CAUSALITY

the effect is produced. Thus it is noticeable that while the former or more complete definition corresponds with that expressly given in J. S. Mul's Logic, his inductive methods are entirely devoted to explaining modes of discovering causes in the narrower or popular signification.

It is in this meaning of the term that science investigates causes. In doing so, it goes on the presupposition that every event or change has a cause. This has been called the Law of Universal Causation, and may be expressed by saving that the explanation of every event is to be found in antecedent conditions. Scientific investigation also presupposes the Law of the Uniformity of Nature, that the same conditions or cause will be followed (at all times and places) by the same effects. The grounds and mutual relation of these two assumptions form the chief subject of controversy in the philosophical theory, of causality. It is to Hume that the credit is due of having drawn attention to the difficulties in volved in the principle of causation, in such a way as to determine the whole course of subsequent philosophy. All reasoning about matters of fact, he abows-all physical science, therefore-depends on the relation between cause and effect. Yet, between the cause and the effect there is no diseuverable connection. There appears not, through al nature, any one instance of connection which is conceivable by us. All events seem entirely loose and separate. One event follows another; but we berer can observe any tie between them. They wem conjoined, but never connected.' Hume's own Botion of the difficulty is found in the law of tental association. The mind,' he says, 'is tarred by habit upon the appearance of one event to expect its usual attendant, and to believe that will exist. This connection, therefore, which we feel in the mind, or customary transition of the in gination from one object to its usual attendant, is the sentiment or impression from which we form the idea of power or necessary connection. Nothing further is in the case.... When we say, therefore, that one object is connected with another, we mean only that they have acquired a connection in ear thoughts, and give rise to this inference by which they became proofs of one another's exist ence: a conclusion which is somewhat extraorinary, but which seems founded on sufficient evidence. The conclusion to which Hume is driven is thus that, while all reasoning about matters of fact is founded on the principle of essality, this principle has itself no other basis Man the mental tendency to pass from one impres mon to the idea of another impression previously Experienced in conjunction with the former. Hume's solution is thus not sceptical (except as and the application of causality or any other Prople beyond experience), but it is subjective: the connection of things is resolved into a customary #urcession of ideas. Of the numerous theories of musation put forward since the question was thus ned, the two most important are J. S. Mill's realsitation of Hume's doctrine to suit the requrements of scientific investigation, and the of sex doctrine of Kant and his philosophical

it is characteristic of Mill's doctrine that the inciple of causality is made a consequence of the Law of the Uniformity of Nature: the familiar truth that invariability of succession is found by mervation to obtain between every fact in nature And some other fact which has preceded it. This priple, which is assumed in every scientific in duction, is itself held to be the generalisation of a wade and uncontradicted experience.

A different position is given to the causal prin tip in Kant's philosophy. The Scottish philoso-,

phers and others, as well as Kant, had attempted replies to Hume, contending that causality is an intuitive judgment antecedent to experience. But such a reply remains an arbitrary assertion until it is shown how the causal judgment is connected with experience. In Kant's Critique of Pure Reason this connection is thoroughly investigated; the refutation of Hume is only part or consequence of a complete inquiry into the relation of reason to experience. It was, however, largely Hume's doctrine of causality that led to Kant's new point of view, and to the doctrine that experience is the product of the understanding, the realisation of its a priori forms. It is not the sequence of events in time, Kant holds, that gives rise to the principle of causality; but the pure notion of causality finds its realisation in this time-sequence, in which each event is determined by its antecedent. Kant's doctrine, as thus stated, is in full harmony with the principles and methods of modern science; asserting the principle that every change-i.e. each successive state-of the universe is the result of its preceding state, and at the same time leaving to empirical investigation the connection in experience of any one definite thing with any other. The most important discussions of causality are those of Hume, Treatise of Human Nature, book i part iii., and Essay Of the Idea of Necessary Connection; Kant, Critique of Pure Reason; and J. S. Mill, System of Logic, book iii. chaps. iii.-v. There is also elaborate treatment of the subject in the works of Reid, Stewart, and Hamilton. Dr Thomas Brown's Inquiry into the Relation of Cause and Effect contains much acute analytical thinking.

Cause Célèbre, a convenient French term for a specially interesting and important legal trial, criminal or civil, such as the Douglas Cause (1769-71), the Dred Scott case in the United States as to the possession of a negro (1856), the Tichborne case (1871-74). There is a great French collection of Causes Celebres et interessantes (22 vols. 1737-45), by Gayot de Pitaval, with modern continuations. See TRIALS.

and informal essay on any subject in a newspaper Causerie, a name applied to a somewhat short or magazine. More familiar in manner and slighter stood, it is an excellent medium for a writer whose in structure than the formal essay as usually underpersonality interests the reader as much as the value of his thoughts. The name owes its literary currency mainly to the famous Causeries du Lundi of Sainte-Beuve; hardly less valuable examples manner of Matthew Arnold. were many of the occasional essays in the later

Caustic (Gr., burning'), in Medicine and in Chemistry, is the term applied to such substances as exert a corroding or disintegrating action on the skin and flesh. Lunar caustic (so called because silver was called luna, the moon, in the alchemists' mystical jargon) is nitrate of silver, and common caustic is potash. When used as a caustic in medicine, the substance is fused and cast into moulds, which yield the caustic in small sticks the thickness of an ordinary lead pencil, or rather lessCaustic is also used in chemistry in an adjective sense-thus caustic lime, or pure lime, Cão, as distinguished from mild lime, or the carbonate of lime, CaCO,, caustic magnesia, MgO, and mild magnesia, MgCO,, caustic potash, caustic soda (for these, see POTASH, SODA, &c.). See CAUTERY.

Caustics. When the incident rays are parallel to the principal axis of a reflecting concave mirror, they converge, after reflection, to a single point, called the principal focus. In the case of parabolic mirrors this is rigorously true. For, as is easily seen from the fundamental property of the para

CAUVERY

adot legal measures for his relief. Co-cautioners, or persons bound together, whether their obliga. tas be embodied in one or several deeds, are entified to mutual relief. But where a co-cautioner obtains relief from the others, he must communicate to them the benefit of any deduction or ease which Lay have been allowed him in paying the debt. Letters of credit and recommendation raise much the same relation of parties as a formal cautionary obligation, but since 1856 a mere verbal introduétes cannot have that effect. For the forms and effects of ordinary mercantile guarantees, and for the forms of guarantee insurance of fidelity, see GUARANTEE. For the Scottish cautionary obligation in cash credit bond, see BANKING, II. 713. JUDICIAL CAUTION, in the Law of Scotland, is | of two kinds-for appearance, and for payment. If a creditor makes oath before a magistrate, that he leeves his debtor to be meditating flight (in meditatione fugr), he may obtain a warrant for his apprehension; and should he succeed in proving the alleged intention to flee, he may compel him to find caution to abide the judgment of a court jeden sisti), The cautioner, or surety, undertars that the defender shall appear to answer any tion that may be brought within six months. The old Bond of Presentation, by which in order to time the surety undertook to produce the de for or pay the debt at a future date, is now superseded by the abolition of imprisonment for There is also a form of judicial caution card judicatum solvi, given in cases of general ing of arrestment of ships, in which the surety becomes liable for the whole debt. The commonest form of judicial caution, however, is the security aily given in the Bill Chamber (q.v.), when a bill ur bond is brought under suspension; the security is for the principal sum and expenses, if the suspenson should be refused. Interdict is also frequently granted upon caution for the damages that may result from the interdict, should it turn out to have been wrongly obtained.

Cavagnari, SIR LOUIS, born in France in 1841, was educated at Christ's Hospital, London, and in 1957 was naturalised as a British subject. He had seen twenty-one years' military and political service in India, when on 3d September 1879 he was murdered at Kabul. See AFGHANISTAN.

Cavaignac, LOUIS EUGENE, born in Paris, 15th October 1902, was a son of General Jean Baptiste Cavagnac (1762-1829), a member of the National Convention. Educated for the military profession, he first served in the Morea, and afterwards in Ana, whither he was sent in 1832 into a kind of

honourable exile, in consequence of a too free expression of opinion in favour of republican instituHere he won great distinction by his energy, mess, and intrepidity, was made chef de bataillon in 1937, and rose to the rank of brigade-general in 1944. In 1848 he was appointed governor-general of Algeria, but in view of the impending revolunary dangers, was called to Paris and assumed the office of Minister of War. He was appointed itary dictator in order to suppress the formid, e insurrection of June, which he quelled only

after a most obstinate contest continued from the 23d to the 26th June. It is estimated that a rater number of Frenchmen fell in the struggle than in the bloodiest battles of the first Empire, Cavagnar's clemency to the vanquished was equal

to his generalship, His task being done, he resigned his power into the hands of the National Assembly, which appointed him President of the Council. As a candidate for the presidency of the republic, when Louis Napoleon was elected, he received nearly a million and a half of votes out of 7,327,345. On the coup d'état of December 1851, Cavaignac was arrested, but released after a short detention; and though he consistently refused to give in his adhesion to the Empire, he was permitted to reside in France without molestation. He died, 28th October 1857, at his country house near Tours. Cavaignac was an able soldier, a zealous republican, and in every way an honourable man. See his Life by Deschamps (2 vols. Paris, 1870).

Cavaillon (ancient Cabellio), a town of the French department of Vaucluse, 18 miles SE. of Avignon by rail, with a cathedral, and some Roman remains. Pop. 5164.

Cavalcanti, GUIDO, Italian poet, born in 1230, was banished, for mercantile transactions with a whose chiefs he had married, and returned in Guelph, by the Ghibellines, a daughter of one of broken health to Florence only to die there, about 1300. His works -sonnets, ballads, and canzoniare remarkable alike from their language and depth of thought, although his epicurean philosophy gained him, among his contemporaries, the reputation of an atheist. See Ercole, Guido Cavalcanti BARTOLOMMEO (1503-62), a noble and eloquent e le sue Rime (Milan, 1885).-Another of the name, Florentine, led a revolt against the Medici, and was afterwards employed by Pope Paul III.

Cavalcaselle, GIOVANNI BATTISTA, Italian art writer, born 224 January 1820, at Legnago, early visited the art centres of Italy, and in 1846 proceeded to Germany, where he met J. A. Crowe (q.v.), with whom he returned to Italy. Banished for his share in the revolution of 1848, he accom panied Crowe to London, and there their first joint work, Early Flemish Painters (1857; 3d ed. 1879), 1858, and in 1861 commenced with Crowe the History was published. Cavalcaselle returned to Italy in of Painting in Italy (Lond, 5 vols, 1864-71), Other joint works are Titian (1876) and Raphael (1883); importance. He is head of the art department in Cavalcaselle's independent writings are of less the ministry of Public Instruction at Rome.

Cavalier (Fr., from Lat, caballus, 'a nag'), from horseman' acquired the meaning of knight" speare (Henry V., III. 24), like cavalero, in Henry or gallant, in which sense it is used by ShakeIV., Part II., V. iii. 62. In 1641 'Cavaliers' was applied as a nickname to Charles's partisans in opposition to the Roundheads, or friends of the Parliament; and from a term of reproach it came to be adopted as a title of honour, until, after 1679, it was superseded by Tory. For the Cavalier Parliament (1661 79), see CHARLES II.

Ribaute, near Anduze, who, born in 1681, in 1702 Cavalier, JEAN, a journeyman baker, from became a famous leader of the Camisards (q.v.), withal a prophet and preacher. He surrendered to Villars in 1704, and entered the service of

Savoy; but in 1711 we find him settled with a British pension in England, and he died at Chelsea, See a long governor of Jersey, 17th May 1740. article in vol. ix. of the Dict. of National Biography (1887).

Cavaliere Servente. See CICISBEO,

Cavalry is a general name for horse-soldiers or troopers trained to act in a body. In the British army there are 31 regiments of European, and 30 of native Indian cavalry. The former comprise 2 regiments of Life Guards (red), 1 of Horse Guards

(blue), and 7 of Dragoon Guards, classified as heavy cavalry; 3 regiments of Dragoons, and 5 of Lancers, classified as medium; and 13 Hussar regiments or light cavalry-all carrying carbines and swords. The war strength of each is 1 lieutenant-colonel, 1 major, 8 captains, 9 lieutenants, 7 sub-lieutenants, 1 adjutant, 1 paymaster, 1 quartermaster, I medical officer, 1 veterinary surgeon, 75 non-commissioned officers, 8 farriers, 8 shoeing-smiths, 8 trumpeters, 4 saddlers, 2 wheelers, 15 bandsmen, 480 troopers, and 22 drivers, 559 riding and 44 draught horses, and 11 wagons.

The native Indian cavalry are all light, and some have the front ranks armed with lances, the rear with sabres. Bengal has 19 regiments, each of 8 troops, consisting of 10 European officers (1 in command and 1 surgeon), 17 native officers, and 536 native non-commissioned officers and troopers. Madras has 4 regiments of only 6 troops each, the same number of European, but 12 native officers and 396 of other ranks. Bombay has 7 regiments with the same organisation and numbers as Bengal, but only 518 native non-commissioned officers and troopers. Besides these regiments there is a troop of native cavalry at Aden, and one as a body-guard for each lieutenant-governor, and the governorgeneral of India.

The auxiliary cavalry in Great Britain comprises 39 regiments of Yeomanry, 2 of Volunteer Light Horse, and 1 of Volunteer Mounted Rifles, of various strengths. There is a cavalry depôt at Canterbury, and a school of instruction for auxiliary cavalry at Aldershot.

After the American civil war, the United States' cavalry was reduced to 10 regiments of 936 privates each. The commissioned officers of a regiment consist of 1 colonel, 1 lieutenantcolonel, 3 majors, 12 captains, 14 first lieutenants, and 12 second lieutenants.

History. For the place of cavalry in the ancient armies, see ARMY. In the middle ages horsemen -knights, esquires, and their attendants-formed the most important part of the great armies; but after the disappearance of the Roman cohort with its 132 highly trained horsemen, the organisation of cavalry, as we now understand the word, was neglected until 1445, when Charles VII. of France grouped his men-at-arms into companies 100 strong. The method of fighting, from 1645 until Frederick the Great introduced the charge or shock tactics, was to advance to close quarters, fire pistols from the saddle, and then commence cutting with the sword. The value of dismounted cavalry able to act as infantry was then recognised, and dragoons armed with muskets were much in vogue until the beginning of the 19th century. They then lost favour, and though all European nations continued to train their troopers to dismount and use their carbines to hold some important point until the arrival of infantry, it was taught that the sword was their proper weapon, and the saddle their proper place. But Russia has lately armed all her cavalry, except the Cossacks, with long rifles, thus turning them into dragoons, and it is now generally felt that the dismounted service of cavalry must be developed to a greater extent than has hitherto been the case. Mounted infantry too, using their horses merely as a means of rapidly covering the ground, have been found so useful in the British army, that in 1887 a school for this arm was formed at Aldershot; and it has been decided that a force 900 strong shall accompany the cavalry division on active service.

Formation.-A cavalry regiment in the field is divided into 4 squadrons, each of 2 troops. The men of each squadron when in line are 6 inches from knee to knee, and formed in two ranks, a horse's length apart. The officers are at a similar distance

CAVAN

in front, and the 'serrefiles,' or supernumerary noncommissioned officers, in rear. There is an interval of 12 yards between squadrons. The pace is, walk 4 miles an hour, trot 8, gallop 12. The maximum distance covered by cavalry is 68 miles by day (6 A.M. to 10 P.M.) and 18 by night-86 for the 24 hours; but after such a march there must be a rest all next day. For a continuous march 35 miles a day, at 5 miles an hour, is a good rate.

Duties on Service.-In large armies, from oneeighth to one quarter of the whole force should be cavalry. Their duties are to cover the movements of their own army, and to find out those of the enemy-besides taking part in the actual battles by guarding the flanks, seizing all opportunities of charging, completing success by an active pursuit, or covering defeat. The screening and reconnoitring duties are performed by the cavalry divisions, each of two or more brigades, one or two days' march in front of the main body. The light Brigades (q.v.) are perhaps best for the actual scouting, but must be supported by heavy cavalry in order to meet that of the enemy, which would otherwise have the advantage of greater weight in the charge. Each brigade of two or more regiments is accompanied by a battery of Horse Artillery.

The battle of Mars la Tour in the Franco-German war of 1870, supplies the best examples of a cavalry fight on a large scale, and of a charge (that of Barby and Bredows' brigades) directed against infantry. The action of the German cavalry throughout the same campaign illustrates the screening and reconnoitring duties of the arm. The capture of Cairo by the rapid advance of the British cavalry after the battle of Tel-el-Kebir (1882), shows its value after a successful engagement.

Tactics.-Unless acting dismounted, cavalry must either attack or retire; it cannot otherwise defend itself. Against cavalry it must therefore manœuvre with its first line, so as to attack to the best advan tage-i.e. against the adversary's flank. Its second line following, en échelon, in order to have a clear front, protects the flanks of the first from counter attack, and supports its movement, completing its victory, or covering its retreat. Horse artillery on the protected flank fire upon the enemy up to the last moment before the charge. A third portion, formed into a reserve, follows, and behind it the other two can rally after the charge, which, even when successful, creates great confusion. Cavalry attacks artillery in two bodies-one in line formation charges the escort, and the other in extended order, the men a horse's length apart, converges upon the guns. Infantry can defend itself from a cavalry charge, unless surprised by a flank attack, which would generally be delivered by comparatively small bodies in successive lines, but such an opportunity rarely occurs on a modern battlefield.

Cav'an, an inland county in the south of Ulster. It lies in the narrowest part of Ireland, 18 miles from the Atlantic, and 20 from the Irish Sea. Area, 746 sq. m., of which less than a third is under crops. Bogs and hills, with many small lakes, are found in the north-west, where Cuilcagh attains a maximum altitude of 2188 feet. The chief rivers are the Erne, the Woodford, and the Annalee. The eastern half of Cavan rests on clay-slate and graywacke; the mountain district in the west is carboniferous formation. Of minerals, Cavan affords coal, iron, lead, and copper, with many mineral springs. The climate is cold and damp; and the soil is poor, wet, and clayey, except along the streams. The chief crops are oats and potatoes, the cultivation of flax having greatly decreased since 1850. The farms are small. Agriculture forms the staple industry, but linen is manufactured to a considerable extent. The chief towns are Cavan, Cootehill, and Beltu** returns two members to parliament.

Cavan

(1851)

CAVATINA

174,064; (1881) 129,176, of whom 104,328 were Cathones, and 18,990 Episcopalians.-CAVAN, the County town, stands on a branch of the Annalee, simies NW. of Dublin by rail. It has a courtbose and a grammar-school; and the beautiful demesne of Lord Farnham lies between Cavan and Lough Oughter, which is about 5 miles west. Pop. 11881-3050.

Cavati'na, a short form of operatic air, of a smooth and melodious character, differing from the ordinary aria in consisting only of one part, and frequently appearing as part of a grand scena. Examples of cavatina are found in many wellknown operas, as Sonnambula and Les Huguenots. The term is also often used for a complete air or song, such as the 'Salve dimora' in Faust.

Cave, or CAVERN (Lat. cavus, 'hollow'). The natural hollows which occur in and underneath rocks have originated in various ways-some being due to the chemical and mechanical action of water, others to dislocations and disruptions produced by movements of the crust, or by superficial ra falls and landslips, while yet others are tunnels wach now and again occur in or under thick sheets of lava. Caves formed by marine erosion are frequently met with along the coast-line of Britain and other countries, Fingal's Cave at Staffa (q.v.) being ap'endid example. They are not confined to any particular kind of rock-although, other things .ng equal, they are of course more easily formed in readily yielding rocks than in more durable kinds. It is rather the character of their natural divisionFates or beds and joints than their composition and texture that determines whether the rocks at hase of a sea-cliff shall be hollowed out or not by the action of the waves. If the rocks are thin beded and abundantly and regularly jointed, it is gous that as soon as any portion is undermined by the sea, the overlying masses will immediately yield along their division-planes and topple down. 1t, on the other hand, the rocks are meagrely and regularly jointed, and occur in massive beds, then they will not so readily collapse when undermined, and caves will tend to be formed. Caves which have had this origin are not uncommonly met with ng the line of old sea-margins in many regions which have been elevated in recent geological Most frequently, however, the entrances to such caves are concealed by the rock-rubbish which has been detached from time to time by the action of the weather from the cliffs above. Caves of erosion are also formed by river-action at the base of crags and cliffs in many valleys, And now and again such hollows may be detected at various levels in river-clifts, as if they had been formed during the gradual excavation of the ravines in which they occur.

In Britain and other countries long occupied by than most of such river-cliff caves or rock-shelters have been artificially deepened and widened, and this to such an extent that it is often hard to say how much of the work can be attributed to nature. By far the most important caves, however, are those which owe their origin to the art. n of underground water. But before these are descrised, mention may be made of the hollows wach occur now and again in and under lavaflows. Where lava has flowed over and solidified alone a mass of snow and ice, the subsequent melting of the latter will leave a hollow behind. Near the Casa Inglese, on the south-east side of the highest cone of Etna, a mass of ice of unknown exiest and thickness, covered by lava, was seen by Lyell in 1828 and again in 1858. But this, must be remembered, is at a height of 10,000 feet above the sea. In lava itself, however. Cave of considerable extent occur. Many of

these are simply great blisters or hollows formed by the expansive power of the highly heated vapours contained in the lava at the time of its eruption. Others again may have been caused by the sudden conversion into steam of the water of lakes or streams suddenly overwhelmed by a lavaflow-the steam thus generated might either violently rupture the lava by its explosive force, or produce great tunnels and irregular cavities under the liquid lava, already inclosed in its solid crust, by pressing it upwards. The extensive Fossa della Palomba of Etna is supposed by some to have had such an origin. But probably the greater number of the larger caves under lava have been formed by the escape of the lava itself from its own solidified envelope. When lava pours out from a volcanic orifice it very rapidly coagulates above and below, so that the liquid rock becomes imprisoned in a hardened crust of its own material. The great pressure of the inclosed lava, however, upon the crust at the terminal point of the flow suffices again and again to rupture it, and the lava then flows out freely until it is again imprisoned in the same manner. In the case of very liquid lavas this escape is often completed in a perfect manner -and a long underground tunnel is left behind, from the roof of which depend long stalactites of black glassy lava. Extensive caves formed in this way-some of them measuring over 100 feet in width-occur in the Azores, the Canary Islands, Iceland, and other volcanic regions.

Another class of caves embraces such hollows as have originated during earthquakes or other movements in the crust of the earth. At such times rocks are rent asunder, and when they fall rudely together irregular cavities are left between the disjointed masses, and similar results often take place when great landslips occur. But the most extensive caves and underground galleries have been excavated by the chemical and mechan ical action of underground water. Sometimes these hollows continue more or less persistently in one direction, but most usually they wind tortuously about, and often open into similar intricate galleries, which, in like manner, communicate with lateral extensions of the same character. There can be no doubt that caves of this kind are the channels of underground streams and rivers, and that they have been excavated, in the first place, by the chemical action of acidulated water making its way downwards from the surface along the natural division-planes of the rocks, until eventually space has been licked out for the passage of a subterranean stream. The cavities would then tend to be enlarged by the filing action of the sand and gravel which the underground stream and its numerous feeders might sweep along. Many such underground watercourses are well known at the present day, and the direction of some of them can be traced by the swallow-holes, chasms, and sinks,' which indicate places where the roofs of the cavities have given way, or have been pierced by the action of acidulated water. certain regions almost all the drainage is thus conducted underground-rivers after flowing for a considerable distance at the surface suddenly dis appear, and follow a hidden course, for it may be many miles, before they emerge again to the light of day. Sometimes, indeed, they never come to the surface again, but enter the sea by subterranean channels. Should anything occur (such as earthquakes, &c.) to interrupt such a system of underground drainage, and the streams and rivers be compelled into new channels, the old subterranean courses will then become galleries more or less dry, which may be accessible by one or even by several openings.

In

As it cannot be doubted that all such great