six steel sliders could be plainly seen, all radiating from the centre pin; at the end of the key there were six corresponding radiating notches, but the length of each notch was different.

In using the lock, the key was first pushed endways into the barrel as far as it would go, when it was felt to be entering in opposition to a spring. The key acted against all the six sliders at once, but it pushed back each slider to a different distance, according to the lengths of the several notches in the key, which were just suitable for placing each one in, what might be called, its unlocking position; and all the six sliders being so placed at the same time, they would leave the barrel at liberty to be turned round by the key; the bolt of the lock was shot, by a curious crank-pin motion, in a slot, but the key itself had no communication with the bolt, as in all other locks.

The machines, before mentioned, were adapted for cutting the grooves in the barrels, and the notches in the steel plates, with the utmost precision. The notches in the keys, and in the steel sliders were cut by other machines, which had micrometer screws, so as to ensure that the notches in each key should tally with the unlocking notches of the sliders in the same lock. The setting of these micrometer screws was regulated by a system, which ensured a constant permutation in the notches of succeeding keys, in order that no two should be made alike. Mr. Bramah attributed the success of his locks to the use of those machines, the invention of which had cost him more study than that of the locks; without the machines, the locks could not have been made in any great number, with the requisite precision, as an article of trade. There was great originality in those machines, which were constructed before analogous cases (beyond the clock-maker's wheel-cutting machines) were in existence. It might be concluded, that a good Bramah's lock was not easily picked, by finding out its combination; but unfortunately if a Bramah's key fell into dishonest hands, even for a very short time, an impression could be easily taken, and a false key as easily made. A turkey quill notched into the form of a key, had sufficed to open a Bramah's lock; and an efficient false key could be formed out of a pocket pencil-case. Such facility of fabrication was an invitation to dishonesty, and as an abortive attempt left no trace, the impunity was an encouragement to repeat the attempt until success was attained.

CHUBB'S LOCKS.

The original patent for Chubb's lock was taken out in the year 1818, by Jeremiah Chubb; this has been improved upon by the successive patents of Charles Chubb, in 1824; by Charles Chubb and Ebenezer Hunter, in 1833; by John Chubb, in 1846; and by John Chubb and Ebenezer Hunter, in 1847.

It will be sufficient to describe the last patented lock, which, while retaining the peculiarities of the former inventions, has received such modifications and improvements as were, in practice, found to be necessary.

It may here be stated, in order to render the drawing more intelligible, that Chubb's lock consists of six separate and distinct doubleacting tumblers, with the addition of a "detector," by which any attempt to pick, or open the lock, by a false key, is immediately notified on the next application of its own key. The detector is the great and peculiar feature by which Chubb's lock is so well known.

The wood-cut gives a representation of a lock made on this principle. A is the bolt, B the square stud riveted into, and forming part of the bolt; C are the tumblers, six in number, moving on the centrepin D, placed one over the other, but perfectly separate and distinct, so as to allow all of them to be elevated to different heights. E is a divided spring, forming six separate springs, pressing upon the ends of the six tumblers. F is the detector-spring. It will be observed, that the bottom tumbler has a tooth near the detector-spring. G is a stud, or pin fixed into, and forming part of the bottom tumbler, and H is the key. Now, it will be obvious, that the whole of the tumblers must be lifted precisely to the different heights required, to allow the square stud B to pass through the longitudinal slots of the tumblers, so that the bolt may be withdrawn. There is no means of telling when any one tumbler is lifted too high, or not high enough, much less can the combination of the six be ascertained; and if a false key should be inserted, and any one of the tumblers should be raised beyond its proper position, the detector-spring F, will catch the bottom tumbler C, and retain it, so as to prevent the bolt from passing; and thus, upon the next application of the true key, immediate notice will be given of an attempt having been made to pick the lock, as the true key will not then at once unlock it. By turning the key, however, the reverse way, as in locking, the tumblers will be brought to their proper bearing, allowing the bolt to move forward, and the stud B to enter into the notches I. The bevelled part of the bolt A will then lift up the detector-spring F, and allow the bottom tumbler C to fall into its place. The lock being now restored to its original position, may be opened and shut in the ordinary manner. It will be seen, that when the lock is detected, nothing but its own key can restore it to its former condition.

Chubb's lock was a very improved modification of Barron's, containing six double-acting tumblers combined together, and also possessing the important adjunct of the "detector." In no instance had one of Chubb's locks been opened by picklocks, and, indeed, with a combination of six tumblers, it became exceedingly difficult to make a false key sufficiently accurate to open a lock, because each step of the key required to be just sufficient to lift the tumbler, to which that step belonged; if the step was too long, the tumbler would be overlifted, and would thereby detain the bolt, or if the step was too short, it would not lift the tumbler high enough to release the bolt; no indication could be obtained by the trial of a false key in the lock, as to which of the steps was too long or too short. The lock would be secured against unlocking, by any one or more of the six tumblers being either overlifted or not lifted high enough; but it could not be ascertained which tumbler detained the bolt, or which step of the false key was incorrect. In such a state of uncertainty, all attempts to rectify the inaccuracy of the false key must be directed by mere guess, and alterations were as likely to be made in the steps which were nearly correct as in those which were wrong.

A convict on board one of the prison-ships at Portsmouth dockyard, who was by profession a lock-maker, and who had been employed in London in making and repairing locks for several years, and subsequently had been notorious for picking locks, asserted that he had picked, with ease, one of the best of Bramah's locks, and that he could pick Chubb's locks with equal facility. One of the latter was secured by the seals of the late Sir George Grey, the commissioner, and some of the principal officers of the dockyard, and given to the convict, together with files, and all the tools he stated to be necessary for preparing false instruments for the purpose; as also blank keys to fit the pin of the lock, with a lock exactly the same in principle, so that he might examine it, and make himself master of its construction: promises of a reward of £100 from Mr. Chubb, and of a free pardon, were also made to him in the event of his success.

After trying for two or three months to pick the sealed lock, during which time, by his repeated efforts, he repeatedly overlifted the detector, which was as often undetected, or re-adjusted, for his subsequent trials, he gave up the attempt, saying that Chubb's were the most secure locks he had ever met with, and that it was impossible for any man to pick or to open them with false instruments.

Chubb's locks, like the others, are made in series, having a separate and different key to each, and a master key for opening any number that may be required. So extensive are the combinations, that it would be quite practicable to make locks for all the doors of all the houses in London, with a distinct and different key to each lock, and yet that there should be one master key to pass the whole.

A most complete series of locks was constructed, some years ago, by the late Mr. Chubb, for the Westminster Bridewell. It consists of about eleven hundred locks, forming one series, with keys for the master, sub-master, and warders. At any time the governor has the

power of stopping out the under keys, and in case of any surreptitious attempt being made to open a lock, and the detector being thrown, none of the under keys will regulate it, but the governor must be made acquainted with the circumstance, as he alone has the power, with his key, to replace the lock in its original state. These locks, although they have been in constant wear for sixteen years, are still in perfect condition.

In order to ascertain the result of friction on Chubb's detector lock, one of them was subjected to the alternate rectilinear motion of a steam engine, in Portsmouth dock-yard, and was locked and unlocked upwards of four hundred and sixty thousand times consecutively, without any appreciable wear and tear being indicated by a guage applied to the levers and the key, both before and after this alternate

The lock patented by John Chubb in 1846 is especially intended for the fastenings of bankers' and merchants' strong rooms, and other analogous uses. It is called "The Quadruple Lock," and consists of a combination of four separate and distinct locks in one, all being acted upon at the same time by a single key with four bits. It will be seen in the above figure, that the main bolts are attached to an eccentric wheel, throwing them each way; and to these bolts ten, or twenty bolt-heads may be fitted. The quadruple lock has six tumblers in each set, making altogether twenty-four tumblers, all of which must be acted upon simultaneously, by the motion of the proper key, before the eccentric wheel can be turned; it is thus utterly impossible, from

the extensive combinations, for any attempt by a false instrument to succeed in unlocking it.

As a further security, there is a check-lock, with a small key which throws a hard steel plate over the large key-hole. Thus, in a banking establishment, a confidential clerk may carry the quadruple key, and the principal having the smaller key can at all times prevent the fire-proof safe, or strong room from being opened, unless in his own presence.

"JACK IN THE BOX."

We stated some time since that we had recently had our confidence in the apparent security of an iron strong-room door very much shaken by the inspection of an instrument most ingeniously and skilfully constructed, expressly for the purpose of tearing out the centre locks of iron doors. It is in the possession of Messrs. Chubb, of St. Paul's Church-yard, and was presented to them by the Commissioners of the Metropolitan Police, by whom it was taken from some burglars. We have now the opportunity of giving an engraving of it, which will explain its construction better than any written description. It is well known to the thieving fraternity by the name of the "Jack-in-the-Box." It is small in compass, so that it might be easily carried about the person, and yet it has the power of lifting three tons weight; and the pressure being applied to the key-hole of an iron door of the ordinary kind, it will force the door open in less than fifteen minutes!

The following is a description of this formidable instrument :A was the stock, made of solid brass; B was a strong screw with a point, which was worked at the end C by means of a spanner, or lever key, E. D was a powerful screw, working in the upper part of the