The accuracy of pendulum clocks depends essentially on being able to keep the length of the pendulum constant, notwithstanding variations in temperature. John Ellicot - one of the best English clock makers of the XVIIIth century - tried to counter these fluctuations by casting the rods of the pendulum in steel and brass, with a complicated system of levers inside the pendulum itself, for raising and lowering it when the rods expanded or contracted. Even though a detailed description was published by Ellicot himself in the Philosophical Transactions of the Royal Society (op.cit.), there were very few clocks built by this design, because of the difficulties in building and adjusting them properly. As attested by a note dated 15 April 1787 in Reg. Sp. Acc. Scienze Bo., vol.XI (Arch. Dept. Astron. Bo.), this clock was installed on that date in the Meridian Room, where it replaced the regulator clock by George Graham, purchased in 1757 and today unfound. The same note informs us that the clock had been bought from the Assunteria of the Institute for 750 Bolognese lire, but neither the date of sale nor of manufacture are recorded. Ellicot was already dead by that time which means the clock had been bought used or else from Ellicotís atelier, if it still existed.
In Ceschiís 1843 Inventory we read the following description: "Regulator Clock built by the Englishman Ellicot which marks hours, minutes and seconds, with pendulum made of two rods of different metals, and with lens carrying the correction mechanism. This pendulum is kept in its elegantly decorated mahogany tower, and furnished with locks and keys. Key for winding up the pendulum which is done once a month."
The dial face, in inlaid and burnished silver, has separate dials for minutes and seconds; a small half-moon shaped window shows the hours in Roman numbers, while yet another dial at the top indicates whether the clock needs winding.
Restored by G. Morigi (Bologna) in 1979, it has been rehoused in the Meridian Room.
A similar exemplar to the Bologna clock was purchased in 1765 by Harvard College - where it can be found today - for £35 14 sh.
E. Baiada, A. Braccesi (1983) pp. 122 e 110, fig. 22a-22b.
J. Ellicott (1753).
D.P. Wheatland (1968) p. 71.