It shall be lawful for the registrar for the time being of Her Majesty’s Privy Council appointed under the said Act, or such other person or persons as shall be appointed for this purpose by Her Majesty in Council or by the said Judicial Committee, to examine witnesses and take affidavits and depositions upon oath in all appeals, causes, and matters whatsoever pending before Her Majesty in Council or before the said Judicial Committee, and to administer oaths accordingly.