Day by day, the prison governors from all parts of the country are sending in records to be added to the files, and police authorities, also from all parts of the country, are asking for prisoners to be identified. An interesting story concerns two men whom we will call Robinson and Jones, who were tried for different offences the same day. Robinson was rich; Jones was not. Robinson received a long sentence, Jones a light one. Probably they arranged it all in the prison van, but anyhow, when they reached the gaol they had changed identities--and sentences. All went well until a short time before the _soi-disant_ Jones was due to be released. Then his finger-prints were taken, compared with those of Jones in the files, and found not to correspond. Half an hour later wires were being exchanged between Scotland Yard and the prison, and, to the mutual consternation of the two men, the little scheme was revealed. Finger-prints had outwitted them. Save for a few filing cabinets stretching from floor to ceiling in a well-lighted room, there is little apparent difference between the Finger-print Department at Scotland Yard and the interior of an ordinary City office. Men pore over foolscap sheets of paper with magnifying glasses, comparing, classifying, and checking, day in, day out. They are all detectives, but their work is specialist work, totally different to that of the bulk of the men of the C.I.D. It may be that sometimes they realise that a man's life or liberty depends on their scrutiny, but for the most part they do their work with cold deliberation and machine-like precision. Is one set of finger-marks identical with another? That is all they have to answer. It is the pride of the department that since it has been established it has never made a mistake. At its head is Chief Detective Inspector Charles Collins, an enthusiast in identification work, who has seen the system change from the old days when detectives paid periodical visits to Holloway Prison to see if they could recognise prisoners on remand, and when profile and full-face photographs were used for the records, to that now in use which he has had no small share in bringing to its high state of efficiency. He can read a finger-print as other men can read a letter, and has even, for the purposes of study, taken prints of the fingers of monkeys at the Zoo. Many times has he given evidence as an expert in cases where finger-prints have formed part of the evidence. His cold, scientific analysis has always convinced the most sceptical, and always a conviction has followed. He wrote the chapter dealing with the photographing and enlarging of finger-prints in Sir Edward Henry's standard work on the subject, and is something of a magician in the way he can detect a mark when none is obvious to the naked eye.