the last specimen, but the tumblers are raised independently by means of a T-shaped key (fig. 121, Plate X.), similar to that used with the Scandinavian lock (fig. 3C, Plate IV.). The key from the outside is put into the vertical slit between the tumblers, when it is turned a quarter circle so as to bring the arms of the T in a horizontal plane. It is then pressed back, when the returns of the T enter notches provided for them in the tumblers. The tumblers are then raised, and the key or handle, _a_, turned. From the inside the tumblers are raised with the two fingers before shooting the bolt. [34] 'La Ferronnerie,' tome ii., p. 236, fig. 492. [35] 'Journal of the Archæological Association,' vol. xii., p. 121, Plate XIV., fig. 1. M. LIGER supposes that the lifting key of the Roman lock was of Asiatic origin, and that the revolving key came into use amongst the Romans about the commencement[36] of our era, and many of the keys from Pompeii are constructed on this principle having slits for the passage of wards. Fig. 122, Plate X., is a Roman key of this kind in my collection. The ward system came into general use afterwards and was much relied upon to the exclusion of others in the Middle Ages. The ward system may be defined as a system of lock in which obstructions are placed to prevent any but the proper key from entering to turn the bolt; as such it is distinct from the tumbler system, in which security depends on obstruction introduced to prevent the bolt from being drawn by the key. The tumbler is, in fact, a bolt of a bolt. Reference to fig. 10B, Plate II., representing the Egyptian lock, will show that besides the two pins with which the key is provided for lifting the tumblers, there is a pin attached to the under side of the lock opening, which enters a hole in the key. This is of the nature of a ward, since none but a key with a hole in the proper place could be raised up high enough to lift the tumblers clear of the holes in the bolt. Mr. ROMILLY ALLEN also mentions that in one of the Scotch locks from Snizort, a notch is placed in the key and a corresponding pin in the lock, to prevent the lock from being picked, and that the key-hole is divided by a thin iron plate which is the only thing approaching a ward that appears in any of the wooden locks of Scotland. The peculiar shape of the tumblers and tumbler-holes in the bolts of the Roman lock, already described, with teeth made especially to fit them, must be regarded as a kind of ward, although applied to tumblers, since their object is to prevent any but the proper form of key from entering. [36] 'La Ferronnerie,' tome i., p. 264.