And be it enacted, That it shall be lawful for the principal Officers of Her Majesty's Ordnance for the Time being to enter on, survey, and mark out, or to cause to be surveyed and marked out, any Lands, Buildings, or other Hereditaments or Easements wanted for the Service of the Ordnance Department, or for the Defence of the Realm, or to stop up or divert any public or private Footpaths or Bridle-roads, and to treat and agree with the Owner or Owners of such Lands, Buildings, Hereditaments, or Easements, or with any Person or Persons interested therein, either for the absolute Purchase thereof, or for the Possession or Use thereof during such Time as the Exigence of the public Service shall require.