Ordnance Survey Map, S.E. Harleck, Merionethshire. Number 75.

21 Sectional linen backed ordnance survey map.. Engraved in outline by J.W. Troggelt. The Hills by J. A. Peake...... British major-general and director of the Ordnance Survey (OS). A Fellow of the Royal Astronomical Society and Royal Society, Colby was one of the leading geographers of his time. An officer in the Royal Engineers, Colby overcame the loss of one hand in a shooting accident to begin in 1802 a lifelong connection with the Ordnance Survey. His most important work was the Survey of Ireland. He began planning this enormous enterprise in 1824 and directed it until 1846, in which year the final maps made by the survey were almost ready for issue. He was the inventor of the -Colby Bar- (a compensation bar), an apparatus used in base-measurements.