The twentieth century criminal makes a business of crime. A man of this character made bold to tell me that he had been a thief for nearly forty years and he meant to be a thief to the day of his death. He refused to work for a living. Pickpockets and thieves of the lower order make a business of following circuses, county fairs, picnics, races and conventions, and they always make a good haul at such places. A few days before the Dewey Parade in this city, September, 1900, which drew together from one to two hundred thousand strangers, Captain George W. McClusky, then Chief of the Detectives, captured nearly four hundred well known crooks in his dragnet and locked them up till the “show” was over. In this crowd there were _tramps_, _pickpockets_, _sneak thieves_, _second story men_, _country thieves_, _professional criminals_ of every ilk, including the irresponsible thief. They were held in prison for a few days as suspicious characters. After the crowds left the city they were discharged. While locked up in the Tombs they were in an ugly mood and abused every one in sight. If the direct perpetrators of a crime cannot be found in the ordinary way, then our modern Sherlock Holmes must fall back upon “clues” and follow them up to their legitimate end. But if there are no clues, then the brainy detective must work out a satisfactory solution of the mystery for himself and solve it. The method of Thomas F. Byrnes, who had been long and successfully connected with the New York City Police Department, was to bring the suspected criminal back to the scene of the crime for sake of the startling effect. If an atrocious homicide had been committed Chief Byrnes usually took the murderer back to the place where the deed was done, and then watched him. If a burglary, and the property found, it would be placed before the suspect and be watched. Criminals are made of different classes or types. The beginner in crime is often a petty offender. He steals small sums although never arrested. The scale is a descending one, rather than ascending. Few men leap over a moral Niagara all at once; they are going down hill gradually for a long time before the law gets hold of them. After a few years the man who was once a greenhorn plans crime like a general who plans a campaign. It is then that the Department needs an expert Sherlock Holmes to capture them. The history of a crime is often full of thrilling experiences and when unraveled by a keen-minded detective and all the details of the plot laid bare, the final revelations show it to be the work of a master mind. The great crimes of the past hundred years were not the work of ignoramuses but of men capable of commanding an army. They were brainy criminals.