146. Mode of purchase.

The purchase may be by agreement or under the compulsory powers of the railway or other authority1 and the provisions of the empowering statute apply to minerals2 worked by surface workings as well as to those worked by underground workings3. The mines4 and minerals may be purchased as a separate tenement5. The mere fact that the authority has already purchased the surface does not exhaust the power; the mines and minerals may be purchased at any time subsequently within the period limited for the exercise of the power, and it is optional on the part of the authority whether