The ascent to the dome is made through a door in the south aisle opening on to a winding staircase, and leading to long galleries above the aisles, with massive rafters of timber overhead.
In the southern gallery is the Library, founded by Bishop Compton, and containing thousands of books. The decorations of this room are extremely beautiful. The floor consists of 2,300 small pieces of oak artistically arranged, and huge brackets of oak finely carved support the gallery.
At the end of this gallery is the geometrical staircase, designed by Wren, and on the left a steep flight of steps leads to the clock room, in the south-west tower, with the great bell on which the hours are struck. This bell was cast in 1709, is about 10 feet in diameter, and weighs 11,474 lb.
On it is the inscription, "Richard Phelps made me, 1716". The dial on the outside of the clock is 57 ft. in circumference; the minute hand is 8 ft. long, and weighs 75 lb., and the hour hand is 5 ft. in. long, and weighs 44 lb. The bell is christened "Great Tom," and is never used except to ring out the hour or to toll forth the tidings of the death or funeral of some royal person, of a Bishop of London, a Dean of St. Paul's, or a Lord Mayor in office.