Extension of the triangulation of the Ordnance Survey into France and Belgium :with the measurement of an Arc of parallel in latitude 52(degree) N. from Valentia in Ireland to Mount Kemmel in Belgium. Published by order of the right Hon. Sir George C, Lewis, Bart. Secretary of State for war. By Colonel Sir Henry James, R.E., F.R.s., &c. Director of the Ordnance Survey. London : Printed by George Edward Eyre and William Spottiswoode, Printed to the Queen's most excellent Majesty. for the Majesty's Stationary Office. 1863