of what may be called the functions of police; how far liberty may legitimately be invaded for the prevention of crime, or of accident. It is one of the undisputed functions of government to take precautions against crime before it has been committed, as well as to detect and punish it afterwards. The preventive function of government, however, is far more liable to be abused, to the prejudice of liberty, than the punitory function; for there is hardly any part of the legitimate freedom of action of a human being which would not admit of being represented, and fairly too, as increasing the facilities for some form or other of delinquency. Nevertheless, if a public authority, or even a private person, sees any one evidently preparing to commit a crime, they are not bound to look on inactive until the crime is committed, but may interfere to prevent it. If poisons were never bought or used for any purpose except the commission of murder, it would be right to prohibit their manufacture and sale. They may, however, be wanted not only for innocent but for useful purposes, and restrictions cannot be imposed in the one case without operating in the other. Again, it is a proper office of public authority to guard against accidents. If either a public officer or any one else saw a person attempting to cross a bridge which had been ascertained to be unsafe, and there were no time to warn him of his
