Now we turn to look at the London ones. There is a separate box for them to be posted in. Perhaps you who live in the country have never seen that. At every large London office there are two boxes side by side, and into one the people put their letters meant for the country, and into the other those for London. The London letters are gathered from the box and thrown out upon large tables, and down each side a row of boys and men stand and sort them out like a pack of cards, putting them all together, face up, and with the stamp in the same position. When they are arranged the boys carry a great bundle to another man who has to stamp them, so as to mark the stamp in case it should be used again. There is a very clever contrivance for this. A little round wheel spins at a tremendous pace, and on it are dark lines covered with wet ink. A man holds the letters and pushes them one by one up to the wheel, which, when it touches them, drags them through a narrow space in front, and as they pass the wheel the ink-lines run across the stamp and mark it so that it cannot be used again. So quickly does the little wheel whirr and the letters spin past that five hundred are done in a minute. Think of that; it means nearly nine a second. Nine letters stamped while you say 'One--two,' which is a second. Some letters are too thick and others too big to go through the little space by the wheel, so the man who is looking after them picks out those and throws them up on to a tray, from which they are gathered up and carried to another man, who stamps each by hand, a much slower process.