Turret clock, English, 1795.
© Science Museum / Science & Society Picture Library
Although this clock is inscribed: 'Vulliamy, London, 1795', it was probably made by Thwaites and sold by him to the Vulliamy firm. It is made of iron and controlled by a pendulum with an anchor escapement. The striking mechanism is of the rack type, which is uncommon in clocks of this size. With this mechanism, the hour struck depends only on the position of the hour hand, so that if the clock has to be reset after a stoppage, it is not necesary to wait for the hours to strike in succesion. The clock was taken from the pediment of a building which was formerly the headquarters of the Metropolitan Police Force in London.