Mannhardt, _Mythologische Forschungen_ (1884). - - - - -HYLOZOISM (Gr. [Greek: hyle], matter, [Greek: zoe], 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 antiquites_. - - - - -HYMENOPTERA (Gr. [Greek: hymen], 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 6(1/2) 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 regne 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, _Mem. savants etrangers_, 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 genitale 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, _Etudes sur les - fourmis, les guepes 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 Pera], -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: pateron -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: hymnesantes exelthon]), 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: -psalleto]), and St Paul "psalms and hymns and spiritual songs" ([Greek: -psalmois kai hymnois kai odais pneumatikais]) St Paul also, in the 14th -chapter of the first epistle to the Corinthians, speaks of singing -([Greek: psalo]) and of every man's psalm ([Greek: hekastos hymon -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: ten -Dauidiken melodian]), 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 polon adaon] (or, according to some editions, -[Greek: basileu hagion, loge pandamator]--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: phos hilaron hagias -doxes]"--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: mnoeo Christe] ("Lord Jesus, think -of me"), by Synesius; [Greek: se ton aphthiton monarchen] ("O Thou, the -One Supreme") and [Greek: ti soi theleis genesthai] ("O soul of mine, -repining"), by Gregory; also [Greek: anothen 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 Liege) 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 Perefixe, 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 Abbe 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 hochsten Nothen 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:--Bartholomaus 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 schon 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 Hauflein 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 Lutzen 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 Matthaus Lowenstern, 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 lasst -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 -Konigsberg, 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 Schutz, "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 Dusseldorf, and a friend of Spener -and Schutz (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 Wurttemberg who, falling -into ill-health during the latter part of his ministry, published a -_Geistliche Liederhostlein_ 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 Wurttemberg; 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 Blumengartlein 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. - - - Fouque. - -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 Fouque, 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. Fouque 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, _Poetarum veterum - ecclesiasticorum_ (Frankfort, 1578); Cardinal J. M. Thomasius, - _Hymnarium in Opera_, ii. 351 seq. (Rome, 1747); A. J. Rambach, - _Anthologie christlicher Gesange_ (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'eglise 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 breviaire romain_ (vols. 1-3, - 1874-1884, unfinished); A. W. F. Fischer, _Kirchenlieder-Lexicon_ - (Gotha, 1878-1879); J. Kayser, _Beitrage zur Geschichte der altesten - 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 uber die altesten christlichen Rhythmen_ - (1879); E. Bouvy, _Poetes et melodes_ (Nimes, 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 Meril, _Poesies - populaires latines anterieures au XIII^e siecle_ (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 - altesten Zeit bis zum Anfang des 17. Jahrhunderts_, vol. i. (Leipzig, - 1864); E. Dummler, _Poetae latini aevi Carolini_ (1881-1890); the - _Hymnologische Beitrage: 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. Danko, _Vetus hymnarium ecclesiasticae Hungariae_ - (Budapest, 1893); J. H. Bernard and R. Atkinson, _The Irish Liber - Hymnorum_ (2 vols., London, 1898); C. A. J. Chevalier, _Poesie - liturgique du moyen age_ (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. Schuck, _Svensk - Literaturhistoria_ (Stockholm, 1890); Rudolf Wolkan, _Geschichte der - deutschen Literatur in Bohmen_, 246-256, and _Das deutsche Kirchenlied - der bohm. Bruder_ (Prague, 1891); Zahn, _Die geistlichen Lieder der - Bruder in Bohmen, Mahren u. Polen_ (Nuremberg, 1875); and J. Muller, - "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. Kummerle, _Encyklopadie der evangelischen Kirchenmusik_ (4 - vols., 1888-1895); Chr. Palmer, _Evangelische Hymnologie_ (Stuttgart, - 1865); and P. Urto Kornmuller, _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: aither], 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. Dorpfeld, 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: hypallage], 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 Ptolemais, 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 -(Etienne 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. - Guldenpenning, _Geschichte des ostromischen 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 PN^2: AN.NA': : SX^2: - AX.A'X, i.e. PN^2 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 = BC^2; similarly if g and G be the corresponding - intersections of the normal, PG : Pg : : BC^2 : AC^2. 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' = CS^2. The geometry of the rectangular - hyperbola is simplified by the fact that its principal axes are equal. - - Analytically the hyperbola is given by ax^2 + 2hxy + by^2 + 2gx + 2fy - + c = 0 wherein ab > h^2. Referred to the centre this becomes Ax^2 + - 2Hxy + By^2 + C = 0; and if the axes of coordinates be the principal - axes of the curve, the equation is further simplified to Ax^2 - By^2 = - C, or if the semi-transverse axis be a, and the semi-conjugate b, - x^2/a^2 - y^2/b^2 = 1. This is the most commonly used form. In the - rectangular hyperbola a = b; hence its equation is x^2 - y^2 = 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 = k^2; obviously the axes are oblique in the general - hyperbola and rectangular in the rectangular hyperbola. The values of - the constant k^2 are (1/2)(a^2 + b^2) and (1/2)a^2 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 Perpherees, 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 Perpherees 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. Schroder 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. Schroder in - _Archiv fur 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: graphe paranomon], 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, _Etudes - sur l'antiquite 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-ion]), but the quantity of the vowel is against this; (2) -he who is above ([Greek: hyperi-on]). Others take it to be a patronymic -in form, like [Greek: Kronion, Molion]. - - - - -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: trophe], -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 -Puysegur, 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 Puysegur. 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 Salpetriere 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. -Liebeault, who for twenty years had used it very largely and -successfully in his general practice among the poor of Nancy. Liebeault -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 repere_, 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 fur Hypnotismus_. Of special historical interest are the - following:--_Etude sur le zoomagnetisme_, par A. A. Liebeault (Paris, - 1883); _Hypnotisme, suggestion, psycho-therapie_, par Prof. Bernheim - (Paris, 1891); _Braid on Hypnotism_ (a new issue of James Braid's - _Neurypnology_), edited by A. E. Waite (London, 1899); _Traite 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 -Treves (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 hypostaseos e 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 tinon idiomaton]). 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: hypotheke]), 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_, S 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'hypothese_ (1880), and textbooks of - logic, e.g. those of Jevons, Bosanquet, Joseph; Liebmann, _Der Klimax - d. Theorien_. - - - - -HYPOTRACHELIUM (Gr. [Greek: hypotrachelion], the lower part of the neck, -[Greek: trachelos]), 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._ (1/2), - _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 1/4 to 1/2%. 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 medicinale_, 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-yonah_). 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: hysteresis], 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. Mobius 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, _Lecons sur les maladies du systeme 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, _Lecons cliniques sur - l'hysterie et l'hypnotisme_ (1891); Richer, _Etudes cliniques sur la - grande hysterie_ (1891); Gilles de la Tourette, _Traite clinique et - therapeutique de l'hysterie_ (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 2(1/2) -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 a 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: psyche]), 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: zoe]), and (realized) intellect ([Greek: nous])--is -distinguished by him into spheres of intelligible gods ([Greek: theoi -noetoi]) 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 noetoi 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: -psyche], 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: psyche] 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: hyle]). 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 plere theon], as Thales said), but thought that each man -had a special divinity of his own--an [Greek: idios daimon]--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 tes - koines mathematkes epistemes]), ed. J. G. Friis (Copenhagen, 1790), N. - Festa (Leipzig, 1891). (4) The book _On the Arithmetic of Nicomachus_ - ([Greek: Peri tes Nikomachou arithmetikes eisagoges]), along with - fragments on fate ([Greek: Peri heimarmenes]) and prayer ([Greek: Peri - euches]), ed. S. Tennulius (1688), the _Arithmetic_ by H. Pistelli - (1894). (5) The _Theological Principles of Arithmetic_ ([Greek: - Theologoumena tes arithmetikes])--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. agypt. 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'ecole d'Alexandrie_ (1846), ii. 57 sq.; J. Simon, _Hist. de l'ecole - 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: -Babyloniaka], 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 _Yania_; 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 L120,000; 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 Gotterlehre_, i. (1857); C. H. - Volcker, _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 -Boe 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. - - - - -IBAGUE, or SAN BONIFACIO DE IBAGUE, a city of Colombia, and capital of -the department of Tolima, about 60 m. W. of Bogota and 18 m. N.W. of the -Nevado de Tolima. Pop. (1900, estimate) 13,000. Ibague 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. Ibague 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, 1(1/4) 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: Iberes]), 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, _Etudes sur l'alphabet iberien_ -(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 (_Prufung der Untersuchungen uber 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'Iberie_, 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 Blade (_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, "Uber die cantabrische oder - baskische Sprache" in Adelung, _Mithridates_ iv. (1817), and _Prufung - d. Untersuchungen u. die Urbewohner Hispaniens vermittelst der - waskischen Sprache_ (Berlin, 1821); L. F. Graslin, _De l'Iberie_ - (Paris, 1838); T. B. G. M. Bory de St Vincent, _Essai geologique sur - le genre humain_ (1838); G. Lagneau, "Sur l'ethnologie des peuples - iberiens," in _Bull. soc. anthrop._ (1867), pp. 146-161; J. F. Blade, - _Etudes sur l'origine des Basques_ (Paris, 1869), _Defense des - etudes_, &c. (Paris, 1870); Phillips, _Die Einwanderung der Iberer in - die pyren. Halbinsel_ (Vienna, 1870), _Uber 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 iberienne 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," _Mem. Soc. Eth._ N.S. 1, pp. 183-328 (1884); G. C. C. - Gerland, "Die Basken und die Iberer" in Grober, _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. Blade, _Les - Vascons avant leur etablissement 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 ogmicas," _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, "Uber die iberische Rasse," - _Ausland_, lxvi. 342-344 (1894); F. Oloriz y Aguilera, _Distribucion - geografica del indice cefalico en Espana_ (Madrid, 1894), "La Talla - humana en Espana" 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, resume" _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. "Uber 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. Ec. d'anthr._ v. 155-181, 214-220 (1895); R. Collignon, "Anthr. - du S.-O. de la France," _Mem. Soc. Anthr._ S 3. 1. 4. p. 1-129 (1895), - _Ann. de geogr._ v. 156-166 (1896), and with J. Deniker, "Les Maures - de Senegal," _L'Anthr._ vii. 57-69 (1897); G. Herve, _Rev. mens. Ec. - 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 prehistorique 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. Geze, "De quelques rapports entre les langues berbere et - basque," _Mem. 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 _Etudes sur l'alphabet iberien_ (Paris, 1852). - and _Numismatique iberienne_ (Beziers, 1859); Aloiss Heiss, _Notes - sur les monnaies celtiberiennes_ (Paris, 1865), and _Description - generale des monnaies antiques de l'Espagne_ (Paris, 1870); Phillips, - _Uber 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. - Hubner, _Monumenta linguae Ibericae_. - - [3] W. van Eys, for example, "La Langue iberienne 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 resume 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 4(1/2) -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 Museum_, -iv. 116-135) and Savigny (_Hist. nat. et mythol. de l'ibis_) in 1805. -They, however, removed it from the Linnaean genus _Tantalus_ and, -Lacepede 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. fur -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. fur Ornithologie_ (1877), pp. 143-156; Elliot's in _Proc. - Zool. Society_ (1877), pp. 477-510; and that of Oustalet in _Nouv. - Arch. du Museum_, 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 dixieme -congres 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. -Wustenfeld's _Specimen el-Lobabi_, Gottingen, 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 deg. 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 cortege 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. Defremery 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. Wustenfeld (Gottingen, 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 Baumker's _Beitrage - zur Gesch. d. Philosophie_, Bd. i. Hefte 2-4 (Munster, 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, _Melanges_ (quoted above); - Guttmann, _Die Philosophie des Sal.-ibn Gabirol_ (Gottingen, 1889); D. - Kaufmann, _Studien uber Sal.-ibn Gabirol_ (Budapest, 1899); S. - Horovitz, "Die Psychologie Ibn Gabirols," in the _Jahresbericht des - jud. theol. Seminars Franckel'scher Stiftung_ (Breslau, 1900); - Wittmann, "Zur Stellung Avencebrols ..." (in Baumker's _Beitrage_, Bd. - v. Heft 1, Munster, 1905). (A. Cy.) - - -FOOTNOTES: - - [1] _Jud. Har. Macamae_, ed. Lagarde (Gottingen, 1883), p. 89, l. 61. - - [2] See the passage quoted by Munk, _Melanges de philosophie arabe et - juive_ (Paris, 1859), pp. 264 and 517. - - [3] _Liber Juchassin_, ed. Filipowski (London, 1857), p. 217. - - [4] _Hebr. Ubersetzungen_ (Berlin, 1893), S 219, note 70; cf. - Kaufmann, _Studien uber 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 Morgenlandischen 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. -Wustenfeld (Gottingen, 1858-1860). An abridged German translation has -been made by G. Weil (Stuttgart, 1864; cf. P. Bronnle, _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 Tlemcen. A few years later he was taken -prisoner by Abdalaziz ('Abd ul 'Aziz), who had defeated the sultan of -Tlemcen and seized the throne. He then entered a monastic establishment, -and occupied himself with scholastic duties, until in 1370 he was sent -for to Tlemcen 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 Tlemcen 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 Berberes_ (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. Quatremere (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. - Wustenfeld (Gottingen, 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 Grunert -(Leiden, 1900). The _Kitab ush-Sharab_ is still in manuscript. The -_Kitab ul-Ma'arif_ has been edited by F. Wustenfeld as the _Handbuch der -Geschichte_[1] (Gottingen, 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 Noldeke in his - _Beitrage_ (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, - _Melanges_ (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. Muller (Konigsberg, 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 Aboh), -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. Schon 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 Seve (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 Seve 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'Egypte au XIX^e siecle_ (Paris, 1847); Aime - Vingtrinier, _Soliman-Pasha_ (_Colonel Seve_) (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 Oehlenschlager. 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 Ostraat_, 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 Bjornson, -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 Said_. 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 Ostraat_) -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, Hjalmar 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 - _Asthetiske Studier_ (Copenhagen, 1868); Les Quesnel, _Poesie - 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, _Bjornson 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 Lemaitre's articles in his _Les Contemporains_ and _Impressions - de theatre_ 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, _Poetae 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 Reaumur scales, and 32 -deg. 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 deg. 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 deg. Fahr, or 4 deg. -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 deg. C. = .9175 - " water at 0 deg. C. = .99988 - " " 4 deg. C. = 1.00000 - " " 10 deg. C. = .99976 - " " 100 deg. C. = .95866 - -Under the influence of heat, ice itself behaves as most solids do, -contracting when cooled, expanding when heated. According to Plucker, -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 -deg. 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 deg. 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 deg. 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 debris from the -glacier and gradually strew their load upon the sea floor. They do not -travel far before losing all stony and earthy debris, 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 deg. 22' and 24 deg. 35' W., and -between 63 deg. 12' and 66 deg. 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 Hunafloi and Breiethifjorethr, so -that there are really two tablelands, a larger and a smaller. The -isthmus which connects the two is only 4(1/4) 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 Glamu and Drangajokull,[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 -Vatnajokull, which covers 3300 sq. m. The axis of highest elevation of -Iceland stretches from north-west to south-east, from the head of -Hvammsfjorethr to Hornafjorethr, 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 Vatnajokull, which is separated from -Tungnafellsjokull by Vonarskard (3300 ft.). Between Tungnafellsjokull -and Hofsjokull lies the broad depression of Sprengisandr (2130 ft.). -Continuing north-west, between Hofsjokull and the next snow-capped -mountain, Langjokull, lies Kjolur (2000 ft.); and between Langjokull and -Eiriksjokull, Flosaskard (2630 ft.). To the north of the _joklar_ 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 Myrdalsjokull, 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 Vatnajokull 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 Myrdalsjokull 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--Markarfljot, Thjorsa and Oelfusa--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 Faxafloi, -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 Borgarfjorethr, the western -part Myrar. - -The great bays on the west of the island (Faxafloi and Breiethifjorethr),[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 Vatnajokull, and lowest on the north-west peninsula, to the -south of North Cape. Without exception the great _neves_ 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 Vatnajokull (3280 sq. m.), -Hofsjokull (520) Langjokull (500) and Myrdalsjokull (390). The glaciers -which stream off from these snowfields are often of vast extent, e.g. -the largest glacier of Vatnajokull 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 Vatnajokull that they -descend lowest; the lower end of Breidamerkurjokull 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 Hvita, 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. Myvatn, -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. Myvatn fills a depression between lava streams, and -has a depth of not more than 8(3/4) ft. The group of lakes called -Fiskivotn (or Veidivotn), which lie in a desolate region to the west of -Vatnajokull, consist for the most part of crater lakes. The groups of -lakes which lie north-west from Langjokull 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 Skapta. 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 7(1/2) m. The largest unbroken lava-field in Iceland is -Odaethahraun (Lava of Evil Deeds), upon the tableland north from -Vatnajokull (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 Almannagja 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 deg.-8 deg.; (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 -(_jokulhlaup_), 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 Oeraefajokull, 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 -Odaethahraun. Its crater measures 34 sq. m. in area. At Myvatn 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 Skjalfandi and Axarfjorethr in the north, where violent earth -tremblings are extremely common; (2) at Faxafloi, where minor vibrations -are frequent; (3) the southern lowlands, between Reykjanes and -Myrdalsjokull, 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 Snaefellsnes, north of -Faxafloi. - - _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 Faeroes, 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 deg. Fahr., whereas the - present mean is 35.6 deg. 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 Lon, there exist a few - mountains of gabbro, a rock which does not occur in any other part of - Iceland. Near Husavik 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 deg. F. in Stykkisholmr on Breiethifjorethr, 38.5 -deg. at Eyrarbakki in the south of Iceland, 41 deg. at Vestmannaeyjar, -36 deg. at Akureyri in the north, 36.7 deg. on Berufjorethr in the east, -and 30.6 deg. at Modrudalr on the central tableland. The range is great -not only from year to year, but also from month to month. For instance, -at Stykkisholmr the highest annual mean for March was 39.7 deg., and the -lowest 8 deg., 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 deg. and 31.3 deg. F. respectively; the summer means, 42.8 -deg. and 44.6 deg.; and the means of the year, 33.1 deg. and 35.6 deg. -The winter means of the south and west coasts average 32 deg. and 31.7 -deg. respectively; the summer means, 48.2 deg. and 50 deg.; the annual -means, 37.4 deg. and 39.2 deg. The rainfall on the south and east coasts -is considerable, e.g. at Vestmannaeyjar, 49.4 in. in the year; at -Berufjorethr, 43.6 in. On the west coast it is less, e.g. 24.3 in. at -Stykkisholmr; 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 Berufjorethr 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 - Breiethifjorethr, 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 Faxafloi, 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 -Isafjorethr (pop. 1000) on the north-west peninsula, Akureyri (1000) on -the north and Seydisfjorethr (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 Faeroes 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 L276,596. - -_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 L170,000; while in 1891-1895 the imports averaged -L356,000 and the exports L340,000. In 1902 imports were valued at -L596,193 and exports at L511,083. 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 (_vaethmal_) 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 -L133,900 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 (_hjeraeth_) 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 (_landshofethingi_) 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 _syslur_ (counties), and these again into 169 -hreppur (rapes) or poor-law districts. Responsible to the governors are -the sheriffs (_syslumenn_), who act as tax gatherers, notaries public -and judges of first instance; the sheriff has in every _hreppur_ an -assistant, called _hreppstjori_. 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 _syslur_ (county boards), and these again are -under the control of the _amtsraeth_ (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 L70,000 per financial period. -There is a national reserve fund of about L60,000, 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 Modruvellir and -Hafnarfjorethr, 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 Undersogelse" (1893); "Islandske Fjorde og - Bugter" (1901); "Geog. og geol. Unders. ved den sydlige Del af - Faxafloi paa Island" (1903); "Lavaorkener og Vulkaner paa Islands - Hojland" (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 Haeng, 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 goethoreth (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 goethoreth 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 goethi -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, Reykdaela, 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 -Landnamabok of Ari, and the Diplomatarium. K. Maurer has made the -subject his own in his _Beitrage, Island, Gragas_, &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 _Biskupasogur_ (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; goethi 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 (_syslur_), administered by -sheriffs (_syslumadr_) 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 (_hreppstjori_) bailiff, a subordinate of the -sheriff; and the goethoreth, 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_ (_Volsungakiraetha_) (part interpolated in earlier - poems, part underlying the prose in _Volsunga Saga_), all by one poet, - to whom Dr Vigfusson would also ascribe _Voluspa_, _Vegtamskvietha_, - _Thrymskvietha_, _Grotta Song_ and _Volundarkvietha_. - - (b) The Dramatic Poems:--_Flyting of Loki_, the _For Skirnis_, the - _Harbarethslioeth_ 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:--_Grimnismal_, _Vafpruethnismal_, _Alvissmal_, - &c. - - (d) The Genealogical and Mythological Poems:--_Hyndluljoeth_ 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 Thorbjorn Hornklofi, shortly after - 870; Eirik's Dirge (_Eiriksmal_) between 950 and 969; the _Dart-Lay on - Clontarf Battle_ (1014); _Biarka-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 - _Thulur_, 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 _Hymiskvtietha_, 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:--_kvietha_, an -epic "cantilena"; _tal_, 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 _mal_, 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 -Aethelstan; 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 _Eiriksmal_; Gunnlaug, who sang at Aethelred'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_, _Laxdaela_, _Egil's Saga_ (part only), _Grettla_ -(two and a half stanzas, cf. _Landnamabok_), _Biorn's Saga_, _Gunnlaug's -Saga_, _Havard's Saga_, _Kormak's Saga_, _Viga-Glum's Saga_, _Erik the -Red's Saga_ and _Fostbraedra 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-tal_, _Hugsvinnsmal_ (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 _fornkvaedi_, 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 -skrok-sogur), 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 _Skida-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 -_Pislargratr_ ("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-kvaedi_ in its varied forms. Most of the older rimur and diktur -are as yet unprinted. Many of the _fornkvaedi_ 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 (_fornkvaedi_) 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-Rimur_, d. 1707; John -Magnusson, who wrote _Hristafla_, a didactic poem; Stefan Olafsson, -composer of psalms, rimur, &c., d. 1688; Gunnar Palsson, 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 naive 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 Grondal tried the same experiment with Homer in his _Ilion's -Kvaedi_, c. 1825. There is a fine prose translation of the _Odyssey_ by -Sweinbjorn 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 _Laxdaela_. 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-Thorissaga_ 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 -_Heietharirgasaga_ (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 _Laxdaela_. 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 -Aethelstan, 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. _Laxdaela_ (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 _Vatzdaelasaga_ (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-daela_ -(990), which preserves the lives of Askell and his son Viga-Skuti; of -_Svarf-daela_ (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; _Ol-kofra thattr_ 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 Thattr_ 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 rauetha_ -(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 _Fostbraedrasaga_ (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 _Thaettir_ 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-Aesu 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 Froethi -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 _Konungabok_, 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 -_Konungabok_ 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 -_Konungabok_ (_Ynglinga_, and the sagas down to but not including Olaf -Tryggvason's) is that of _Frisbok_. - -The _Book of Settlements_ (_Landnamabok_) 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. _Landnamabok_ 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_ (_Islendingabok_, 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--Islendingabok_--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 Saemund (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. -_Boglunga-Sogur_ 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 Saemund 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 Saemund. 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 -_Landnamabok_ 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. - -_Faereyinga_ tells the tale of the conversion of the Faereys 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 -_Onundar-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 _Aron 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 (_Palssaga_) 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-Sogur_ (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. _Volsunga -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-Sogur_ -they enjoyed great popularity in the 15th century, and gave matter for -many Rimur. _Thidrek's Saga_, a late version of the Volsung 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 Sogur_. 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 Holar. 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 Holar, 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 _Arbaekr_ 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 Muller. The - numerous editions of the classics by the Icelandic societies, the - Danish Societe des Antiquites, 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. - Mobius and K. von Maurer, to name only a few), can only be referred to - here. See also Finnur Jonsson, _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 -Jonas Hallgrimsson (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 -Steingrimr 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 -Matthias Jochumsson (b. 1835), who, following another of Jonas -Hallgrimsson'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 -Steingrimr Thorsteinsson, but surpasses him in bold flight of -imagination. He has successfully treated subjects from Icelandic history -_Grettisljoeth_, 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 -Tegner's _Frithiofs Saga_, several plays of Shakespeare and some other -foreign masterpieces. The great religious poet of Iceland, Hallgrimr -Petursson, has found a worthy successor in Valdemar Briem (b. 1848), -whose _Songs of the Bible_ are deservedly popular. He is like Matthias -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 Grondal (b. 1826), whose travesties of the old romantic -stories,[7] and his Aristophanic drama _Gandreiethin_ ("The Magic Ride") -about contemporary events, are among the best satirical and humorous -productions of Icelandic literature. - -Influenced by Jonas Hallgrimsson with regard to language and poetic -diction, but keeping unbroken the traditions of Icelandic medieval -poetry maintained by Sigurethr Breiethfjoreth (1798-1846), is another school -of poets, very unlike the first. In the middle of the 19th century this -school was best represented by Hjalmar Jonsson from Bola (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 Pall 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 Thorsteinn 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; _Jorundr_, a long poem about -the convict king, the Danish pirate Jorgensen, 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 Grimur 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 Jonas Hallgrimsson; it is -nearer the national Icelandic school represented by Pall Olafsson and -Thorsteinn 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 Jon Thoroddsen (1819-1868). -The influence of the realistic school has of late been predominant. The -most distinguished writer of that school has been Gestur Palsson -(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_. Jonas Jonasson (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 _Randiethr from Hvassafell_, an historical -novel of the middle ages. Besides these we may mention Torfhildur Holm, -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 Matthias Jochumsson has written several dramas, but their chief -merits are lyrical. The most successful of Icelandic dramatists as yet -is Indrethi Einarsson, whose plays, chiefly historical, in spite of -excessive rhetoric, are very interesting and possess a true dramatic -spirit. - -In geography and geology Thorvaldr 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 Pall Melsteeth'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 Thorkell Bjarnason (_History of -the Reformation in Iceland_). Jon Thorkelsson (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 Jon Thorkelsson, formerly head of the Latin -school at Reykjavik, whose _Supplement til islandske Ordboger_, 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, Bjorn Magnusson Olsen -(_Researches on Sturlunga_, _Ari the Wise_, _The Runes in the Old -Icelandic Literature_--the last two works in Danish); Finnur Jonsson, -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 Valtyr Guethmundsson, lecturer at the -University of Copenhagen (several works on the old architecture of -Scandinavia) and editor of the influential Icelandic literary and -political review, _Eimreiethin_ ("The Locomotive"). - - See J. C. Poestion, _Islandische Dichter der Neuzeit_ (Leipzig, 1897); - C. Kuchler, _Geschichte der islandischen 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] _Jokull_, plural _joklar_, Icel. snowfield, glacier. - - [2] _Floi_, bay; _fjorethr_, 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 _Saemund'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 _Vegtamskvietha_ 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 -2(1/2) 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, 7(1/2) 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 deg. 42' N. and (approximately) 111 -deg. 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 -versa_. 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 L531,229, and -in 1904 to L424,442, the principal import being cotton yarn and the -principal export opium. - - - - -ICHNEUMON (Gr. [Greek: ichneumon], 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. Forster - (_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: graphe], -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 THIS PROJECT GUTENBERG EBOOK ENCYCLOPAEDIA BRITANNICA *** - -***** This file should be named 40370.txt or 40370.zip ***** -This and all associated files of various formats will be found in: - http://www.gutenberg.org/4/0/3/7/40370/ - -Produced by Marius Masi, Don Kretz and the Online -Distributed Proofreading Team at http://www.pgdp.net - - -Updated editions will replace the previous one--the old editions -will be renamed. - -Creating the works from public domain print editions means that no -one owns a United States copyright in these works, so the Foundation -(and you!) can copy and distribute it in the United States without -permission and without paying copyright royalties. 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