Detection depends largely, of course, upon the knowledge, astuteness, ingenuity, and logical powers of police officers, although they find many independent and often unexpected aids, as we shall see. The best method of procedure is clearly laid down in police manuals: an immediate systematic investigation on the theatre of a crime, the minute examination of premises, the careful search for tracks and traces, for any article left behind, however insignificant, such as the merest fragment of clothing, a scrap of paper, a harmless tool, a hat, half a button; the slow, persistent inquiry into the antecedents of suspected persons, of their friends and associates, their movements and ways, unexplained change of domicile, proved possession of substantial funds after previous indigence--all these are detailed for the guidance of the detective. It will be seen in the following pages how small a thing has often sufficed to form a clue. A name chalked upon a door in tell-tale handwriting; half a word scratched upon a chisel, has led to the identification of its guilty owner, as in the case of Orrock. A button dropped after a burglary has been found to correspond with those on the coat of a man in custody for another offence, and with the very place from which it was torn. The cloth used to enclose human remains has been recognised as that used by tailors, and the same with the system of sewing, thus narrowing inquiry to a particular class of workmen; and the fact is well illustrated in the detection of Voirbo, to be hereafter told. The position of a body has shown that death could not have been accidental. A false tooth, fortunately incombustible, has sufficed for proof of identity when every other vestige has been annihilated by fire, as in the case of Dr. Webster of Boston. [Illustration: _Photo: Cassell & Company, Limited._ BROKEN BUTTON AT THE BLACK MUSEUM: A CLUE. (_The white paper has been placed upon the cloth to show up the button._)]