A most important George III mahogany longcase regulator signed “Josiah Emery, Charing Cross. London,” circa 1785

pendulum

The gridiron is of the form introduced by John Arnold, consisting of two zinc and three steel rods. The large brass-clad bob is pierced with rectangular openings forming a bridge acting as the point of suspension. In this configuration, the bob's center of gravity rests on a screw threaded into the lowest cross piece of the pendulum. The screw may be turned for adjustment by means of a pin inserted into small holes around the edge of a calibrated rating scale below the cross piece. The screw also carries a spherical fine adjustment weight below the bob and terminates with an index to the silvered beat scale.
The beat adjustment is above the suspension. Just below its suspension, the pendulum rod is fitted with an open work, lozenge-form, brass and steel brace to engage the crutch.