We next find Bramah turning his attention to the invention of a lock that should surpass all others then known. The locks then in use were of a very imperfect character, easily picked by dexterous thieves, against whom they afforded little protection. Yet locks are a very ancient invention, though, as in many other cases, the art of making them seems in a great measure to have become lost, and accordingly had to be found out anew. Thus the tumbler lock--which consists in the use of moveable impediments acted on by the proper key only, as contradistinguished from the ordinary ward locks, where the impediments are fixed--appears to have been well known to the ancient Egyptians, the representation of such a lock being found sculptured among the bas-reliefs which decorate the great temple at Karnak. This kind of lock was revived, or at least greatly improved, by a Mr. Barron in 1774, and it was shortly after this time that Bramah directed his attention to the subject. After much study and many experiments, he contrived a lock more simple, more serviceable, as well as more secure, than Barron's, as is proved by the fact that it has stood the test of nearly eighty years' experience,[1] and still holds its ground. For a long time, indeed, Bramah's lock was regarded as absolutely inviolable, and it remained unpicked for sixty-seven years until Hobbs the American mastered it in 1851. A notice had long been exhibited in Bramah's shop-window in Piccadilly, offering 200L. to any one who should succeed in picking the patent lock. Many tried, and all failed, until Hobbs succeeded, after sixteen days' manipulation of it with various elaborate instruments. But the difficulty with which the lock was picked showed that, for all ordinary purposes, it might be pronounced impregnable. The new locks were machines of the most delicate kind, the action of which depended in a great measure upon the precision with which the springs, sliders, levers, barrels, and other parts were finished. The merits of the invention being generally admitted, there was a considerable demand for the locks, and the necessity thus arose for inventing a series of original machine-tools to enable them to be manufactured in sufficient quantities to meet the demand. It is probable, indeed, that, but for the contrivance of such tools, the lock could never have come in to general use, as the skill of hand-workmen, no matter how experienced, could not have been relied upon for turning out the article with that degree of accuracy and finish in all the parts which was indispensable for its proper action. In conducting the manufacture throughout, Bramah was greatly assisted by Henry Maudslay, his foreman, to whom he was in no small degree indebted for the contrivance of those tool-machines which enabled him to carry on the business of lock-making with advantage and profit.