The second of the two classes into which we have divided infractions of library rules consists of those that are also contrary to statute law or municipal regulation. How far shall these be dealt with purely from the library standpoint, and when shall they be turned over to the public authorities? If a small boy yells at the desk-assistant through door or window he is a disturber of the peace; if he throws at her some handy missile, such as a vegetable or a tin can, as occasionally happens in certain sections of unregenerate New York, he is technically committing an assault; shall he be handed over to the police? Of course one must not treat trifles too seriously. Yet probably libraries have been somewhat too timid about dealing with petty offences. There is an unwillingness to drag the libraries into the police reports that seems to be a relic of the days when all libraries were haunts of scholarly seclusion. The modern public library cannot afford to be considered an “easy mark” by those who wish to indulge in horse play or commit petty misdemeanors, and in some cases it is in danger of getting this reputation. When we come to more serious offences, the library’s duty is clearer. Theft, wilful mutilation of books, or grave disorder must of course be punished. In many cases, however, the detection of the first two offences is very difficult. Theft from open shelves is easy. For the thousands of books lost yearly in this way hardly a culprit meets punishment. I have known a professional detective to confess that the open shelf baffled him. “If you will only shut the books up,” he said, “I can find out who takes ’em; but here everybody is taking out books and walking around with them.” When the professional acknowledges himself beaten, what shall the librarian do? Mutilation is even harder to detect. In both these cases the offender has simply to wait his opportunity. Sooner or later there will be a second or two when no assistant is looking, even if the man is under long-standing suspicion, and in that brief time the book is slipped into the pocket or the leaf is torn out. Even when the offender is caught in the act, the magistrate may not hold, or the jury may fail to convict. A persistent mutilator of books in one of our branch libraries escaped punishment last winter because the custodian of the reading-room where he was caught did not wait until the leaf on which he was working was actually severed. The man asserted that the sharp lead pencil that he was using to separate the leaf was merely being employed to mark a place, and thus by confessing to a minor defacement he escaped the penalty of the more serious offence. For a library that is thus forced to appeal continually to the law to protect its assistants, its users, and its collections, a manual of library law would be useful, and I am not sure that the appointment of a committee of this Association to take the matter in charge would not be eminently justified.