When so much of his apprenticeship has been accomplished the marine climbs the ship's side and makes acquaintance with his duties as a marine policeman. The end of the first month afloat finds him on guard at every post in the ship. He knows each compartment and gangway; has been instructed in the working of the guns from the heavy turret pieces to the six-pounders; has watched the magazines and carried messages to the officers, and has even gone down to the coal bunkers, if the ship happens to be coaling in a hurry, and taken his turn at passing coal. However, he is still only a marine in the making, and this fact is brought home to him when the ship goes out for target practice and, with a bluejacket for a teacher, he learns to handle and supply ammunition to the lifts in the magazines and to work the lifts themselves, so that when the need comes he can take Jack's place and do his work. In the old days of sailing ships the marines had to know how to splice a rope or furl a sail; nowadays he does not need to, but he must learn to make his way quickly and nimbly to the fighting tops. In doing so he does not have to climb to a ratline, one minute almost in the sea and the next at the very top of the heavens, but he gets painfully dizzy when for the first time he feels the ship sinking away from under him as he looks down. In the end he masters that also and, with practice, is soon able to make the little guns in the fighting tops talk as fast as the best of the jackies. When he has learned to descend from his aerial nest to the deck at a dignified pace and to land safely upon his feet, his education is practically completed, and it has taken him from six months to a year to get it. Every navy yard in the country has its detachment of marines, but the barracks at the Brooklyn yard are the most popular, and as the marines have their choice of stations when they return from a cruise, the largest number, seldom less than three hundred, are usually quartered there. In the part of the yard set aside for the marines is a long and narrow building of gray brick, with a piazza running its entire length, shaded by a line of trees. This is the barracks, the living quarters of the men. A roomy parade ground stretches out in front, and in a group of trees to the left, with a garden behind, is the house of the commandant of marines, while at about the same distance to the right are the quarters of the other officers, each approached by a stone walk canopied and shaded by rows of pear trees.