at Naples, the long bar at the top denoting its descent from the Roman padlock, although the construction of the lock is different. We now come to the principle of the revolving key in common use at the present time. It has been already shown that in using the Roman lock (figs. 15B to 20B, Plate III.) the part of the key containing the pins had to be put in vertically, and then turned a quarter circle, so as to bring the teeth horizontally beneath the tumblers previously to lifting them. It is possible that this may have suggested the first idea of employing the twist thus given to the key to the shooting of the bolt. Fig. III, Plate IX., taken from M. LIGER'S work,[34] represents a Roman key found in London; it has a plate furnished with teeth, evidently intended to raise tumblers, and the stem of the key is piped for the purpose of fitting into a broach or pin, so that the plate with the teeth, when the key is turned round on its pivot, may fit into its proper place beneath the bolt and raise up the tumblers. Fig. 112, Plate IX., is a drawing of another key similarly formed, having two teeth and a piped stem; it was found in Lothbury, in London, 16 feet beneath the surface, and is figured in Mr. SYER CUMING'S paper on keys in the 'Journal of the Archæological Association.'[35] These keys appear hardly to admit of any doubt as to their mode of use, and may therefore be regarded as the earliest specimen of revolving keys, although applied to a different purpose from the revolving key of our own time. The most primitive kind of lock with a revolving key that I have met with is one represented in figs. 113, 114, 115, 116, Plate X. It is from India, and is in the India Museum. The key is applied to a square vertical tumbler of the Scandinavian type with two arms to fit into two notches in the bolt; the lower end of the tumbler terminates behind the bolt, in a semicircular form; the key, when turned upon its broach or pin, as the case may be, impinges upon the sides of the semicircular portion and raises the tumbler out of the notches on the top of the bolt, and afterwards the end of the key-plate passes into one of a series of notches on the under side of the bolt and moves it, whilst the tumbler is, at the same time, raised clear of the bolt. The key being turned several times continues the movement, pushing the key forward notch after notch, until the tumbler again falls into other holes provided for it, and keeps the bolt secure. All here is of wood, except the key, which is of metal, and it is provided with slits to pass the wards, adjusted to them in the revolution of the key-plate upon its pivot. It might be supposed from this that it was a modern adaptation to an ancient system of vertical tumblers, had not a very similar, but simpler, lock existed in China. The drawing (figs. 117, 118, 119, 120, 121, Plate X.) of a Chinese lock was kindly sent me by Mr. ROMILLY ALLEN. In this specimen the bolt is shot in nearly the same manner as