Fig. 220.—Yale key turning.
There are other well-known locks, such as those invented by Bramah and Hobbs. But as these do not lend themselves readily to illustration no detailed account can be given. We might, however, notice the time lock, which is set to a certain hour, and can be opened by the right key or a number of keys in combination only when that hour is reached. Another very interesting device is the automatic combination lock. This may have twenty or more keys, any one of which can lock it; but the same one must be used to unlock it, as the key automatically sets the mechanism in favour of itself. With such a lock it would be possible to have a different key for every day in the month; and if any one key got into wrong hands it would be useless unless it happened to be the one which last locked the lock.
Fig. 221.—The wrong key inserted. The pins do not allow the lock to be turned.
THE CYCLE.
There are a few features of this useful and in some ways wonderful contrivance which should be noticed. First,
THE GEARING OF A CYCLE.