And in some verses by Carew, written about the same time, there is an analogy drawn, in which one of the things compared is—

In the Memorabilia of Vanhagen von Ense, written about the middle of the seventeenth century, a commendatory notice is given of a letter-lock, or combination-lock, invented by M. Regnier, Director of the Musée d’Artillerie at Paris. “Regnier,” we are told, “was a man of some invention, and had taken out a patent for a sort of lock, which made some noise at the time. Every body praised his invention, and bought his locks. These consisted of broad steel rings, four, five, or eight deep, upon each of which the alphabet was engraved; these turned round on a cylinder of steel, and only separated when the letters forming a particular word were in a straight line with one another. The word was selected from among a thousand, and the choice was the secret of the purchaser. Any one not knowing the word might turn the ring round for years without succeeding in finding the right one. The workmanship was excellent, and Regnier was prouder of this than of the invention itself. The latter point might be contested. I had a vague recollection of having seen something of the sort before; but when I ventured to say so, my suspicions were treated with scorn and indignation, and I was not able to prove my assertion; but many years afterwards, when a book, which as a boy I had often diligently read, fell into my hands, Regnier’s lock was suddenly displayed. The book was called Silvestri a Petrasancta Symbola Heroica, printed at Amsterdam in 1682. There was an explanation at p. 254, attached to a picture; these were the words:—Honorius de Bellis, serulæ innexæ orbibus volubilibus ac literatis circumscripsit hoc lemma—Sorte aut labore.[3] However, neither luck nor labour would have done much more towards discovering the secret of opening Regnier’s locks, from the variety of their combinations; and their security seemed so great, that the couriers’ despatch-boxes were generally fastened with them.”

This curious extract, which was brought forward by Mr. Chubb, in a paper on locks and keys (read before the Institution of Civil Engineers in 1850), seems to take away the credit from one (Regnier) with whose name the letter-lock has been most intimately associated. We shall presently explain, however, what it was that Regnier effected towards perfecting the letter-lock. In the meantime it may be interesting to note that the British Museum contains a copy of the work mentioned by Vanhagen. At the page indicated there is an engraving (a fac-simile of which is given in fig. 5) containing a drawing of a veritable puzzle or letter-lock; the lock consists of a cylinder or barrel, on which seven rings work; each of these rings is inscribed with letters, and the ends of the cylinder are grasped by a kind of shackle.

It was a natural result of the arrangement of the letter-lock, as invented (conjecturally) by Cardan, that only one particular word or cipher or key could be used in each lock; and it was to increase the puzzle-power of the lock that Regnier doubled all the rings, making each pair concentric, and enabling the user to vary the cipher at pleasure.

The principle of the letter-lock, when applied to doors, requires that sort of modification which renders it what is termed a dial-lock. There are to such a lock one or more dials, with a series of letters or figures stamped on them; there is to each dial a hand or pointer connected by a spindle with a wheel inside the lock; on the wheel is a notch which has to be brought to a certain position before the bolt can be moved. There are false notches, to add to the difficulty of finding the true notch in each wheel. To adjust the notches to their proper position, a nut on the back of the wheel is loosened, and the pointer is set at any letter or figure chosen by the user. The pointers and the dials perform the part of the outer rings, the wheels that of the inner rings; and it is easy to see that the same leading features prevail in the two kinds of lock, however they may differ in detail.

These dial-locks have not been numerous; they require wheel and pinion work within the body of the lock, which gives delicacy and complication to the mechanism. The letter padlock, be its merits great or small, is strong and durable, not liable to get out of order; and in so far as it requires no key or key-hole, it occupies rather a special position among locks. One of our great “merchant-princes” has been a letter-lock inventor, as the following will shew.

Early in 1852, Mr. William Brown, the distinguished member for South Lancashire, read a paper before the Architectural and Archæological Society of Liverpool, of much interest in relation to our present subject. His object was to describe a letter-lock which he had invented, and which had up to that time given high satisfaction. We cannot do better than transcribe the paper, as reported in one of the Liverpool Journals, with a few abridgments.

“As your society are desirous of seeing any improvements or attempts at them, I send you a stock-lock for inspection. The idea for its construction I took from a letter-padlock. I had a lock of this description made by Mr. Pooley twenty-five years ago, which has been in use ever since on Brown, Shipley, and Co.’s safe....

“Its advantages I conceive to be—First, it cannot be picked, for there is no key-hole. Second, it cannot be blown up by gunpowder, for the same reason. Third, you cannot drill through the door so as to reach the lock, for you are intercepted by a steel plate on which your tools will not act: thus you cannot introduce gunpowder that way to force the lock off. Fourth, you cannot bounce off the wheels in the interior with a muffled hammer, for vulcanised India-rubber springs resist this. Fifth, you cannot drill the spindles out, as their heads are case-hardened. Sixth, you cannot drive them in, for they are countersunk in the door about half-way through....

“Now let us set the lock to the word W O O D (any other four letters might be used). When you set the lock, make a private record of them, so that you may not forget them. If parties do not know your letters, nothing but violence, applied by some means or other, can enable them to get into your safe; for the lock will not open to any thing but its talisman. Take off all the large wheels and open the lock: you will see that the large wheels have a number of false chambers; if you get the spurs of the bolt into three real chambers and one false, you are as fast as ever, for all four must be right.

“Having placed your key and pointer outside the door to point to W on brass-plate No. 1, the small wheel inside obeys the same impulse; then maintain your small wheel steadily on this point, and the large wheel No. 1 will only fit on at the right place, the true opening compartment being opposite the spur of the bolt. It being necessary at the time you set your lock that it should be open, proceed with Nos. 2 and 3 in the same way, your pointer standing steadily at O. No. 4 is the same, the pointer being held steadily at D. You should then shoot your lock two or three times, to be sure you have made no mistake. Every time you shoot your bolts out, turn your wheels away from the true chamber, and see when you again turn your pointers to W O O D that your lock opens freely; it is the proof that you have made no mistake, and you may now venture to lock your safe. When you unlock the door, and find it necessary to leave it open for a time, you should shoot the bolts as if locked, and turn the wheels, so that no one may find what your real letters are; and again adjust them to their proper places, in order that the bolt may go back and enable you to re-lock. Once having locked the door and turned the wheels from your real letters, you need not trouble yourself with carrying the key, but leave it in any place beside the lock.

“I believe two wheels would make a perfectly safe lock; three would be quite so. I adopted four to make security doubly sure, as it would be impossible in any given time to work the changes. On two wheels by chance the lock might open; you can, however, calculate the chances against this; and also three or four, the false compartment on the outer rim being taken into calculation. ***

“If this lock is of any value, it should be known; if it has weak points, let them be pointed out, and they may admit of a remedy; for we ought not to be led to believe a lock is safe which is not so.”

In relation to the “first advantage” which Mr. Brown not unreasonably supposed to be possessed by his lock—viz. that “it cannot be picked, because it has no keyhole”—we shall have something to say in a future page, where certain fallacies on this subject will be noticed. In the meantime we may remark, that it is not a little creditable that a leading Liverpool merchant should have invented a lock worthy of occupying a position on his own safe for a quarter of a century; for we may be quite certain that he would not have allowed the lock to maintain that post of honour unless it had really (so far as experience had then gone) served worthily as a safeguard to his treasures. And if it were possible to collect all the by-gone specimens of lock-oddities, we should probably find among them many highly-ingenious letter-locks; for supposing a man to have a mechanical turn of mind, a lock is by no means an unworthy medium for displaying it; the pieces of metal are so small as to be easily manageable at a small work-bench in a small room. The fondness for this sort of employment evinced by the unfortunate Louis XVI. of France led to the common remark, “He is a capital locksmith, but a very bad king.”

In an amusing article in the Observer, during the progress of the “lock controversy,” was the following paragraph relating to combination-locks of the letter or puzzle kind: “The French, in their exposition of 1844, availing themselves of the permutation principle, produced some marvels in the art; but the principle has not been adopted in this country. The Charivari had an amusing quiz upon these locks when they first came out. It said the proprietor of such a lock must have an excellent memory: forget the letters, and you are clearly shut out from your own house. For instance, a gentleman gets to his door with his family, after a country excursion, at eleven o’clock at night, in the midst of a perfect deluge of rain. He hunts out his alphabetical key, and thrusts it into his alphabetical lock, and says A Z B X. The lock remains as firm as ever. ‘Plague take it!’ says the worthy citizen, as the blinding rain drives in his eyes. He then recollects that that was his combination for the previous day. He scratches his head to facilitate the movement of his intellectual faculties, and makes a random guess B C L O; but he has no better success. In addition to his being well wet, his chances of hitting on the right combinations and permutations are but small, seeing that the number is somewhere about three millions five hundred and fifty-three thousand five hundred and seventy-eight. Accordingly, when he comes to the three-hundredth he loses all patience, and begins to kick and batter the door; but a patrol of the National Guard passes by, and the disturber of the streets is marched off to the watch-house.”

CHAPTER IV.
WARDED LOCKS, WITH THEIR VARIED APPENDAGES.

The more ordinary locks are of an oblong quadrangular shape. In nearly all of them, either a bolt shoots out from the lock, to catch into some kind of staple or box, or a staple enters a hole in the edge of the lock, and is there acted upon by the bolt. A common room-door lock will illustrate the first of these kinds, a tea-caddy lock the second. The key, as is well known, enters a receptacle made for it; and the shaft of the key generally serves as a pivot or axis around which the web or flat part of the key may move in a circular course. During this movement the web acts directly or indirectly on the bolt, driving it in or out according to the direction in which the key is turned; the key impels the bolt one way, certain springs act upon it in another, and the balance between these two forces determines the locking and unlocking of the bolt. Wards, or wheels, are contrivances for rendering the opening difficult without the proper key; and it is of warded locks that we shall chiefly treat in this chapter.

The annexed cut, fig. 6, represents the interior of an ordinary back-spring lock, without tumblers. Such a lock may usually be known from a tumbler-lock by this simple circumstance, that it emits a smart snapping noise during the process of locking, occasioned by the pressure of the spring when the bolt is in a particular position. In the woodcut the bolt is represented half out, or half shot. At a a are two notches on the under side of the bolt connected by a curved part; b is the back spring, which becomes compressed by the passage of the curve through a limited aperture in the rim c c of the lock. When the bolt is wholly withdrawn, one of the notches a rests upon the rim c c; and the force with which the notch falls into this position, urged by the spring b, gives rise to the snapping or clicking noise. When the bolt is wholly shot, the other notch rests in like manner upon the edge of the aperture in the rim.

It must be obvious at a glance, that this back-spring lock is objectionable on the score of security, on account of the facility with which the bolt may be forced back by any pressure applied to its end, a pressure which may often easily be brought to bear. At the centre of the lock is seen the end of the key acting on a notch in the bolt, and surrounded by wards.

It is not at a first glance that the relation between the clefts in a key and the wards of a lock can be duly appreciated; because the wards present themselves to view as portions of circles to which nothing in the key seems to correspond; but if it be borne in mind that the key has a rotary motion within the key-hole around the pipe or barrel as an axis, the circular form of the wards will be accounted for, and their section will be regarded as exhibiting the looked-for relation to the wards of the key. In the annexed cut, for example (fig. 7), which represents a portion of the interior of a warded lock, the curved pieces of metal are the wards (two in this case); and there are two clefts in the bitt of the key to enable the latter to take its circular course without interruption from the wards. If the clefts were other than they are, either in number, position, or size, this freedom of the key’s movement could not be obtained.

When once the opinion became established that a lock is rendered secure by virtue of its wards, (a theory which we shall have to discuss in a later page,) much ingenuity was displayed in varying the wards of the lock, the clefts of the key, and the shape of the keyhole. Even if the two former were unchanged, a change in the latter might add to the puzzlement of the arrangement. For instance, in the annexed cut (fig. 8), all the six keys represented may have clefts or cuts exactly alike, all alike adapted to the wards of one particular lock; yet the differences in the thickness of the web are such, that if the keyholes were shaped in conformity therewith, each keyhole would be entered by one of these keys; b and c differing from a in the relative thickness at different points, and d, e, and f having certain curvatures and cavities not to be found in the other three.

But without waiting for the detailed examination of the relative security and insecurity of locks, we may at once shew how simple is the principle which renders the warded system fallacious. In fig. 9 we shall be able to illustrate this. Numbers 1, 2, and 3, all appear very different keys, and it is quite true that neither one would open a lock adapted for either of the other two; and yet the very simple arrangement No. 4 would open all three. This No. 4 is called a skeleton-key; and the relation which it bears to the others may be expressed in the form of a proposition thus: at any point where there is solid metal in all the keys, there must (or may) be solid metal in the corresponding part of the skeleton-key; but at any point where there is a vacancy or cavity in any of the keys, there must be a cavity in the corresponding part of the skeleton-key. If Nos. 1, 2, 3, 4, be examined, this proposition will be found to be borne out; there is so much cavity in No. 4 that it avoids the wards in all the three locks, nothing being required but the tongue of metal to move the bolt. Sometimes, to add to the safety, wards are attached to the front as well as the back plate of the lock; and then there may be a double series of notches required in the key, such as in No. 5; but if this be compared with Nos. 9, 10, 11, it will be found that although no one of the four would open a lock adapted for either of the other three, yet the skeleton-key No. 12 would master them all, having cavities wherever any of the others have cavities. This is the theory of the master-key, by which one key may be made to command many locks. Nos. 6 and 7 have complicated wards; but the key is so much cut up as to be weakened more than is desirable. No. 8 enables us to point out the difference between two distinct classes of keys. Keys with pipes or barrels fitting on a pin or pipe-shaft can only open a lock on one side of the door or box; but a key with a solid stem, as No. 8, has the clefts so cut as to open the lock from either side, as in a street-door lock: it is, in fact, two warded keys fixed end to end, only half of which is employed at one time in opening the lock.

Some of the warded locks of the last century are curious. While the idea prevailed that a complicated ward gave security, there was room for the exercise of ingenuity in varying the shape of the wards. Fig. 10 is copied from the great French work. It represents the cuts in the key, and also (seen perspectively) the complicated forms of the pieces of metal which constitute the wards corresponding with those cuts. The aperture in the key at 16 fits upon the metal surrounding the keyhole at 18; and the M-shaped cuts at 17 fit in like manner upon the similarly-shaped metal pieces at 19.

Another example of a similar kind is shewn in fig. 11, where an anchor appears to have been the favourite form. The anchor cuts in the key are shewn at 26; while in the wards the bottom of the anchor is near the keyhole at 28, and the top at 29.

A similar illustration occurs in fig. 12, where the star-like cuts at 34 on the key correspond with the star-like wards at 33.

From the fifteenth to the eighteenth centuries locks were made in France, on which a vast amount of care and expense was bestowed. They were, in an especial degree, decorative appendages as well as fastenings. They were of three kinds: room-locks, buffet-locks, and chest-locks; they were fixed on the outside of the door or lid, so as to be fully visible. The key had a multitude of perforations which bore no particular relation to the wards of the lock, but which were regarded as tests of the workman’s skill. The honorary distinctions awarded to apprentices and aspirants in the art depended very much on the number and fine execution of these perforated keys. The locks, considered as fastenings, had slender merit; although usually throwing four bolts, they were not very secure. Fig. 13 represents the exterior of a lock made about the year 1730, by Bridou, a celebrated Parisian locksmith. It was a lock belonging to a coffer or strong chest; all the works being sunk below the level of a carved architectural moulding or ornament. There is a secret opening near the part C, forming a portion of the ornamental design; it allows a bolt, shewn at D, fig. 14, acted on by the spring E, to be touched, by which a doorway opens upon the hinges at B B. A A are a sort of pilasters, which aid in forming a hold for the bolts. The little ornament at C is drawn down by the hand, opening the secret door and revealing the key-hole G. S S, O O, Z Z, are ornaments fastened on at b c d, fig. 14, by nuts and screws, intended to display the skill of the workman. The lock itself, access to the keyhole of which is obtained within the secret door, has nothing very remarkable about it.

Mr. Chubb, in his paper read before the Institute of Civil Engineers, illustrated the insecurity of the warded lock by the example of one which had actually been placed in the strong-room of a banking house, and which is represented in the annexed cut (fig. 15). The wards are here shewn, surrounding the central key-pin; and from the appearance of the key, shewn at a, it is evident that these wards must have been rather complex. But the uselessness of the wards was proved by the result. A burglar employed an instrument, shaped like that at b, having on one of its faces, or sides, a layer of wax and yellow soap; this instrument, being introduced through the keyhole and turned a little way round, brought the soft composition in contact with the ends of the wards, and these ends thus left their impress on the composition. A false key was then made, as at c, which, however clumsy it may appear, has a cavity, or vacuity, where there is a cavity in the true key; and by such a surreptitious instrument was the lock opened. Even so rude an instrument as d, by passing round the wards, might open such a lock.

We are somewhat anticipating the full consideration of this subject; but it is desirable at once to explain how and why an improvement on the warded lock was sought for.

In connexion with the fanciful eighteenth-century locks, lately adverted to, we may remark, that no less a man than Louis XVI. was an amateur workman in this department of mechanical art—or at least in smith’s work, which in France is generally considered to include lock-making. Sir Archibald Alison says, in his History of Europe:—“He had an extraordinary fondness for athletic occupation and mechanical labour; insomuch that he frequently worked several hours a-day with a blacksmith of the name of Gamin, who taught him the art of wielding the hammer and managing the forge. He took the greatest interest in this occupation, and loaded his preceptor in the art with kindness; who returned it by betraying to the Convention a secret iron recess which they had together worked out in the walls of the cabinet in the Tuileries, wherein to deposit his secret papers during the storms of the Revolution.” There are not wanting indications that the unfortunate monarch wrought upon locks, as well as upon safes and strong-rooms.

Besides wards, there have been numerous other contrivances for adding to the security of locks—including screws, escutcheons, spiral springs, wheel-and-pinion work, alarums, and multiple bolts. As these are not of sufficient importance to be treated in separate chapters, we shall here give just so much notice of them as will illustrate their general character. Some of them are found combined with the “tumbler” principle, presently to be described; but all of them, it is now well known, were employed in various, ways when the tumbler lock was but little understood, and when the warded lock was held in esteem.

The Marquis of Worcester, whose curious Century of Inventions, written nearly two hundred years ago, contains so many suggestions which ingenuity has since developed into practical completeness, gives four of his inventions in the following words:—

69. “A way how a little triangle screwed key, not weighing a shilling, shall be capable and strong enough to bolt and unbolt, round about a great chest, an hundred bolts, through fifty staples, two in each, with a direct contrary motion; and as many more from both sides and ends; and, at the self-same time, shall fasten it to the place beyond a man’s natural strength to take it away; and in one and the same turn both locketh and openeth it.

70. “A key with a rose-turning pipe and two roses pierced through endwise the bit thereof, with several handsomely contrived wards, which may likewise do the same effects.

71. “A key, perfectly square, with a screw turning within it, and more conceited than any of the rest, and no heavier than the triangle screwed key, and doth the same effects.

72. “An escutcheon, to be placed before any of these locks, with these properties: First, the owner, though a woman, may with her delicate hand vary the ways of causing to open the lock ten millions of times beyond the knowledge of the smith that made it, or of me that invented it. Second, if a stranger open it, it setteth an alarum a-going, which the stranger cannot stop from running out; and besides, though none shall be within hearing, yet it catcheth his hand as a trap doth a fox; and though far from maiming him, yet it leaveth such a mark behind it as will discover him if suspected; the escutcheon or lock plainly shewing what money he hath taken out of the box to a farthing, and how many times opened since the owner had been at it.”

Mr. Partington, in his edition of the marquis’s singular work, makes a few comments on these lock-and-key contrivances. He says that the lock is evidently intended to operate on the principle of applying a screw for the purpose of moving the bolt, instead of using a key as a lever for this purpose. That such a plan might be applied to locks generally, he observes, there can be no doubt; and by a similar contrivance the large keys at present in use for outer doors, iron chests, &c. might be advantageously reduced by this means. By employing the escutcheon mentioned by the marquis, much additional security would be obtained. It must be confessed, however, that many of the marquis’s statements are difficult to credit.

The escutcheon has been a favourite resource with lock-makers. Mr. Mordan’s escutcheon, for instance, introduced before the Society of Arts in 1830, is a contrivance to be placed temporarily over the keyhole of a door, to prevent the picking of the lock during the owner’s absence. The escutcheon, or “protector,” has a short pipe which, after the door has been locked, is thrust into the keyhole; attached to the pipe is a small lock, on Bramah’s or any other convenient principle, so contrived that, on turning its key, two lancet-shaped pieces fly out laterally and bury themselves in the wood. The escutcheon cannot be removed until the small key has reacted upon the small lock; and until this removal has taken place, the large key cannot reach the keyhole.

A curious application of the escutcheon principle attracted some attention among locksmiths about seventy years ago. One of the first premiums awarded by the Society of Arts, after the commencement of their “Transactions,” was to Mr. Marshall, for a “secret escutcheon,” in 1784. In his description of his new invention, he adverts to the marquis of Worcester’s wonderful escutcheon, and to the many attempts which have since been made to produce an apparatus which should realise the marquis’s description. He supposes that the letter padlock originated as one among many varieties of these imitative inventions; but this may be doubted. Mr. Marshall’s contrivance, however, was in effect an endeavour to improve upon the letter-lock. He considered it an objection that, in ordinary locks of this kind, the letter-rings admit of no variation of place; and he sought to remedy this defect. It is not so much a new lock, as an escutcheon for a lock, which he produced. There is a studded bar passing through a barrel; there are five rings which work concentrically on this barrel; there are letters on the outer surfaces of the rings, and notches on the inner surface; but when, by the usual puzzle-action of the rings, the notches in them have been brought into a right line with the studs of the bar, the result is, not that the hasp of a padlock is raised, but that the escutcheon is removed from the keyhole of an ordinary lock. Mr. Marshall’s contrivance, therefore, is not so much a ring padlock, as a puzzle-ring security for the escutcheon of a fixed lock.

Some locks work by a screw and a spiral spring, instead of an ordinary key. Mr. W. Russell received a silver medal from the Society of Arts, about thirty years ago, for a new mode of locking the cocks of liquor-casks. Under ordinary circumstances, as is well known, the cock of a barrel or cask is in no way secure from the action of any one who can approach near enough to touch it; and different methods have been adopted of obtaining this security or secrecy. One plan is to employ a perforated cap, soft-soldered to the barrel of the cock, immediately over the grooved plug, the top of which plug is formed to the shape of the perforation, and a socket-key of the same form is introduced to turn the plug or open the lock. Another plan is to employ an iron saddle or staple, passing over the plug and below the bottom of the cock, through which a bolt is put, and a pendent padlock attached. The first method is very inefficient; the second is much superior, and has been largely adopted for locking the cocks of coppers, stills, vats, and other large vessels. But Mr. Russell thought some further improvement wanted. He caused a hole to be bored through the barrel, and to some depth into the plug when the latter is in the position for closing the cock. A stud works into this hole in such a way, that when the stud is driven home, the plug cannot be turned or the lock opened. The stud is attached at its other end to a spiral spring connected with a screw; a key is employed, the hollow pipe of which has an internal screw; and when this key is inserted in the cock-barrel and turned twice round, it draws back the stud, and allows the plug to be turned round in the proper way for opening the cock.

It is not often that wheel-and-pinion work is introduced into locks; the delicacy, the costliness, the weakness, and the tendency to get out of order, would all militate against the frequent adoption of such a course. It is, however, adopted occasionally. Mr. Friend’s secret-lock, introduced to the notice of the Society of Arts in 1825, had a train of wheels which acted upon the bolt, driving it out whenever the circular arcs of three wheels moved against it, but allowing a spring to force it back again whenever a deep cleft in each of the wheels locked into a stud on the bolt. There were certain numbers on a guide-plate, and a power of combining these numbers in great variety; and a provision that the bolt could be unlocked only by the same combination of numbers which had locked it. The guide-plate was a separate piece of apparatus, carried in the pocket of the user as a companion to the key. The key was of no use without the guide-plate, nor the guide-plate without the key. The user ‘set’ the numbers on the guide-plate, then applied it to the face of the lock, then introduced the key into the key-hole, and turned the key partially round; the bolt was now shot, and the guide-plate removed. If the key were used without the guide-plate, the bolt might be locked, but it was always unlocked again by the time the key had made a complete circuit. There was considerable ingenuity in the idea of this lock; but we believe it never went further than a model. Indeed many of the locks elaborately described in books have never had an existence as acting working locks.

A very ingenious principle has been occasionally introduced, in which clock-work regulates the interval of time which must elapse before a lock can be opened, even with its proper key. The object is, to ensure the safety of the lock during a journey, or until a particular person be present, or until the locked article is conveyed to a particular room. A patent was taken out in 1831 for a lock on this principle by Mr. Rutherford, a bank agent at Jedburgh. Against the end of the bolt of the lock is placed a circular stop-plate, so adjusted that the bolt cannot be withdrawn until a particular notch in the rim of the circular plate is opposite the end of the bolt. The plate is put in rotation by clock-work. As the notch can be set at pleasure to any required distance from the end of the bolt, the lock may be secured against being opened, either by its own or any other key, until any assigned number of minutes or hours after it has been locked; for the plate may be made to revolve either slowly or quickly, by varying the number of wheels in the clockwork. When the lock is used for boxes or portable packages, the clockwork must be moved and regulated by a spring; but when it is applied to closets or safes, a descending weight and a pendulum may be employed. It is manifest that this system is susceptible of being greatly varied in its mode of application; and it has many points of interest about it. That a man cannot open his own lock with his own proper key, until the lock gives permission by assuming a particular state or condition, certainly strikes one as being susceptible of many useful applications, where time is an element taken into the account.

A curious alarum-lock was invented by Mr. Meighan, in 1836, in which the bell or alarum is not placed behind a door, as in many alarum contrivances, but within the lock itself. Two or more studs are placed on the bolt, which press against the lower end of a small tumbler; the movement of the tumbler elevates a hammer; but as soon as the point of the tumbler becomes released from the stud, a spring presses the hammer down forcibly, and causes it to strike against a small bell placed near it. This sounding of the bell will be repeated, during the shutting of the bolt, as many times as there are studs to act upon the point of the tumbler.

Much of the ingenuity which has been displayed in locks depends on the employment of multiple bolts, there being all the additional strength which results from the use of two or more bolts instead of simply one. Ordinary doors seldom afford us examples of these double bolts; but they may be frequently seen in cabinets and desks, where two staples fixed to the lid fall into two holes in the lock, and are retained by two bolts. The most remarkable and complicated varieties, however, are those in which the bolts, instead of shooting parallel and nearly together, shoot in wholly different ways; one up, one down, one to the right, one to the left, and so on. It is on safes, strong boxes, and the doors of strong rooms containing valuable treasures, that such locks are usually placed. The mechanism is such that the key acts upon all the bolts at once, through the intervention of levers and springs of various kinds.

The above woodcut represents a very curious specimen of these multiple-bolt locks. It is copied from the great French work; and the ponderous chest to which it is attached is, we are told by Réaumur, “known at Paris by the name of the strong German coffer.” He further says, “nothing is wanting in these coffers on the score of solidity. They are made entirely of iron; or if of wood, they are banded both within and without with iron; and can only be broken open by very great violence. Their locks are almost as large as the top of the coffer, and close with a great number of bolts. The one which we have engraved has twelve fastenings; they have been made with twenty-four, or more.” His next remark on the subject is a sensible one: “Notwithstanding the large size of these locks, and all the apparatus with which they are provided, they correspond but ill with the solidity of the rest of the coffer. If we have given a representation of one, it is chiefly to shew how little confidence one could have in such a lock, and what are its defects, in order that we may avoid them.” It is not difficult, by tracing the action of the several levers, to see how one movement of the key, in the centre of the lid, would act upon all the bolts. In the engraving (fig. 16) a, f, h, c, are the four corner bolts; six others, a d e, a d e, are on the long sides, three on each; and two, b g, on the short sides. Every bolt is provided with a spring, of which three or four are shewn at Z Z Z. There is no staple or box to receive each bolt; but all shoot or snap beneath the raised edge E running round the top of the box just within the exterior at A A. The keyhole in the front of the box at D is a deception or mask; the real keyhole is in the middle of the lid concealed by a secret door opened by a spring. When the key has moved the great central bolt, this acts upon the other bolts P Q R S T, &c.; V V are studs which act upon two of the bolts; Y Y are staples confining the great bolt; k, l, c, p, x, are small levers which transmit the action to the corner bolts; q, r, s, t, n, are the small levers which render a similar service to the side and end bolts; L L within the chest, and M M on the lid, are contrivances for limiting the movement of the latter; C H, H C are iron straps or bands by which the interior of the chest is strengthened. After all, this is not so much a lock as a series of spring latches.

If a lock can be picked, the picking is as effective whether the lock has one bolt or twelve bolts. This fact led Mr. Duce, in 1824, to construct, instead of a four-bolt lock, four distinct one-bolt locks, fixed in the same frame and opened by the same key; the bolts to be moved in succession instead of simultaneously. It would require four times as long to pick this as a four-bolt lock of similar action.

There have been many other varieties of the multiple bolt, but we need not stop to describe them.

CHAPTER V.
ON TUMBLER, OR LEVER LOCKS.

Security being the primary object in all locks, any considerations as to mechanical ingenuity and graceful decoration give place to those which relate to safety. A spring lock may be ingenious and even beautiful in its construction, but an imitative key will easily open it. Hence arose the invention of wheels or wards; and as wards failed in trustworthiness, they in their turn yielded to something better. We have already explained how the insecurity of mere warded locks arises; and we shall have something more to say on the subject in a future chapter. It is sufficient here to remark, that wards, springs, screws, alarums, wheel-work, escutcheons,—all, however useful for particular purposes, are wanting in the degree of surety which we require in a lock. Hence the invention of tumblers, levers, or latches, which fall into the bolt and prevent it from being shot until they have been raised or released by the action of the key. We have been unable to ascertain at what time, or in what country, or by whom, tumbler-locks were invented. The invention has been claimed by or for persons subsequently to the year 1767, when the celebrated French treatise (Art du Serrurier) already referred to was published; and yet this treatise contains numerous examples of simple tumbler locks of ingenious construction, as will presently be shewn.

One of the most elementary forms of tumbler-lock is shewn in fig. 17. In this case the bolt, instead of having two notches in the bottom edge, like those in the back-spring lock, fig. 6, has two square notches or slots in the upper edge; and as the key acts upon the bolt, these notches must of course share in whatever movements the bolt is subjected to. Behind the bolt is a kind of latch or tumbler (the lower part of which is shewn by dotted lines), with a stump or projecting piece of metal at a; the tumbler moves freely on a pivot at the other end, and is made to rise through a small arc whenever the key acts upon the bolt. When the bolt is wholly shot, the stump falls into one notch and prevents the motion of the bolt; when wholly unshot or withdrawn, the stump falls into the other notch, and equally prevents the motion of the bolt. It is not, therefore, until the key, by elevating the tumbler, has raised the stump out of the notch, that the bolt has freedom of movement. If the shape of the key does not enable its web to effect this elevation to a sufficient degree, the bolt remains immovable; and to this extent a certain additional security is obtained by making the shape of the key significant as well as the wards.