If no method of naming arbitrators be provided, or if for any other reason there shall be a lapse in the naming of arbitrators, then upon the application of either party to the controversy the court aforesaid or the court in and for the county in which the arbitration is to be held shall designate and appoint an arbitrator or arbitrators as the case may require, who shall act under the said agreement with the same force and effect as if he or they had been specifically named therein; and, unless otherwise provided in the agreement, the arbitration shall be by a single arbitrator.