And at last, after innumerable adventures, each more wonderful than the last, Tom saw before him a huge building. He walked towards it, wondering what it was, and having a strange fancy that he might find Mr. Grimes inside it, till he saw running toward him, and shouting "Stop!" three or four people, who, when they came nearer, were nothing else than policemen's truncheons, running along without legs or arms. Tom was not astonished. He was long past that. Neither was he frightened; for he had been doing no harm. So he stopped; and when the foremost truncheon came up and asked his business, he showed Mother Carey's pass; and the truncheon looked at it in the oddest fashion; for he had one eye in the middle of his upper end, so that when he looked at anything, being quite stiff, he had to slope himself, and poke himself, till it was a wonder why he did not tumble over; but, being quite full of the spirit of justice (as all policemen, and their truncheons, ought to be), he was always in a position of stable equilibrium, whichever way he put himself. "All right--pass on," said he at last. And then he added: "I had better go with you, young man." And Tom had no objection, for such company was both respectable and safe; so the truncheon coiled its thong neatly round its handle, to prevent tripping itself up--for the thong had got loose in running--and marched on by Tom's side. "Why have you no policeman to carry you?" asked Tom after a while. "Because we are not like those clumsy-made truncheons in the land world, which cannot go with-out having a whole man to carry them about. We do our own work for ourselves; and do it very well, though I say it who should not." "Then why have you a thong to your handle?" asked Tom. "To hang ourselves up by, of course, when we are off duty." Tom had got his answer, and had no more to say, till they came up to the great iron door of the prison. And there the truncheon knocked twice, with its own head. A wicket in the door opened, and out looked a tremendous old brass blunderbuss charged up to the muzzle with slugs, who was the porter; and Tom started back a little at the sight of him. "What case is this?" he asked in a deep voice, out of his broad bell mouth. "If you please, sir, it is no case; only a young gentleman from her ladyship, who wants to see Grimes, the master sweep." "Grimes?" said the blunderbuss. And he pulled in his muzzle, perhaps to look over his prison lists. "Grimes is up chimney No. 345," he said from inside. "So the young gentleman had better go on to the roof." Tom looked up at the enormous wall, which seemed at least ninety miles high, and wondered how he should ever get up; but when he hinted that to the truncheon, it settled the matter in a moment. For it whisked round, and gave him such a shove behind as sent him up to the roof in no time, with his little dog under his arm. And there he walked along the leads, till he met another truncheon, and told him his errand.