the black bell in the temple of fate struck once , unexpectedly , but by then the silver pedal-driven carillon in the fools ' guild would be tinkling , the gongs , bells and chimes of all the guilds and temples would be in full swing , and it was impossible to tell them apart , except for the tongueless and magical octiron bell of old tom in the unseen university clock tower , whose twelve measured silences temporarily overruled the din .