Whether the modern Egyptian lock is a survival of an ancient Egyptian form, or whether it is of Roman origin, it is certain, from the relics of Roman bronze and iron keys and bolts found in various parts of Europe, that the Roman lock was constructed on the same principle. Figs. 15B to 20B, Plate III., may be taken as illustrations of the Roman lock when put together. It is a reproduction from original fragments preserved in the Museum at Mainz. Fig. 20B is the bronze key; it has four teeth which, besides being at variable distances apart, are also of different forms, some being triangular and others square. Fig. 19B is the bronze bolt, made with apertures to fit the key, and also to admit of similarly formed tumblers, shown in fig. 18B. The way in which these are put together is represented in the section of the lock, figs. 16B and 17B. The key _a_ is put into the keyhole _d_, fig. 15B, with the bar of the key containing the teeth in a vertical position, as represented by the dotted line _a_, fig. 16B. It is then turned round, and the teeth brought up beneath the bolt _b_. When pressed up vertically, the tumblers are driven up out of the bolt, and replaced by the teeth of the key, which hold the bolt so that it can be forced back by moving the key to the right. When the bolt is withdrawn, it releases the hasp _e_, fig. 15B. Of such hasps, fig. 21B is a drawing of an original in my collection, found at Hetternheim. By reference to fig. 16B, it will be seen that the tumblers, _f f_, are vertical, and would therefore fall into their places in the bolt, like those of the Egyptian and Scandinavian specimens; but being so small, and being probably made of wood, their weight would be insufficient to secure certainty of action, if dependent on weight alone; they are therefore pressed down by a flat plate _h_, figs. 16B and 17B, acting under the influence of a spring _g_, figs. 16B and 17B. This is an important addition, for it is evident that as soon as the spring comes into use, the tumblers can easily be made to press into the bolt horizontally, by means of a spring at the side, thereby enabling the lock to be used in any position in which it may be required; and there seems to be little doubt that some of the bolts and tumblers were so constructed in Roman locks. The existence of a spring in Roman locks is determined by the discovery of one with the spring in it, which is figured in M. LIGER'S work 'La Ferronnerie.'[6] [6] 'La Ferronnerie, Ancienne et Moderne,' par F. LIGER, Paris, 1875, tome i., p. 266, fig. 213.