I have seen a man press his fingers on a clean sheet of paper, apparently without leaving the faintest trace. But Mr. Collins is not baffled so. A pinch of black powder--graphite is commonly used--scattered over the paper, and behold the prints standing out in high relief. A grey powder will act in the same way on a dark surface, and a candle which has been pressed by the fingers may have the print rendered clear by a judicious use of ordinary printer's ink. A corps of expert photographers, equipped with the latest appliances, is attached to the department, and their services are in constant requisition by the C.I.D. for many purposes other than those of finger-prints. One room is entirely devoted to a powerful lantern apparatus by which every photograph may be thrown up to a hundred times its normal size for the purpose of minute study. This has often proved useful in detecting forgeries as well as aiding the work of the Finger-print Department. I have said that the primary purpose of the department is not the detection of crime. Nevertheless, it has played no small part in the solution of mysteries where other clues have failed. There was the case of the Stratton brothers, for instance, where the print on a cash-box led to arrest, although other evidence aided the conviction. Perhaps the most interesting case is that which first focussed the public attention on the value of the system. It occurred in 1898, shortly after the present Commissioner initiated the system in India. He himself tells the story. The manager of a tea-garden was found murdered, and a safe and despatch-box robbed of several hundred rupees. Suspicion was at first divided among the coolies and cook, the relatives of a woman with whom the dead man had carried on an intrigue, a wandering gang of Kabulis, and an ex-servant whom he had prosecuted for theft--a wide enough field, in all conscience. But the police were unexpectedly helped in their investigation by the discovery in the despatch-box of a small light-blue book, a calendar in Bengali characters. On the cover were two indistinct smudges. Under a magnifying-glass these proved to be the impressions of a blood-stained finger. Search was made in the records of the Bengal police, and it was found that the finger-print was that of the right thumb of the ex-servant. He was arrested some hundreds of miles away, and charged with murder and robbery. On the ground that it would be unsafe to convict him of murder, as no one saw him do it, he was acquitted on that charge, but was convicted of theft. It would be possible to write largely on cases where finger-prints have afforded culminating proof of a person's guilt. One that has a grim touch of humour may be recalled.