fig. 64.
The writer may observe that it was the study of the circumstances of the great gold robbery on the 15th of May, 1855, by Agar and his confederates (when two of the best lever locks were picked, and gold stolen weighing upwards of 200 lbs., while in transit on the South-Eastern Railway from London to Paris, packed in three sealed iron-bound boxes, inclosed in a bullion safe, secured by those locks), and of the various modes of picking locks, which led him to turn his attention to the achievement of what had been so long and perseveringly sought after, namely, an unpickable lock. The principle of a detached bit has been previously tried, in so far as that locks have been made in which the bit of the key was deposited in the lock by unscrewing the key stem, and then withdrawn by screwing in the stem again. But inasmuch as the detached bit, even though it failed to open the lock in the case of a counterfeit key, could always be brought back again to the keyhole and removed, this admitted of a repetition of attempts with successive alterations of the one counterfeit key, without the certainty that any warning would be given by the lock of such attempts having been made.
In another still more complicated lock with a detached bit there were two keyholes, into one of which the bit of the key was put, and the stem being then unscrewed from the bit, was put into the second keyhole and turned round so as to close the first keyhole over the bit; a separate handle was then turned to work the lock, six separate operations being required for either opening or closing the lock. Further, a kind of retainer has been attempted by so arranging the lock that, if any key was put in but the right one, it was held in the keyhole in such a manner that it could never be got out. In this case, however, if the false key would not open the lock, neither would it let even the right one do so, and it would be necessary to break open the door secured by the lock.
In the new lock here described, the special points that have been aimed at are the following:—
Firstly, in no position of the lock is there any access to the works from the outside through the keyhole. This access through the keyhole is more or less a defect in all other principles of lock, as it admits of feeling and manipulating the works for the purpose of getting information for picking the lock in the absence of the right key; whereas in the new lock there is no opening whatever at any time, except the two plain parallel recesses into which the key and the bit are fitted. From the moment the turning of the lock commences both these recesses are effectually blocked up: the one for the bit being conveyed bodily away from the keyhole, and its place taken by the solid metal of the cylinder; while the other is completely filled by the key, which cannot be withdrawn except by turning it back to the original position. In consequence of this construction no injury can be done to the lock by explosion of gunpowder in the keyhole, the only openings from the outside being parallel at their sides, and not communicating with any portion of the interior of the lock; and the simplicity and solidity of construction are such that the revolving cylinder is made practically air-tight within its bearing. This effectually prevents all attempts to open the lock by picklocks, and leaves no alternative but the attempt to make a sufficiently accurate copy of the true key.
Secondly, as no clue whatever can be obtained from the outside of the lock respecting the key required, the attempts upon the lock are thus limited to the chance of obtaining a wax impression of the true key. The difficulty of making a counterfeit key sufficiently correct by this means for opening one of the best of the previous constructions of lock is very great; but in the new lock this difficulty is greatly increased by the fact of the levers remaining absolutely stationary while the stump enters the gatings, in consequence of which the gatings are made so close a fit to the stump that an exceedingly minute error in the lifting of any of the levers is sufficient to prevent the lock being opened. This extreme delicacy of construction can be carried out practically without objection in the new lock, because there is no possibility of putting a strain from the key upon the stump, so as to cause injury by forcing it at the moment of entering the gatings; for the only force acting upon the stump at that time is the uniform pressure of its own spring. In addition to this source of increased safety, there is the still more important circumstance that only a single trial can be made of each counterfeit bit; because, if carried forwards far enough to try its effect in opening the lock by passing the levers, the bit is inevitably lost by falling through the lock and inside the door. Thus not only is all chance prevented of a second trial with the same key, but the bit retained inside the door gives warning of the attempt having been made, and shows how near the counterfeit key has approached to the original. The numerous cases that have occurred of attempts to open locks by counterfeit keys, such as the remarkable instance previously referred to, show that even with the most practised hands it is next to impossible to make from a wax impression a key that will serve for opening a good lock the very first time it is tried; and the striking importance is therefore seen of this arrangement in the new lock, which prevents more than a single attempt being made with a counterfeit.
Thirdly, another advantage to be named in this lock is that the stem alone of the key is required to lock it, but it can only be unlocked by the complete key. The stem, therefore, can be left by the principal of an establishment for locking up by a subordinate; but the bit, which is the essential part of the key required for opening the lock, need never be used or seen by any one but the principal himself. As the hole in the external door-plate for the stem of the key has a notch on one side only to admit the key stem, and the cylinder is prevented from making a complete revolution, the stem of the key cannot be withdrawn from the lock except when the bolt is shot; so that its absence from the keyhole serves as a proof that the bolt is shot.
Fourthly, one other advantage in this lock is its simplicity and solidity of construction. It contains no more parts than the simpler forms of lever lock having the same number of levers, and the total number of separate pieces in the complete lock is only sixteen. The principle of security, therefore, upon which the new lock is constructed, avoids entirely the complications and the delicate and minute class of work rendered necessary in other locks by the use of detectors and the other auxiliary contrivances employed for increasing the difficulty of picking.
Mr. Fenby exhibited, at a conversazione of the Institute of Civil Engineers, and at the meeting of Mechanical Engineers, specimens of his adytic lock, and showed its action both with the true key and with counterfeit keys; and he showed by trial that the counterfeit failed to open the lock, notwithstanding that by means of the permutating cutting machine it had been made a much nearer approach to a perfect copy than was practicable in the best handwork from a wax impression. He also exhibited the key-cutting machine employed for cutting the bits; and also a set of burglar’s tools employed for drilling into the door of an iron safe sufficiently for breaking open or removing the lock, showing that the hold required for giving the cutting pressure upon the powerful drill employed for the purpose was obtained by a steel cross piece inserted into the keyhole and turned at right angles, so as to hold across inside the lock; but in the new lock, as the keyhole had no opening into the lock, and only a slight shoulder on one side, no means were afforded for obtaining the required hold for the drill.