The contract in question is governed by the arbitration agreement contained in clause 21 of the form W.S.B. 133 which states as follows : "Arbitration: In the event of any question or dispute arising under these conditions or any special conditions of contract or in connection with this contract (except as to any matters the decision of which is specially provided for 226 by these conditions) the same shall be referred to the award of an arbitrator to be nominated by the Purchaser and an arbitrator to be nominated by the Contractor, or in case of the said arbitrators not agreeing then to the award of an Umpire to be ,appointed by the arbitrators in writing before proceeding on the reference and ' the decision of the arbitrators, or in the 'event of their not agreeing, of the Umpire appointed by them, shall be final and conclusive and the provisions of the Indian , and of the Rules thereunder and any Statutory modification thereof shall ' be deemed to apply to and be incorporated in this contract.