Pierre le Loyer, a French writer on law and the supernatural, mentions in his "Discours des Spectres," the case of a man who mysteriously vanished, having, as was supposed, been murdered. A few weeks later the ghost of the absentee appeared to his brother, took him to a lonely spot, and there pointed out where he had been murdered and buried by his own wife and her lover. Enraged at this domestic perfidy and wickedness the brother denounced his sister-in-law, and on his testimony she was condemned to be strangled and her body afterwards burned. About half a century ago a peculiar case of fraud was disclosed by remarkable means during the hearing of a law-suit in Tuscany. The decision of the court turned on the point whether a certain word had been erased from a particular document of importance. Chemical processes were alleged to have been employed, and acting on scientific knowledge one of the lawyers proposed that the document should be heated, as thereby a slight difference of shade or colouring between the paper and the letters supposed to have been removed might become visible. Permission was given to try the experiment, and on the application of heat the important word in question immediately appeared, and the court gave a verdict in accordance with this ingeniously devised testimony. Since that time the progress and development of science have enabled criminal investigation to be conducted by methods which would otherwise be impossible, and with almost unerring certainty and decision. The microscope and the spectroscope have been employed in numerous cases of murder and forgery where less subtle means of discovery would have proved useless; chemical analysis has become an important agent of detection, while photography has also rendered signal service in the cause of justice. We may not have concerned ourselves with the numerous methods by which bank-note forgeries are detected; hitherto our references have been mainly to the more serious crime of murder, and with a few instances of this character brought to light through modern science our list must close.