It shall be the duty of the marshal of the United States for the district in which the testimony is to be taken to serve, or cause to be served, all subpoenas issued in behalf of the United States under this section and section 190l of this title, in the same manner as if issued by the district court for his district; and he shall, upon being first paid his fees therefor, serve any subpoenas that may be issued at the instance of such private party or parties. And the said master may, in his discretion, appoint any other person to serve any subpoena. Such master shall have full power to administer oaths to witnesses, and the same power to issue attachments to compel the attendance of witnesses and the production of books, papers, and documents, as the district court of his district would have in a case pending before it; and it shall be his duty to report the conduct of contumacious witnesses before him to the House of Congress appointing such committee. The compensation of such master in chancery, and the fees of marshals and deputy marshals, and of any person appointed to serve papers, shall be the same as for like services in equity cases in the district court of the United States; and the compensation of witnesses shall be the same as for like attendance and travel of witnesses before such district courts; and all such fees and compensation of officers and witnesses on behalf of the United States, and other expenses of all investigations which may be had under the provisions of this section and section 190l of this title on the part of the United States, shall be paid out of the contingent fund of the Senate, in the case of a committee of the Senate, or the applicable accounts of the House of Representatives, in the case of a committee of the House of Representatives. Said master, when the examination is concluded, shall attach together all the depositions and exhibits, and attach thereto his certificate setting forth or referring to the authority by which they were taken, any notices he may have given, the names of the witnesses for whom subpoenas or attachments were issued, the names of witnesses who attended, with the time of attendance and mileage and fees of each witness on behalf of the United States, which he may require to be shown by affidavit, his own fees, the fees of the marshal, his deputies or other persons serving papers, giving the items, and such other facts in relation to the circumstances connected with the taking of the depositions as he may deem material. He shall then seal up such depositions and papers securely, direct them to the chairman of such committee at Washington, stating briefly on the outside the nature of the contents, and place the same in the post office, paying the postage thereon; and said package shall be opened only in the presence of such committee. The chairman of any committee ordering testimony to be taken under this section and section 190l of this title shall, at least ten days before the time fixed for such examination, and within two days after the adoption of such order, cause a copy thereof to be directed and delivered to the Attorney General of the United States, or sent to him by mail at the Department of Justice, to enable him to give such instructions as he may deem best to the United States attorney of the district where such testimony is to be taken, who may, and, if required by the Attorney General, shall, though not requested by the committee, appear for the United States in person or by assistant, and take such part in such examination as the Attorney General shall direct.