|In order to ensure orderly operation, John Shelton provided printed instructions for the proper installation of his astronomical regulators. The necessary stable conditions were hard to achieve at the temporary observing sites of transit expeditions.
The regulators incorporated John Harrisons innovation of the gridiron pendulum, displayed below out of its clock case. The alternating brass and steel rods are designed to minimise the effects of temperature change. This was important in any precision timekeeping, but especially when a clock was being taken either to the tropics or towards the arctic.