Section 2. County commissioners shall cause changes in the boundaries of towns, in the courses of highways, railroads and canals, and other topographical alterations to be correctly delineated on the county maps, which shall remain in their possession.

The state secretary, as often as necessary, shall transmit the manuscript county maps in his office to the respective county commissioners who shall cause a competent engineer or surveyor under their direction to transfer thereto all changes, and shall, within two months after their receipt, return them to the secretary, who shall forthwith cause the changes to be copied on the plates of the state map.