The right of appointing to and removing from the office of Assessor of Railways and Canals in Scotland, constituted in terms of section twenty of the [17 & 18 Vict. c. 91.] Lands Valuation (Scotland) Act, 1854, shall be transferred to and vested in the Secretary of State, and such assessor shall he designated and known as the Assessor of Public Undertakings (Scotland).