A key, perfectly square, with a screw turning within it, and more conceited than either of the rest, and no heavier than the triangle screwed key, and doth the same effects. No. LXXII. An escutcheon, to be placed before any of these locks with these properties. 1. The owner (though a woman) may, with her delicate hand, vary the ways of coming to open the lock ten millions of times, beyond the knowledge of the smith that made it, or of me who invented it. 2. If a stranger open it, it setteth an alarm a going, which the stranger cannot stop from running out; and, besides, though none should 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. NOTE. The two principal properties of this escutcheon may be readily contrived; and the first of them has, in fact, been already applied to a very ingenious padlock, invented by Mr. Marshall, and for which the Society of Arts voted him a reward of ten guineas. In Mr. M.'s escutcheon the letters or figures commonly used in the ring padlock allow an almost endless variety of changes, and the owner may in one minute alter the arrangement in such a manner that even the maker would experience as much difficulty to open it, as an entire stranger to its construction. To render the combination of letters variable, the characters must not be engraved upon the outside of the rollers themselves, but upon a thin brass hoop made to fit on its outer surface; and a spring fastened to the roller, and pressing upon the inside of the hoop, will cause a sufficient degree of friction to make them move together. The other part of this invention is equally simple with the preceding. An alarum, such as is attached to a clock, may easily be wound up prior to closing the box; and the lid provided with a chamfered bolt or staple, capable of effecting its discharge when the box is opened. To register the amount of money taken from the box, it will be necessary either to place each distinct piece of money in separate divisions, or to put a number together in one deep recess capable of admitting but one piece to pass at a time. As the pieces are shaken out, they will in their passage raise a lever capable of moving a wheel one division in the passage of each piece. The Bank of England have a method somewhat similar for registering the number of notes worked from the printing press of that establishment. No. LXXIII. A transmittable gallery over any ditch or breach in a town-wall, with a blind and parapet, cannon proof. No. LXXIV.