Since it was replaced in the early eighteenth century, the Trinity clock has been notable for striking the hour twice, first on a low note (the 'Trinity' chime) and then on a much higher one (the 'St John's' chime). This phenomenon was recorded by William Wordsworth in his poem 'The Prelude' (1850):
Near me hung Trinity's loquacious clock,
Who never let the quarters, night or day,
Slip by him unproclaimed, and told the hours
Twice over with a male and female voice.
The running of the 1910 clock has been the the subject of an engineering project coordinated by a Fellow of Trinity, Dr Hugh Hunt, calibrating the clock's movements against the National Physical Laboratory time signal and various variables, including the amplitude of the pendulum, humidity, air temperature, air pressure, and air density.
For more information and research regarding the clock, visit the Trinity College Clock project