Section 20

Whenever the tribunal consists of an arbitrator, assisted by assessors and any vacancy occurs in the numbers of assessors, the tribunal may in the discretion of the arbit-rator either act notwithstanding such vacancy or consent to another assessor being nominated and appointed to fill such vacancy. Any such 6ew assessor shall be nominated by the party whose original nominee had vacated his office as an assessor.

No act, proceeding or determination of the tri-bunal shall be called in question or invalidated by reason of any such vacancy.