In the early to mid-14th century, large mechanical clocks began to appear in the towers of several Italian cities. There is no record of any working models preceding these public clocks that were weight-driven and regulated by verge-and-foliot escapements. Verge-and-foliot mechanisms reigned for more than 300 years with variations in the shape of the foliot, but all had the same basic problem: The period of oscillation depended heavily on the amount of driving force and the amount of friction in the drive so the rate was difficult to regulate.
