In order that police supervision may be safe and effectual, it is of course necessary that the identification of habitual criminals should be certain and the registration of convicts complete. The present system would have been fraught with the gravest dangers to public liberty had it been attempted at the time when there was no possibility of any more reliable record than that founded upon the memories of policemen and prison-warders; but since the introduction of photography, and especially since the recent adoption of the system of anthropometry which is associated with the names of M. Alphonse Bertillon and Mr Francis Galton, the chance of any miscarriage of justice, due to mistakes in identification, has been reduced to a minimum. Photography was first adapted to police purposes in 1854, when the governor of Bristol Gaol began to make daguerreotype pictures of the prisoners who passed through his hands; and gradually what was at first but the experimental hobby of an amateur developed into the officially recognised system. The "Prevention of Crimes" Act (1871) had directed that registers of all persons convicted of crime in England should be kept at Scotland Yard, but it was soon found by experience that a less voluminous record would be of greater practical value. Accordingly it was decided in 1877 that, in future, the registers (the compilation of which was at this time transferred from Scotland Yard to the Home Office) should contain only the descriptions of habitual criminals, officially so called. In 1880 a new department was opened at the Head-Quarters of the Metropolitan Police, called the Convict Supervision Office, which was largely occupied with the classification of offenders by means of books containing the photographs of habituals. These albums, together with a register of distinctive marks, including a record of tattooed symbols and initials so universal amongst criminals, formed a regular rogues' gallery, and were instrumental in proving the identity of many inveterate delinquents who might otherwise have improperly participated in the leniency intended only for first offenders. Some of the more energetic police forces in the provinces, also, prepared local registers; and something like a general scheme for tracing the antecedents of criminals was evolved by means of circular "Route Forms" (as descriptions of offenders whose identity was uncertain were technically called) which were forwarded in rotation from one police district to another, wherever the required information was likely to be forthcoming. The results obtained, however, hardly justified the expenditure of time and energy incurred in the process; accordingly in 1893 a Parliamentary Committee was appointed "to enquire into the best means available for identifying habitual criminals," and it was on the recommendation of this expert committee that the perfect anthropometric system of identification now employed was based.