Where any Tailzie executed after the First Day of August One thousand eight hundred and forty-eight does not expressly prohibit the granting of Feus or Building Leases of the entailed Estate, or any Part thereof, though containing a Prohibition against Alienation and long Leases generally, the Heir of Entail in possession of such entailed Estate for the Time shall have the same Powers of granting Feus and Building Leases for more than Twenty-one Years as are by the said recited Act, or by any other Act of Parliament conferred upon Heirs of Entail in possession of entailed Estates holding the same under Tailzies dated prior to the said First Day of August One thousand eight hundred and forty-eight: Provided always, that Application shall be made in the Form prescribed by the said recited Act with reference to Applications authorized to be made under the said Act, for the Authority of the Court of Session to the granting of such Feus or Building Leases; and such Court, having regard to the Interests of the Heirs Substitute of Entail, shall be satisfied that the granting of such Feus or Leases is an Act of beneficial Administration of the entailed Estates