Any corporation, as originally formed under this chapter, or a corporation resulting from the consolidation of two or more corporations may extend its territory by filing in the office of the officer charged with the duty of recording deeds of the county in which such new territory is located a certificate subscribed and acknowledged in the same manner as an original certificate of incorporation under this chapter by the president or a vice-president and the secretary or an assistant secretary of the corporation, which shall set forth: The name of the corporation; a reasonable description of the new territory; that the corporation is ready and able to extend forthwith its system into such new territory to the extent that it may economically do so. In the event that such new territory includes part of the territory of another corporation or corporations, then such certificate shall contain a statement to the effect that such other corporation or corporations have been requested in writing to construct the extensions which the corporation wishing to extend its territory is ready and able to construct and that such other corporation or corporations are not ready and able to do so. Unless such other corporation or corporations shall commence construction of such extensions within 30 days after being requested so to do, this shall be conclusive evidence as to the fact that such other corporation or corporations are not ready and able to construct such extensions. Construction of such extensions begun by such other corporation or corporations within said 30 day period must be continued with reasonable diligence.