1. In all cases where further proof is ordered by the court, the depositions which may be taken shall be by a commission, to be issued from this court, or from any Circuit Court of the United States.

2. In all cases of admiralty and maritime jurisdiction, where new evidence shall be admissible in this court, the evidence by testimony of witnesses shall be taken under a commission to be issued from this court, or from any Circuit Court of the United States, under the direction of any judge thereof; and no such commission shall issue but upon interrogatories, to be filed by the party applying for the commission, and notice to the opposite party or his agent or attorney, accompanied with a copy of the interrogatories so filed, to file cross-interrogatories within twenty days from the service of such notice; Provided, however, That nothing in this rule shall prevent any party from giving oral testimony in open court in cases where by law it is admissible.