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CONSTBUCTION OF LOCKS AND KEYS. 23 of course be crushed, and the contents destroyed, in case of timbers, or brickwork, falling upon them. They should consist of a double casing of strong wrought-iron, the intermediate space being filled with a good non-conducting substance; bolts should shoot out from all sides of the door, so that if the whole building fell, the iron safe would not be injured either by the heat, or by the fall of the materials. The best practical proof of the efficiency of strong, well-constructed fire-proof safes, was, that of some thousands made on this principle by Mr. Chubb, there was not a single instance ot a failure having occurred from any cause. Some years ago, one of Chubb's locks, fixed on a common iron safe, was forced open by a burglar's instrument, called a " Jack-in-the-Box." That instrument was of such ingenious construction as to demand a particular description. anvil - fire!—(Fig. 9.) Fig. 9, JACK-IN-THE-BOX. 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 stock A, and turned backwards, or forwards, by the handle of the lever E. The point of the screw D was made hollow, to receive a straight steel bar F. G was a steel clamp, with square shoulders at each end. The manner in which this instrument was used to open doors and safes might be thus described. One end of the clamp G was inserted sideways into the keyhole, and turned a quarter round, whilst the other end was slipped into the groove H in the stock. The point of the screw g was then screwed up close to the front of |
On the Construction of Locks and Keys by John Chubb