Section 111. Where there are two or more arbitrators, if they do not within such a time as the Companies agree on

111. Where there are two or more arbitrators, if they do not within such a time as the Companies agree on, or, failing such agreement, within thirty days next after the reference is made to the arbitrators, agree on their award thereon, then the matters referred to them, or such of those matters as are not then determined, shall stand referred to their umpire.