Collection search - Plan shewing relative positions of Government property at Longueil & St Helen's with Montreal, from a survey by Major Henderson & Lieut Smyth, R.E. in 1818. District Royal Engineer Office Montreal 5th July 1843. Fras. Ringler Thomson, Majr & Captn Royl Engr. M. Vavasour. Lt. Royal Engr July 1843. [cartographic material]