The clock inside the tower was the world's largest when it was installed in the middle of the nineteenth century. The name Big Ben actually refers to the clock's hour bell, the largest of the clock's five bells. The other four are used as quarter bells.
There were two bells cast as the clock tower's hour bell. A first, sixteen ton weighing bell was cast by John Warner and Sons in 1856. Since the Clock Tower was not yet completed, the bell was hung temporarily in the Palace Yard. The bell soon cracked so it was recast in 1858 in the Whitechapel Bell Foundry as a 13.5 ton bell. Unfortunately soon after this bell was placed in the belfry in July 1859, it cracked as well. This time, instead of yet again recasting the bell, the crack was repaired and a lighter hammer was used to prevent any more cracks.