last century. Their mistakes taught them what not to do, but in the meantime the patient sometimes died.

Methods of scientific reasoning so as to draw deductions from observed facts cannot be acquired by solitary night watches upon a “beat,” nor does the facility for breaking up a tangle in traffic which the constable acquires as the outcome of his daily duties, necessarily render him more capable of extricating from a mass of confused details the essential facts upon which stress should be laid.

In some of the unsolved mysteries that have occurred during the last few years the presence of a highly trained intellect at the first hour of the investigation might conceivably have led to the detection of the criminal. As a rule, it is only after the first examination is over and the case appears likely to be a difficult one, that the best brains of the department are brought to bear upon the facts, and it may then be too late for effective action.

It should be made possible for a man who possesses a facility for this type of work to join the criminal investigation department without having to go through the routine work of a police constable, which will probably add nothing to his powers of following up a clue; but, on the other hand, this period of probation should be occupied by practical training in scientific methods of working.

The present conditions both of payment and of status are not of the kind that will attract the highest type of brain to the work of criminal investigation, and yet there is no reason why it should not be made to offer the advantages of other branches of professional work.

An apt illustration of the use of acute observation and deduction in solving a mystery is afforded by the strange story of a shooting accident, that, according to a writer in one of the leading morning papers, took place many years ago.

A country gentleman was found lying dead upon a sofa, with the whole of the charge of a sporting gun in his body. The discharged gun was hanging in its usual place upon the wall, and there were no indications of any struggle having taken place. All the circumstances apparently pointed to the man having been murdered in his sleep, for it was impossible for him to have shot himself and have then replaced the gun upon the wall, and strong suspicion fell upon one of the servants in the house.

This man was arrested, and would probably have been convicted had it not been for the detective noticing that the dead man’s watch, which had been smashed by some of the shot, had been stopped early in the afternoon, and that at exactly the same moment the sun was focussed through a bottle of water that was standing upon the table in such a way that the ray fell upon the nipple of the gun upon the wall.

Accordingly he loaded the gun again, hung it in the same spot, and placed a dummy figure upon the sofa, and as soon as the sun’s rays passed through this unintended burning-glass and were focussed upon the gun, an explosion occurred and the contents were discharged into the figure.

The writer has been unable to trace the date of this occurrence, but even if it is not founded upon fact it is not impossible, for there are undoubtedly cases where papers have been set on fire by the rays of the sun being concentrated upon them, through a bottle of water.

An instance of the way in which one small fact may give conclusive proof that a crime has been committed is afforded by the trial of Swan and Jefferies in the early part of last century.

The prisoners, who were indoor servants, had committed a murder and then raised an alarm with the object of throwing the suspicion upon burglars, who they alleged had broken into the house. But an examination of the grass outside the house showed that although dew had fallen heavily through the night there were no indications of its having been disturbed by footsteps. This piece of circumstantial evidence led to their arrest, and they were subsequently convicted and executed.

Equally convincing were the clues that led to the arrest of Courvoisier in 1840, for the murder of Lord William Russell, who was then seventy-five years of age.

The prisoner had only been in the service of the murdered man for a short time. He stated that on the night before the murder he had left his master reading in bed, as was his frequent custom, and a fact in support of this was that the candle had burned down to the socket.

Early in the morning the housemaid found the silver plate scattered about the room, and various articles of value tied up in bundles, as though burglars had broken into the house and had been interrupted in their work.

She called Courvoisier, and he appeared almost immediately, fully dressed, and going into the room of Lord William Russell found him with his throat cut.

On a door were marks which indicated that it had been broken in by the supposed burglars, but closer examination showed that the damage had been done from the inside. In addition to this, any burglars entering the house through this door must have passed over a wall, and this was found to be thickly coated with dust which had not been disturbed.

For a long time no trace of the missing valuables were discovered, but finally after a thorough search of the premises, some of the money was found hidden behind the skirting in the pantry of the accused, while later on the stolen plate was discovered in the keeping of a man with whom Courvoisier had formerly lived.

Mainly on the circumstantial evidence of these facts the prisoner was convicted; afterwards he made a full confession of the crime.

Clever deductive reasoning was also shown in the following case, in which the author of a shooting outrage that occurred in 1831 at Ayr was discovered in a singular manner. Someone had maliciously fired a gun into a church, and had hoped to escape detection. It was noticed, however, that some of the bullets, after having passed through the windows, had left a mark upon the wall opposite. By drawing a straight line between these marks and the holes in the windows, and extending the line outside the church, the other end was found in a window on the other side of the street. Subsequently other proof was obtained that the gun had been fired from this window.

Numerous cases might also be quoted where the trained observation of a doctor has called attention to some slight point which would otherwise have been overlooked, but which has furnished the clue to the detection of a crime.

In the year 1806 a man named Blight was shot with a pistol at Deptford by someone unknown, and died from the wound. Sir Astley Cooper, who was called in to attend to the victim, carefully noted the relationship of the body to other objects in the room, and from the position of the wound concluded that the shot had been fired by a left-handed person. This inference drew suspicion upon a gentleman named Patch who was the only left-handed person who had been seen with Mr. Blight. He was a close personal friend of the latter, and no one had dreamed of suspecting him of the crime. The results of further inquiries proved that this man had fired the shot, and after his conviction he confessed that he had been guilty of the murder.

The fact that a weapon is tightly held in the hand of a person who has been shot is strong presumptive evidence that it is a case of suicide, since it is improbable that the hand of a dead man could subsequently be made to grasp a pistol.

There is a remarkable case on record, however, in which the fact that a pistol was found clenched in the hand of a dead man was at first regarded as evidence of a murder. A son of the deceased, who had slept in the same room was accused of having killed him and of then