The Police Districts are mapped out into divisions, the divisions into sub-divisions, the sub-divisions into sections, and the sections into beats, all being numbered and carefully defined. To every beat, certain policemen are detailed, specifically, and they are provided with little slips of pasteboard, on which are printed the routes they are to take. So thoroughly has this management been perfected, that every street, lane, road, alley, and court, within the Metropolitan District--that is, the whole of the metropolis--(excepting that part in a radius of three-quarters of a mile from St. Paul's, which is called the City of London Proper)--including the County of Middlesex, and all the parishes, 220 in number, in the Counties of Surrey, Kent, Essex, and Hertfordshire, which are not more than 15 miles from Charing Cross in any direction, comprising an area of about 700 square miles, and 90 miles in circumference, and with a population of 3,500,000,--is visited constantly, day and night, by some of the police. Within a circle of six miles from St. Paul's, the beats are traversed in periods of time varying from twenty to fifty minutes, and there are some points, such as the Bank, the Mint, the Cathedral of St. Paul, the Abbey of Westminster, the Houses of Parliament, Buckingham Palace, the Horse Guards, and the Inns of Court, which are never free from inspection for a single moment. There are 130 police stations in the metropolis, and by a telegraph signal a Police Commissioner at White Hall, in Parliament street, which is contiguous to Scotland Yard,--the headquarters of the Metropolitan Detective force, who are separated in their duties from the Old Jewry or City of London Detective force,--can concentrate in an hour and a half as many as 6,000 men for instant duty. This vast force, each man receiving but three shillings to three and sixpence a day, is really under a wonderful control. Each officer has to walk twenty miles a day in his rounds beside attending the police courts, which is equal to five miles in addition. 98,000 persons were arrested in one year--1869, of which number 40,000 were discharged. The cost of the Metropolitan Police for one year was about £525,000, and the City Police, for the same term, £60,000--the City Police numbering 700, the Metropolitan force nearly 7,000.