|THE crimes of London are the crimes of humanity plus those of a great city. There are amateur criminals and professional criminals. The amateur criminal is the man or woman who yields to a sudden impulse or the stress of circumstance. The professional criminal is the man or woman who makes a business of crime, and practises it for the purpose of profit. Education and modern invention have brought our methods of crime to a fine art, and there are criminal organizations which, having brains and capital behind them, are able to realize immense sums annually for division among the partners. The mystery of many a jewel-robbery which startles the public and baffles the police would be solved if what has long been suspected could only be proved--namely, the existence in London of a system of planting confederates--male and female--in the houses of the wealthy as domestic servants. The servant so planted is always well-behaved, and inspires the greatest confidence. He or she comes with a personal character that is irreproachable. Let us take an example of the methods resorted to to "place" a confederate. "A lady going abroad wishes to find a situation for her footman, whom she can thoroughly recommend. Address in the first instance by letter," etc. The desire to secure a footman who can be thoroughly recommended induces a number of ladies to write. From the applications sent in, the best addresses are selected, rapid inquiries are made of tradespeople and others, and the lady whose house it is believed will best suit the purpose of the thieves is communicated with. The footman, who is in league with a band of expert jewel-thieves, is a trained servant. It is necessary that he should be so to retain the place long enough for the plans of the gang to be matured. He soon finds out the ways of his employers and the whereabouts of the "stuff" that is desired. The rest is easy. He communicates all the necessary information to his colleagues, gives them notice of the arrival of a favourable opportunity, leaves everything arranged to facilitate a noiseless entry into the premises, and has nothing further to do with the "job." These jewel robberies generally take place in the evening, while the family are at dinner at home, or dining out, or at the theatre. No one has any suspicion of the footman. He always arranges to be with the other servants as much as possible at the time the robbery is being skilfully effected. The lady's maid is a favourite "plant" servant, and is sometimes more useful to the gang than the footman. The lady's maid has frequently possession of her mistress's keys, and she is able to take a "squeeze" of any key that may be required by the burglars, who want to go to work noiselessly and expeditiously.