The Board shall have power to petition any court of appeals of the United States, or if all the courts of appeals to which application may be made are in vacation, any district court of the United States, within any circuit or district, respectively, wherein the unfair labor practice in question occurred or wherein such person resides or transacts business, for the enforcement of such order and for appropriate temporary relief or restraining order, and shall file in the court the record in the proceedings, as provided in section
2112 of title
28. Upon the filing of such petition, the court shall cause notice thereof to be served upon such person, and thereupon shall have jurisdiction of the proceeding and of the question determined therein, and shall have power to grant such temporary relief or restraining order as it deems just and proper, and to make and enter a decree enforcing, modifying and enforcing as so modified, or setting aside in whole or in part the order of the Board. No objection that has not been urged before the Board, its member, agent, or agency, shall be considered by the court, unless the failure or neglect to urge such objection shall be excused because of extraordinary circumstances. The findings of the Board with respect to questions of fact if supported by substantial evidence on the record considered as a whole shall be conclusive. If either party shall apply to the court for leave to adduce additional evidence and shall show to the satisfaction of the court that such additional evidence is material and that there were reasonable grounds for the failure to adduce such evidence in the hearing before the Board, its member, agent, or agency, the court may order such additional evidence to be taken before the Board, its member, agent, or agency, and to be made a part of the record. The Board may modify its findings as to the facts, or make new findings by reason of additional evidence so taken and filed, and it shall file such modified or new findings, which findings with respect to questions of fact if supported by substantial evidence on the record considered as a whole shall be conclusive, and shall file its recommendations, if any, for the modification or setting aside of its original order. Upon the filing of the record with it the jurisdiction of the court shall be exclusive and its judgment and decree shall be final, except that the same shall be subject to review by the appropriate United States court of appeals if application was made to the district court as hereinabove provided, and by the Supreme Court of the United States upon writ of certiorari or certification as provided in section
1254 of title
28.