131. Implication from express covenants.

A covenant by lessees to work mines1 fairly and regularly according to the best and most improved method in use in the district indicates an intention to authorise, even if it does not enjoin, the lessees to work on the longwall system if that is the best and most improved system in use in the district2. Further, a mining lease may impose on the lessee an obligation to perform certain acts which are plainly inconsistent with the support of the surface3, as where the lessee is under covenant to work so as to produce from the mine the greatest