A Victorian slate sundial by Richard Melvin

A Victorian slate sundial by Richard Melvin, with bronze gnomon (two missing), the central dial with a compass and Roman numerals, signed 'R. MELVIN Fecit LONDON Latitude 51° and 50° North' with further faint inscriptions to North and South, with subsidiary dials to the corners for morning, afternoon, evening and night, c.1850, 35.5 x 36cm.