The ''Congreve'' rolling ball clock, with single silver-plated roman dial, with visible eight day single fusee driven movement, regulation is achieved by the traverse of a ball along the zigzag grooves and inclined plane, the ball trips the escapement at the end of each traverse reversing the slope of the platform; with protective glass cover and wooden base, the backplate stamped 'RWS England', no jewels 588, height of clock 9 1/4in., total height of case 13 1/2in. PROVENANCE Purchased Bramwell's Jewellers, 24 Elvet Bridge, Durham, 31.10.1998. See illustration