The extent of the Tower within the walls is twelve acres and five roods. The exterior circuit of the ditch--now a garden, or rather an apology for a garden--surrounding it, is three thousand one hundred and fifty-six feet. On the river side is a broad and handsome wharf or graveled terrace, separated by the ditch from the fortress and mounted with sixty pieces of ordnance, which are fired on the royal birthdays, or in celebration of any remarkable event. From the wharf into the Tower is an entrance by a drawbridge. Near it is a cut or short canal connecting the river with the ditch, having a water entrance called the "Traitor's Gate,"--State Prisoners having been formerly conveyed by this passage to Westminster, where the two Houses of Parliament now sit, for trial. Over the Traitor's Gate is a building containing the waterworks which supply the interior with water. Within the walls of the fortress are several streets. The principal buildings which it contains are the White or principal Tower, the ancient Chapel of St. Peter-ad-Vincula, the Ordnance-Office, the Record Office, the Jewel's House, the Stone Armory, the Grand Storehouse, and the Small Armory, besides the house belonging to the Constable of the Tower and other officers, the barracks of the garrison, and the sutler's shops, commonly used by the soldiers. It is generally a regiment of the line which serves as a garrison for the tower. The principal entrance to the Tower is to the west. It consists of two gates on the outside of the ditch, a stone bridge built over the ditch, and a gate at the end of the bridge. These gates are opened every morning with a strange, and for the Nineteenth century, a very fantastical ceremony. The Yeoman-Porter with a sergeant and six men march to the Governor's house for the keys. Having received them, he proceeds to the innermost gate, and passing that, it is again shut. He then opens the three outermost gates at each of which the guards rest their firelocks while the keys pass and repass. The gravity with which the guards perform this ceremony, and the nice precision with which they manoeuvre, is calculated to make everybody but an Englishman laugh. On the return of the Yeoman-Porter to the innermost gate, he calls to the warden on duty to take the Queen's keys, when they open the gates, and the keys are placed in the warden's hall. At night the same formality is used in shutting the gates; and as the Yeoman-Porter and the guard, return with the keys to the Governor's house the main guard which, with its officers, is under arms, challenges him saying: "Who comes there?" He answers: "The Keys." The challenger replies: "Pass Keys." The guards by order rest their firelocks and the Yeoman-Porter says: "God save the Queen." The soldiers then answer back: "Amen." The bearer of the keys then proceeds to the Governor's house and there leaves them.