Portrait, engraving, stipple and line: John Harrison (1693-1776), Engraved by William Holl after the mezzotint of 1768 by PJ Tassaert after the oil of c1767 by Thomas King (in the Science Museum). Plate from Charles Knight's Gallery of Portraits, 1834-37, published under the superintendance of the SDUK. Sheet 27.5x18.5cm, image 12.5x10.2cm. HL seated beside longitude timekeeper H4.