The policy of education at the museum is a wise one, for many young constables, whatever their natural abilities, come fresh to London from the plough, and no more reliable method of destroying a too trustful faith in appearances could have been devised than this which shows them the actual equipment of criminals. I have deliberately avoided giving too close a description of these things. Nor have I in any way given a complete description of the museum. The mere manuscript catalogue occupies two portly volumes. Each of the relics contains a story in itself,--a story that has often ended in a shameful death. To recall them would be beyond the scope of this book. CHAPTER XIV. PUBLIC CARRIAGES. "Keep very still, please. Thank you." A constable replaced the cap on the lens of a big camera, and with a sigh of relief a man rose from the chair where he had been seated under a cardboard number. It was the photograph-room of Scotland Yard, through which every cab-, omnibus-, and tram-driver, and every conductor has to pass once in three years. "The Yard" is as careful with a cabman on licence as with a convict on licence, although for different reasons. But the chief idea is the same--the safety and comfort of the public. There are thousands of dossiers stored in the vaults, which give a complete history of each man holding a licence in connection with a public vehicle--records of warnings, convictions, medical tests, and so on. Officially stamped photographs are placed on every document which passes into a man's possession, so that there can never be cases of personation, such as I believe have happened many years ago. It is no mean work that is performed by the Public Carriage Department, although it is done quietly, smoothly, and for the most part out of sight of the public. Not a cab, omnibus, or tramway car that plies for hire in the metropolis--and they average about 16,000 a year--but has passed stringent tests by experts, and this applies equally to the men in charge. Every human precaution that years of experience can suggest is taken to guard against the passing on the streets of any man or vehicle that might be a nuisance or a danger in congested traffic. Rigid regulations, numbering forty in the case of taxicabs, and sixty-two in the case of motor omnibuses, insist upon details as far apart as adequate brakes and freedom from noise. We speak about the perils of the street; but they would be increased, perhaps tenfold, but for the unobtrusive care of the Public Carriage Department. There are other detectives at Scotland Yard than those of the Criminal Investigation Department--detectives, that is, in all but name--for the control and supervision of traffic does not end with the issue of an annual licence.