The professional criminal, or the habitual offender, as he is called by some, comes next in numerical strength, but first of all, in my opinion, in importance. I consider him the most important because he frankly admits that he makes a business of crime, and is prepared to suffer any consequences that his offences may bring upon him. It is he who makes crime a constant temptation to the occasional offender, and it is also he with whom we have the most trouble in our criminal courts; he is almost as hard to convict as the man with "political influence." On my "beat" he was more in evidence, in the open at least, than any of the other offenders mentioned, except the tramp, but, as I stated, the warm months are the time when he comes out of his hiding-places, and it was natural that I should see a good deal of him. My fifth category is made up of what a friend calls "the unknown thief," whom he considers the most dangerous and despicable of all. He means, by the unknown thief, the man in official life, or in any position which permits of it, who protects, for the sake of compensation, the known thief. "If you will catch the unknown thief," he has frequently said to me, "I will contract to apprehend and convict the known," and he believes that until we make a crusade against the former, the latter is bound to flourish in spite of all our efforts. He sees no use, for instance, in spending weeks and sometimes months in trying to capture some well-known criminal, as long as it is possible for the man to buy his freedom back again, and it is his firm belief that this kind of bargaining is going on every day. Although there was no doubt that the unknown thief was to be located on any "beat," if looked for, my instructions were not to disturb him unless he seriously disturbed me, and as he made no effort to interfere with my work I merely made a note of his case when we met, and doubtless he also "sized me up" from his point of view. How strong his class is, compared with the others, must remain a matter of conjecture, but I have put his class fourth in my description because it is the quality of his offences, rather than their quantity, which makes his presence in the criminal world so significant. There are those who believe that he is to be found in every town and village in the United States, if enough money is offered him as bait, but I have not sufficient data to prove, or to make me believe, such a statement. The league between him and the known thief--the man whose photograph is in the "rogue's gallery"--is so close, however, that I have devoted special chapters to both offenders.