the segments of the abdomen, and give the wasp a very extra-leases for the prescribed terms " for any purpose whatever, whether involving waste or not." Permissive waste is by act of omission, ordinary appearance. BIBLIOGRAPHY.-In addition to various systematic memoirs such as allowing buildings to fall out of repair. A fermor "a term enumerated at the end of the article on Hymenoptera, reference which here includes" all who held by lease for life or lives, or for years may be made to De Saussure (Monographie des guêpes sociales, by deed or without deed " by the statute of Marlborough (1267)-Genève, 1853-1858), P. Marchal (Arch. Zool. Exp. Gen. (3), iv., may not commit waste without licence in writing from the reversioner. 1896), C. Janet (Mem. Soc. Zool. France, viii., 1895) and O. H. Latter In case a tenant for life or for any smaller interest holds (as is often (Natural History of Common Animals, ch. v., Cambridge, 1904). the case by the terms of a will or settlement)" without impeachment (A. E. S.; G. H. C.) of waste" (sauns impeachment de wast, i.e. without liability to have his waste challenged or impeached), his rights are considerably WASSAIL (O. Eng. was hál," be whole," be well "), primarily greater, and he may use the profits salva rerum substantia (to use the the ancient form of " toasting," the term being applied later to the language of Roman law, from which the English law of waste is in Christmas feasting and revelries and particularly to the bowl of great measure derived). For instance, he may cut timber in a spiced ale or wine which was a feature of the medieval Christmas. husband-like manner and open mines; but he may not commit what is called equitable waste, that is, pull down or deface the One of the earliest references to the wassail-bowl in English mansion or destroy timber planted or left for ornament or shelter history is in the description of the reception of King Vortigern (Weld-Blundell v. Wolseley, 1903, 2 Ch. 664). Acts of equitable waste by Hengist, when Rowena "came into the king's presence, were, before 1875, not cognizable in courts of common law, but by with a cup of gold filled with wine in her hand, and making a the Judicature Act 1873, s. 25 (3), in the absence of special provisions to that effect an estate for life without impeachment of waste does low reverence unto the king said, Waes hael hlaford Cyning,' not confer upon the tenant for life any legal right to commit equitable which is Be of health, Lord King." " In a collection of ordinances waste. A copy-holder may not commit waste unless allowed to do for the regulations of the royal household in Henry VII.'s so by the custom of the manor. The penalty for waste is forfeiture reign, the steward or Twelfth Night was to cry wassail of the copyhold; Galbraith v. Poynton, 1905, 2 K.B. 258 (see COPYthree times on entering with the bowl, the royal chaplain respond of their provisions giving compensation for improvement, as regards HOLD). The Agricultural Holdings Acts 1900 and 1906, by reason ing with a song. Wassailing was as much a custom in the the holdings to which they apply, override some of the old common monasteries as in laymen's houses, the bowl being known as law doctrines as to waste. The act of 1900 provides (s. 2 [3]) that poculum Caritatis. What was popularly known as wassailing where a tenant, who claims compensation for improvements, has was the custom of trimming with ribbons and sprigs of rosemary landlord shall be entitled to set off the sums due to him in respect wrongfully been guilty of waste, either voluntary or permissive, the a bowl which was carried round the streets by young girls of such waste, and to have them assessed by arbitration in manner singing carols at Christmas and the New Year. This ancient provided by the acts of 1900 and 1906. Under the act of 1906 the custom still survives here and there, especially in Yorkshire, tenant is permitted to disregard the terms of his tenancy as to the where the bowl is known as "the vessel cup," and is made freedom of cropping in such a manner as to injure or deteriorate his mode of cropping on arable land, but if he exercises his statutory of holly and evergreens, inside which are placed one or two dolls holding, the landlord is entitled to recover damages for such injury, trimmed with ribbons. This cup is borne on a stick by children &c. (s. 3). who go from house to house singing Christmas carols. In Devonshire and elsewhere it was the custom to wassail the orchards on Christmas and New Year's eve. Pitchers of ale or cider were poured over the roots of the trees to the accompaniment of a rhyming toast to their healths.

WASTE (O. Fr. wast, guast, gast, gaste; Lat. vastus, vast, desolate), a term used in English law in several senses, of which four are the most important. (1) "Waste of a manor" is that part of a manor subject to rights of common, as distinguished from the lord's demesne (see COMMONS, MANOR). (2) " Year, day, and waste" was a part of the royal prerogative, acknowledged by a statute of Edward II., De Praerogativa Regis. The king had the profits of freehold lands of those attainted of felony and petit treason, and of fugitives for a year and a day with a right of committing waste in sense (3) thereon. After the expiration of a year and a day the lands returned to the lord of the fee. This species of waste was abolished by the Corruption of Blood Act 1814 (see FELONY, TREASON). (3) The most usual signification of the word is "any unauthorized act of a tenant, for a freehold estate not of inheritance, or for any lesser interest, which substantially alters the permanent character of the thing demised (i.) by diminishing its value, (ii.) by increasing the burden on it, (iii.) by impairing the evidence of title and thereby injuring the "inheritance" (West Ham Charity Board v. East London W.W., 1900, I Ch. 624, 637; cf. Pollock, Law of Torts, 7th ed., 345).

Waste in sense (3) is either voluntary or permissive. Voluntary waste is by act of commission, as by pulling down a house, wrongfully removing fixtures (q.v.), cutting down timber trees, i.e. oak, ash, elm, twenty years old, and such other trees, e.g. beech, as by special custom are counted timber, in the district, opening new quarries or mines (but not continuing the working of existing ones), or doing anything which may-for this is the modern test-alter the nature of the thing demised, such as conversion of arable into meadow land. Although an act may technically be waste, it will not as a rule constitute actionable waste, or be restrained by injunction, in the absence of some prohibitive stipulation if it is ameliorating," i.e. if it improves the value of the land demised (see Meux v. Cobley, 1892, 2 Ch. 253, 263). In the case of " timber estates "upon which trees of various kinds are cultivated solely for their produce and the profit gained from their periodical felling and cutting, the timber is not considered as part of the inheritance but as the annual fruits of the estate, and an exception arises in favour of the tenant for life (see Dashwood v. Magniac, 1891, 3 Ch. 306). Under the Settled Land Act 1882 a tenant for life may grant building, mining and other

"

Remedies for Waste.—Various remedies for waste have been given At common law only single damages seem to have been recoverable. to the reversioner at different periods in the history of English law. This was altered by the legislature, and for some centuries waste was a criminal or quasi-criminal offence. Magna Carta enacted that a guardian committing waste of the lands in his custody should made a "fermor make amends and lose his office. The statute of Marlborough (1267) (as above defined) committing waste liable to grievous amercement as well as to damages, and followed Magna Carta in forbidding waste by a guardian. The statute of Gloucester (1278) enacted that a writ of waste might be granted against a of waste the tenant was to forfeit the land wasted and to pay thrice tenant for life or years or in courtesy or dower, and on being attainted the amount of the waste. This statute was repealed by the Civil Procedure Acts Repeal Act 1879. In addition to the writ of waste the writ of estrepement (said to be a corruption of exstirpamentum, and to be connected with the French estropier, to lame) lay to prevent injury to an estate to which the title was disputed. This writ has long been obsolete. Numerous other statutes dealt with remedies for waste. The writ of waste was superseded at common law by the "mixed action" of waste (itself abolished by the Real Property Limitation Act 1833), and by the action of trespass on the case (see TORT, TRESPASS). The court of chancery also intervened by injunction to restrain equitable waste. At present proceedings may be taken either by action for damages, or by application for an injunction, or by both combined, and either in the king's bench or in the chancery divisions. By the Judicature Act 1873, s. 25 (8), the old jurisdiction to grant injunctions to prevent threatened waste is considerably enlarged. The Rules of the Supreme Court, Ord. xvi. r. 37, enable a representative action to be brought for the prevention of waste. In order to obtain damages or an injunction, substantial injury or danger of it must be proved. In England only the high court (unless by agreement of the parties) has jurisdiction in questions of waste, but in Ireland, where the law of waste is similar to English law, county courts and courts of summary jurisdiction have co-ordinate authority to a limited extent (cf. Land Act 1860, ss. 35-39).

The law of waste as it affects ecclesiastical benefices will be found under DILAPIDATIONS.

(4)" Waste of assets" or "devastavit" is a squandering and misapplication of the estate and effects of a deceased person by his executors or administrators, for which they are answerable out of their own pockets as far as they have or might have had assets of the deceased (see EXECUTORS AND ADMINISTRATORS). Executors and administrators may now be sued in the county court for waste of assets (County Courts Act 1888, s. 95).

Scotland.-In Scots law "waste" is not used as a technical term, but the respective rights of fiar and life-renter are much the same as in England. As a general rule, a life-renter has no right to cut timber, even though planted by himself. An exception is admitted in the case of coppice wood, which is cut at regular intervals and allowed to grow again from the roots. Grown timber is also available

AUTHORITIES.-English law: Bewes, Law of Waste; Fawcett, Law of Landlord and Tenant; Foa, Law of Landlord and Tenant; Woodfall, Law of Landlord and Tenant. Scots law: Erskine, Principles (Edinburgh). Irish law: Nolan and Kane, Statutes relating to the Law of Landlord and Tenant in Ireland (Dublin); Wylie, Judicature Acts (Dublin). American law: Bouvier, Law Dict. (Boston and London). Indian law: Shepherd and Brown, Indian Transfer of Property Act 1882. (A. W. R.) WATCH (in O. Eng. wacce, a keeping guard or watching, from wacian, to guard, watch, wacan, to wake), a portable timepiece. This is the most common meaning of the word in its substantival form, and is the subject of the present article. The word, by derivation, means that which keeps watchful or wakeful observation or attention over anything, and hence is used of a person or number of persons whose duty it is to protect anything by vigilance, a guard or sentry; it is thus the term for the body of persons who patrolled the streets, called the hours, and performed the duties of the modern police. The application of the term to a period of time is due to the military division of the night by the Greeks and Romans into "watches" (duλakai, vigiliae), marked by the change of sentries; similarly, on shipboard, time is also reckoned by "watches," and the crew is divided into two portions, the starboard and port watches, taking duty alternately. The transference of the word to that which marks the changing hours is easy.

In the British navy the twelve hours of the night are divided into three watches of four hours-from eight to twelve the first watch, from twelve to four the middle watch, and from four to eight the morning watch. The twelve hours of the day are divided into four watches, two of four hours-eight to midday, midday to four P.M.-and two of two hours, from four to six and six to eight. These are the "dog watches," and their purpose is to change the turn of the watches every twenty-four hours, so that the men who watch from eight to midnight on one night, shall watch from midnight till 4 A.M. on the next. The" watch bill" is the list of the men appointed to the watch, who are mustered by the officers. Time was originally kept by an hour-glass, every half-hour; the number of the half-hour I

FIG. 4..

improved watches. But a defect still remained, namely, | give a little recoil the wrong way, or slightly to resist the unlocking, the influence of temperature upon the hair-spring of the balance- because otherwise there would be a risk that a shake of the watch wheel. Many attempts were made to provide a remedy. John engaged from the lever. There is also a further would let a tooth escape while the pin is disHarrison proposed a curb, so arranged that alterations of tempera- provision added for safety. In the cylinder ture caused unequal expansion in two pieces of metal, and thus which carries the impulse pin P there is a actuated an arm which moved and mechanically altered the length notch just in front of P, into which the other of the hair-spring, thus compensating the effect of its altered the notch has got past the cylinder it would pin S on the lever fits as they pass; but when elasticity. But the best solution of the problem was ultimately prevent the lever from returning, because the proposed by Pierre le Roy (1717-1785) and perfected by Thomas safety-pin S cannot pass except through the Earnshaw (1749-1829). This was to diminish the inertia of the notch, which is only in the position for letting it balance-wheel in proportion to the increase of temperature, by engaged in the lever. The pallets in a lever pass at the same time that the impulse-pin is means of the unequal expansion of the metals composing the rim. escapement (cxcept bad and cheap ones) are Invention in watches was greatly stimulated by the need of a always jewelled, and the scape-wheel is of brass. good timepiece for finding longitudes at sea, and many successive holes in expensive watches, and the scape-wheel has in all good The staff of the lever also has jewelled pivotrewards were offered by the government for watches which ones. The holes for the balance-pivots are now always jewelled. would keep accurate time and yet be able to bear the rocking The scape-wheel in this and most of the watch escapements generally motion of a ship. The difficulty ended by the invention of the beats five times in a second, in large chronometers four times; and chronometer, which was so perfected towards the early part of the wheel next to the scape-wheel carries the seconds-hand. the 19th century as to have even now undergone but little change through the cylinder, which is on the verge of the balance, at the Fig. 5 is a plan of the horizontal or cylinder escapement, cutting of form. In fact the only great triumph of later years has been level of the tops of the teeth of the escape-wheel; for the triangular the invention of watch-making machinery, whereby the price pieces A, B are not flat projections in the same plane as the teeth, is so lowered that an excellent watch (in a brass case) can now but are raised on short stems above the plane of the wheel; and still be purchased for about £2 and a really accurate time-keeper for shown at ACD is cut away where the more of the cylinder than the portion about £18. wheel itself has to pass. The author of this escapement was G. Graham, and it resembles his dead escapements in clocks in principle more than the lever escapement does, though much less in appear. ance, because in this escapement there is the dead friction of the teeth against the cylinder, first on the outside, as here represented, and then on the inside, as shown by the dotted lines, during the whole vibration of the balance, except that portion which belongs to the impulse. The impulse is given by the oblique outside edges Aa, Bb of the teeth against the edges A, D of the cylinder alternately. The portion of the cylinder which is cut away at the point of action is about 30° less than the semicircle. The cylinder itself is made either of steel or ruby, and, from the small quantity of it which is left at the level of the wheel, it is very delicate; and probably this has been the main reason why, although it is an English invention, it has been most entirely abandoned by the English watchmakers in favour of the lever, which was originally a French invention, though very much improved by Mudge, for before his invention the lever had a rack or portion of a toothed wheel on its end, working into a pinion on the balance verge, and consequently it was affected by the dead friction, and that of this wheel and pinion besides. This used to be called the rack lever, and Mudge's the detached lever; but, the rack lever being now quite obsolete, the word "detached" has become confined to the chronometer, to which it is more appropriate, as will be seen presently. The Swiss watches have almost universally the horizontal escapement. It is found that--for some reason which is apparently unknown, as the rule certainly does not hold in cases seemingly analogous-a steel scape-wheel acts better in this escapement than brass one, although in some other cases steel upon steel, or even upon a ruby, very soon throws off a film of rust, unless they are kept well oiled, while brass and steel, or stone, will act with scarcely any oil at all, and in some cases with none.

A modern watch consists of a case and framework containing the four essential parts of every timepiece, namely, a mainspring and apparatus for winding it up, a train of wheels with hands and a face, an escapement and a balance-wheel and hair-spring. We shall describe these in order.

The Mainspring.-As has been said, the mainspring of an oldfashioned watch was provided with a drum and fusee so as to equalize its action on the train. An arrangement was provided to prevent overwinding, consisting of a hook which when the chain was nearly wound up was pushed aside so as to engage a pin, and thus prevent further winding (see fig. 1). Another arrangement for watches without a fusee, called a Geneva stop, consists of a wheel with one tooth affixed to the barrel arbour, working into another with only four or five teeth. This allows the barrel arbour only to be turned round four or five times.

The "going-barrel," which is fitted to most modern watches, contains no fusee, but the spring is delicately made to diminish in size from one end to the other, and it is wound up for only a few turns, so that the force derived from it does not vary very substantially. The unevenness of drive is in modern watches sought to be counteracted by the construction of the escapement and balance-wheel. Watches used formerly to be wound with a separate key. They are now wound by a key permanently fixed to the case. The depression of a small knob gears the winding key with the hands so as to enable them to be set. With this contrivance watches are well protected against the entry of dust and damp.

Watch Escapements.-The escapements that have come into practical use are (1) the old vertical escapement, now disused; (2) the lever, very much the most common in English watches; (3) the horizontal or cylinder, which is equally common in foreign watches, though it was of English invention; (4) the duplex, which used to be more in fashion for first-rate watches than it is now; and (5) the detached or chronometer escapement, so called because it is always used in marine chronometers.

The vertical escapement is simply the original clock escapement adapted to the position of the wheels in a watch and the balance, in the manner exhibited in fig. 3. As it requires considerable thickness in the watch, is inferior in going to all the others and is no cheaper than the level escape ment can now be made, it has gone out ot

FIG. 3.

use.

The lever escapement, as it is now universally made, was brought into use late in the 18th century by Thomas Mudge. Fig. 4 shows its action. The position of the lever with reference to the pallets is immaterial in principle, and is only a question of convenience in the arrangement; but it is generally such as we have given it. The principle is the same as in the dead-beat clock escapement, with the advantage that there is no friction on the dead faces of the pallets beyond what is necessary for locking. The reason why this friction cannot be avoided with a pendulum is that its arc of vibration is so small that the requisite depth of intersection cannot be got between the two circles described by the end S of the lever and any pin in the pendulum which would, work into it; whereas, in a watch, the pin P, which is set in a cylinder on the verge of the balance, does not generally slip out of the nick in the end of the lever until the balance has got 15. past its middle position. The pallets are undercut a little, as it is called, i.e. the dead faces are so sloped as to

a

FIG. 5.

The duplex escapement (fig. 6) is probably so called because there is a double set of teeth in the scape-wheel-the long ones (like those of the lever escapement in shape) for locking only, and short ones (or rather upright pins on the rim of the wheel) for giving the impulse to the pallet P on the verge of the balance. It is a single-beat escapement; i.e. the balance only receives the impulse one way, or at every alternate beat, as in the chronometer escapement. When the balance is turning in the direction marked by the arrow, and arrives at the position in which the dotted tooth b has its point against the triangular notch V, the tooth end slips into the notch, and, as the verge turns farther round, the tooth goes on with it till at last it escapes when the tooth has got into the position A; and by that time the long tooth or pallet which projects from the verge has moved from p to P, and just come in front of the pin T, which stands on the rim of the scape-wheel, and which now begins to push against P, and so gives the impulse until it also escapes when it has arrived at t; and the wheel is then stopped by the next tooth B having got into the position b, with its point resting against the verge, and there is dead friction between them, and this friction is lessened by the

FIG. 6.

drop in the duplex and this lever chronometer or others on the
same principle.
There have been several contrivances for remontoire escapements;
but there are defects in all of them; and there is not the same
advantage to be obtained by giving the impulse to a watch-balance
by means of some other spring instead of the mainspring as there is
in turret-clocks, where the force of the train is liable to very much
greater variations than in chronometers or small clocks.

distance of the points of the long teeth from the centre of the scape wheel. As the balance turns back, the nick V goes past the end of the tooth b. and in consequence of its smallness it passes without Visibly affecting the motion of the scape-wheel, though of course it does produce a very slight shake in passing. It is evident that, if it did not pass, the tooth could not get into the nick for the next escape. The objection to this escapement is that it requires very great delicacy of adjustment, and the watch also requires to be worn carefully; for, if by accident the balance is once stopped from swinging back far enough to carry the nick V past the tooth end, it will stop altogether, as it will lose still more of its vibration the next time from receiving no impulse. The performance of this escapement, when well made, and its independence of oil, are nearly equal to those of the detached escapement; but, as lever watches are now made sufficiently good for all but astronomical purposes, for which chronometers are used, and they are cheaper both to make and to mend than duplex ones, the manufacture of duplex watches has almost disappeared. The chronometer or detached escapement is shown at fig. 7 in the form to which it was brought by Earnshaw, and in which it has remained ever since, with the very slight difference that the pallet P, on which the impulse is given (corresponding exactly to the pallet P in the duplex escapement), is now generally set in a radial direction from the verge, whereas Earnshaw made it sloped backward, or undercut, like the scape-wheel teeth. The early history of escape-hair-spring to get such an adjustment that the rate is not influenced ments on this principle does not seem to be very clear. They appear to have originated in France; but there is no doubt that they were considerably improved by the first Arnold (John), who died in 1799. Earnshaw's watches, however, generally beat his in trials.

The balance-wheel and hair-spring consist of a small wheel, usually of brass, to which is affixed a spiral, or in chronometers a helical spring. This wheel swings through an angle of from 180° to 270° and its motions are approximately isochronous. The time of the watch can be regulated by an arm to which is attached a pair of pins which embrace the hair-spring at a point near its outer end, and by the movement of which the spring can be lengthened or shortened. The first essential in a balance-wheel is that its centre of gravity should be exactly in the axis, and that the centre of gravity of the hair-spring should also be in the axis of the balance-wheel. True isochronism is disturbed by variations in the driving force of the train or by variations in temperature, and also by variations in barometric pressure. Isochronism is produced in the first place by a proper shape of the spring and its overcoil It is usual to time the watch's going when the mainspring is partly wound up, as well as when it is fully wound up, and then by removing parts of the by the lesser or greater extent to which the watch has been wound. The variations in length and still more in elasticity caused in a hairspring by changes of temperature were for long not only a trouble to watchmakers but a bar to the progress of the art. A pendulum In fig. 7 the small tooth or cam V, on the verge of the balance, requires scarcely any compensation except for its own elongation is just on the point of unlocking the detent DT from the tooth T by heat; but a balance requires compensation, not only for its of the scape-wheel; and the tooth A will immediately begin to give own expansion, which increases its moment of inertia just like the the impulse on the pallet P, which, in good pendulum, but far more on account of the decrease in the strength chronometers, is always a jewel set in the of the spring under increased heat. E. G. Dent, in a pamphlet on cylinder; the tooth V is also a jewel. This compensation balances, gave the following results of some experipart of the action is so evident as to requirements with a glass balance, which he used for the purpose on account no further notice. When the balance returns, of its less expansibility than a metal one: at 32° F., 3606 vibrations the tooth V has to get past the end of the in an hour; at 66°, 3598.5; and at 100°, 3599. If therefore it had detent, without disturbing it; for, as soon as been adjusted to go right (or 3600 times in an hour) at 32° it would it has been unlocked, it falls against the have lost 7 and 8 seconds an hour, or more than three minutes a banking-pin E, and is ready to receive the day, for each successive increase of 34°, which is about fifteen times next tooth B, and must stay there until it is as much as a common wire pendulum would lose under the same again unlocked. It ends, or rather begins, in a increase of heat; and if a metal balance had been used instead of a stiffish spring, which is screwed to the block glass one the difference would have been still greater. D on the watch frame, so that it moves without FIG. 7. any friction of pivots, like a pendulum. The passing is done by means of another spring VT, called the passing spring, which can be pushed away from the body of the detent towards the left, but cannot be pushed the other way without carrying the detent with it. In the back vibration, therefore, as in the duplex escapement, the balance receives no impulse, and it has to overcome the slight resistance of the passing spring besides; but it has no other friction, and is entirely detached from the scape-wheel the whole time, except when receiving the impulse. That is also the case in the lever escapement; but the impulse in that escapement is given obliquely, and consequently with a good deal of friction; and, besides, the scape-wheel only acts on the balance through the intervention of the lever, which has the friction of its own pivots and of the impulse pin. The locking-pallet T is undercut a little for safety, and is also a jewel in the best chronometers; and the passing spring is usually of gold. In the duplex and detached escapements, the timing of the action of the different parts requires great care, i.e. the adjusting them so that each may be ready to act exactly at the right time; and it is curious that the arrangement which would be geometrically correct, or suitable for a very slow motion of the balance, will not do for the real motion. If the pallet P❘ were really set so as just to point to the tooth A in both escapements at the moment of unlocking (as it has been drawn, because otherwise it would look as if it could not act at all), it would run away some distance before the tooth could catch it, because in the duplex escapement the scape-wheel is then only moving slowly, and in the detached it is not moving at all, and has to start from rest. The pallet P is therefore, in fact, set a little farther back, so that it may arrive at the tooth A just at the time when A is ready for it, without wasting time and force in running after it. The detached escapement has also been made on the duplex plan of having long teeth for the locking and short ones or pins nearer the centre for the impulse; but the advantages do not appear to be worth the additional trouble, and the force required for unlocking is not sensibly diminished by the arrangement, as the spring D must in any case be

fairly stiff, to provide against the watch being carried in the position

in which the weight of the detent helps to unlock it.

An escapement called the lever chronometer has been several times reinvented, which implies that it has never come into general use. It is a combination of the lever as to the locking and the chronometer as to the impulse. It involves a little drop and therefore waste of force as a tooth of the wheel just escapes at the " passing beat where no impulse is given. But it should be understood that a single-beat escapement involves no more loss of force and the escape of no more teeth than a double one, except the slight

"

The necessity for this large amount of compensation having arisen from the variation of the elasticity of the spring, the first attempts at correcting it were by acting on the spring itself in the manner of a common regulator. Harrison's compensation consisted of a compound bar of brass and steel soldered together, having one end fixed to the watch-frame and the other carrying two curb pins which embraced the spring. As the brass expands more than the steel, any increase of heat made the bar bend; and so, if it was set the right way, it carried the pins along the spring, so as to shorten it. This contrivance is called a compensation curb; and it has often been reinvented, or applied in a modified form. But there are two objections to it: the motion of the curb pins does not correspond accurately enough to the variations in the force of the spring, and it disturbs the isochronism, which only subsists at certain definite lengths of the spring.

The compensation which was next invented left the spring untouched, and provided for the variations of temperature by the construction of the balance itself. Fig. 8 shows the plan of the ordinary compensation balance. Each portion of the rim of the balance is composed of an inner bar of steel with an outer one of brass soldered, or rather melted, upon it, and carrying the weights b, b, which are screwed to it. As the temperature increases, the brass expanding must bend the steel inwards, and so carries the weights farther in, and diminishes the moment of inertia of the balance, the decrease of rate being inversely as the diameter of the balance-wheel. metals are generally soldered together by pouring melted brass round a solid steel disk, and the whole is afterwards turned and filed away till it leaves only the crossbar in the middle lying flat and the two portions of the rim standing edgeways. The first person to practise this method of uniting them appears to have been either Thomas Earnshaw or Pierre le Roy.

The

FIG. 8.

tre, and requires a good deal of time. It must be done inThe adjustment of a balance for compensation can only be done dependently of that for time-the former by shifting the weights, because the nearer they are to the crossbar the less distance they will move over as the rim bends with them. The timing is done by screws with heavy heads (t, t, fig. 8), which are just opposite to the ends of the crossbar, and consequently not affected by the bending of the rim; other screws are also provided round the rim for adjusting the moment of inertia and centre of gravity of the balance-wheel. The compensation may be done approximately by

WATCH

the known results of previous experience with similar balances; ad many watches are sold with compensation balances which have never been tried or adjusted, and sometimes with a mere sham compensation balance, not even cut through.

Secondary Compensation.-When chronometers had been brought to great perfection it was perceived that there was a residuary error, which was due to changes of temperature, but which no adjustment of the compensation would correct. The cause of the secondary error is that as the temperature rises the elasticity of the spring decreases, and therefore its accelerating force upon the balancewheel diminishes. Hence the watch tends to go slower.

In order to compensate this the split rim of the balance-wheel is made with the more expansible metal on the outside, and therefore tends to curl inwards with increase of temperature, thus diminishing the moment of inertia of the wheel. Now the rate of error caused by the increase of temperature of the spring varies approximately with the temperature according to a certain law, but the rate of correction due to the diminution of the moment of inertia caused by the change of form of the rim of the wheel does not alter proportionally, but according to a more complex law of its own, varying more rapidly with cold than with heat, so that if the rate of the chronometer is correct, say, at 30° F. and also at 90° F., it will gain at all intermediate temperatures, the spring being thus under-corrected for high temperatures and over-corrected for low. Attempts have been made by alterations of shape of the balance-wheel to harmonize the progress of the error with the progress of the correction, but not with very conspicuous success.

We shall give a short description of the principal classes of inventions for this purpose. The first disclosed was that of J. S. Eiffe (sometimes attributed to Robert Molyneux), which was communicated to the astronomer-royal in 1835. In one of several methods proposed by him a compensation curb was used; and though, for the reasons given before, this will not answer for the primary compensation, it may for the secondary, where the motion required is very much smaller. In another the primary compensation bar, or a screw in it, was made to reach a spring set within it with a small weight attached at some mean temperature, and, as it bent farther in, it carried this secondary compensation weight along with it. The obvious objection to this is that it is discontinuous; but the whole motion is so small, not more than the thickness of a piece of paper, that this and other compensations on the same principle appear to have been on some occasions quite successful.

Another large class of balances, all more or less alike, may be represented by E. J. Dent's, which came next in order of time. He described several forms of his invention; the following description applies to the one he thought the best. In fig. 9 the flat crossbar rr is itself a compensation bar which bends upwards under increased heat; so that, if the weights, were merely set upon upright stems rising from the ends of the crossbar, they would approach the axis when that bar bends upwards. But, instead of the stems rising from the crossbar, they rise from the two secondary compensation pieces stu, in the form of staples, which are set on the crossbar; and, as these secondary pieces themselves also bend upwards, they make the weights approach the axis more rapidly as the heat increases; and by a proper FIG. 9. adjustment of the height of the weights on the stems the moment of inertia of the balance can be made to vary in the proper ratio to the variation of the intensity of the spring. The cylindrical spring stands above the crossbar and between the staples.

Fig. 10 represents E. T. Loseby's mercurial compensation balance. Besides the weights D, D, set near the end of the primary compensation bars B, B, there are small bent tubes FE, FE with mercury in them, like a thermometer, the bulbs being at F, F. As the heat increases, not only do the primary weights D, D and the bulbs F, F approach the centre of the balance, but some of the mercury is driven along the tube, thus carrying some more of the weight towards the centre, at a ratio increasing more rapidly than the temperature. The tubes are sealed at the thin end, The with a little air included. action is here equally continuous with Dent's, and the adjustments for primary and secondary compensation are apparently more independent of each other; and this modification of Le Roy's use of FIG. 10. mercury for compensated balances (which does not appear to have answered) is certainly very elegant and ingenious. Nevertheless an analysis of the Greenwich lists for seven years of Loseby's trials proved that the advantage of this method over the others was more theoretical than practical; Dent's compensation was the most suc cessful of all in three years out of the seven, and Loseby's in only one. xxviu 7

maker, whereas the principles both of Eiffe's and of Dent's methods | Loscby's method has never been adopted by any other chronometerhave been adopted by several other makers.

A few chronometers have been made with glass balance-springs, secondary compensation, on account of the very small variation in which have the advantage of requiring very little primary and no One of the most important and interesting attempts to correct the their clasticity, compared with springs of steel or any other metal. temperature changes in the moment of inertia of the balance-wheel temperature errors of a hair-spring by a series of corresponding has been made by means of the use of the nickel-steel compound called invar, which, on account of its very small coefficient of expansion, has been of great use for pendulum rods. In a memoir invar, shows that in order to get a true secondary compensation published in 1904 at Geneva, Dr Charles Guillaume, the inventor of curve of the rim of the wheel to change at an increasing rate as what is wanted is a material having the property of causing the compared with changes in the temperature. This is found in those specimens of invar in which the second coefficient of expansion is at lower ones. It is satisfactory to add that such balance-wheels negative, i.e. which are less dilatable at higher temperatures than have been tried successfully on chronometers, and notably in a deck watch by Paul Ditisheim of Neuchâtel, who has made a chronometer with a tourbillon escapement and an invar balance-wheel, which It is obvious that in order that a watch may keep good time the holds the highest record ever obtained by a watch of its class. centre of gravity of the balance-wheel and hair-spring must be exactly in the axis; for if this were not the case, then the wheel would act partly like a pendulum, so that the time would vary according as the watch was placed in different positions. It is errors are eliminated. Accordingly it has been proposed to exceedingly difficult to adjust a watch so that these "position neutralize their effect by mounting the balance-wheel and hairspring upon a revolving carriage which shall slowly rotate, so that is assumed, and thus errors are averaged and mutually destroy one in succession every possible position of the balance-wheel and spring another. This is called the tourbillon escapement. several forms of it, and watches fitted with it often keep excellent time.

There are

Stop watches or chronographs are of several kinds. In the usual remains at rest, but which, when the winding handle is pressed in, and simplest form there is a centre seconds hand which normally A second pressure arrests its path, enabling A third pressure almost is linked on to the train of the watch and begins to count seconds, usually by fifths. instantaneously brings the seconds hand back to zero, this result the time to be taken since the start. being effected by means of a heart-shaped cam which, when a lever presses on it instantaneously, flies round to zero position. The number of complete revolutions of the seconds hand, i.e. minutes, is recorded on a separate dial.

Calendar work on watches is, of course, fatal to great accuracy of time-keeping, and is very complicated. A watch is made to record days of the week and month, and to take account of leap years usually by the aid of star-wheels with suitable pauls and stops. The type of this mechanism is to be found in the calendar motion of an ordinary grandfather's clock.

Watches have also been made containing small musical boxes and arranged with performing figures on the dials. Repeaters are striking watches which can be made at will to strike the hours and either the quarters or the minutes, by pressing a handle which winds up a striking mechanism. They were much in vogue as a means of diswhen to obtain a light by means of flint and steel was a troublesome covering the time in the dark before the invention of lucifer matches, affair. From what has been said it will be seen that for many years the form of escapements and balance-wheels has not greatly altered. The great improvements which modern science has been able to effect in watches are chiefly in the use of new metals and in the employment of machinery, which, though they have altered the form but little, have effected an enormous revolution in the price. The cases of modern watches are made sometimes of steel, artificially blackened, sometimes of compounds of aluminium and copper, known as aluminium gold. Silver is at present being less employed than formerly. The hair-springs are often of palladium in order to render the watch non-magnetizable. An ordinary watch, if the wearer goes near a dynamo, will probably become magnetized and quite useless for time-keeping. One of the simplest cures for this accident is to twirl it rapidly round while retreating from the dynamo and to continue the motion till at a considerable distance. The use of invar has been already noticed.

It would be impossible to enumerate, still more to describe, the vast number of modern machines that have been invented for making watches. It may be said briefly that every part, including the toothed wheels, is stamped out of metal. The stamped pieces are then finished by cutters and with milling machinery. Each machine as a rule only does one operation, so that a factory will watchmaker therefore is not so much of a craftsman as an engineer. contain many hundreds of different sorts of machines. The modern The effect of making all the parts of a watch by machinery is that each is interchangeable, so that one part will fit any watch.

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