The patrol-boats beat to and fro, each with two men and a sergeant, in all weathers, amid blinding sleet and snow in the winter, fog in November, and more pleasantly on summer nights. Eyes are strained through the darkness at the long tiers of barges, ears are alert to catch the click of oars in rowlocks. They know who has lawful occasion to be abroad at such times. Occasionally the sergeant hails some boat. He can usually identify the voice of the man who replies, but should he fail to do so, the police-boat slips nearer. A stranger or a suspicious character is invited to give an account of himself. Should he not be able to do so satisfactorily, he is towed along to the nearest police station until inquiries have been made. Sometimes, not often, when a man, who on the river corresponds to the sneak thief ashore, is caught red-handed stealing rope or metal or ships' oddments there is resistance. But always the police win. They know the game. A hand-to-hand struggle in a swaying boat, even a fall overboard with a desperate prisoner, does not concern them greatly. "You see," explained a veteran to me, "if you fall out while you've got hold of a man it's ten to one that he tries to get his breath as he goes under. That makes matters worse for him. All you do is to hold your breath, and let him wear himself out. He's usually quiet enough when you come up again." Of course, every man in the division is an expert swimmer. There are other tricks of boatcraft in such a case which all river-police officers know. The flashing of a light is an equivalent of a police-whistle ashore, and will bring the assistance of any police-boat in sight. At the floating police-station at Waterloo Pier a dingey is always in readiness to put off to rescue would-be suicides who fling themselves from the "bridge of sighs." In the little station itself there is a bathroom with hot water always ready, and every man in the division is trained to the Schafer method of resuscitation of the apparently drowned. A still more grim side of the work is the finding of dead bodies. The average number is somewhere around a hundred a year. Most of these are suicides, a few accidents. The duties of the patrols are to keep vigil over the river and its banks. There are other patrols at work for the Customs and the Port of London Authority, who see that the revenue is not defrauded, and that the traffic regulations are kept. But this does not free the police from all responsibility in these matters. Here are a few of the things they have to do:-- Secure drifting barges and inform owner, Detect smuggling, illegal ship-building or illegal fitting out for service in a foreign State, Report damaged cargoes or food, and offences against the Port of London Authority's bye-laws, Arrest any drunken person navigating a boat, Detect cases of navigation without sufficient free-board below Battersea Bridge, Search all suspicious-looking craft,