more elaborate, but symmetrical tierceron vaulting, the crossing vaulting, Galilee Porch and western facade screen. Tower clock A clock by John Thwaite was installed in the north west tower in 1775. This was later improved by Benjamin Vulliamy and moved to the broad tower around 1835. It was replaced in 1880 by a new clock built by Potts and Sons of Leeds, under the instruction of Edmund Beckett QC. Cambridge Chimes were a feature of the new clock. The machinery, featuring a double three-legged gravity escapement to Beckett's designs, weighs about , with the driving weights being , suspended by steel-wire ropes long, and the pendulum weight of . The beat is 1.5 seconds. The hour hammer is , striking upon the Great Tom bell. The striking trains require winding daily, when done manually it took 20 minutes. The going train required winding twice per week. The clock mechanism contains the inscription Quod bene vortat Deus Opt. Max., Consiliis Edmundi Beckett, Baronetti, LL.D., Opera Gul. Potts et Filiorum, civium Leodiensium, Sumptibus Decani et Capituli, Novum in Turri positum est Horologium, A.D. MDCCCLXXX. Bells The South West tower of the cathedral contains a fine ring of 13 bells all cast by John Taylor and Co in Loughborough. The back 8 bells were cast in 1913, with 4 new trebles being added in 1927. In 1948 a flat 6th was added to allow for ringing on the middle 8 bells. The treble bell weighs 5cwt 0qr 2lb, with the tenor weighing 23cwt 3qr 23lb and striking the note D (nominal 600.0Hz). The bells are rung from the section of the tower just above The Great West Front, with the ringing chamber having 3 windows on all but one side. The bells themselves are hung below the louvers to minimise tower movement as much as possible. Modern history Wartime history Lincolnshire was home to many Bomber Command airfields during the Second World War, giving rise to the nickname of "Bomber County". The station badge for the nearby RAF Waddington depicts Lincoln Cathedral rising through the clouds. Until the opening of the RAF Bomber Command Memorial in 2012, the cathedral had the only memorial in the United Kingdom dedicated to Bomber Command's large losses of aircrew in the Second World War. During the war, "priceless British treasures" were placed in a chamber sixty feet beneath the cathedral for safekeeping. This did not include the